what dictates the frequency of the waves?

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?

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?

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?

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

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?

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?

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?

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?

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?

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?

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?

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?

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?

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?

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?

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?

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?

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?

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?

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...

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?

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?

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?

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.