Why does overeating chocolate make you feel sick?

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?

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?

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?

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?

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?

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?

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?

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?

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.

I make it sound like it’s all easy and a problem that's been solved. It is being used in a limited way, but it’s certainly not mainstream yet by any stretch of the imagination.

Why does cooled water sometimes suddenly freeze?

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.