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.

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

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?

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?

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?

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?

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

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?

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.