What's between my internal organs?

15 November 2016
Presented by Chris Smith.

This week on the Naked Scientists, we've gathered the bright and the brainy to answer your science questions, from why ants are stealing your toenail clippings to what's between your internal organs and could you survive being eaten by a snake?

In this episode

Could I survive if I was eaten by an anaconda?

Chris Smith put this to zoologist and naked scientist Georgia Mills...

Georgia - It's a great question - I hope no one's eating. The Anaconda, one of the biggest snakes; it's actually the heaviest snake, not quite the longest. It lives around the Amazon in South America. So what would happen if you got eaten by one?

There's a number of problems:

Firstly the anaconda is not going to want to eat you, most likely. Humans are just a bit too big for them. There's not many cases of an anaconda actually going for a human - I think most of the cases are Anaconda researchers getting a bit too cheeky and getting snapped at. But they have been documented for going for children and very small humans. So first off, probably not going to want to eat you.

Secondly they will constrict you. It's what they do before they eat anything. Eating something while it's still alive is dangerous for them, so they will wrap around you and they will crush you so hard that your blood will cease to pump and it won't get to your brain and you'll pass out and die very, very quickly. And they will know that you're dead because they can monitor your heartbeat.

But, for the questions sake, provided this anaconda does decide it wants to eat you and it does decide it doesn't want to crush you first, what will happen then. So then the snake's incredible jaws; they're not actually fused together, there are four separate parts and they're elastic. So it can sort of stretch it's mouth really wide and sort of crawl over you gong chomp, chomp, chomp.

Chris - How does it go again?

Georgia - Chomp, chomp, chomp. That is a guess actually. So then it will use a lot of saliva to lubricate you, as it were. So you might actually drown. That might happen to you first. Provided you don't drown you sort of got inside the snake. Your shoulders would probably be too broad so it would have to break your shoulders. Then you're in there - you're going to need air. You're not going to have any air - you'll suffocate.

Provided you do have air, then what happens is that the acid and the enzymes will start to digest you, and it's hard to say how long this would take to actually kill you. Scientists had an experiment where they - I think an anaconda ate a crocodile. They scanned it and they found that all the soft tissues had gone within about three days, so that's quite fast-acting stuff. And if you think about how tough the skin of a crocodile is, as well, it doesn't bode well for us soft squishy humans.

Chris - So did they give the crocodile to the snake and say "eat that and make it snappy!"

Georgia - I hope so! Provided all these other things haven't killed you - will the snake regurgitate you?

I actually found a video on YouTube where this guy's goats had been eaten by a snake and he squeezed them back out.

Chris - Not intact, presumably?

Georgia - They were definitely dead but he managed to just... This poor snake was just writhing around like "oh no," and he squeezed these goat back out and they're useless to him so he may as well have let the anaconda have them.

Chris - I suppose he could have eaten then afterwards.

Georgia - Yes, that's true. A bit gross eating a snake vomit meal.

Chris - So can snakes actually vomit then? That was the last part of the question.

Georgia - Yeah. It's dangerous for them to do it so I don't think they do it often because it takes a lot of energy and a lot of time and all of that time they're regurgitating, they're vulnerable to being.

Chris - I think the same applies to me actually! Okay, so I think that's a no really for the anaconda. I know there are some stories of pythons eating kids, aren't there. I mean there one or two stories of that.

Georgia - Yeah. But people love spreading these stories when they're not true and I found several stories of snake eating different people and it was all the same photo. So, actually documented cases are very low.

If you could hover, would buildings crash into you?

Chris Smith put this to physicist Andrew Norton from the Open University...

Andrew - The short answer is no, but I think you want a longer answer. We've got to understand the Earth is rotating and if we take the equator of the Earth, that's about 40,000 kilometers all the way round, and the Earth rotates once in every 24 hours. So if you're on the equator, you're moving at about 1,670 kilometers per hour. And here, a little bit further north, we're moving a little slower than that but nonetheless, we're moving very fast as the Earth rotates.

So, if you do decide to hover with your jetpack, or whatever it may be, then you've already got that sort of sidewise motion, whether or not you're hovering or standing on the Earth. So you and the buildings will continue moving sideways east to west at that same speed so, no the building wouldn't crash into you. You and the building would keep moving, keep rotating round the Earth with the speed that you've got.

I guess what you're thinking of maybe is if you could somehow take away that rotational speed that you've got by giving yourself an equivalent speed in the opposite direction, then that could well do it. But you'd have to work very hard to give yourself that extra speed in the opposite direction to cancel out the rotation that you start with.

Chris - A flight time to America is different in duration to a flight time from America though for the reason the Earth is turning to an extent, isn't it?

Andrew - It's partly because the Earth's rotating, partly also it's affected by the high altitude winds that either give you til wind or a head wind on the plane. But yes, the rotation of the Earth does make a difference to that.

Can cows predict bad weather?

Chris Smith put this to climate scientist Doug Crawford-Brown from the University of Cambridge...

Doug - Yeah, well again this goes into those sort of myth categories. It does have some scientific basis. I mean cows do - well all animal sense when air pressure is changing, and when you're getting ready to have rain you usually are accompanied by some sort of a change in the pressure. However, there are much more compelling reasons why cows lie down - they're not feeling well, they're tired and so forth. I would doubt that a cow lying down would be very good indicators that rain is coming along.

Chris - Are there actually any indicator species that we can rely on that predict the weather - not just cows but other things in the environment that do tell us, aha this is going to happen climatically or something?

Doug - Yeah, various birds or bats for example - well not strictly birds but bats are a reasonably good indicator that you're getting ready for bad weather anyway, low and high pressure zone is about to collide. But most of the animals are responding to many other things. Air pressure tends to be the one that most animals respond to because they've got sensors in their ears, let's say - not exactly but in their ears.

Georgia - What do the bats and birds actually do? Because I can remember reading an Asterix and Obelix cartoons that were saying.

Chris - Ah well known scientific source of information.

Georgia - Obelix was always saying "birds are flying low, we shall have rain." Is that what they do?

Doug - No, they simply tend to get more agitated and to fly around more. So you start to see large swirls of sparrows, for example, that are swirling about like in horror movies. And that usually indicates there's a storm coming along the horizon. But it's not a good indicator. I would not bet my retirement fund on these animals' behaviour.

Can you change the way you laugh?

We put this to Chris Smith, from the Naked Scientists...

Chris - I think it is a very personal thing and I think it's a habit. I don't know, I don't think there's a straightforward answer to this question. Certainly it's something I think you probably can practice and I have heard some real screechy people. I mean, you must have all heard people with this kind of laugh from hell. There was one woman I remember, I was at this holiday place and there was this lady with this laugh that sort of went - she almost sounded like she was being strangled. So she would laugh and then there would be this huuuh... huuuh noise between bouts of laughter. And I'm sure that it must be just a rehearsal thing, you get into a habit of laughing that particular way. I don't know for sure, but I suspect if you did practice you could certainly, in the same way as you can change your accent and the way you speak, you could certainly, I think, change the way that you laugh. Georgia - And laughters such a strange thing. Something to try at home that's really funny is to laugh but try not to smile. It's so strange because laughter is such an automatic reaction. If you try and just keep you face sad and then laugh, honestly it's.

Chris - Do you make yourself laugh doing it?

Georgia - Yeah, yeah. The room will go into hysterics because it's such a weird thing to do, but yes.

Peter - Haw haw haw - it sounds like Father Christmas.

Georgia - It's really difficult.

Chris - Father's Christmas has come early. There you go. So send in some samples of your laughter and we'll play them on the programme and maybe the best one will win a prize.

Are flexible smartphones possible?

Chris Smith put this question to tech investor Peter Cowley...

Peter - Yes, there's quite a lot of press in that direction. But first of all my first thought when I saw this question was why? Why do you want it flexible - is that so you can sit on it. You might remember a few years ago there was one of big manufacturers had a problem with them bending in back pockets. Is it because you could drop it and not worry about it? Why do you want it to be flexible? So that's the first point. But, assuming it's because it's novel or something and there's some reason to do that.

The next thing is what is flexible? How thin does it have to be to be actually called flexible.To answer some of those questions, look a the actual structure of a phone because the front is a piece of glass for protection which is then the touch screen and the display - that can be made flexible. Some 20 years ago here in Cambridge there some technology that was invented within the University, and a number of applications of that are printed displays. So that's okay.

The next level back will be some sort of printed circuit board. Again, that's been flexible for many years, probably 30 or 40 years. On that you'll have some chips. Those chips can't be flexible because they're made of silicon, but they can be very, very small so flexibility will allow that.

But the big issue is the battery. They're just getting to the point now where a battery which is only half a millimeter thick will bend up to 25 degrees. So that doesn't sound like much flexibility and it's not very thick so it won't give you much capacity.

So, yes. We're heading that way. Not quite sure why we're heading that way, but we're heading that way. But I don't think it will get to the short of flexibility that I imagine you're meaning which is sort of rolling it up and putting it in your pocket.

Georgia - I was just thinking of Harry Potter. They have the newspapers where all the things sort of show up and the headlines move along. Could that be possible?

Peter - Yes. A display by itself is possible - there are flexible displays. We'll be getting to the point soon where you will buying packing on say a Coca Cola or something bottle which will vary depending on who you are almost. That's got the battery in there, that's got the display, but it's the other elements of it that are difficult to make that, but yeah.

Chris - Will it change the price so it'll deter you if you're on a diet? Don't buy this because.

Peter - Do you want to talk about price changing supermarkets. As you walk round a supermarket, there is no reason why a price shouldn't change depending on how much money you've got on your credit card.

Chris - That's what I was thinking. I can see this going this way where, potentially, you walk along and they think - oh, he looks like a sucker, we'll just put the price up because they know you're keen and you'll pay it.

Peter - Shelf edge labeling - yes exactly that?

Chris - There must be some consumer laws against that though, surely?

Peter - Why?

Georgia - I think a well known company was doing that based on where you were. The more affluent your area, the higher the prices. But I think they got in trouble and it's no longer allowed.

Peter - Much to my amazement. One of my sons is working for one of these consumer survey organisation now in London which does 60,000 people scan all their shopping every week and then photograph their receipts. And.

Chris - What photograph there lunch and put it on Instagram as far as they can tell?

Peter - Well this is in return for something, some sort of gift. But the point is that, actually, the pricing around the country doesn't vary nearly as much as you'd expect. That the people in the less well off areas and the people in Surrey - sorry anybody from Surrey - pay the same price.

Why are ants stealing my toenail clippings?

Chris Smith put this to zoologist and naked scientist Georgia Mills...

Georgia - Well firstly, may I suggest investing in a bin if you want to avoid this in future. I actually had a look on.

Chris - Sounds like he doesn't needs one. It seems like he has a sort of natural...

Georgia - . cleaning ants, yeah. Well, actually, I looked online and there's quite a few people have noticed this. People from all around the world are saying what is going on here, why do ants really like toe nails - it's a bit disgusting really?

So nails, they're made of a protein called keratin. It's the same thing your hair is made of and it's a protein. So there is nutrients in proteins, but the thing about keratin is it's notoriously difficult to digest. There's only a few species of insects that we know can digest keratin and ants, as far as I can tell, aren't one of them.

So what are they doing with it? It could be that these ants are making a terrible mistake because, if you think about your fingers, you're touching food a lot, there's dead skin cells under them, there's bacteria. It could be that there's a smell that they're very attracted to. So they think oh, there's a nice bit of food, taking it back, and then they're like oh no, we can't eat this, what have we done! We've wasted so much time!

There was one theory that I read that was quite interesting. So something we know that can digest keratin is fungus and a lot of ants are known to have these relationships with fungus where they kind of grow it as farmers and then they eat the fungus. So it could be they're putting the nails on the fungus, the fungus is getting energy from it and then the ants are benefitting from that. But, these funguses only exist in the Americas, and I think people have been reporting this from all over the world, so it must be something else going on. And I think some people have reported that ants have been seen harvesting keratin from dead bodies as well. So maybe there's a PhD in this, maybe they are digesting the keratin and there is some process we don't know about yet.

Chris - When I was wondering around in Zambia in the Luangwa forest, there were lots of remains of animals dotted about, horns and things and they all did have holes in them. And I asked the guide what had made these holes because the horns of animals are keratin aren't they and he said well, actually, certain moths will come in and lay eggs on the horns because the moths, in the same way as they eat your clothing in your cupboard, that's why you get holes from clothing moths - they do have the ability to break down and digest these horns. That wasn't ants, it clearly wasn't ants.

Peter.

Peter - Yes, keratin is also in hair isn't it - is that right?

Georgia - Yes. Which is why it's a very bad idea for you to eat balls of your own hair.

Peter - But are the ants interested in hair?

Georgia - I did actually search that and apparently not. But the keratin in your fingernails and the keratin in your hair are different structures, so maybe that's got something to do with it.

What would be the gravitational consequences of Noah's flood?

Chris Smith put this to physicist Andrew Norton from the Open University...

Andrew - The first problem I think is that the amount of water in the atmosphere is really very tiny; it's only about, I think, one thousandth of one percent of the total water budget of the Earth. So if all that water in the atmosphere fell to Earth, it would only cover the surface to a depth of two or three centimeters, something like that, so it wouldn't be enough to cover to the tops of mountains. If you could somehow flood the Earth to the depth such that all the mountains were covered, then I guess we'd be in a sort of a waterworld planet. The atmosphere would then sit on top of that. But there's no reason why the density of the atmosphere would get any lower. Maybe your questioner was thinking about additional gravity, the Sun or the Moon pulling on it. But, on the scale of the solar system, that extra few thousand feet is not going to make any difference to the pull of gravity on the atmosphere. So we'd all just be swimming around but breathing just the same.

Chris - There have been times in the past though when the Earth has been a lot wetter, hasn't there Doug? Because if you go back 30 million/40 million years or so to the Eocene, it was much, much warmer and we had not North Pole, did we?

Doug - Yes, there were lots of times when the Earth has been wetter, almost always having to do with changes of temperature. In fact, we go through this cycle every few tens of thousand of years of wetter and warmer, and then cooler and drier temperatures.

Is the world polluted beyond redemption?

Chris Smith put this to climate scientist Doug Crawford-Brown from the University of Cambridge...

Doug - Yeah. The first thing I'll say is we just don't know, either on the IPCC or on the UK Climate Change Risk Assessment Committee, we don't know the exact timing of this. It's probably something around 2050 to 2080, somewhere in that range. There are some people, even in the scientific community who think we're already there, we're already seeing inconvenience in the weather. I don't happen to be one of those people. I do happen to be one of those people who think that by 2050 and 2080 will really start thinking about this. I'm already making a list of people who have been climate deniers so that in 2050 and 2080 I can roll that list out and say, "whatever were you thinking of." But, of course, most of them are about my age and they'll be dead by that time so I'll have no glee at all.

Chris - You're clearly a glass half full man aren't you?

Doug - Yeah.

Chris - Andrew.

Andrew - Yeah, I was just wondering, linking back to the last question as well. If the icecaps were to melt completely, what change would that make to the global sea level?

Doug - Well it raises it by hundreds of metres.

Andrew - Hundreds of metres?

Doug - Hundreds of meters, yeah. So you flood almost all the coastal areas.

Chris - Of course, not the North Pole because that's floating ice, which means it's already displaced it's own mass already so that's not going to change a lot. But what's on Greenland? I mean Greenland alone adds, potentially quite a big rise in sea level, just Greenland, doesn't it Doug?

Doug - Tens of metres, yeah.

Chris - Yeah, and the Antarctic's interesting. I read a paper where they were actually looking at the gravitational effect of having that much mass, even though in the Antarctic the ice is on land so it's not displacing water. It is nonetheless, gravitationally active so it attracts a big bulge of water around the bottom of the planet holding the water down there, so it's not washing around up here and, therefore we have artificially lower levels of sea than we would otherwise have were that to be released. And, if we melt that, obviously then that water's going to redistribute and we'll see higher sea levels. Georgia...

Georgia - Trump wants to build a wall between the USA and Mexico. If a wall that big could you just build one around Greenland and just keep all the water in there?

Doug - Mexico, by the way, have said they're going to build the wall to keep Trump out of Mexico.

Chris - But what's the carbon footprint of that concrete, because 40 percent, isn't it, of CO2 emissions worldwide are just making cement?

Doug - That's right, there's a large carbon footprint to making cement. However cement, when put into buildings and so forth, then reabsorbs carbon dioxide. So, about half of that will be reabsorbed during the process of making something.

Chris - But you've still got to run the furnace to boil up the limestone in the first place.

Doug - I have no idea how big the carbon footprint is of the Mexican wall.

How does bluetooth work?

We put this question to tech investor Peter Cowley...

Peter - Yes, how does bluetooth work? I mean, there's obviously a very complicated answer to that which we won't go into now but, in principle, it's the same as any other form of wireless based communications. Same as wifi, same as mobile communications where something's transmitting one end and something's receiving the other end. Unlike a radio and television where the receiver doesn't transmit back again, it does, so they're talking to each other all the time. It uses the same frequency as wifi which is 2.4 ghz, which is a band that's open to the whole world. But the big difference between that and wifi and mobile comms is that the power output is very, very much less. So if you take the call power of a modern smartphone the absolute maximum it can transmit at is 2 watts and it's usually about 250-500 milliwatts, so that's a quarter to half a watt. And bluetooth is about 1-2 milliwatts, so it it's about 250 times less

Now there's some interesting statistics here which I think those with a medical bent i.e. Chris will be quite interested in. Apparently, the brain will get damaged if there's at least a 4 degree increase in temperature and, if you're on the phone for 20 minutes, your ear increases by - and this is research that's been done so don't worry I'm not making up - about 0.3 degrees centigrade. And the brain, just inside the ear, by 0.15 degrees centigrade. And that will stay stable then, it's not going to increase for every 20 minutes once it's on so once you've had a 4 hour call.

Chris - Cumulatively.

Peter - And, just out of interest, the other way round. Some people may know that if you type a certain number in on the phone you can actually measure the signal strength wherever you are and that works out at home, my home where I get about two bars about a billionth of a watt so the amount of power coming through the local cells transmit is very, very small.

So, to finish answering the question - bluetoothing very much less powerful than a mobile phone. As he says it's on all the time but it's not on the whole time. The only time it will be transmitting backwards and forward, or certainly in one direction, is when you're listening to something, say an earpiece in your ear which is then bluetoothing at the same time. Otherwise it's occasionally polling, which means checking if there's anything out there, perhaps once a second or something like that. So there's very, very little power there that's being transmitted. So don't worry.

Do dogs get colds?

Chris Smith put this to zoologist and naked scientist Georgia Mills...

Georgia - Hello Heath. Hello Bertie. So there's a few things there. How come dogs don't catch colds? Well, they can get something very similar to a cold with similar symptoms to us but they cannot catch our equivalent of a cold. So the virus that affects us is very specific and will only attack us, and we won't be able to transfer it dogs and vice versa, It won't come back the other way so you can't catch a cold off your dog.

And then so why does he get in these lakes and not get a cold. So swimming in an icy lake in itself will not give you a cold. You need to come into contact with a virus to actually come down with it. Swimming in icy lakes can harm your immune system, so it might make you more likely to catch the cold, but it won't give you one.

So why don't dogs seem to get ill that often? Well firstly, they can't tell us when they are ill and...

Chris - Do you know what they say if they do?

Georgia - Are they feeling "rough" Chris? I saw that one coming.

Chris - You know me too well!

Georgia - And the other thing is, if you think about how many people you bump into in a day on your commute at work, at home - so many people. Dogs do not have that level of interactions with other dogs. There's not enough of them for these diseases to proliferate that much. And, in fact, one of the diseases like a cold that a dog can get is kennel cough. So called because they often get it when they're in kennels where a lot of them are in the same place. So, the fact that Bertie isn't in a kennel, he's free to enjoy these icy lakes and probably will be fine.

Chris - We published an article on The Naked Scientists a few years back now. It was called "Can my Dog Give me Diarrhea." Because people are actually looking at the viruses that cause diarrhea in people. Noroviruses are very common causes of diarrhea; they cause millions of cases in humans, but dogs have their own forms of noro call calici viruses.

And there's some evidence that dogs, if you recover dog poos from your pet and analyse it, and people have done this study - very dedicated scientists - you can see that the same norovirus is in the person as in the dog, but there's no evidence that the dog was symptomatic with the infection. So it might be able to pick up it's owners infection but probably doesn't become symptomatic with it. But people are looking. They've doing a study to recover dog turds and compare them with owners with symptoms and see if there's any evidence linking the two.

Does gravity affect how the body ages?

Chris Smith put this to physicist Andrew Norton from the Open University...

Andrew - Well, Tuomo is absolutely right. There are two effects here, and what we're talking about here is relativity. We're talking about special relativity and general relativity. And, as Einstein first figured out over a hundred years ago now, if things move very fast then time will slow down for the rapidly moving body - that's special relativity. And if you come close to a very massive object, such as a black hole, then time will slow down in a very strong gravitational field - that's general relativity. And these thing have been measured; they're absolutely measured to high precision that we can in many experiments.

If we take the example say of a GPS satellite (Global Positioning Satellite), they're in orbit above the Earth at about 20 thousand kilometers up. Now they're orbiting the Earth, so they're going quite fast and as a result of the speed that they're going, a clock on a GPS satellite will run slow by about 7 microseconds in the course of 24 hours.

Chris - 7 millionths of a second?

Andrew - 7 millionths of a second, yeah, in the course of 24 hours. Now that's one effect, that's the special relativity effect. But, of course, the GPS satellite is also further away from the Earth than we are, so it's further away from the strong gravity of the Earth, if you like. And, as a result of that effect, the clock on the GPS satellite would run fast by about 46 microseconds over the course of 24 hours. So these two effects are going in opposite directions - 46 microseconds fast due the general relativity and 7 microseconds slow due to the special relativity, so there's a net effect of one minus the other there.

As to what is causing it? If it's a person on that satellite would their body clock feel those same effects? They would indeed. It's nothing to do with the body, or the clock, or the satellite, it's that time itself changes the rate that it flows. It doesn't necessarily flow forwards at the rate of one second per second as a result of high speeds in special relativity or strong gravitational fields in general relativity.

Chris - But it does for you. You're the person experiencing the time effects so for you your watch continues to tick one, two three. You think that a year has gone or however long but the people who are not in the same frame as you, for them time is running faster?

Andrew - That's exactly right Chris, yeah. So it's a real effect, but the time as you experience it is affected by the speed that you're moving, by the location that you're in relative to other people of other anything. It doesn't need another person there. But time doesn't always flow at the same rate.

Chris - Peter.

Peter - Yes. So if you take an airline pilot who spends the whole time - I mean how many miles do they do in a lifetime? A hundred million miles, that's seven hundred miles an hour. Any idea how many microseconds younger is it, than they would be from the person staying on the ground?

Andrew - Well again, there's both effects. They're moving fast so they're getting the slowing down due to special relativity but they're also at high altitude, so they're getting the speeding up due to being further away from the gravity of the Earth. I haven't worked it out but I would guess that for people in aeroplanes it's probably a similar effect to being on a satellite, so one of the effects will outweigh the others. There will be a certain distance above the Earth at which the two effects would cancel out, actually.

Chris - There's another factor which is that being that much higher up in the atmosphere you exposed to more incident radiation coming in from space. So people who pilot aeroplanes, and cabin crew have higher rates of cancers and lymphomas (cancers of white blood cells). So actually there is an advanced ageing effect owing to radiation exposure which outpaces the effect of relativity. Sorry to rain on your parade there boys.

Could a microwave be used to heat a home?

We put this question to tech investor Peter Cowley...

Chris - Here's one for you Peter: this might be a potential new money-spinner for your business arsenal who knows? This is a question from Jules who wrote to us to say:

Could we install and use microwave technology for domestic central heating systems, to heat the water and radiators in the home, cost effectively?

Peter - Yes, thank you, yes. This amused me quite a bit because I actually misread it to start with and I thought could a microwave be used to heat a home? And I thought Um, you could put the microwave around the home.

Chris - It wouldn't look so good in the fireplace though would it?

Peter - Well actually the other way round. So yes, interesting idea actually because we use microwaves for heating small items very, very effectively compared with putting them on the stove, but it isn't going to work for a number of reasons.

First of all based on a consumer microwave it's actually very inefficient. Its at the order of 70 percent efficient and that means that for every kilowatt, 300 watts are disappearing in heat.

Secondly, the cost. My own gas boiler at home is 91 percent efficient compared with 60 or 70 percent and it works out about £35 a kilowatt. Whereas a microwave would probably cost about £100 to £150, so it's about four times more expensive.

Thirdly, and a very big one here, at the moment with the consumer microwaves the MTBF, which is the mean time between failures, is only about 2,000 hours. So 2,000 hours is about 12 weeks of heating so you'd have to change your "boiler" every 12 weeks. A boilers about the order of about 10 years, we hope, but probably a bit less nowadays, but that's 88,000 hours compared with 2,000 hours. And so, it works out because of that reliability the capital cost is about 100 times more.

And then on top of that, mains gas, which my boiler is, is about 3 or 4 times cheaper per kilowatt hour than electricity. So, all in all, something very major would have to happen or destructively change in order to use a microwave to heat the water in a house.

Chris - Georgia.

Georgia - I have a question about the waste. You said there was about 30 percent wasted energy but it was wasted as heat. Surely that's not a problem if you're trying to heat things.

Peter - No, that's right. But it's heating in the environment where the microwave is, so you'd actually also have to cool and take water through that air as well. But you're right, that is converting electricity.

Why do cold weather fronts move faster than warm fronts?

Chris Smith put this to climate scientist Doug Crawford-Brown from the University of Cambridge...

Chris - Now: Watching the weather forecast has made Martha ponder the following:

How do cold fronts move faster than warm fronts, if cold air molecules moves slower than warm air molecules? Doug - Right. So continuing in the same theme of there being a lot more going on here than one would normally think. Molecules move for a lot of different reasons; they spin around, they rotate, they move laterally meaning that they're being pushed by air currents for example. They have diffusion so they're moving in all sorts of directions. Cold air molecules do move more slowly by diffusion than do warm air molecules.

But cold fronts also bring in closer isobars, in other words you get a greater drop in pressure per unit distance when you're dealing with cold weather fronts. And what drives the wind is really what that pressure difference is, as Darcy's Law shows, which is why the weather person always shows you the isobars. Take a look at the map sometimes and you'll see a cold weather front have isobars that are lines of equal pressure that are really close together, whereas the warm weather fronts have them far apart.

Chris - What causes the changes in pressure across the Earth's surface?

Doug - A lot of different things but, ultimately, it's all driven by sunlight hitting the surface of the Earth and being absorbed up in the atmosphere too, so ultimately it's driven by the Sun.

Chris - And that gives energy to the atmosphere which makes it expand?

Doug - It does, because it's non-homogeneous, it's going to have different pressures at different places.

Chris - Doug, thank you very much.

What is between the internal organs?

We put this to Naked Scientist Chris Smith...

Chris - Right. We've got this question from Luke:

What is in between the internal parts of the body. I'm assuming it can't be air or blood which would get stale and prone to infection due to lack of circulation. It's not going to be a vacuum, and I doubt that the organs are all jammed in with absolutely zero space. So what is in there? Chris - What do you reckon Georgia - what's in there?

Georgia - in between? Jelly.

Laughter

Chris - In my case I think it's expanding amounts of flab. But the answer is, we know the answer to this rather well because we've actually got very good imaging modalities now. We've got CT scans, we have MRI scans, we have X rays and so we can see what's inside a body when it's in its intact state.

And the answer is that, actually, there is no free gas inside your body unless you have a problem. If you do a chest x ray on somebody you can see where the gas is in their lungs and you can also see that the lungs go right out to the chest wall and there's no gas outside the lungs. Now sometimes people get a condition called a pneumothorax, and this is where the lung pops and you get air outside the lung, and doctors looking at an X ray of the chest would see that there's a bubble of gas around the lungs and you can see that it's clearly where it shouldn't be.

The same is true in the abdomen. The innards, if you actually look inside the abdomen actually most of the stuff in their, your guts and all the internal organs, they're all slippery and slimy and covered in water. But they're very closely packed in and sliding past each other and there is no free gas in there.

If you do a chest X ray on somebody, you do this to diagnose abdominal problems because you do a chest X ray with someone upright and you can see where their diaphragm is and you can see a bubble of gas forming under the diaphragm. And that's always pathological and shows they've had some kind of rupture of one of their internal organs, or that a nice surgeon has been in there and done something recently and left some gas in there. Because when we do laparoscopic surgery, when they put a camera in, actually what you do is to put a needle in and you blow up the person's abdomen with carbon dioxide and inflate their tummy, so that it lifts the abdominal wall away from the internal organs and that way, when you put your instruments in to start with you don't do damage and you also create space for yourself in which to work. And you use carbon dioxide because it's easy for that to be reabsorbed into the body. It dissolves back in your body fluids and then it disappears off through your lungs. Peter.

Peter - Isn't there something called peritonitis? Isn't that something where there's an infection within the abdomen - what is that?

Chris - Well, peritonitis is where you have infected the layers around your peritoneum. Your peritoneal cavity is your abdominal cavity, and if things get out of your intestines and into that space, they set up peritonitis inflammation there. You can also get chemical inflammation of the peritoneal space but, on the whole, that's always pathological, and it can also be because of say, cancer. That can do that too. Doug?

Doug - Just quickly because we have two physicists in the room here. I think we would point out that the vast majority of the things in our body are, in fact, empty space between the nucleus and the electrons. So, we are mostly not there at all.

Chris - I thought you were going to say like in some people's heads there's quite a gap as well. Your non-adopted county's newly elected president has something going on in that department, doesn't it.

Doug - I can see a theme developing here! So the audience knows I am British now, okay.

Chris - To summarise the question: what's inside a body. Well the answer is that there is no free space, there is no wasted space, and it's largely fluid and things all in a position with each other. But where you do end up with a whole or something that's no there you do sometimes get a bubble of gas and doctors can spot that, and they know when they see that that there is something going wrong.

Do animals get aroused watching other animals copulate?

Chris Smith put this to zoologist and Naked Scientist Georgia Mills...

Chris - Georgia - Luke has asked this rather provocative question:

Is there any evidence that animals become aroused while watching others of their species do what comes naturally to them to reproduce, let's say? Georgia - Do as they do on the Discovery Channel? Actually, they do use footage of Pandas mating in Zoos because Pandas are notoriously difficult to get to breed in captivity, and this has had mixed results. There was one study where they got monkeys, which are a social species, male monkeys will sacrifice their fruit juice privileges to look at a picture of a female monkey's rear quarters, rear hindquarters. So there's some evidence that there is some.

Chris - So here, let me just get this straight. They do an experiment where you're offered a choice between a monkey's bum and some fruit juice?

Georgia - Yes, and the monkeys choose the bum almost all the time, so this shows at least that species values that image. But in terms of watching animals copulate, humans are a very very visual species, but it's easy to forget most other animals rely on a whole different host of cues as their major "turn ons" I suppose, so smells, and sounds, and movements. So, in general, it's probably a mainly human trait.

Chris - I'll bare that in mind.

What can an ordinary person do to be more sustainable?

Chris Smith put this to climate scientist Doug Crawford-Brown from the University of Cambridge...

Doug - Yeah, we've packed a lot of questions in there. When I was born there were 2.5 billion people on the Earth, and I'm not that old.

Chris - Is that back when you had your first Brontosaurus?

Doug - When I hear that fact, I fell off my dinosaur, yeah. If we were to go back to that number of people - problem sorted. Every time we discuss this at the conference of the parties meetings on climate change, it gets into a big argument between the United States saying "well, you China produce more CO2," and China saying "but we have more people," and the United States saying "oh, but your are producing more CO2," and back and forth.

So population has been on the table for a long time. People worry about discussing it simply because it causes such discord between the developed and developing nations.

Chris - I suppose it's a hard nut to crack isn't it, because you've basically got to tell people how many kids they can have, which has always been something people have regarded as an almost God given right, isn't it?

Doug - In the US, I used to go round to churches and give these presentations. And every time I would talk about climate and talk about all sorts of mitigation measures, which is what the first half of the question was, everybody was fine. The minute I talked about population control, the response was uniformly 'God will tell me how many children to have' and I just learned to back away from that.

What can we do to make the changes? The example I always use is on the 7th of March, 2008 at 07.05 am, my carbon footprint went down by 60 percent. And I'm always asked by people "well what happened" and well, what happened was that was the time at which my wife and myself and my son migrated from the US to here. Any my life in Cambridge is just as good as my life in Chapel Hill, North Carolina, but it's 60 percent less CO2. Smaller house, we don't drive a car, because you can't really drive one in Cambridge, and so forth. So those are the things: make your house smaller, make your house a little bit cooler in the winter, and so on.

Chris - You say cooler in the winter. Do you mean like fairly light, Christmas lights, that kind of thing? Georgia.

Georgia - Well speaking of Christmas actually, that is like if you think about reducing the amount of waste, Christmas has so many things that we just throw away immediately. Think about crackers - you pull them and they immediately go in the bin. Wrapping paper - so much paper that is there to look nice. So things like recycle so boring - recycle your wrapping paper and things like that.

Chris - But you raise a good point about wrapping paper because I was pretty horrified when I just didn't put the bin out for a couple days at home, and I looked at how much packaging, like plastic packaging, that everything. You cannot buy something these days without it coming with impenetrable layers of plastic packaging. What's with that?

Peter - The Germans started about 25/30 years ago when I was living there they changed that quite a bit. There wouldn't be much packaging and you would take off the packaging before you left the supermarket. Obviously, you're taking a risk then that you damage an item on the way home but the reduction in packaging, I assume they're still doing it, was considerable compared with other countries.

Chris - So Doug, just wrap up the question then. Could you give us a little checklist of say your top five tips for what Heath, and the average person, can do to cut their carbon footprint.

Doug - Well, the biggest one, by far, is how much temperature you have in you house and turn the thermostat down if you even have a thermostat - a 3 or 4 degrees centigrade temperature drop.

Number two. Don't do what I do, which is fly all over the world and lecture people about how they can reduce their carbon footprint.

Chris - About climate change.

Doug - I think St Peter and I are going to have a conversation about that at some point in time.

I mean number three is consumption patterns. And, ultimately, I think people need to understand that they are the ones driving this system. You know, quite blaming the producers, the companies, the countries that produce this stuff. We turn that system on every time we consume refrigerator, computers, and so forth.

That's not five, but it's three.

Is wireless charging more or less efficient than wired?

Chris Smith put this question to tech investor Peter Cowley...

Peter - Very, very much the latter as I'll explain in a minute. First of all, wireless charging, we already starting to use. Many of us have toothbrushes that are wireless charged. I think all smart watches are wireless charging in order to keep them waterproof. Some phones are wireless charging at the moment. So we are moving that way.

The power comes into domestic property through a consumer unit. We can't all end up bunched round the consumer unit collecting power from that, so the power has to get out in wires around the house. So, presumably, we're taking it from the point when it comes to the wall and from there, instead of plugging something into it using effectively copper and copper connection, you have wireless.

The wireless part of it means converting the AC signal, the AC power, through to a radio frequency and then back again. I'm sure it's getting better but, at the moment, you're losing about 5 percent converting it to radio frequency and back again, so that's 10 percent. You're losing about 11 percent actually through the air. So you're losing in the order of 20 percent. So if you take 20 percent as the amount you lose, how does that compare with the amount of cable that you were going to plug into it?

And you get some crazy, crazy numbers here. If you were running a full 13 amps out of that, you would need a cable that was 140 meters long to be equivalent to the loss you've got through the air, and it gets massively worse. If you actually put a phone charger, and instead of the phone charger you put RF, you'd need a cable from that point there, 100 kilometers long would lose the same amount of energy. So no is the answer in a very quick way.

Why does it go dark when we turn the lights off?

Chris Smith put this to physicist Andrew Norton from the Open University...

Andrew - This is a great question - I love this. The thing you've got to realise is that mirrors aren't 100 percent efficient. A typical mirror will only reflect 90 percent of the light that falls on it. You can get better quality ones that will reflect more. But say your mirror reflects 90 percent of the light, that means 10 percent of the light is absorbed on every reflection, and that heats the mirror up and that sort of thing.

So, if you've got to reduce the amount of light by one part in a billion of what you started with, that will only take 200 reflections. So the light bounces backwards and forwards 200 times, and you're already down to less than one part in a billion of the light you started with.

Now if you've got a typical sized room like this studio we're in - it's a few meters across. The light bouncing backwards and forwards 200 times would take maybe 2 microseconds, 2 millionths of a second. So, within 2 millionths of a second, the light bounce backwards and forwards 2 hundred times and you're down to one part in a billion. That's why it gets dark.

Is there any proof that vampires exist?

Chris Smith put this to zoologist and Naked Scientist Georgia Mills...

Georgia - So the short answer here is no, there is no evidence for the sort of story book creatures which drink you blood, and hate garlic, and only come out at night, but there are a lot of animals who do drink blood. Blood is an excellent source of proteins and lipids, so it's a nice sort of meal on tap as it were for a lot of animals. So we've got mosquitos, leeches, there are even some birds that drink the blood from other birds, which I had no idea about.

Chris - How do they get the blood - do they go and peck at them?

Georgia - Yeah. It's a very small, I think it might be finch, I might be wrong, that lands on a bird called the booby. It just kind of pecks on its back and, apparently, if the booby let's it get away with it, but it it's too greedy the booby will chase it away.

Chris - I think I would chase it away under any circumstances. Does it do this all the time or is it like the mosquito where the female is the one that seeks out the blood meal because it's rich in protein when she needs to lay eggs?

Georgia - I think it happens more when food is scarce. I don't think it's sole diet is blood. And in terms of vampiric animals, there's the vampire bat as well. Thinking about when they bite you you turn into a vampire, this doesn't happen for any animals but when you bite blood you transfer a lot of blood borne diseases. So things like malaria...

Chris - Rabies?

Georgia - ... rabies, exactly. And that's arguably a lot worse than turning into an immortal vampire.

But there's actually some really interesting research and it might imply that maybe vampirism is a good idea in the future. What scientists have done is they got old mice and young mice and have sort of done a mutual blood transfer, and they found out the old mice got smarter, they looked younger, they tended to do better on all the tests, and the young mice started to mess up a bit and seem a bit older. They think they might be growth factors in the blood of younger animals that, if transferred to older animals, they can then reap the benefits, and they're actually looking into this for treating Alzheimer's.

Chris - Not so good for the young animal though which accelerates its aging, is it?

Georgia - Yes, but you'd hope if they did it with humans, they wouldn't then transfer the old blood into the younger creatures and just do a simple donation.

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