Questions With Answers

How does snow form?

2011-06-27T22:37:00.003+05:30

How does snow form?

High up in the atmosphere, the air temperature is very cold. The water vapour may fall as rain if the water does not freeze. However, if the air temperature is so cold that the water droplets freeze, tiny ice crystals form in the clouds. These ice crystals collide with each other in the clouds or grow delicate shapes. The ice crystals combine to form snowflakes. There may be hundreds of tiny ice crystals in a single snow flake. These snow flakes fall from the clouds to form snow on the ground.

If the air temperature is not too cold and the air is very moist, the snow flakes may grow into very large flake up to 1 or 2 centimetres across.

Every snow flake is different. However, each snow flake has 6 sides.

What is sleet?

2011-06-27T22:35:00.002+05:30

What is sleet?

When the air temperature is very cold, water vapour in clouds may fall as sleet, hail, or snow. Water droplets in the clouds get cold, but may not freeze completely. Sleet forms when partially frozen water droplets, or rainwater, in the clouds falls and freezes completely when it hits the surface of the Earth.

Like freezing rain, sleet may be dangerous because it coats roads and sidewalks with ice. Cars may not be able to stop on the slippery roads and many collisions between cars may occur. Slippery sidewalks are very difficult to walk along.

What is freezing rain?

2011-06-27T22:33:00.002+05:30

What is freezing rain?

When the air temperature is very cold, water vapour in clouds may fall as sleet, hail, or snow. Water droplets in the clouds get cold, but may not freeze. Under certain circumstances, the temperature of the water droplet may drop below the freezing temperature of water, but the water remains in the liquid state. This water is super-cooled. When super-cooled water falls to the surface of the Earth, the water freezes instantly on any surface it hits. This is called freezing rain.

Freezing rain may cause lots of damage. Trees and power lines may break under the weight of the heavy ice. Cities may have to go without electricity when major power lines are broken.

How do clouds form?

2011-06-27T22:32:00.002+05:30

How do clouds form?

As warmer air pass over the ocean or large open lakes, the air picks up water vapour. As the air warms, it rises because warm air is less dense than cold air. As the warm air rises, the air cools and the water vapour in the air condenses to form clouds of water droplets.

Clouds that form at the surface of the Earth are known as fog.

What is potential energy?

2011-06-23T22:35:00.001+05:30

What is potential energy?

Potential energy is stored energy. An apple sitting on the edge of a table has stored potential energy. The potential energy changes to kinetic energy when the apple falls to the ground. A compressed spring has potential energy. That potential energy is converted to kinetic energy when the compressed spring is released.

What is energy?

2011-06-23T22:27:00.001+05:30

What is energy?

Energy is the capacity to do work. Our energy comes from food, which contains stored chemical energy. Our bodies take the stored chemical energy and converts it to mechanical energy, heat energy or other forms of energy.

Light, sound, heat, and electricity are forms of energy

How does the sun produce photons?

2011-06-08T09:00:00.002+05:30

How does the sun produce photons?

The surface of the Sun is very hot of course. It’s so hot that hydrogen becomes ionised into plasma so that you have photons and electrons as separate bodies, rather than bound together into atoms. And as those different charges interact, they exchange energy at the surface of the Sun and in the process of saving energy, they can lose energy and that is radiated as the photons that we see. Now that's not actually the powerhouse that drives luminosity of the Sun. That is the fusion of hydrogen atoms into helium which occurs at the core of the Sun. In fact, only in the central 20% or so of the Sun and so, you have another process which is convection which is carrying that heat which is generated at the centre of the sun out of the surface to keep the surface hot so that it continues to shine.

Are there no photons being produced deep inside the Sun? Presumably there are, but they just can't get out.

Photons are being produced all throughout the Sun, but the Sun is made of a cloudy material because these protons and electrons can interact with that light. And that means the photons produced deep down can only actually travel a few centimetres before they're reabsorbed.

And of course Bryan Fulton who was on this program, he’s professor of Astrophysics at the University of York. I think the point he made was that the photons that get made in the Sun are actually a million years old plus by the time they emerge because they have spent their entire life being bombarded around and absorbed and reabsorbed, ad infinitum almost before they finally escape. So if the Sun went out tomorrow, went out as in all reaction stopped, we’d still have a million years of the light locked inside.

The light is travelling at the speed of light, but it’s only hopping a few centimetres at a time and we don't know what direction it’s going to come back out again. It may end up going back towards the centre of the Sun again and it takes a million years. It’s quite a random walk for that energy to get to the surface.

Are air cavities in the body a problem when diving deep?

2011-06-06T22:28:00.001+05:30

Are air cavities in the body a problem when diving deep?

It is a very good film and it does seem very futuristic, but it is actually partly reality. These chemicals, these liquids do exist. They're called perfluorocarbons. They include fluorohexane for example, so a string of 6 to 8 carbon atoms with lots of flourines hanging off the side and they're very good at dissolving oxygen. So, one way of doing this would be to instil these fluids into the respiratory tract and you saturate them with the oxygen, and then you move the fluid in and out, in the same way that you would when you were breathing.

Why this is helpful is that when a person descends underwater, the pressure they feel from the surrounding water goes up and up, the deeper they go. So, you have to therefore put the gas into the lungs to keep the lungs inflated, under progressively higher and higher pressures. One consequence of this is that it drives other gases like nitrogen and things into the tissues at extremely high pressures which means that then when you decompress, those gases come out of solution in the tissues and form bubbles which can cause the bends, they can cause damage to the brain, and cause damage to bones and muscles and so on. So if you use a fluid in the lung, because fluids are incompressible then you wouldn’t have the same problem because the fluid would withstand the pressure being applied by the outside water much better.

The issue with these fluids though is that they're not very good at removing CO2. They're very good at putting oxygen in. They're not good at getting carbon dioxide out and to compensate for the fact that they don't move CO2 very well, you'd have to move a lot of the fluid a lot of the time, and that's one of the major hold ups with doing this. In terms of the liquid getting into other body cavities and body parts, this isn’t such a problem actually. The eustachian tubes that you mentioned, they run between the back of the throat and the ear, so they would just fill up with the fluid anyway. The other body cavities, well, they wouldn’t actually be exposed to the fluid directly because it will be in the respiratory tree. So, there wouldn’t be a problem there and if there were any leakages of the fluid into other places, you would just pass it, I would think. It certainly wouldn’t become part of the systemic circulation, so it should be okay.

If dark skin absorbs more heat, why aren't native African people white, and Inuit people black?

2011-06-05T19:41:00.002+05:30

If dark skin absorbs more heat, why aren't native African people white, and Inuit people black?

Logically, it should be the case that if you have pale skin it’s going to reflect more light and more heat and would be suited to warmer, sunnier places. But what is actually happening is people with darker skin have more melanin, more pigment, in their skin and this prevents the short wavelengths of light, the UV, from penetrating deep into the skin. It also means the skin can produce vitamin D in suitable levels. So if you live in more northern climes where there is less sunlight, so for example in the UK, then it’s much better to have pale skin which allows more sunlight to get into your skin and more vitamin D to be produced. Vitamin D is great for strengthening bones. Iit prevents you from getting diseases like rickets which would be very selective against a population if you were living in northern Europe.

UV radiation damages folic acid which you need for the development of the nervous system. If you get folic acid depleted you get diseases like spinabifida, so in continents like Africa where there is a lot of UV in the sunlight, if you don’t protect yourself with lots of melanin you will depete your folic acid, leading to an excess of neural tube defects like spinabifida and this would manifest in a cost to reproductive fitness in the population. So as there is so much sunlight, Africans can afford to have dark skin and still make enough vitamin D and not lose their folate but once you get up to the parts of the latitudes we live in, where it’s miserable all the time, vitamin D becomes the real problem. You need to make enough vitamin D and so you have to have pale skin. There’s so little UV because we hardly ever see the Sun anyway that it doesn’t become a problem from the folic acid depletion, neural tube defect perspective.

Are any viruses good for us?

2011-06-04T08:42:00.002+05:30

Are any viruses good for us?

This may be true, despite that fact that most people think of a virus as being something that makes them feel awful! A recent piece of research in Nature by Skip Virgin, suggested that being infected by one of the family of viruses known as Herpes viruses, such as herpes simplex, which causes cold sores, Epstein-Barr virus, which causes glandular fever. When they infected mice with the rodent equivalent of those infections, the mice developed a much better immune system than mice which had ever been infected. To prove this, they exposed the mice to the bacteria which causes plague and also listeria, and they found these mice to be 100% protected against these bacteria compared with animals which had never been infected with a Herpes virus. When they studies these mice they found molecules called interferon gamma at a much higher level, and this molecule is known to stimulate the immune system.
They think that because we've been living with herpes viruses for millions of years, the body has come to rely on infection to provide additional gene function which our body no longer has. This stimulated the immune system and we get some benefit. It's almost a symbiosis, we give the virus a home and it gives us a better immune system.

Why does lightning rumble?

2011-06-04T08:38:00.002+05:30

Why does lightning rumble?

If a lighting strike is very close to you it sounds like a very sharp crack and then a bit of a rumble afterwards, the further away you get the longer the rumble can sound. So a lightning bolt will make a sharp short noise, but first of all the noise is produced along a line up to a couple of kilometers long (if you live in Arizona), so because sound travels at 330m/s it could take up to 6 seconds for the sound from the top to reach you so the sound will be spread out over several seconds. The sound is then further spread out as you move further away from the lightning because the sound can get to you directly or by bouncing off things. This means that the sound will take lots of different times to get to you and therefore be spread out over several seconds as a rumble

How does food become radioactive?

2011-06-02T22:18:00.001+05:30

How does food become radioactive?

there are various ways that food can become radioactive. It becomes radioactive when plants absorb it through their roots as they grow or animals ingest it and then you eat the animals. You also get fallout. So, in the initial blast where they vented the steam, there would’ve been some dissolved caesium and iodine, and probably some particles of fuel - very small amounts - in those vents, and those would have then come down around about the Fukushima prefecture. That's why the Japanese government has banned the sale of various different vegetables and milk within a certain radius of the plant.

Why does overeating chocolate make you feel sick?

2011-06-02T22:13:00.001+05:30

Why does overeating chocolate make you feel sick?

This is probably down to the sugar and I've conducted lots of experiments in this area! You may notice that you feel sick after over indulging on any kind of very sweet food, whether it’s chocolate or cakes, or sweets... Not very good for you but tremendous fun! This gives your body a massive hit of sugar, all in one go. It raises the level of sugar in your bloodstream and causes something known as hyperglycemia. It’s this state of being hyperglycaemic that makes you feel sick. Now in most people, this just sends our pancreas into overdrive. We produce loads of insulin. The cells of our body take up this excess sugar, everything returns to normal, apart from maybe wanting to stay off the cake for a bit. But actually, in people who have diabetes, this doesn’t happen properly. Either they don't produce enough insulin or their cells don't respond to the insulin properly and take up the sugar. In fact, one of the symptoms of undiagnosed diabetes is feeling sick because you can't actually control this blood sugar and you do suffer from hyperglycemia. So yes, overeating chocolate will make you feel sick, but if you feel sick all the time after eating, you should probably go and get that checked out.

Is hot water heavier than cold water?

2011-06-01T22:40:00.002+05:30

Is hot water heavier than cold water?

Hot water is actually a little bit heavier than cold water because as Einstein told us E=mc2. So if E, the energy in the water, goes up because it’s hotter then mass, m, must also go up to keep the equation balanced [c, the speed of light in a vaccuum, doesn't change]. So there will be a very subtle and very tiny increase in mass of the hot water, compared to the cold water.

The reason the ice floats is actually because it’s a lot less dense than the water. The ice is made of water but it’s pushing a bigger volume of water out of the way, than the ice itself weighs. For that reason, it’s actually feeling a big push up from the water underneath it which makes it float, so that's the reason.

Does Aspirin alter blood pressure?

2011-06-01T22:36:00.001+05:30

Does Aspirin alter blood pressure?

A very small effect. If you take high doses of Aspirin, it can increase blood pressure slightly, but it’s not a problem in clinical practice.

Is the Sun Alive?

2011-06-01T22:32:00.002+05:30

Is the Sun Alive?

No it isn’t. It is a big flaming ball of exploding helium or hydrogen, one of the two. Physics not my strong point but no, it is not alive. It is not cells in it.

We also put this to Dave Ansell, for whom physics is a strong point!

To think about this question we really need a definition of life, whilst it is obvious that a cat is alive at a first glance it is less obvious that lichen is alive, you would only notice if you look at it for a period of years.

There are various properties that we associate with living things.

Metabolism - converting energy from one form to another. Normally with living creatures this is light or chemical energy being converted into other forms, but there is no fundamental reason life shouldn't be powered by nuclear fusion like the sun.

Homeostasis - the regulation of an internal environment, eg your body maintains its temperature by sweating, but simple creatures will regulate the chemistry in their cell. If the sun gets too hot it will expand, slowing down the nuclear reactions that power it and cooling it down so it could be said to do this.

Response to stimuli - if you metaphorically poke almost all living things they will react in some way. Some creatures will react directly to being actually poked, but even single cell creatures will react to sunlight, or food. - I guess a star will alter if you apply a large enough stimulus, but not in a way very like a living creature.

Reproduction - this is a really important one, all living things can reproduce themselves and in the process they normally have to grow. - I can't think of any way in which the sun could reproduce. Conceivably large stars that go supernova trigger the formation of other stars, but this falls down on:

Inheritance - When a living thing reproduces, the children inherit features from their parents, such as the colour of eyes, shape of foot, the ability to make an enzyme which interferes with penicillin etc. And critically this inheritance isn't quite perfect - it is liable to mutation - so the creature can evolve.

Even if you could say that a star can reproduce by going supernova the created stars do not inherit features from the star which went bang, and although a star does appear to metabolise hydrogen to form helium I don't think that you could say that a star is alive.

Saying that, the surface star is a hugely complex thing with interactions between plasmas, nuclear fusion and magnetic fields It is conceivable that there is some form of life, entirely unlike creatures on earth, and we may not recognise it even if we were looking straight at it. But at the moment this is well into the realms of science fiction.

How does blood clot?

2011-05-31T21:58:00.002+05:30

How does blood clot?

In blood, there are several elements. They include little bits of cells called platelets, which are programmed to recognise holes in blood vessels and bind on to them. There are also proteins which are dissolved in the blood which are able to work like tiny pairs of scissors and cut other proteins to produce a cascade of changes which culminate in formation of a fibrin network. This looks like a fishing net inside a blood vessel which traps blood cells in it, and acts as a plug to block a hole in a blood vessel, for example.

So if we look at how it works: If you have a blood vessel and injure it, what happens first is that the platelets, which are circulating in the blood, recognise the fact that when the blood vessel is punctured there are now foreign surfaces exposed to the blood. The platelets bind on and then release various factors that trigger the blood vessel to constrict, so it gets narrower and reduces blood loss from the area. It also starts to recruit these other proteins dissolved in the blood, the coagulation factors, activating them sequentially. They cut each other, activating other coagulation factors, and culminating in the production of this cleavage of a protein called fibrinogen, to make this fibrin network.

All of this happens in a very short space of time - literally seconds for platelets blocking up the hole, to minutes for the formation of one of these fibrin networks. Once the gap in the vessel has been plugged, then the cells locally which line the vessel over-grow the area which has been breached, and they establish a new smooth lining to the blood vessel. The clot is then slowly metabolised away by other cells called macrophages.

The thing that the platelets and some of these other factors are recognising is collagen, the main building block of connective tissue. The proteins, including one called Von Willebrand factor, in the bloodstream are able to recognise the presence of collagen which is not normally ever seen inside a blood vessel or in a healthy organ, because they’re normally kept separate from it. So whenever that interaction occurs, this tells the factors in the bloodstream that a vessel must have been breached, and therefore you activate the clotting system and it plugs up the hole wherever this occurs. Normally blood vessels keep themselves clear because the lining of the blood vessel, the endothelium, produces various factors which are anti-thrombotic, they antagonise or prevent blood from clotting. Obviously if you damage the blood vessel, you remove that anti-coagulative ability, so it shifts the blood into a pro-coagulation state, and then it starts to clot.

Can we extract energy from the Cold?

2011-05-29T16:39:00.001+05:30

Can we extract energy from the Cold?

That is a very interesting question. You can't gain energy directly from cold, but what you can do is get a lot of energy by moving heat from somewhere which is warm to somewhere which is cold. And that’s essentially what a steam engine does or a car engine, any of the heat engines work exactly like that. However, the colder you get that cold into the system, the more efficient the process is. So if that cold end is absolute zero, then if you move a kilojoule of energy from something warm to there, then you've got a kilojoule of useful work out of that. If it’s hotter than that, then it gets a lot less. So, once you collect energy from cold directly, you can get a lot of energy by transferring heat to somewhere very cold

Why do roads look reflective?

2011-05-29T16:36:00.001+05:30

Why do roads look reflective?

This is called a mirage. On a hot day the air above the road gets hotter than the air above that. When air gets hot it expands and becomes less dense. The less dense the air is the faster light goes through it. The light is going slower high up than it is really close to the road. The light then refracts as is comes down from the bright sky. It bends upwards and goes into your eye. What you’re seeing is an image of the sky in front of you.

Chris: When you have toast cooking in your toaster and you look at the air above it it’s all twisty and shimmery.

Dave: It’s the same phenomenon. You get hot air in swirly patterns above the toaster that bends the light which produces a distorted image behind.

How much water is in the world?

2011-05-28T09:05:00.002+05:30

How much water is in the world?

Best estimate, is we think there are 1.37 billion cubic km of water on Earth!

Are air cavities in the body a problem when diving deep?

2011-05-27T08:33:00.002+05:30

Why does cooled water sometimes suddenly freeze?

2011-05-27T08:29:00.001+05:30

Why does cooled water sometimes suddenly freeze?

It’s a beautiful effect it’s called super-saturation or super-cooling a liquid. What’s going on is that O°C is the temperature below which water is more stable as a solid than as a liquid. That doesn’t mean you can’t cool water below O°C. That’s because forming a very very small crystal takes quite a lot of energy and is quite unstable. So with water, it could be down to -3°C, you can supercool water to almost -20 °C, and if its below 0 every time a little tiny crystal starts to form it just gets knocked apart, so there are no small crystals there and nowhere the ice crystals can grow from, and the whole thing won't freeze. But if somewhere you get a crystal which is bigger than the certain critical size it’s much more stable for that crystal to grow and grow so you get a few small crystals spreading out and the whole things freezes very quickly, because its below zero. You also get that effect with sodium acetate. There are hand warmers based on this principle. You heat them it melts the liquid inside, you cool them down again, you flick a little clicky thing and that releases some crystals which causes the whole thing to crystalise. This releases lots of heat which warms your hand nicely.

We get bacteria in our gut. Where does it come from? Is it from our mums in the womb?

2011-05-27T08:27:00.001+05:30

We get bacteria in our gut. Where does it come from? Is it from our mums in the womb? Does it come from the environment after we’re born or is it dropped off by the stork?

It will probably surprise you to learn that we’re actually passengers in our own body.

If you count the number of bacteria that live on us an in us there are roughly 50 times as many of them as there are cells in our entire bodies. There are roughly ten thousand trillion cells in humans so that’s a lot of bacteria.

Where do they come from? Well, the answer is when a baby first pops out, assuming it comes the normal way, its first taste of life is quite literally a mouthful of muck. It’s its mums muck. It’s bacteria and other debris that are all over the pelvic floor and perineum of the mother. When the baby comes out those bugs that are there on the mum go into the baby and they get washed down into the stomach and then into the intestine where they take root.

The reason babies can do that and in us most bacteria get killed is because babies don’t have much stomach acid at that stage so the bacteria can very easily get in and settle down into the gut. After a few years they develop and turn into a very unique spectrum which is almost as unique to you as your fingerprint is. If you come out via a different route, say you have a caesarean then the kinds of bacteria that a baby picks up will be different and that’s been demonstrated.

Because of the spectrum of bacteria being a bit different there can be consequences for your risk of future diseases including things like getting allergies and also having bouts of diarrhoea. Recent studies have shown that babies born by caesarean section are actually twice as likely in their first year of life to have doses of diarrhoea and to have allergic reactions to things. Coming out the right way and getting a mouthful of muck unless you absolutely have to come out the wrong way is probably the best way.

With home electrical wiring, why should the wires oxidise?

2011-05-27T08:25:00.001+05:30

With home electrical wiring, why should the wires oxidise?

Normally, the current passing through the wires in your house does not generate enough heat in order to make them react with oxygen. Most wiring is copper, and you need to get copper to quite a high temperature to make it react with oxygen and produce copper oxide. This shouldn’t happen unless the wiring actually catches fire.

However if the wires get wet dissolved oxygen can react with the copper much more easily, so they will oxidise even at normal temperatures

Could we make a vaccine for coughs and colds?

2011-05-27T08:22:00.001+05:30

Could we make a vaccine for coughs and colds?

Not easily because (a) there are hundreds of different types of cold virus and (b) they’re continuously on the move. They’re a moving target because they use a genetic form of information called RNA which makes mistakes when it copies itself and that means that they’re continuously changing their shape. It’s like having a facelift at the level of a virus on a daily basis so you don’t recognise them from the perspective of your immune system very easily. They can easily re-infect you and a really good example of this is norovirus which is causing diarrhoea and has had 3 million people locked to a loo seat for longer than they’d like in the UK this year.

Norovirus is an example of this. It very quickly adapts and changes its appearance so, even though you’ve had it once, six months later you can catch it again because it looks entirely different by then.

How many 'flu inoculations can you make from a single egg?

2011-05-26T08:25:00.001+05:30

How many 'flu inoculations can you make from a single egg? Secondly, how do people ensure that the eggs that are used don’t contain the bird flu virus?

The answer is that you put the vaccine virus into the egg, which has a chick inside. The chick turns into chicken soup with some 'flu added. You get the 'flu out, purify it and you end up with about three doses per egg.

So, if you do some maths, if you want to immunise the entire population of the U.K. with, let’s say (for "eggs-ample"), 60 million to make the numbers easy, you would need - just for the U.K. - 20 million laboratory grade chicken’s eggs. So a lot is the answer.

In terms of egg-safety, the eggs used are laboratory grade eggs. They are high-grade, disease-free, guaranteed to be safe chickens' eggs. And also, the testing that goes on is incredibly rigorous. The eggs are tested, the vaccine progeny is testesd and what comes out is tested to make sure that there’s nothing in there that shoudn't be.

Do children typically grow out of food allergies?

2011-05-26T08:23:00.002+05:30

Do children typically grow out of food allergies?

That depends on the food allergy. So if you had egg or milk allergy as a young child, there's a very good chance of growing out, but if you had a peanut allergy, only a tiny minority of the very mild ones might grow out. So it’s very dependent on which food we’re talking about.
We don’t know for sure why this is, but we’ve done some research on egg allergy, looking at those who resolve and those who persist, and we can see changes in the immune system. The development of these T regulatory cells and various chemicals they produce occurs in the children who grow out of egg allergy. So it may be that it’s somehow easier with certain foods, like egg and milk, to develop the right sort of immunity to grow out. And perhaps that’s due to small amounts of these things being in foods.

How true is it that some genes that protected people from the Black Death

2011-05-26T08:20:00.001+05:30

How true is it that some genes that protected people from the Black Death are the same genes that are now protecting people from HIV today?

There was a hypothesis a little while ago that a mutation in one of the receptor proteins; a so-called Delta 32 for CCR5, might have had some protective effects against the plague. I'm not sure that that’s ever really been verified, but it’s certainly true that the Delta 32 allele, if one has two copies of that gene, there’s no functional receptor for the virus, so individuals with that genetic composition are in general resistant to infection.

How is bone marrow turned to blood and how is the marrow replaced once it’s used up?

2011-05-26T08:15:00.002+05:30

How is bone marrow turned to blood and how is the marrow replaced once it’s used up?

Bone marrow is found in the bone marrow cavity of bones, so if you cut across a bone and have a look, you'll see there’s a sort of hole in the middle with lots of plates of bone which jut out into that hole, and those plates in healthy bone are covered in stem cells. These stem cells are dividing very, very fast to produce new blood cells. In fact, the body destroys something like 1011 cells every single day and makes another 1011 cells every single day, and that's just red blood cells. In fact, we worked out over the course of lifetime, that you make a quarter of a million kilograms –a quarter of a ton of new red blood cells over the course of a whole lifetime, so it’s a very fast process. And these cells are just dividing all the time and pumping out daughter cells which then slowly, over a course of maturations, turn themselves into the new blood cells. This includes platelets as well. You have big cells called megakaryocytes and those megakaryocytes bleb off little bits of their cytoplasm, the stuff inside the cell, which become these little bits that floats around inside the blood, and they’re what causes you to be able to clot if you have a hole in the blood vessel, the platelet would stick on, and it causes the blood to clot. And then you have white blood cells as well, lymphocytes. They're also made by stem cells in the bone marrow which then go out from the bone marrow, go around the body, and turn into mature immune cells.

what dictates the frequency of the waves?

2010-03-29T08:17:00.002+05:30

what dictates the frequency of the waves?

The frequency of ocean waves depends on the wind speed, the time that the wind has been blowing and the length of the sea that it is been blowing over which is what we call the fetch. We actually prefer to talk about the period of waves, which is the inverse of frequency because people like to think about numbers greater than one rather than thinking about small decimals. If you started with the wind blowing over calm water, the waves start with small heights and short lengths but these steadily increase. In deep waters, the waves with the longer lengths travel more rapidly and the growth continues until the speed of the waves is about the same as the speed of the wind when it can’t put any more energy in. And we describe this as a fully-developed sea. There’s actually been a mixture of periods and people are quarrelling about how you define the period in the mixture of them. Real seas often have a spectrum with more than one peak, showing that the waves are coming from more than one place or maybe that the wind speed changed while they were growing. Periods in seconds of the same sort of order as wind speeds measured in meters per seconds, a bit more or a bit less depending on how you define your period. And most sea waves have periods in the range of 5 to 15 seconds with the longer ones coming when you had a really fast wind blowing for a long time over a long bit of sea.

Why is flu more prevalent in winter?

2010-03-29T08:14:00.001+05:30

Why is flu more prevalent in winter?

we think flu spreads better in winter because of human behaviour because it does this reproducibly in every country in the world and in which it is winter time - it doesn’t mean it goes away completely in summer but it does come much more commonly in winter.

We think that’s because it spreads better in winter because of what humans do. We go indoors more in winter so there are more people together indoors with the windows closed. Also, unlike summer time, it’s less light and therefore there's less ultraviolet radiation to dry out the virus and kill it. So 'flu finds it easier to persist on surfaces spread by coughs and sneezes, and it hangs around for longer.

As a result you have a higher chance of passing it on so that’s what we think goes on. And then the big determinant, the disproportionate determinant, is the school year. The long summer school holiday powerfully knocks 'flu on the head because kids stop mixing and spreading the infection amongst themselves. What normally happens is that they become infected and then go home and give it to their parents and the parents then carry the infection to all of the other parts of the social and age strata, usually through their workplace.

Why does lemon make green tea go clear?

2010-03-29T08:13:00.001+05:30

Why does lemon make green tea go clear?

There’s probably two reasons for this. The first one is that the lemon is acidic and so it’s affecting the pH of your tea and it may be that it’s causing changes in the chemicals that are in your tea and making them change to a different colour. So, like you can make indicator paper and change colour with different acids or bases and I think also, certainly down the south, we have a lot of limescale which is calcium carbonate in our water and it can make your tea cloudy. So, if you put in an acid, it will help to dissolve the calcium carbonate in it so it makes it go clearer.

Are glow-in-the-dark watches a radiation hazard?

2010-03-06T18:00:00.001+05:30

Are glow-in-the-dark watches a radiation hazard?

It depends very much on the type of dial that you’re considering. By far the most common watch that you come across that’s glow in the dark is called a phosphorescent watch. Essentially the watch is coated in a paint which absorbs light and then re-emits it. These watches are completely harmless.

The second type of watch is called a tritium watch. The modern way to do this is you have the same phosphorescent paint but this time it’s mixed with small tubes filled with tritium. Tritium is radioactive and emits beta particles. These have the same effect of exciting the phosphorescent paint. This time tritium has got a half-life of 12 years. The beta particles that are emitted are not very energetic so if anything they couldn’t even penetrate the outermost skin layer.

The third watch I’d like to mention is a radium watch. They have very much the same design but this time instead of tritium they’re mixed with radium. The half-life is sixteen hundred years. However, they may not seem to be as radioactive because the phosphor in the paint gets eaten up by the radium. I’ve got a small demonstration here so I’ve got an old watch that I’m going to hold a Geiger counter to. If I turn the Geiger counter on you’ll hear it clicking:

Virus to blame for blood pressure

2010-03-01T15:10:00.001+05:30

Virus to blame for blood pressure

US Scientists have discovered that a common human viral infection may be linked to hypertension, also known as high blood pressure.

Writing in PLoS Pathogens, Beth Israel Deconess Medical Center researcher Clyde Crumpacker and his team infected mice with the rodent equivalent of CMV (cytomegalovirus), which infects 80% of human adults. They found that, compared with uninfected controls, the CMV-exposed animals had significantly higher blood pressure in the weeks after the infection.

They also fed a second group of mice on a high-fat diet and infected half of them with the virus. In the CMV-exposed group the animals again developed hypertension but also showed signs of early atherosclerosis (arterial disease).

To find out why, the team studied the animal's blood vessels and found that the virus was establishing a persistent infection in the vessel wall that led to the production of inflammatory hormones called cytokines including IL-6, TNF-alpha and MCP-1, which have been linked previously to vascular disease. The team also found increases in the activity of two genes that directly control blood pressure - renin and angiotensin.

Next, to find out whether the results also apply to humans the team infected human umbilical cord blood vessels with human CMV with the same results. These findings are important because CMV is part of the herpes virus family, members of which characteristically establish life-long "latent" infections, meaning that CMV is well-placed to provoke long-term injury to blood vessels that could lead to vascular disease. The next step will be to discover whether there is a real association between human onset of hypertension and CMV infection, which increases in prevalence with increasing age, just like blood pressure diagnoses...

Does snow cool the world by reflecting light?

2010-02-26T21:53:00.002+05:30

Does snow cool the world by reflecting light?

Well, the thing about snow is that it’s quite reflective compared to bare ground. A good thick snow cover will reflect back up to 80 percent or even more of the sunlight that’s falling on it. Whereas bare ground or grasslands might only reflect 10 or 20 percent of the sunlight falling on it and so, the sunlight warms it up considerably. So, if you replace that bare ground by snow cover, then a lot of the sunlight that would’ve heated the ground just gets reflected back into space. So, if you remove a snow cover by ploughing it up or sweeping it away or whatever, revealing the bare ground underneath, then the ground is going to absorb a lot more sunlight, and will warm up a lot more quickly than if the snow were there. We are having an effect on the reflectivity, the albedo of the planet by changing land use for instance; cutting down forests and replacing them with grasslands. But that generally has the opposite effect, forests absorb quite a lot of sunlight, grassland is less reflective. People have suggested that we could partially offset global warming by painting the roofs of all of our buildings white. I think some calculations have been done that have showed that this will be a good thing, but it wouldn’t have a very large effect because you're only talking about a rather small area of the planet that you'll be changing the reflectivity of.

Why is chocolate toxic for dogs?

2010-02-26T21:50:00.001+05:30

Why is chocolate toxic for dogs?

Yes. Chocolate, unfortunately, is toxic to dogs. And the reason for that is because it contains a compound called theobromine. Theobromine and caffeine are both present in chocolate but theobromine is the problem. They’re both methyl xanthines. In dogs, theobromine is very long lasting. So it’s got a very long half-life of about 18 hours. Whereas in people, the half-life is only two or three hours. And people readily absorb the theobromine.

It’s just a fact that every species has a different metabolism. We see differences between dogs and cats. With certain drugs, say for example, you shouldn’t give a cat paracetamol whereas dogs can tolerate paracetamol. So it’s just a species difference; probably down to different enzymes that are present in the system.

So how much theobromine is toxic, you might ask yourself. So if a dog eats a couple of M&Ms, that’s not going to cause any problem. The toxic levels vary from 20 mg per kilogram of theobromine to about 150 mg per kilogram of theobromine. So what does that mean in reality?

Well, putting into a typical scenario, if you got a labrador and that ate a 200 gram bar of dark chocolate, that, potentially, is enough to kill your dog. So it’s actually not very much. And the big problem this time of year is someone gives you a box of chocolates, wrapped up, and you put it under the Christmas tree, and the dog eats the box of chocolates. If that happens you certainly should call your vet as soon as possible.

Can we create artificial nerve signals?

2010-02-26T21:49:00.002+05:30

Can we create artificial nerve signals?

Yes we can. We actually know quite a lot about how nerve information travels. If you can imagine a nerve cell as a bit like a long straw, with sides and a space in the middle - what nerves do is to move positively charged ions, in this case sodium ions, from the inside of the nerve, to the outside world. So the inside of the nerve is a bit negative compared to the surroundings.

When a nerve impulse travels along a nerve, what happens is that some "positive" (some sodium) goes back inside the nerve through tiny pores, which are on the surface of the nerve. This is called de-polarising the nerve, and it makes that section of the nerve become, transiently, a bit positive.

Now this does two things; it starts an electrical signal rather like a Newton’s Cradle running inside the nerve, but it also activates other little channels and pores on the surface of the nerve a bit further downstream. They open and let in some more "plus" to sustain and maintain the propagation of the signal. In a big nerve, this signal is actually travelling along at something like 100m/s.

The impulse (or action potential) only goes in one direction though because, in the opposite direction - where it’s just come from, the nerve pumps the "plus" back out again, so it goes back to being net minus and the nerve resets itself.

This process happens in milliseconds, so you can literally conduct hundreds if not thousands of these impulses down a nerve in less than a second. The information can travel very, very fast.

You can also make this happen by artificially stimulating the nerve. If you apply a little bit of electricity to the wall of the nerve fibre itself you can actually make that process trigger off, and then it self-sustains. The signal will propagate along the nerve to wherever it goes – in both directions.

Scientists use this for a number of reasons; one is that you can artificially activate muscles that way – so if you've been paralysed, for example, you can use techniques like this to restore movement to certain muscle groups by electrically stimulating certain nerves that supply those muscles. Another reason is to use brain stimulation – this has been done quite effectively in Parkinson’s disease. Scientists implant a little electrode in a part of the brain which makes movements and is involved in the same circuit as is affected by Parkinson’s disease. If you stimulate those bits of the brain electrically, you can trigger off impulses in the right way and the right rate to help people who have Parkinson’s symptoms to overcome their symptoms and move a bit more easily.

So, it is possible to re-create nerve signals. At the moment it's fairly low resolution: you’re not stimulating individual nerve cells, you’re stimulating clusters of nerve cells. But at the same time, you can do that.

Also, if you listened to last week’s programme, you’ll know that we talked about cochlear implants, which are things that basically stimulate the nerve that conveys hearing information into the brain stem. They’re doing effectively the same thing – stimulating nerve cells directly to send sound information into the brain.

Do rockets punch holes in the ozone layer?

2010-02-14T15:47:00.002+05:30

Do rockets punch holes in the ozone layer?

we know that the major culprit for making holes in the ozone layer are chemicals called CFCs — chloro-fluoro carbons. These are things that were used in aerosols, even in aspirin inhalers, but also in fridges as refrigerants, and they were used in huge amounts until the Montreal Treaty came in, in the late 80s to try and ban them. What provoked that was that a group of scientists including Brian Gardner had actually noticed this massive hole opening up over Antarctica in the mid-to-late 80s and this hole actually grew to be the size of Australia at its peak. It stopped growing; it’s actually beginning to shrink a little bit now and that’s because we have stopped using these chemicals. The reason that they concentrate down in the Antarctic is because the Antarctic is an isolated continent. It’s completely surrounded by ocean and this creates something called a circumpolar current, and this has a sort of whirlpool-like effect in terms of air; and it draws in and concentrates these molecules over the Antarctic over winter when it’s very dark. They then accumulate in high clouds over the Antarctic and when the sun comes out the following spring the sun breaks down the CFCs and they get turned into reactive chemicals that would then react with the ozone and deplete it. They are, by far, in a way the worst culprit. We don’t send enough rockets and spaceships up into space to make a huge difference, I wouldn’t have thought, in grand scheme of things. So I think although we have to be environmentally conscious, I think the benefit of sending rockets into space in terms of what they can do for satellites and furthering research is far greater than the small bit of damage they might make to the ozone layer. So I think on the whole, probably not, it’s probably more a man made, anthropogenic problem.

If you don't cut and /or wash your hair, does it grow any slower?

2010-02-14T15:46:00.001+05:30

If you don't cut and /or wash your hair, does it grow any slower?

Unlike most other mammals, we have a very specific personal care and hygiene regime. Washing doesn't affect the hair growth itself except for some effect you may get from massaging the scalp as you are washing the hair by ensuring optimal blood circulation in the scalp, which may have some positive benefits for the hair follicle itself. Shaving does not impact on the quality of the actual hair fibre produced in that the hair is a dead entity above the surface of the skin.

There is a perception of thickened hair re-growth because if you were to cut it with a sharp instrument like a razor you would end up getting a sharpened end of the hair at its thickest point rather than that more fine, tapered end. Hair growth is very important for the success of the mammal and nature has provided enormous back-up systems to ensure that the hair continues to grow. In the wild you can imagine the loss of a coat would really be disastrous for a mammal in terms of regulations or camouflage etcetera. As a result the skin has invested enormous power into maintaining the hair follicle. That's why it's hard to grow when you want it to grow or stop growing when you want it to stop growing. That's because the principal driver for hair growth is hormonal, especially in those areas of the body with changed hair pattern after puberty.

There's a lot of clinical evidence to suggest that if you have abnormalities of the endocrine system or the hormone system you can have altered patterns of hair growth: either too much or too little.

What dictates the frequency of waves?

2010-02-10T23:04:00.001+05:30

What dictates the frequency of waves?

The frequency of ocean waves depends on the wind speed, the time that the wind has been blowing and the length of the sea that it is been blowing over which is what we call the fetch. We actually prefer to talk about the period of waves, which is the inverse of frequency because people like to think about numbers greater than one rather than thinking about small decimals. If you started with the wind blowing over calm water, the waves start with small heights and short lengths but these steadily increase. In deep waters, the waves with the longer lengths travel more rapidly and the growth continues until the speed of the waves is about the same as the speed of the wind when it can’t put any more energy in. And we describe this as a fully-developed sea. There’s actually been a mixture of periods and people are quarreling about how you define the period in the mixture of them. Real seas often have a spectrum with more than one peak, showing that the waves are coming from more than one place or maybe that the wind speed changed while they were growing. Periods in seconds of the same sort of order as wind speeds measured in meters per seconds, a bit more or a bit less depending on how you define your period. And most sea waves have periods in the range of 5 to 15 seconds with the longer ones coming when you had a really fast wind blowing for a long time over a long bit of sea.

Can lightning re-start your heart?

2010-02-05T22:20:00.001+05:30

Can lightning re-start your heart?

Firstly the short answer is yes, it is possible that being struck twice by lightning would firstly stop your heart and then restart your heart. The answer is a bit more complicated than that though. The heart cells maintain a voltage drop across them which controls the inflow and outflow of ions. These ions allow the heart to beat. If the heart’s struck by lightning that voltage drop is immediate and the heart will contract. Unfortunately if the lightning strikes the heart at the wrong part of its relaxation the cells will not contract together, rather chaotically. The heart will enter a rhythm called fibrillation. This doesn’t allow it to pump. For that reason the pulse would stop and the heart would be said to be arrested.

If a second strike of lightning or an electric shock occurred at the same point when a heart was fibrillating it would be possible that the heart cells would all contract together in a more ordered fashion. However, there is a problem. The heart could also be struck by lightning and instead of going into this fibrillating chaotic rhythm it could go into no rhythm at all. It could quite simply not beat again. That’s called asystole. It doesn’t end there unfortunately, our poor unfortunate victim also suffers elsewhere. It’s likely that the chest would become relatively stiff and the chest muscles would go into spasm. These muscles take a lot longer to recover than heart muscles so it would be very unlikely that your victim would be able to breathe again. For that reason, although the heart may well restart the victim may well die.

How long would it take to wipe all trace of man from Earth?

2010-02-05T22:17:00.001+05:30

How long would it take to wipe all trace of man from Earth?

Thinking first in terms of archaeological timescale if the human race were to become extinct tomorrow then our buildings and roads would gradually decay and possibly within a hundred or hundreds of years many buildings would start to collapse. The sturdier stone built buildings would stand a lot longer than this as we know because we still have Greek Temples and Egyptian pyramids with us today. If we think in terms of those ancient civilisation sit will only be a few millennia before our city would firstly be overcome by vegetation and then would be buried by silt and sediment. If you consider the fabrics used in modern day construction: reinforced concrete, plastics etcetera these would certainly survive the burial for at least as long as the two million year-old stone tools dating from the early humans from Africa, for example. If we think in terms of a geological timescale – this country and indeed most of Europe has been under the sea for a much greater period of geological history than it has been land. The one thing we can be certain of is that sea levels will rise again and this country will be flooded once more by shallow sea and then all of our cities will become deeply buried by marine sediments. Over geological time, over millions of years they’ll be preserved in a rock stratum in just the same way that dinosaurs are preserved in rock strata from 65 million years ago.

When we consider that the oldest fossils we have on Earth are 3 and a half billion year-old single-celled microscopic, soft-bodied bacteria. If such tiny and delicate organisms can survive for that long then certainly the robust skeletons of Homo sapiens can survive for similar timescales. In actual fact organisms that live in the sea are much more likely to be fossilised than organisms like ourselves that live on land. So human fossils will always be rather scarce. We know this already because although hominids have been around for say five million years the actual numbers of fossil human skeletons is very low. Certainly some of us will be fossilised and we will survive buried in rock strata. To answer the question, when the human race does eventually become extinct, as it certainly will, although evidence of our existence will disappear from the Earth’s surface relatively quickly – say within a few millennia – evidence of our existence will survive buried at depth probably for as long as the planet survives.

Would someone with a psychiatric disorder be better able to pass a lie detector test as they may not feel remorse?

2010-02-05T22:15:00.001+05:30

Would someone with a psychiatric disorder be better able to pass a lie detector test as they may not feel remorse?

Old-fashioned lie detectors like the polygraph only detect stress. If the lack of remorse meant that the interviewees had reduced stress levels that would help them pass. Our lie detector, Silent Talker, makes its judgement on non-verbal behaviour: crudely what people call body language. Silent Talker can detect stress but lying involves other factors. We can only juggle a certain number of mental variables at once while we’re thinking. If we’ve got to try and maintain a whole load of different factors about an imaginary story it’s very difficult to do all the mental processing to keep that consistent. That’s what’s known as having a high cognitive load which affects non-verbal behaviour. Also duping delight occurs when liars get a kick out of getting a lie across successfully and again this affects non-verbal behaviour. In one of our own experiments on the general population we taught silent talk to recognise guilty feelings the participants felt while they were lying. When we added this information to the general lie detection we got more accurate classifications. In another independent study conducted by a different university using Silent Talker it was found that Silent Talker was effective at detecting lies told by psychopaths in interviews. So there we have it: evidence that remorse is a factor in the general population but also evidence that in the case of one disorder it’s not the only factor.

Would a helium balloon float on the moon?

2010-02-05T22:13:00.001+05:30

Would a helium balloon float on the moon?

As far as the balloon’s concerned you need two things to make a balloon float. First you need an atmosphere for it to float in. The second thing you need is gravity. That’s because the reason why a balloon floats is that the balloon itself is less dense than the air around it so gravity pulls on the air around it more than the balloon. The air around it actually tries to push underneath the balloon. That forces the balloon up and makes it float. Unfortunately the moon hasn’t got an atmosphere at all. Therefore you’re missing one of the two things that you need to make a balloon float. In that case a balloon on the moon wouldn’t float at all. It would just land on the floor. However, that doesn’t mean you can’t have balloons or other bodies in space at all. Actually the Russians launched a space mission in the 80s called Vega. That involves putting a balloon in the atmosphere of Venus which is the second-closest planet to the sun. Balloons in space are possible and have been done in the past. Looking to the future there’s a possibility we might be looking at putting balloons on titan which is one of Saturn’s moons. Titan has got an atmosphere and it’s really cold there. There’s obviously gravity there. Therefore you’ve got all the things you might need to have a balloon on Titan. The reason to do that would be to have atmospheric instruments that you would hang from the bottom of the balloon and they would measure Titan’s atmosphere. That’s exactly what we’ve done on Venus with the Vega mission. So unfortunately no balloons on the moon but they do have uses elsewhere in the solar system. Not just on the Earth.

Why should we sit far from the TV?

2010-02-03T22:35:00.002+05:30

Why should we sit far from the TV?

Televisions really do give off radiation. But having said that, it’s only a little bit of radiation and it’s not that dangerous. What happens is that anything with a cathode ray tube, a tube where you shoot high-energy electrons at some sort of screen, when those electrons hit the screen, they give off very low energy x-ray radiation. This is the same way that x-rays are produced in regular x-ray tubes. So, if you're sitting close to a cathode ray tube, whether a computer monitor, a television screen, a radar set or anything else with that type of technology, you're going to be getting low doses of x-ray radiation.

Now having said that, I’ve got to emphasize, they're low doses of radiation. It’s not enough to be dangerous and in fact, if you watch your television for several hours a day all year, you're getting less radiation than you would from a single medical x-ray and less radiation than you get from the radioactivity that’s just naturally within your body. So, it’s something that we can measure, but it’s not something that’s harmful.

LCD and plasma screens don't give off any radiation at all. They don't use high-energy electrons. It’s a different type of technology. I could not say that they're safer because I don't consider the radiation from cathode ray tubes to be a risk, but I can say that they give off less radiation. As far as sitting too close to the television goes, the further back you are, the lower the radiation dose will be. But having said that, I don't consider the radiation dose even at a distance of just one metre to be dangerous.

Can tress or plants feel? What happens when you chop a branch off?

2010-02-03T22:32:00.001+05:30

Can tress or plants feel? What happens when you chop a branch off?

Plants can detect it when you damage them in some way. They are usually more sensitive to things like caterpillars eating them, which will happen in their natural life. For example, an oak tree which is being attacked by caterpillars will respond by producing tannins in its leaves, which makes its leaves bitter. What’s even more interesting is that trees adjacent to the one that’s being attacked can somehow detect some signal and will also start to produce tannins in their leaves, even before caterpillars have been eating. So given that, I think they can almost certainly detect if a branch has been cut off. The problem is that they don’t really have any response to that except to grow another branch.

What keeps the Earth's core so hot?

2010-02-03T22:30:00.002+05:30

What keeps the Earth's core so hot?

It's a combination of things. One, the earth's quite a big planet relative to Mars which is a bit smaller. There was a lot of heat that was in the Earth to start with. When the planets were first forming around the sun in what's called a protoplanetary disc a lot of the swirling and spinning material was crammed together and squeezed together. It had a lot of heat from that, those frictional effects. Also the Earth has what's loosely termed as radioactive compounds in the Earth. As these radioactive compounds break down and decay they produce heat. The heat is obviously concentrated in the core of the Earth and then filters up towards the surface. Because the Earth's a big planet it's got a big core. It's got lots of radioactive decay going on. Some of the heat that we're seeing is because the Earth is sustaining it's own heat by radioactive decay.

Why isn’t beetroot dye broken down by digestion?

2010-01-23T12:10:00.001+05:30

Why isn’t beetroot dye broken down by digestion?

Well, in some people it is, but in some people it isn’t. The chemical that’s in beetroot that makes them red and makes some people wee red and also pass red faeces, which is what can happen if you eat a lot of beetroot, is a chemical called betacyanin. It’s actually an anti-oxidant that the beetroot makes and it can be used a colour change indicator too, but it doesn’t necessarily breakdown in the intestines of all people.

The things that seem to make it breakdown more are acidity, so if you have very strong stomach acid then it breaks down more. If you have weaker stomach acid, then more can get through into the small intestine, and there, pancreatic juice is alkaline. So that can encourage it to pass through into the colon which is actually where it’s absorbed.

People have done experiments on patients who have had things called ileostomies, which is where you take the ileum, the terminal bowel, and you bring it to the surface of the skin. And you take the contents away into a bag, for example. If you feed these patients with the betacyanins in beetroot they don’t ever get beeturia, in other words, the red dye getting into their urine. That shows that the absorption must take place in the large intestine.

The other things that seem to affect the absorption is a chemical called oxalate, oxalic acid, which you get from rhubarb and rhubarb leaves. That actually gets broken down by bacteria in the small intestine and in the large bowel. So it’s possible that there’s a combined effect whereby some people have a certain genetic makeup that makes them break this stuff down more than others because they have more acidity. It’s also possible that they have certain bacteria living in the intestine that breaks this stuff down more than others, and so that affects whether or not you see it appearing in the bloodstream.

But in people who do get beeturia, what seems to happen is that the pigment comes through the wall of the bowel, doesn’t get broken down, goes around in the bloodstream, and then it gets filtered out by the kidneys and goes into urine, and makes urine go red. But what’s really interesting is that on its way to the kidneys, of course, it has to go through the blood. And I was rooting around on the Internet, and I found this wonderful paper. It was published in the Christmas BMJ 2005 by two doctors, Julia Handysides and Stuart Handysides, who work in Essex... What they did was to - well, they’ve written this paper. I’ll read you this because it’s hilarious.

“One Sunday evening in 2004, our 11-year old son went to bed after various delaying tactics, arguments about friends staying up later, forgetting to brush his teeth, forgetting to come down for a drink of water, and so on. But shortly afterwards, the dining door room opens, and in he comes, cupping a bleeding nose in one hand and gripping the bridge of his nose with the other. We led him to the kitchen sink and helped him to clean up and stem the bleeding, but oddly, the blood on his hands would not wash off. And it also looked brighter than usual. The poor child was interrogated. Is this some kind of ruse or lark to stay up later?

The bleeding stopped, his hands, although stained pink, were now clean and dry. Upstairs, we found crimson stains on the bathroom carpet which proved impossible to shift and remain there over one year later. Our garden’s harvest of beetroot was very good in 2004, and we had eaten some the day before the nosebleed. It dawned on us that on its way to staining urine, the pigment in beetroot might also stain blood as well.”

So that means potentially, all of your internal organs are getting stained bright red by beetroot, and if you bleed, the stuff can come out and stain your skin

Does too much calcium make your bones brittle?

2010-01-23T12:06:00.001+05:30

Does too much calcium make your bones brittle?

The answer is, yes it does, surprisingly. Calcium links up with phosphates to make the chemical "apatite" (calcium phosphate), one of the hardest chemicals we know, which is what makes bones hard and stony, and tough.

But if you have too much calcium, that can be as bad as having too little, as in condition osteoporosis where the bones actually begin to lose their calcification and the matrix of the bone, which makes them weak and more likely to break. There’s also another disease called "osteomalacia" where you have too little just of the calcium and that also makes bones weak.

But some people actually lay down too much calcium in bone, a condition called "osteopetrosis" from "petros" as in stony. This is where people can have say, five times the amount of calcium in their bones that they should have. It’s a genetic condition. It’s very rare and I think it also goes by the name "Albers-Schonberg disease" or something like that, but it’s very rare.

In these individuals, the cells that break down bone, called "osteoclasts", don't work properly. This is because the way bone is normally formed involves an equilibrium between laying down new bone and breaking down old bone, and that’s how bones are continuously remodelled.

So if you shift that equilibrium on one direction or the other, you either lose or gain bone. And what scientists have found is that in people who have osteopetrosis, the osteoclasts that normally breakdown bone cannot work properly. They have a deficiency of an enzyme called "carbonic anhydrase" and you need that to break down the calcium phosphate, the apatite, in order to remodel the bone.

As a result, they just keep on making their bones get harder and harder, and harder. Eventually they go beyond the point of this being beneficial and the bones become less flexible and more likely to break, so they get very brittle.

How do mosquitoes lay their eggs? We never see them doing so...

2010-01-23T12:05:00.001+05:30

How do mosquitoes lay their eggs? We never see them doing so...

Mosquitoes depend on water for their life cycle. Different mosquitoes live in different environments and as a result they depend on different types of water - stagnant water, big ponds of water, dumped car tyres with a bit of water and so on. You can actually tell which species of mosquito you're dealing with depending upon where they're laying eggs.

The bottom line is the mosquito goes down to the water once it’s mated and different species of mosquito lay eggs in different ways. But they all lay their eggs into water.

Certain species lay them as individual eggs which drift off; others lay big rafts of eggs. The eggs mature and hatch into little larvae, which then have an aquatic phase; they grow in the water and eat algae and things, growing into large mosquito larvae. These then mature into full blown mosquito flies that then take off and come and bite you.

You just have to keep an eye on a patch of water and you’ll see the mosquitoes coming down to lay their eggs!

How are seedless grapes grown?

2010-01-12T21:03:00.001+05:30

How are seedless grapes grown?

The correct answer is that the plants that grow them are actually clones. So instead of growing them from seeds, they're grown from cuttings, so from existing plants. So obviously the first seedless grapes were a plant that arose through mutation, that means that they don't have seeds. And some growers must have noticed this. And you can basically take a little shoot or a stem off the plant, dip it in rooting powder, put it in the ground, and a new tree will grow. This is how a lot of plants are cultivated now, and also a lot of seedless varieties. It's causing problems now with bananas though. Because they're all clones, they're getting struck down by funguses and things. If a population is genetically identical, it can very easily be wiped out because it has the same resistance to different pathogens.

Why can you see the moon during the day?

2010-01-12T20:59:00.001+05:30

Why can you see the moon during the day?

Why shouldn’t you be able to see the moon during the day? The moon is orbiting around the Earth. It takes the moon about 28 days to go right away around the Earth, come back to where it started. The Earth turns. Obviously, it does a complete evolution in one day, 24 hours, since so you would expect to see the moon go across the sky every day, pretty much. At some point so it might not be visible on some occasions so much but it should be there. So that’s not so unusual

Why does cutting hair make it stronger?

2010-01-12T20:58:00.001+05:30

Why does cutting hair make it stronger?

Actually, this is a myth. There is no evidence that cutting hair, shaving, doing anything like that actually makes hair grow more or adjust its strength or its length. Hair goes through three phases and its lifetime. The hair follicle has an anagen phase, when actually grows and makes hair and depending upon what sort of hair, where on the body surface you’re looking, that phase last different lengths of time.

On the head, for example, it lasts for several years, whereas on the face, it might last for weeks and an eyelash, for example, only grows for about three weeks before it goes into the next phase which is called the catagen phase when the hair falls out. And that’s when the hair follicle stops for a while. Obviously, you can imagine if your eyelashes grew for three years that would be a bit disadvantageous because you’ll be looking out through under these curtains, won’t you? So, it’s good that doesn’t happen. Then the third phase is something called the telogen phase, when the follicle rests before it re-starts itself again.

People often say when a person dies, their hair carries on growing after they die. Or, when you cut the hair it comes back far bushier. Both of those things are down to, in the case of someone dying, the skin dries and shrinks a bit around the hair coming out through the skin surface and this makes the hair look artificially a lot longer; and, when you cut hair, instead of having this tapered thin end, it’s got a very abrupt, cut off, sharp end, so the hair looks thicker when it comes back.

So, it’s just sort of illusion; it’s not really any fatter.

Why is flu more prevalent in winter?

2009-12-28T19:30:00.001+05:30

How does 'flu actually infect our cells?

2009-12-28T19:27:00.001+05:30

How does 'flu actually infect our cells?

The way flu gets hold of cells is down to proteins on the surface of the virus particle. Each virus particle is tiny, about 1/10,000th for the millimetre across. If you could zoom in on the surface, you’d see that it had these spikes on the surface. These spikes are a structure called haemagglutinin, which is a tiny protein resembling a molecular grappling hook. It’s viral Velcro. It gets hold of something called sialic acid, which is a chemical on the surface of the cells that line our nose and throat, and this enables the virus to grab hold of those cells and pull itself in very close.

Through this interaction the cell thinks the virus is something that it has to take inside the cell. So the cell then does something called receptor-mediated endocytosis, which basically means it pulls the virus inside the cell. Once inside the virus releases it’s genetic material and productively infects the cell.

It’s a bit like a Trojan horse actually because the Trojan horse was this juicy tidbit sitting outside the gate of Troy. The guys inside the city thought, “Wow! That looks fantastic. We’ll pull that inside because it looks good.” And it goes inside the city. And then of course, lurking inside are all these people who are then wreak havoc inside the city. And that’s basically what a flu virus does. It hijacks the cell, turns it into a virus factory and then it infects all of the cells around it and all the people around you!

Why do washing powders remove stains but not dyes?

2009-12-22T21:13:00.001+05:30

Why do washing powders remove stains but not dyes?

one of the main and important ingredients used is surfactants and the surfactant molecule is clever in the way that on one side it has a hydrophobic component, that’s a water-hating molecular chain. And on the other side, a hydrophilic water-loving component. The hydrophobic chain finds itself sticking to the stains on your clothes and the hydrophilic heads have a stronger attraction to water. They’re able to surround the dirts and roll it up into a small globular-type ball and the end result is that they’re able to lift the stain from your cloth, into the wash water.

Some of our detergents contain enzymes which are naturally derived molecules. Generally, we use different enzymes such proteases which break down proteins and amylase which breaks down starch and then finally, another major ingredient that we use, like most other detergent manufacturers is bleach. The bleach turns the stain into more soluble colourless particles that can be easily removed and carried away into the wash water. So, in actual fact, it can remove bleachable dye stains. So, to kind of answer the other part of the question, laundry detergents can remove certain dyes, as well as stains.

Most dyes are composed of molecules that these ingredients can’t target. Surfactants can't globuralize the dyes, nor can enzymes gobble them up, unless they're vegetable-based. But bleach can effect dyes and this is why, washing powders designed for colored clothes don’t contain any bleach.

Why is flu more prevalent in winter?

2009-12-22T21:10:00.001+05:30

why don't woodpeckers get brain damage when they hammer into a tree?

2009-12-14T22:46:00.002+05:30

why don't woodpeckers get brain damage when they hammer into a tree?

In the late 1970s scientists tackled this by using a very fast camera capable of taking 2000 pictures every second. Analysis of these images showed that a woodpecker's head tolerates a force of about 12 thousand times the force of gravity whenever it hits something, which is a considerable force going through its head, so why shouldn't it get brain damage? Well there are various woodpecker adaptations which means they are able to cope with this trauma, and one of them is that their skull bones are quite spongy which mean they can absorb shocks very well. Another adaptation is that a woodpecker's brain is small and so has a very big surface area to weight ratio, and so the force is spread over a large area. The photography also revealed that woodpeckers line their heads up very straight with whatever they tap into, so there's no rotational injury which, at least in people involved in car accidents, is a major cause of brain injury as delicate nerve fibres are torn by the brain trying to twist on itself.

How do whales hunt and eat prey without swallowing gallons of water?

2009-12-14T22:41:00.001+05:30

How do whales hunt and eat prey without swallowing gallons of water?

They filter the water. If you've ever seen a baleen whale, they have a big floppy sack under their jaw, called a baleen, which works like a giant tea strainer. The whale takes a mouthful of water and then squirts it out again through the baleen, trapping all the plankton they want to eat in there so they swallow just plankton and not mouthfuls of water.

Can lightning re-start your heart?

2009-12-09T15:16:00.001+05:30

As lightning can strike in the same place twice if you get struck by lightning and it stops your heart and then you get struck by it again would it restart you heart?

Firstly the short answer is yes, it is possible that being struck twice by lightning would firstly stop your heart and then restart your heart. The answer is a bit more complicated than that though. The heart cells maintain a voltage drop across them which controls the inflow and outflow of ions. These ions allow the heart to beat. If the heart’s struck by lightning that voltage drop is immediate and the heart will contract. Unfortunately if the lightning strikes the heart at the wrong part of its relaxation the cells will not contract together, rather chaotically. The heart will enter a rhythm called fibrillation. This doesn’t allow it to pump. For that reason the pulse would stop and the heart would be said to be arrested.

If a second strike of lightning or an electric shock occurred at the same point when a heart was fibrillating it would be possible that the heart cells would all contract together in a more ordered fashion. However, there is a problem. The heart could also be struck by lightning and instead of going into this fibrillating chaotic rhythm it could go into no rhythm at all. It could quite simply not beat again. That’s called asystole. It doesn’t end there unfortunately, our poor unfortunate victim also suffers elsewhere. It’s likely that the chest would become relatively stiff and the chest muscles would go into spasm. These muscles take a lot longer to recover than heart muscles so it would be very unlikely that your victim would be able to breathe again. For that reason, although the heart may well restart the victim may well die.

Why do some people blink more than others?

2009-12-09T15:09:00.001+05:30

Why do some people blink more than others?

Most people blink once every two-to-ten seconds. Blinking can be triggered by dust or pollen, if you get hay fever in the summer like I do. It’s mainly controlled by nervous impulses from the brain. Everyone has a sort of blinking pacemaker in their brain and everyone’s is different. Everyone’s is set slightly differently.

This area of the brain is known as the chordate nucleus and it controls your blinking by sending impulses down the nervous system into the muscles around your eyelids. There are of course other things that can affect your blinking like fatigue and also some diseases like Parkinson’s and nerve disorders.

What’s quite interesting is that when we blink we don’t actually notice that we’re blinking because our brains filter out the signal. It’s the same as when you move your eyes around a room. Your brain cuts out the signal of when your eyes are moving so that you don’t get confused and feel like the world is spinning. It’s called corollary discharge.

If a mosquito bites someone with HIV and then goes and bites someone else will it pass on the disease?

2009-12-09T15:07:00.001+05:30

If a mosquito bites someone with HIV and then goes and bites someone else will it pass on the disease?

Thankfully, no. Because otherwise Africa would have a much worse problem than it currently has where there are something like 4 million new cases of HIV every year. They’re thankfully not caused by mosquitoes. If they were we would all be in really serious trouble because it would be like malaria. The reason is really simple because we know that mosquitoes are very good at transmitting viruses, certainly things like dengue gets spread by mosquitoes and that’s a virus.

There’s a very good reason why this isn’t the case with HIV which is that HIV is a very specialist virus which has on its surface viral velcro, molecular docking stations that lock on to certain parts of cells, CD4+ cells which you only find in us, in humans. There’s related versions of HIV in chimpanzees (SIV) and they have their own specific cells that it locks onto. Because those specialist cells are only found in us HIV is a very fragile virus. It can’t survive in the mosquito’s intestine, it can’t latch onto cells in the mosquito, therefore the mosquito doesn’t get infected. Therefore the mosquito can’t amplify the dose from the person it bites. Therefore it can’t infect the next person because it can’t inject more viruses than it took in. HIV is very poor at infectivity. It’s actually very hard to catch, believe it or not. You can reassure everyone you’re not going to catch HIV from a bite.

How is oxygen made and recycled on the International Space Station?

2009-12-07T21:30:00.001+05:30

How is oxygen made and recycled on the International Space Station?

The oxygen isn’t strictly recycled. The carbon dioxide that the humans breathe out is filtered out of the air with a molecular sieve then simply dumped overboard. The oxygen is created from the water that comes from the air and from the washbasins and from the loos. After that water is cleaned up it is electrolysed. An electric current is passed through it and it is separated into hydrogen and oxygen. The hydrogen is dumped overboard; the oxygen is fed into the cabin for the crew to breathe.

What happens in scientific terms in a reaction between acid rain and limestone?

2009-12-07T21:27:00.001+05:30

What happens in scientific terms in a reaction between acid rain and limestone?

Limestone is mostly made up of the mineral calcium carbonate ( CaCO 3 ) this is not very soluble so the rocks don't dissolve very quickly. If you add an acid however you add Hydrogen Ions ( H+ ) which will react with the carbonate to form hydrogen carbonate HCO3- ions which are very soluble in water, and the limestone will dissolve. Or if there is more acid about the two Hydrogen ions will react with a carbonate to form H2CO3 which will decompose to form carbon dioxide CO2 and water H2O.

The acid can come from a variety of sources sulphur and nitrogen oxides released by burning fuels will form sulphuric and nitric acids, can carbon-dioxide can dissolve in water to form carbonic acid.

If your hair is red why does it go white? Does it change structure?

2009-12-07T21:22:00.001+05:30

If your hair is red why does it go white? Does it change structure?

The process is very likely to be the same as any other hair colour. All you’re doing is losing from the hair the ability to add some colour. The colour is accounted for by different forms of melanin: the same hormone, the same chemical in the skin that makes you go brown. You just lose the ability to add that to the hair so you see the natural colour of the hair: the keratin and that’s the stuff which is white.

Why do we serve white wine when chilled and red wine at room temperature?

2009-12-07T21:19:00.001+05:30

Why do we serve white wine when chilled and red wine at room temperature?

First of all, red and white wines have different chemical compositions that influence their sensory perception and their sensory traits. The aromatic white wines and these are things like Chenin Blanc, Gewurztraminer, some of the Rieslings, you serve them the coolest so it would be about 8°C. They have a relatively higher proportion of aldehydes and esters and terpenes that fill up the head space of the glass and at the lower temperature. So they will project their fruitiness which is a big part of the appreciation of those wines at a much lower temperature. The cooler temperature accentuates a bit of the acid and so, it creates a crispier, fresher kind of impression of the wine. If you do a Chardonnay-type wine or a wine in that style that is oaked, it can be served at a slightly higher temperature, so maybe 10°C, maybe 11°C. And the red wines, we have the phenolic compounds in the red wines, but with the polyphenols and the tannins, contribute to the structure in the mouth feel and that’s very much linked to the appreciation in a good quality of red wine. These components are better tasted at a slightly higher temperature. So if you chill the red wine, it’s not just that the flavour components don’t come out into the head space as well, but the tannins and the polyphenols feel much more astringent and harsher in the mouth and the acid is accentuated as well. If you serve a red wine that’s really warm, what you get then is the alcohol starts to dominate the head space in the glass and you get the perception of an alcoholic wine, and you don’t appreciate all the fruity components that are in the wine. So if we serve those at about 19°C, you get a much more pleasant overall balanced wine.

What are the dangers of hypnosis?

2009-12-04T21:51:00.001+05:30

What are the dangers of hypnosis?

Hypnosis can help with anxiety, although sometimes the thought of going to a hypnotherapist can make them anxious. However, they have nothing to be nervous about if they go to a properly qualified person. Among professionals, we always say that someone shouldn't treat someone with hypnosis if they wouldn't be competent to treat it without hypnosis. With an anxiety problem, you would probably be thinking about going to see a psychologist. If that psychologist knows how to do hypnosis, he may think about using that as an additional tool. This can help with the effectiveness of the treatment normally given. There is nothing harmful about hypnosis in itself as long as you go to someone properly qualified.

How does something like radiotherapy treat prostate cancer?

2009-12-04T21:43:00.001+05:30

How does something like radiotherapy treat prostate cancer?

There are three ways of using radiotherapy: one is something called x-ray beam radiotherapy where x-rays are fired at a target. Another way is brachytherapy where a radioactive source is put in a tumour, and the third way is injecting a radioactive substance like radioactive iodine, which treats thyroid cancer. The reason it destroys the cancer is due to the way the radioactivity interacts with cells and causes DNA damage. It's specifically the ionising radiation that we use because the interaction with the cell causes electrons to be given off and leaving cells that are ionised. Usually when x-rays or gamma rays interact with the body, they actually interact with water and that water can form free radicals. The free radicals can cause damage to the cells by damaging the DNA.

Does eating chillies help with neuralgia?

2009-12-04T21:42:00.001+05:30

Does eating chillies help with neuralgia?

It's not the actual eating of the chillies. The thing that makes chillies hot is called capsaicin. Not only does it make things taste hot but can also be used as a topical ointment on the skin if you have various pain syndromes. One of those is shingles. If you've had chickenpox in the past then you have chickenpox living in your nerve fibres in your body for the rest of your life. Periodically it can come back out and cause a patch of chickenpox vesicles or blisters on one patch of skin. After they go away, it can be tremendously painful. However researchers have found that if you apply this capsaicin to the painful area, it can actually help to relieve the pain. This could possibly be because pain is mediated in the nervous system by a class of tiny nerve fibres referred to as C-fibres. Capsaicin activated those nerve fibres and in some cases activates them to death. This turns them off and indirectly makes them less sensitive, which is why the pain goes away.

Is it dangerous to live 500 metres away from a mobile phone mast?

2009-12-02T21:32:00.001+05:30

Is it dangerous to live 500 metres away from a mobile phone mast?

It's far less dangerous than using the phone yourself. No one's actually found a dangerous relationship with using a phone. When you use a phone, that transmitter is a couple of centimetres away from your head, and the strength of the signal goes down with the distance squared. So it's going to be thousands and thousands of times weaker than your mobile phone right next to your head.

To explore the science of this - if you look at the energy of a microwave, and the reason we have these things in our kitchen and cook with them and we are happy to put a microwave source or a mobile phone to the side of our heads, is because the energy in the wave of a microwave is not sufficient to break chemical bonds in the same way that an x-ray or a gamma ray, or more intense forms can. And therefore they're viewed as non-ionising forms of radioation, and are viewed to be safe. That said, there's no evidence that if you do expose your nervous system to these things that they won't have a temperature effect; because we think that they might warm your head up a little bit if you're exposed to a phone. But of course the mast is much further away than a phone is. But also, exposing tissue to microwaves for long periods of time may or may not have some sort of growth related effect.

Certainly in terms of cancer there isn't enough energy in phone radiation to damage DNA which is the ultimate cause of cancer. Virtually all the studies that have been done have not found a significant link between mobile phone use and cancer. The one thing we don't have is really long term data and that's hopefully coming in in the next couple of years. But the studies certainly haven't found an effect in terms of cancer.

Is it safe to swallow chewing gum ?

2009-12-02T21:30:00.001+05:30

Is it safe to swallow chewing gum ?

Chewing gum used to be from a rubber plant, but is now artificial. It sticks to the road because it contains long oily polymer chains which are chemically similar to some of the constituents of the road surface. It's very hard wearing stuff and doesn't get digested when you swallow it. It can cling onto the sides of your intestines and distort the gut, are occasionally trigger a dangerous disorder called intussusception where the gut telescopes inside itself, although this is rare in adults. It would be better for the environment if people could swallow it. Until then, it would be good to develop a family of chewing gum-consuming bacteria that could eat it off the pavement !

Why don't spiders run out of silk?

2009-12-01T20:53:00.001+05:30

Why don't spiders run out of silk?

Spiders are really actually quite clever. Ancestrally they go back a couple of hundred million years, we think. They have glands at the back end of the spider and now it turns out also on their feet that make silk. And what scientists think, is that the glands on the back of their abdomen that make silk are just adapted limbs, where they used to have some legs. Silk is the reaction of proteins. So you have a chemical reaction going on at the back end of the spider that literally spins silk on demand. The spider eats something that has got protein in it. So when it goes and catches something in its web, it injects a venom into that insect that kills it by paralysing it. The insect is paralysed and doesn't die instantly so it remains fresh, the spider injects digestive juices which liquify an insect. And because an insect is like a husk, with a hard skeleton on the outside with the soft bits in the middle, the spider can literally suck the good bits out of the inside leaving behind a dry, wizened up shrivelled skeleton. That's why you see these sort of husks of insects left under spider webs. All the protein and goodness from inside the insect ends up inside the spider, the spider digests that, absorbs it, and then the proteins go to the back end of the spider. And they get turned into new web, amongst other things a spider needs to make. And some spiders have taken this a step further. What they've done is to make the process even more efficient, by eating their own web. This doesn't do them any harm because web is just protein. By eating their own web they're getting the proteins back into their body and they can then reuse them. Spiders' web is incredible stuff and it can absorb immense amounts of energy. It's got the tensile strength of steel. Scientists are now looking at ways of using it for bullet-proof vests, for example. If you can make this artificially in enough quantities you've got something with the tensile strength of a piece of steel, and the ability to stop bullets much better than a bullet-proof vest. Which means rather than police having to go around in these very thick outfits which restrict movement, if you could make it out of spider silk it would be a) lighter, b) a breatheable fabric, so it wouldn't make you so hot and uncomfortable, and c) it wouldn't restrict your movement so much.

How are seedless grapes grown?

2009-12-01T20:50:00.001+05:30

Does drinking too much milk, or calcium, reduce your physical endurance or stamina?

2009-12-01T20:46:00.002+05:30

Does drinking too much milk, or calcium, reduce your physical endurance or stamina?

If you drink milk that isn't skimmed, it's got lots and lots of fat in it. Having lots of fat isn't good for you because of the calories, but also because it furs up your blood vessels. Milk is also very rich in calcium which, in people who are prone to stones, can deposit in the kidney and cause kidney stones. And the other side effect of milk that not many people know, is if you have irritation to the stomach lining and you're at risk of getting stomach ulcers, calcium is used as a co-signal by the wall of the stomach to produce acid. If you have calcium levels in the blood going up, you make more acid. Some people think when they have a dodgy stomach that drinking milk will settle it. When you first do that your stomach feels happier because you've given the acid something to eat other than the wall of your stomach. But then the calcium is absorbed and goes into the blood stream and increases the amount of acid your stomach makes, causing a vicious cycle.

Does peanut butter help to lower your cholesterol?

2009-12-01T20:44:00.000+05:30

Does peanut butter help to lower your cholesterol?

eanut butter is a source of mono-unsaturated and polyunsaturated fat. So in the context of a balanced diet, it is likely to have some beneficial effect if you are at the same time cutting out saturated fat. So it's really about replacing say the amount of red meat you might be eating with things that are rich in vegetable fats. Another good example of this would be Soya beans. Soya beans are a good source of vegetable fats.

Everybody knows that salt melts ice. Why are there such big icebergs in the sea?

2009-12-01T20:40:00.001+05:30

Everybody knows that salt melts ice. Why are there such big icebergs in the sea?

Salt makes ice melt at a lower temperature. So in sea water ice will melt at maybe -5 or -6 degrees centigrade. But if you get cold enough, the water will still freeze. And so you can still get icebergs. It's just got to be a bit colder than if it was in a lake. When there's salt in water, the water can get a bit lost in the salt. It gets in the way of the water forming a crystal. It's more difficult for the water to form the crystal, so it has to be a bit colder for it to actually freeze.

Could sound waves be heard on Mars?

2009-11-30T19:47:00.001+05:30

Could sound waves be heard on Mars?

There are two questions here. One is if we had a very loud screaming baby on the Earth, would somebody on Mars in theory hear the baby screaming, or would you need to have some interplanetary baby monitor? The answer is no, you wouldn't be able to hear the sound from Earth on Mars because the space in between Earth and Mars is a vacuum. There's a wonderful experiment you can do where you put an alarm clock under a bell jar and you start a vacuum pump going. You then stop hearing the bell even though the bell is still going. But then the question is, well what if your baby was in the bedroom in your Mars planetary home? Would you be able to hear the baby crying from downstairs in your bedsit? The answer would depend very much on the atmosphere on Mars and my understanding is that there's not very much atmosphere: about 1% of the atmosphere on Earth, so it's getting close to a vacuum. So there are two things: the amount of energy that you can pump into the atmosphere is less; and also the speed of sound would be a lot faster.

Does the sun affect the tides like the moon?

2009-11-30T19:45:00.000+05:30

Does the sun affect the tides like the moon?

Yes, but to a lesser extent than the moon, which is the main determinant of our tides. You can work out if we are on a neap tide or a spring tide - that's a high tide or a low tide - depending on whether these two celestial bodies line up with each other. When the sun is in alighnment with the moon we have a new moon (which means you can't see it because it is not illuminated and is dark) and the two bodies work together gravitationally, producing a spring tide. Two weeks later, however, the moon is at 90 degrees to the sun, so they're not in alignment, so you have a neap tide. Two weeks after that you have a full moon and the two are working together again, and you have a spring tide.

Why is it helium in balloons and not hydrogen?

2009-11-30T19:41:00.001+05:30

Why is it helium in balloons and not hydrogen?

In order to get a floating balloon you want a gas which is as light as possible. Helium is quite a lot lighter than air weight. It’s about and eighth of the density of air. Hydrogen is about a sixteenth the density of air. So it’ll float in air and will even float upwards. You’d have thought that hydrogen would be a better gas as it would give slightly more lift than helium because it’s lighter. This is true. The problem is hydrogen is explosive and if you have children running around with balloons that could catch fire and blow up in their faces, it may have some health and safety implications. The other thing is that although hydrogen is half as heavy as helium it doesn’t give you twice as much lift because the amount of lift you get is in its difference in density with [respect to] air. It’s actually only another sixteenth of the density of air. It’s a little bit better but not very much, so it’s not worth the danger.

Helium is quite expensive, though, because it’s a limited resource here on the planet. It's only created by radioactive decay on Earth. Atomic nucleuses emitting alpha particles that are actually helium nucleuses. They slow down and gain some electrons and turn into a helium atom. It tends to be found in oil wells where you get a gas-proof layer of rock above a load of rocks containing radioactive elements. They break down to helium. It floats up and gets trapped, often at the top of an oil well . The amount of helium that we can access cheaply is very limited because not all our oil wells have it.

What happens when a bomb explodes underwater?

2009-11-30T19:40:00.001+05:30

What happens when a bomb explodes underwater?

Well when any bomb explodes the first thing you're going to get is a lot of high-pressure gas because you've taken a load of solid and turned it into gas. It wants to expand. Water isn't going to move away nearly as quickly as air does. The pressure's going to remain very high, pushing water away. The fastest the water can move away is roughly the speed of sound in water. That's 1400m/s. You're going to form a bubble. As that water is pushed away very fast you're going to get a second powerful sound wave or pressure wave moving away from it. If the water doesn't compress that's going to have a very high pressure and do a lot of damage which is why depth charges can destroy strong things like submarines, even 10-20m away. Apparently it's way that there's a theory of how you might be able to blow up safes. If you fill a safe with water an drop a small charge in then because the pressure change is so much greater it might blow the door off.

Why do babies get jaundice when they are born, and why does a session on a sun bed help get rid of it?

2009-11-29T20:58:00.001+05:30

Why do babies get jaundice when they are born, and why does a session on a sun bed help get rid of it?

Babies are not actually born yellow; it develops when they are first born. Every minute we make lots of red blood cells to replace those that have worn out. When old red blood cells are broken down, a yellow-coloured waste product, called bilirubin, is produced. Bilirubin is insoluble in water until it is metabolised by enzymes in the liver which add sugars to the molecule to help it dissolve meaning that it can be excreted in bile, and in urine. However, a developing baby doesn't need this biochemical pathway for metabolising bilirubin until it is born, because the mother removes the bilirubin via the placenta. But when some babies are first born and can no longer rely on their mother to help remove bilirubin for them, particularly if they are premature or have liver problems, there can be a delay in switching on this metabolic pathway and a backlog of bilirubin builds up around the body, making the child yellow. Because , until it is metabolised, bilirubin is insoluble in water but dissolves very well in fats, it accumulates in the skin, where we store most of our body fats, explaining why the babies appear yellow. If it is allowed to continue for a long time, jaundice can cause permanent damage to the brain, but if the baby is put under a blue light, a photochemical reaction occurs, breaking up the bilirubin and making it water soluble. This allows the baby to excrete the excess bilirubin in its urine. The process was discovered accidentally by Judith Ward who used to take babies into sunlight because she thought it was good for them. Having returned them to the hospital, she found that a previously-jaundiced baby had normally-coloured skin on sun-exposed areas, but yellow skin where the nappy had been. As a result the method was quickly adopted for the treatment of neonatal jaundice.

What ingredients go into antibiotics, and how do they work ?

2009-11-29T20:54:00.001+05:30

What ingredients go into antibiotics, and how do they work ?

Tablets taken by mouth contain a lot of the actual antibiotic. They also contain lots of other substances which enable the manufacturer to produce a tablet that can be kept in packets and are easy to swallow. For example, the smooth outer coatings of some tablets are often made out of vegetable products. Once the tablet is in your stomach, the active bits distribute around the body through the bloodstream, reach the site(s) of infection, and kill the offending bacteria. There are three different ways antibiotics kill bacteria. Some stop bacteria from growing by stopping their protein production; others stop them from making chromosomes; and the third type stop bacteria from making cell walls. Without a proper cell wall, the bacteria explode and die.

Which bacteria or viruses cause ear infections ?

2009-11-29T20:52:00.001+05:30

Which bacteria or viruses cause ear infections ?

The ears have the same linings and are connected to the nose and throat through the eustacian tube. This means that any of the viruses that cause colds and sore throats can get through into your ears. Viruses are the main invaders, but bacteria can cause secondary infection. They seize the opportunity to invade after a virus has caused the initial problem - such as damaging the protective lining of the airway, or blocking up the eustacian tubes in your ears with mucus

Are fizzy and sweet drinks addictive?

2009-11-29T20:50:00.001+05:30

Are fizzy and sweet drinks addictive?

Coca Cola, most other fizzy drinks and cold remedies contain huge amount of caffeine. This is a legal drug that gives you energy and perks you up. This is why taking certain 'flu remedies make you feel more awake and generally much better. These are similar effects to those found when drinking coffee. There are specific receptors in your brain for caffeine. These interact with a part of the brain that uses the reward-chemical dopamine, the same system activated by drugs such as cocaine. Although caffeine and cocaine don't give the same kind of rush effect, both have a common mechanism. It's also worth bearing in mind that tea also contains a lot of caffeine.

What keeps the Earth's core so hot?

2009-11-27T21:55:00.001+05:30

How can we tell what noises the dinosaurs make ?

2009-11-27T21:51:00.001+05:30

How can we tell what noises the dinosaurs make ?

The reason you hear those sounds on TV is to make it more interesting. We know dinosaurs probably made noises because they had very good sense of hearing. If you look at dinosaur fossil skulls, you can trace their ear canals and work out where their ears would have been and the kinds of sound they would have responded to. If they could hear sounds, they could probably make sounds. In the late 90's scientists put a fossil through a CT scanner to look at the bone structure. The headpiece was a series of intricately connected tubes a bit like organ pipes. They analysed the structure of these canals and airways, and used a computer to model what would happen if air were blown past. They found that the dinosaur could probably have produced low pitched rumbling noises that could have carried a long way. So what we use for dinosaur sounds on TV is what can be inferred from studying the shape of their fossilised remains, with a bit of artistic license thrown in.

Why do mints make your breath feel cold ?

2009-11-27T21:48:00.001+05:30

Why do mints make your breath feel cold ?

According to a group of scientists in San Francisco, the reason is that the same nerve fibres that signal hot and cold are also sensitive to menthol, an ingredient in mints. Normally when the temperature changes it causes pores on the surface of the nerve cell to open and close, changing the electrical activity of the cell, which the brain interprets as a change in temperature. But menthol can also affect the function of the pores in the same way and triggers the nerve cell into thinking that the temperature is lower than it is.

Who is sweatier, men or women ?

2009-11-27T21:44:00.001+05:30

Who is sweatier, men or women ?

Men are definitely sweatier than women. Previously this was put down to the larger male stature, but a team of scientists at University of Dortmund, Germany, led by Barbara Griefahn, say different. In their laboratory they have set up a mock 'sweltering car'. 'Volunteers' sit for up to 2 hours under heat lamps, mimicking the effect of the sun beating down through the windscreen. Under these conditions men lose about 250 mls of sweat per hour during the experiment, 70 mls an hour more than female volunteers. This makes them officially sweatier, even allowing for size and weight, say the scientists.

Is it normal for you to have a body temperature lower than 36.7celsius ?

2009-11-26T18:28:00.003+05:30

Is it normal for you to have a body temperature lower than 36.7celsius ?

Normal body temperature is 37?C. This is set by part of your nervous system and the hypothalamus, which is found in the brain stem. The hypothalamus monitors your body temperature and changes it if it becomes too hot or too cold. Your body temperature doesn't have to be exactly 37?C: exercise can make you hotter, while going outside on an icy day can make you cooler. The place in which you measure your temperature is very important. Putting a thermometer under your armpit will show you your peripheral temperature, and this can be quite a bit lower than your 'real' body temperature called your core temperature, or the temperature at the centre of your body. This varies very little at all in day to day life. It can best be measured by putting a thermometer in your bottom! You have to get very cold to change your core temperature, such as being stuck in freezing weather for a long time. People who have a drop in core body temperature have what is known as hypothermia. This makes them drowsy, and if left untreated, they will eventually become unconscious. When the body is cold, the chemical reactions that provide your cells with energy don't work as well. This makes cells function abnormally and, if prolonged, can be fatal.

Does the nicotine vaccine stop the cravings to smoke?

2009-11-26T18:26:00.001+05:30

Does the nicotine vaccine stop the cravings to smoke?

Probably not. The mechanism works by stopping the effects, and so might actually increase the cravings. The vaccine is probably best used in combination with something that helps with the withdrawal symptoms. However, by stopping the effects, it also helps to break the cycle of reinforcement. Eventually this may lead to people stopping people smoking because it does nothing to help the cravings.

Which bacteria or viruses cause ear infections ?

2009-11-26T18:24:00.001+05:30

Which bacteria or viruses cause ear infections?

The ears have the same linings and are connected to the nose and throat through the eustacian tube. This means that any of the viruses that cause colds and sore throats can get through into your ears. Viruses are the main invaders, but bacteria can cause secondary infection. They seize the opportunity to invade after a virus has caused the initial problem - such as damaging the protective lining of the airway, or blocking up the eustacian tubes in your ears with mucus.

What causes narcolepsy?

2009-11-26T18:22:00.001+05:30

What causes narcolepsy?

Narcolepsy is the disorder where people fall asleep repeatedly during the day and there seems to be genetic component to this. Luckily there are drugs which can be used to treat it. There can be frightening aspects to narcolepsy, for instance people have been known to suddenly fall down as they fall asleep, or have nasty hallucinations as they fall asleep. The brain chemistry behind it is better understood now, and we do know about the genes that are linked to this. One particular chemical is a substance called hypocretin, and people with narcolepsy tend to have problems with the receptors for this brain chemical, or an abnormal form of this chemical. There are also people with 'clock' genes that give them a faster or slower body clock, but this shouldn't be mistaken for narcolepsy.

Would someone with a psychiatric disorder be better able to pass a lie detector test as they may not feel remorse?

2009-11-25T21:38:00.001+05:30

Why do we laugh when we find something funny?

2009-11-25T21:35:00.001+05:30

Why do we laugh when we find something funny?

Something that’s funny is by definition something that makes us laugh. I’ll talk about why we laugh. Laughter is really a social phenomenon. If we look back to its origins, laughter, the ‘ha ha’ originated in the ‘pant pant’ of rough and tumble play such as you would find in tickle or the rough and tumble play of children. ‘Pant pant’ became the human ‘ha ha.’ With adults, however the arena of laughter has shifted from tickle and rough and tumble to a more linguistic and cognitive arena whereby, for example, the play of adults has to do with wordplay during conversations. You don’t have to tickle one of your colleagues to get them to laugh. You can tell them the joke. Even within conversation the key to laughter is the presence of another person. Laughter almost totally disappears when we’re alone. The key element for producing laughter is another person and not a joke. In fact we have followed people around and recorded what was said before people laugh. In only 10 or 15% is it anything remotely joke-like. Most laughter follows comments like ‘hey, where have you been? Ha ha!’ or ‘I’ve gotta go now, haha!’ These aren’t jokes so it basically is about developing bonds and relationships with other people.

Why does one get cramp?

2009-11-25T21:31:00.001+05:30

Why does one get cramp?

Cramp is a muscle spasm and we don’t actually know what cramp is. We just know that if people have regular cramps – and it tends to happen quite often at night and it tends to happen in younger people more often than older people and it tends to be relieved with quinine, the same stuff that makes tonic water taste nice. A muscle spasm is when some of the muscle fibres – because a muscle isn’t just one homogeneous giant thing. It’s actually made up of lots of individual little muscle fibres. Some of those muscle fibres go into a spasm. In other words, the contract more than they should and they lock in a contracted state. Surprisingly, muscle actually takes energy to relax, not to contract. When a body of a person dies, they go into rigor mortis because the cells in their muscles run out of energy and their muscles can’t relax and they stay rigid. That’s why a person gets rigor mortis. If you leave them a bit longer then the rigor mortis goes away again when the muscle breaks down and starts to relax. What cramp could be is for some reason that clutch of muscle fibres don’t have enough energy in them, perhaps because there’s been a reduction in blood flow that’s insufficient for the muscles needs. Therefore the muscle runs a little bit short of energy and this trips its inability to relax properly and you get a cramp. Rubbing a muscle and massaging it to get the blood through it can make it better.

Why do we wake up when we need to urinate?

2009-11-25T21:25:00.001+05:30

Why do we wake up when we need to urinate?

It’s the same reflex if you need to roll over in bed when you’re uncomfortable. If you stayed in one position in bed all the time all night you would get a pressure sore because the pressure of tissue against the bed would stop blood flow through that area. As a result you would end up with a de-vascularised bit of skin and it would necrose. Patients who are left in one position in hospital for too long get exactly the same problem. The body has a series of reflexes programmed into it even when you are asleep. You can react and respond to various stimuli with an appropriate thing. If you’re getting uncomfortable in bed you can roll over. If, on the other hand, your bladder’s getting full then your brain says wake up, you need to go to the loo. It’s an automatic reflex. Some people lose that reflex as they get older. Some people when they’re very little actually wet the bed because it hasn’t developed yet. That’s why little kiddies have to respond to those signals the right way. That’s all about potty training and bladder training.

Why are Australian snakes so much more toxic in general than other snakes in other parts of the world?

2009-11-25T21:21:00.002+05:30

Why are Australian snakes so much more toxic in general than other snakes in other parts of the world?

The idea that Australian venomous snakes are more toxic than those anywhere else is, to a large extent, a myth which started out with a study that was published approximately thirty years ago. They took 25 different snake venoms and showed that the top ten of those were Australian. It only included five non-Australian snakes so it’s rather like the American baseball World Series: you can’t lose if you don’t include the competition. In reality the two snakes in the world with the most toxic venoms drop for drop are in fact Australian. Immediately after that when you look at the table of most toxic venom's you start having a large number of other snakes coming in. A large number of Australian venomous snakes are actually not spectacular at all in their potency of their venom. There’s nothing intrinsic about Australian snakes being particularly toxic. The amazing thing is that the snake with the most toxic venom in the world – the inland Taipan has never actually killed anyone. Some snakes live in remote areas and in places where there is no medical treatment and other snakes live in areas which either are very remote and people don’t go to so they don’t bite anyone or there is good anti-venom and good treatment available. If you’re bitten in Australia a flying doctor comes and picks you up and you go to a hospital and 99.5% of cases everything’s going to be just fine. If you get bitten in West Africa then there is no anti-venom, there is no hospital that can treat you and you slowly bleed to death from a snake that has a fraction of the killing power.

Could the retina be repaired using stem cell research?

2009-11-24T19:50:00.002+05:30

Could the retina be repaired using stem cell research?

In the last twelve months we’ve seen evidence that perhaps it can. The stumbling block at the moment is that perhaps we don’t have the stem cells necessarily, ethically, to do it. Scientists in University College London published a paper in the journal Nature about this time last year. They took mice which had been genetically programmed develop a disease like the human disease, macular degeneration, and they took stem cells from the retina of newborn mice. They implanted these stem cells into the eyes of the mice that had macular degeneration. They were able to show that the mice got back their ability to see. By following where the stem cells went in the eyes they found that they migrated to the right part of the retina and turned back into photo-receptors. These cells take the light and turn it into information that the brain can understand.

Sharp Sounds Damage Hearing?

2009-11-24T19:46:00.001+05:30

Which is worse for your hearing - the short sharp sound of a hammer, or the constant drone of a chainsaw?

Whenever you listen to sound, the sound actually hits the eardrum. That sound is actually amplified by a series of tiny little bones in the ear called ossicles. These ossicles vibrate and stimulate the float within the cochlear which, in turn converts the sound energy into electrical energy which is perceived
as noise by the brain.

There are two different types of noise induced hearing loss. You have acute stage hearing loss, for example due to a large explosion or you may have something more gradual. This is more common in most people. This gradual increase in hearing loss is a combination of both the intensity of the sound as well as the duration of the sound. So for example, someone who shoots guns for a hobby may be exposed to very short bursts of noise but very high intensity and they may experience a similar degree of hearing loss compared to someone who's in a slightly different environment where the sound intensity's actually much lower but much more constant (e.g. the mining industry). There are also additional factors that can influence noise induced hearing loss. It's not just the combination of noise because people's tolerance to noise varies. Therefore there's some genetic influences in this as well. Noise induced hearing loss is not just the simple of noise experienced but also the genes that influence your hearing.

If you get cold sores and give blood, can the virus be passed on?

2009-11-24T19:43:00.002+05:30

If you get cold sores and give blood, can the virus be passed on?

There’s probably almost zero chance of that. The virus that causes cold sores, the Herpes Simplex Virus (HSV), most of us acquire this when we’re very young because of our parents kissing us and children dribbling over each other in nurseries – it spreads in saliva. When you first get it, it produces a sore throat, ulcers in the mouth, swollen glands in the neck and a high temperature. It then invades the sensory nerves that supply your mouth and tongue, as well as other parts of the body it can infect. It goes inside these nerve cells and switches off. It exists there as a piece of DNA, loitering alongside the cell’s own DNA, and periodically comes back to life. We don’t know exactly what triggers it to come back to life, but we know that things like damage to the skin, for example sunburn, menstruation, depression and immune depression, can bring it out again. The virus turns back on its DNA, makes new virus particles which come down the nerve and pop out of the skin, causing the infectious lesion, the cold sore. When you kiss someone who’s got one, that’s how you pick it up.

Thankfully, it doesn’t really get into the blood stream, so you should be safe from HSV from blood products. Other members of the herpes family do spread through blood, but not HSV.