What does Falling into a Black Hole Feel Like?

What's the point of mosquitoes? Do your eyes pop out if left open when sneezing?
16 June 2015
Presented by Chris Smith, Georgia Mills
Production by Georgia Mills.


What's the point of mosquitoes? Do your eyes pop out if left open when sneezing? Is the Universe infinitely big? Are birds really related to dinosaurs? What is quantum entanglement? If the space station is held in orbit by gravity, why do things float about inside it? Why does hayfever make your eyes itch? Can animals forecast earthquakes? Find out in this week's show where you're in the driving seat asking us the questions...

In this episode

A mosquito biting a finger

What's the point of mosquitoes?

We put Sean's question to zoologist Max Gray:

Max - So, the problem here is the difference between value to him as an individual versus value to an ecosystem. We don't get a lot of benefit ourselves from mosquitoes but they feed into the food chain much like anything else would to an ecosystem. There's lots of birds and lots of fish, particularly freshwater fish, that eat the larvae of the mosquitoes and then birds will eat the adults more. So, they do feed into our ecosystem in the same way that almost any other small insect would, but we derive no benefit from them but then again, we don't derive much from wasps either, at least not the ones that you see: the yellow and black wasps.

Chris - It's an arrogant belief that we're the important ones, isn't it? At the end of the day, everything here on Earth is exploiting some kind of niche in the environment where it's got its slice of energy and it's trying to defend it and hold on to it and exploit it.

Max - Yeah, exactly. All you need for the mosquitoes to exist is for a niche within that ecosystem to exist and they'll fill it. They'll adapt to fit that need and we don't need to need them so much. The same thing is true with all the diseases. They exist because there's the space for them to exist, not because they're beneficial.

Chris - Is the female ones that are the hungry biting ones, the mosquitoes at least?

Max - Yes, exactly. Females will actually draw blood from humans. The males essentially fly around, breed and die.

Chris - So, what do the males eat then? If the females go for blood, what do the males eat?

Max - So, the males, as far as I'm aware, only really eat as larvae. So, when they're small larvae which is kind of the tiny little thing that swims around in the water usually, stagnant water. and then it will pupate and emerge as an adult, fly around, breed with the females and then die.

Dogs - Social animals

Can animals recognise each other, and us?

We put Steven's question to Naked Scientist Georgia Mills.

Georgia - With animals, it really depends on the animal. There are so many of them, but if there is a need for an animal to tell individuals apart then it's likely that this will evolve. So, for example, animals that work together in groups. I think it's been shown that wasps actually have really good facial recognition.

Chris - As in for humans.

Georgia - No, of other wasps. I guess that's a study to come of whether wasps can tell people apart. But another example is in cooperative breeding. So, that's when a male and a female team up to bring up their young. It really helps if you can remember who your partner is in this kind of situation. So, birds have calls to recognise each other. For example, penguins, when they meet up. When it comes to telling humans apart, that's less useful for most animals. I think dogs, they've been selected over many years to live among humans. So, they're actually quite good at telling us apart by our smell and also by our faces. But for most animals, it's not really beneficial to be able to tell different people apart.

Chris - I did read a study a few years ago now. There were some researchers who did some experiments on mocking birds. They found that if they went to these mocking bird nests and aggravated the birds just to annoy them a little bit, the first time they did it, the birds weren't terribly alarmed. The second time the person did it, the birds knew what was coming and they mounted a sort of response to sort of frighten the person away from their nest. The third time they did, they nearly attack the guy. Then as an experiment, the researchers sent in another member of the research group who hadn't been near the nest and hadn't been seen by the birds before. She approached the nest and got the same reaction that the guy did the first time he went in, proving that they can tell people apart. So, they obviously do have quite a good ability to discriminate between individuals and I suppose they are very seeing creatures aren't they I mean Max, they're very good at seeing, the birds have excellent vision, don't they?

Max - Yeah, they do. They have much better eyesight than we do. Instead of the three cones that we have, most birds have four and can see all the way into the UV spectrum as well, into ultraviolet light.

Chris - When you say the cones, these are the cells at the back of the eye that convert light into brain activity.

Max - Exactly that.

The first stars in the Universe turn on at about 400 million years after the Big Bang. WMAP data reveals the era.

Is the Universe infinitely big?

We put this question to Cambridge University astrophysicist Zephry Penoyre...

Zephyr - So, this old kind of stuff gets actually very worrying. It's even possible that time, although it's bounded by having a start, that as soon as the universe started, it may have instantly been infinite.

Chris - Hang on a minute. How does that work out? How can it be infinite if it's only just got started?

Zephyr - There are theories that it's quite possible that as soon as the universe was born, if you just went to one direction for long enough, you will get back to the same place; that the universe is essentially curved around on itself. Now, it's very difficult for us to see this because the universe now is so very large that we only see a tiny, tiny fraction of it. In our expanding universe, because light travels at a finite speed, the expansion of the universe can actually outstrip the speed of light and there's a finite horizon in which we will ever see or light from us or signals from us will ever be able to get - which is quite a worrying thought if you think about it, and even more worrying that horizon is shrinking. Our universe expands faster and faster and that horizon gets smaller and smaller compared to the total size of the universe.

Chris - So, there are literally some bits of the universe that we could never see even if we wanted to.

Zephyr - Likely, the vast majority, when we calculate things about the universe, we use the size of the universe, we see as a lower limit, but there may be no limit to how big it is. It's certainly so big that we're not seeing the overlap as we go all the way around once.

Chris - We also get the question quite a bit. People say, well, if the universe started with a Big Bang and the Earth has only been here for about 4.5 billion years, what are these echoes of the Big Bang, this light we're detecting as the cosmic microwave background radiation left over from the Big Bang? Why is it only just going past the Earth now if the universe was here and expanded away from us billions of years ago? How does that work?

Zephyr - So, the lovely thing about the cosmic microwave background is that it's almost completely uniform everywhere in the universe we see. This is actually really surprising result and it's the reason we invented inflation because we don't expect it to be in the form of inflation.

Chris - This is not the kind of inflation that Georgia Osborne is interested in. this is the universe getting bigger, isn't it?

Zephyr - Yes. The universe as it starts, grew incredibly rapidly, and then seemed to slow down a lot. And so, what this does is mix all of these cosmic microwave background radiation uniform everywhere in the universe. So, the light that we're seeing getting to us just now would be exactly the same as a light getting to any other point just now or getting to us at a different point in time. And so hence, the light we're seeing just now is completely uniform.


Are chickens and dinosaurs related?

We put Gontse's question to our very own Georgia Mills.

Georgia - Well, the short answer there is that chickens are technically dinosaurs. It's now well established that birds did evolve from dinosaurs. So, at one point there were dinosaurs that were smaller, feathered, there's a really interesting fossil called archaeopteryx which is called a transitional fossil. People sort of see this as quite good evidence that dinosaurs and birds are one in the same really. And so, people say, isn't it a shame that you can't see dinosaurs anymore except for museums, but just go to a local chicken farm. They're dinosaurs, they're avian dinosaurs.

Chris - I've eaten a few then. So, when you've eaten a dinosaur burger, you really have.

Georgia - Revenge for Jeff Goldblum.

09:03 - Science of the Big Bang Theory

TV show the Big Bang Theory centres around the lives of scientists, but what science are they actually doing?

Science of the Big Bang Theory

Dave Zobel is a science humourist and author from LA. Here he tells us about his latest book...

Dave - You must take a deep breath to say the entire title of the book Chris. It is, "The Science of TV's The Big Bang Theory: Explanations Even Penny Would Understand."The Science of The Big Bang Theory

Chris - So go on, explain the motivation behind doing this then.

Dave - Well, the TV show, The Big Bang Theory is enormously popular and there's quite a lot of talk about science on that show. The main characters are all scientists of various types and they occasionally will talk about either their work or their interests or just something they have read recently. They never really explain the science and that's appropriate because it's a sitcom. It's not a TV show that is purporting to teach you anything. It's just trying to give you a good time. But all of the science they talk about is legitimate. It's all vetted actually by a real-life professor of astrophysics at UCLA named David Saltzberg. He makes sure that it's all real subjects. There are no dilithium crystals, there are no infinite improbability drives or sonic screwdrivers. I thought it would be fun to write a little book explaining some of those science references and just talking about, you know when the character says, "I was using a laser." What does it mean to use a laser, when he talks about his noise cancelling headphones? Well, how do noise cancelling headphones work? So, I put together what I thought would be a little book. It ended up being almost 400 pages and I had to leave quite a lot out.

Chris - Give us a sort of taster then. When you say you've taken on some of these questions and explained them, what sort of treatment have you given them?

Dave - Well for example, let's take the example of the noise cancelling headphones which come up a couple of times on the show. In general, they are used by characters in order to drown out the sounds of their roommates, making noises with other people and I will leave the rest of that to your imagination. So, I'd start with a quote from one of the characters, just a scrap of dialogue mentioning the noise cancelling headphones and then I lead in from that to, how do noise cancelling headphones work, what is actually going on, the different types of noise cancelling headphones and the way they are engineered. And I close with a question that I'm sure your listeners would be interested to ponder which is that, if a tree falls in a forest and there's no one there and it lands on a pair of noise cancelling headphones, does it make a noise?

Chris - Answer it for me then. Does it?

Dave - Did you hear me? I just answered it.

Chris - Very good. How has it been received so far?

Dave - It is flying off the shelves at Caltech. Of course, that's earthquake country so there may be another explanation for that. But there's quite a lot about Caltech in the book and that's the California Institute of Technology where these characters work. It is a real institute in Pasadena near Los Angeles and I cover quite a lot of the research that's really going on at the real Caltech.

The International Space Station (ISS) in orbit, photographed from the attending space shuttle Discovery

Why do things float on the space station?

Science humourist Dave Zobel had a go at answering Terry's question...

Dave - Why do the astronauts float about? If they just put on heavy boots, wouldn't they be able to stomp around like the rest of us?

The brief answer Terry, is the same reason that when you jump off of a very high building with your keys in your hand - which I don't recommend - as you are descending to the Earth, your keys sort of float up from your hand. They don't stay anchored in your hand and the things that are in your pockets don't stay anchored there.

And the reason for that is because you and your keys, and everything else are all falling at the same time and at the same rate; well that's what's going on with the International Space Station and really, anything else in orbit.

You are falling not to the Earth but around the Earth, but it's the same idea. And everything is falling. So, it's all falling at the same rate.

That's also the reason that when astronauts train in the aeroplane known colloquially as the "vomit comet" where they go up and then come crashing down towards the Earth and then, at the last moment, pull out and go up again; and do that over and over, and over until everybody has had the chance to see what everybody else had for breakfast. There's that same weightless period and that gives them 20 or 30 seconds to be able to float around and feel what it's like to be in the International Space Station.

The chimpanzee - mankinds closest primate relative.

13:31 - Do chimps think like humans?

Chimps have a fondness for beer and barbecuing, just like humans...

Do chimps think like humans?

Max Gray is a zoologist from the University of Cambridge. He's been looking at some of the latest news regarding chimpanzee behaviours...

Max - I've always been fascinated by things that we find in nature that show that Chimpanzeeanimals aren't that different from us. And in the last couple of weeks, there've been two stories about chimpanzees which is great from my perspective. I find it fascinating. The first of which is, people have been looking at chimpanzees' abilities to understand cooking. Now, chimpanzees don't cook in the wild. They haven't really harnessed the power of the microwave oven or even fire. But they do seem to value cooked food over raw food and they will keep raw food and put it in a cooking device that the experimenters gave for them. They'll wait longer for cooked food. They'll give up a larger amount of uncooked food for a small amount of cooked food, that kind of thing. and then on top of that, a different study that's come out of Oxford Brookes University has shown that finally, we found evidence that something called the drunken monkey hypothesis exists which is something that people have suggested for a while that kind of early apes - the common ancestors we have with apes - had a value for finding alcohol and this has been to do with it because it's a good way of finding fruit because the fruit ferments and if you look for alcohol, and you find good source of fruit trees. But they've actually found that groups of chimpanzees in West Africa, they go for - there's a plant called a raffia palm. On the top of these palms, the sap accumulates and this open to the air, so it kind of slowly ferments and gets slightly alcoholic, around about the strength of weak beer in the end. People will actually harvest this and sometimes known as palm wine. It tastes revolting, but it is about the strength of a beer they said.

Chris - You have samples of this, have you?

Max - I have, yeah. I had the misfortune to try some when I was in Africa once. It tastes somewhere between a bad eggnog and off wine. But the chimpanzees seem to like it and actually...

Chris - I think I've had some of that in my local.

Max - Quite possibly! But yeah, the chimpanzees will seek out. They'll go and they'll drink reasonably large quantities of it, seemingly get drunk, and will return. They don't seem to learn not to.

Chris - What does a drunk chimp look like?

Max - I haven't seen one. I'm not entirely sure. Sadly, the paper didn't describe it in detail. They just said, they've become inebriated and left it at that.

Chris - They sort of beat up their bedrooms and puke all over the place perhaps.

Max - I would imagine that some of them would vomit, yeah.

Zephyr - So, I've loved hearing recently that we've been funny human intelligence to be less and less kind of sacred and I've seen some great studies on similar things of this I saw a great one recently which was that crows can understand poetry.

Max - Eh?

Zephyr -  I think that they have a kind of abstract reasoning in some way they can understand poetry.

Chris - How do you know a crow likes poetry? How on Earth does someone do that?

Zephyr - I actually can't remember the details of the study. I am hoping that what it was was that they gave the crows some terrible poetry and good poetry and the crow showed preference to the good poetry.

Chris - Well it depends what you judge to be good or bad, doesn't it?

Max - Also, in what way is that going to be understanding poetry? It could just be the meter in a way that is in some way comparable to bird song. There are certain frequencies that carry better and sound better in nature. Going so far to say they understand poetry might be pushing it.

Zephyr - But my question is, if we are currently doing this, chimps understand cooking, birds understand poetry, is there going to be any test we can do to just say that the intelligence of these animals corresponds to human intelligence rather than this individual?

Max - It has been done with a few things. There's an experiment called theory of mind experiment, it's basically a test to see whether or not one individual can kind of attribute a so-called state of mind at a degree of empathy towards another individual. Chimpanzees can do this in the way that if there's a dominant individual that either can or cannot see where an experiment is heading some food, the subordinate individual will eat that food if the dominant individual hasn't seen it, but won't if the dominant individual has seen it. That is used as evidence that the subordinate individual kind of understands the state of mind of the dominant one...

Chris - Mental attacking them.

Max - Yeah, exactly.

Chris - Because birds do that too because some scrub jays do cache food based on prior knowledge because Nikki Clayton at Cambridge University has done this experience where they put these birds in a sort of bird hotel and they know that when they're in the - let's call it the dining room, they get fed in there. but the bedroom, they never get fed in there and that every night, they get locked in the bedroom. But in the morning, they have the free run of the whole thing, and so, her reasoning was, if they know they're going to be locked up there and they know they're never fed in the bedroom, then maybe they'll hide food in the bedroom when they've got it available in the dining room. And they do, and so they're obviously thinking, "Wow! I get locked in here and I'm hungry. So, I'm going to hide some food in there on the off chance I might need it later" which is kind of neat, isn't it?

Max - Yeah and there's other examples as well whether or not they understand when an object has been hidden from site, whether if they know it's still there which is something called object permanence. All of these experiments have certain parallels and in some, the same experiments have been done developmentally with humans. You can kind of tag it to the rough age of a human child. And so, with theory of mind in chimpanzees, it starts to emerge in humans at the age of 4 or 5. And so, as far as you can actually quantify it, you can roughly say in adult chimpanzees maybe somewhere around as smart as a human child.

White handkerchief

Do eyes pop out if you sneeze with them open?

Chris Smith and Georgia Mills took on this question...

Chris - Well, the answer to this is it is a myth and there's not actually any evidence whatsoever that your eyes are going to leave your head - be reassured! I know this as well because I've done the experiment on me!

I was driving and obviously, it was very unsafe to close your eyes when you feel a sneeze coming on and you're driving because you might leave the road. I forced myself to keep my eyes open but there is a reflex that does close your eyes.

Why should your eyes need to close when you want to sneeze? Well, think about what a sneeze is. When your nasal passages are irritated by something, either something tickling the hairs in your nose, a bug going into your nose, or a virus causing a chemical tickle in your nose, or an allergy then the nervous system is wired up to cause you to release a sudden rush of air straight down your nose, the idea being that this high velocity - and in fact, we've measured the speed of a sneeze on the Naked Scientists, it's about 100 miles per hour and those are the big particles that you can see - when the rush of air comes through, obviously, the idea is it's going to dislodge whatever the irritant is that's in your nose.

Now, also in your nose are some openings and, specifically, there's an opening which is your "nasolacrimal duct" which carries tears from your eyes down to your nose because you don't want tears streaming down your face. You want them to go away conveniently into your nose and you sniff them up and swallow them. If you look in the inner, lower surface of your eyelid, if you follow your lower eyelid ground towards roughly where it meets your nose, you'll see there's a tiny black dot there and that's called a punctum.

This is like your eye plughole and tears run from the upper outer edge of your eye, across your eyeball, collect in the middle there and go down that hole. It then goes down your nasolacrimal duct and into your nose. When a sneeze comes along at 100 miles an hour - a big pressure wave - imagine what would happen if that duct stayed patent. All the stuff you're trying to blow out, all of the nasties, all the bogies, and that kind of thing, and the snot, mucus - let's give it a proper term - would come flying - not just out of your nose - but into your eyes!

This probably wouldn't be terribly good. It might give you infections. It would certainly jam the duct and that wouldn't be good. So, I think the reflexes evolve to make you screw up your eyes. In that way, you compress the duct closed and keep the pressure up in it so that all of the air then rushes out of your nose during the sneeze and stuff doesn't go up the wrong way.

Georgia - Well, on the subject of hay fever, I was wondering why does it make your eyes itch? I can't fathom the reason for this. I have no self-control. I itch my eyes to death and I feel like I've gone blind. What's going on?

Chris - Well, what is an allergy? When you have an allergy, your immune system has responded to the allergy which is usually a little bit of protein - and pollen has got a lot of protein in it - and that's why bees go and get it actually because it's a good source of food for them. The pollen gets on to the antibody called an IgE antibody which is stuck on to cells called mast cells which are in all your tissues. They're there like depth charges or landmines. They're there as a first defence. The idea being that if something tries to get through your skin or get through your mucus membranes, it triggers these mast cells off so that your immune system gets an early warning that something is trying to come in and it releases all these inflammatory signals saying to the rest of your immune system, "Come in and help me to defend this part of my body."

But, if you've got hay fever, instead of having antibodies - these IgE antibodies - there just to detect things like worms, parasites, and other nasties. You've got antibodies there that unfortunately get triggered by pollen, which your body should ignore and should regard as innocuous. So, the pollen floats into your eye, lands on these antibodies. They send a signal into the mast cell and it then does what's called degranulate. It discharges this big welt of histamine and other chemicals - they're inflammatory - into the local area where the mast cell is sitting.

This goes on to various things including blood vessels and blood vessels in response to histamine open up and this increases the blood flow through the air and making it swell and go red. It also triggers very fine nerve fibres going through the tissue which specifically signal itch and they're activated by histamine. The histamine from mast cell causes the nerve cells to start firing off.

And so, you sense this itchy sensation and you have this desperate urge to rub your eyes. You mustn't, because the mast cells are also sensitive to being rubbed because if you squish them and squeeze them, it makes them discharge more histamine. So, if you rub your eyes, you will not only exacerbate the symptom. You will make it much, much worse because you will burst the pollen grains, you will burst the mast cells, and you will make your eye much more sore than if you were just able to resist the temptation and don't rub it.

So, just to return to Josh's question, you cannot pop your eyes up by sneezing, because there's no physical connection between your airways and your eyes apart from that nasolacrimal duct, which you probably screw up your eyes to stop yourself filling it with bogies and mucus when you sneeze...

An ion trap used with a quantum computer

What is quantum entanglement?

We put this question to Dave Zobel, author of "The Science of TV's The Big Bang Theory: explanations even Penny would understand"

Dave Zobel - Quantum entanglement which Albert Einstein referred to as spooky action at a distance or he actually used the German words for it which sounds like spooky action at a distance if you say it with a German accent is, this concept that we really can't tell why it happens. We can say what happens. It's a bit like some of the other things we've spoken about in the show already. If you have two particles that are created at the same instance by the same process which can happen quite frequently, they can have certain properties that are identical but opposite. One of them is a property called spin which has nothing to do with what we think of when we say the word spin, and that's why we call it spin! If those two particles are moved very far apart but no one has measured their spin, then it's not just that they have spin that is unknown. They don't yet have any meaningful spin. It's not that they have spin zero. They just have no spin that we can speak of. If you then measure the spin of one of the particles, you will find that whatever it is, when you measure the spin of the other particle, it's the exact opposite. It's as if the two particles had spoken to each other and said, "Okay, he's about measure me. I'm going to have spin plus one. You have spin minus one, right?" But, in fact, they can't communicate that way and so, we don't really know what's happening and that, I think, is why Einstein used the German word for spooky. Chris - And I think Niels Bohr said, "If you're not baffled by quantum mechanics then you just didn't understand it!"

How does light change speed?

We put this question to Cambridge University physicist Zephyr Penoyre...

Zephyr - When it goes into the glass, it's moving slower. But also, because the frequency has to be the same, the same waves have to be coming into the glass at the same rate as they're coming out, otherwise you've lost waves somewhere along the way.

Chris - And it's changed colour.

Zephyr - And that's because wavelength has changed. So, the energy of the light is to do with the wavelength of the light. So, as it slows down, the energy gets higher - because the wavelength has shrunk - so the total amount of energy passing through the glass is exactly the same as it was going through the air, it's just moving at a slightly different speed.

fabulous dinosaur

In the era of dinosaurs, why was everything big?

Georgia Mills gets to grips with Alpesh's question.

Georgia - To start with, the dinosaurs were around for hundreds of millions of years and I know we think of the really exciting ones like Diplodocus and T-rex. But actually, a lot of animals around then weren't so big. So insects, their biggest time was around the carboniferous period which was actually a long time before the dinosaurs were around. And I think the largest animal that was ever recorded is of course, the blue whale and that's still around today. Saying that though, a lot of dinosaurs did get very big and there are several theories about why this might be. The main reason is that the ecosystem could just support larger animals and being big is often a really good idea if you're competing for mates. It can help you to fight off the smaller males and if you're competing for food as well. One idea is that the plants that were around during the dinosaur times were quite tough and were quite hard to eat. So, for herbivores, it became quite a good idea to have longer guts so that they could process this food more easily. And so, they could get bigger and then of course, the carnivores could get bigger as well. Another thing to consider is that dinosaurs could've had less physical constraints on them from becoming bigger. So, a problem with warm blooded animals becoming really big is that they could overheat quite easily and dinosaurs, it's not quite known for sure if they were warm blooded or cold blooded, but it's likely they were somewhere in between. So, they wouldn't have had this constraint and they also had quite efficient bird-like lungs which meant that they could take in oxygen and distribute it around the body much more easily.

Max - There's actually a lot of evidence in the fossil record for really large mammals as well after the so-called era of the dinosaurs, after the dinosaurs went extinct and mammals began to become much more prevalent. There's also loads of what we call mega fauna - really large animals. There are some terrifying things - if you look it up - that existed in north and south America, and now, in Australia and Africa as well. The reason we think these are no longer around, is a combination of being over hunted by humans and also, a degree of climate change.

Chris - Equally, did not humans go through a massive phase as well? I remember seeing when I was in Johannesburg, I went to Wits University there. This is the department that Raymond Dart worked in and he was one of the people who was one of the big forefathers, the godfather if you like of sort of palaeoanthropology. There are skeletons there of humans from maybe 300,000 years ago or so and they would have made a pro basketballer look like a dwarf. There are people there who were absolutely huge and I asked Professor Lee Berger who was showing me around, why did people evolve to get so big because the cost of growing to such a big size is extremely costly in the sense that you've got to have enormous amounts of energy to go into growth to get that big. You've got a huge body to maintain. It makes you easier as a target to hit doesn't it? He said, "They got big because everyone got big. If everyone's big, you've got to get big to defend yourself."

Georgia - Yeah. It's interesting that these giant people aren't really around so much anymore. Chris - Not in my case.

Max - There's a few people, like it's generally regarded as a disease now I think, that you do get people topping 7 feet. Huge people do still exist. They're just very rare.

Georgia - Small people still exist though. I'm an example of that, but being big like you said, it's a cost. And also, this is really obvious when you look at the fossil record, when mass extinction events happen, big animals are always the first to go because they're slower breeders. It's easier for them to run out of food. If you look at the animals that are endangered today as well, it's some of the most big ones.

How does diet produce a healthy brain?

Chris - Okay, so the whole idea about what actually gives you a healthy brain and a healthy body, and healthy mind. The bottom line is that that's what food is for. Everyone goes around saying, "Well, we should be taking vitamin tablets and we should be taking this supplement and that supplement." You have evolved and we've just been talking about evolution. You've evolved over millions of years to obtain everything you need for healthy body from that food that you eat and you have evolved to obtain those nutrients in the context in which they're found in nature. In other words, you didn't evolve to get your vitamin C and vitamin E, and your B12, and your folate from a pill. You evolved to absorb those nutrients in the tiny quantities, in low concentrations that they are present in the foods that naturally contain them. To put them into the body in a pill, we don't really have any evidence except in rare circumstances with rare diseases and rare cases of deficiency states where they really are valuable to give these as supplements. There's not really any evidence that these things make a difference above and beyond if you just eat a healthy diet. In fact, there was a big metaanalysis done a few years ago. Goran Bjelakovic, who's a researcher at Copenhagen University, published a big paper where they looked at thousands of cases of people taking vitamin supplements or not. They asked, were these people taking the supplements healthier or not? They in fact, found evidence for a higher mortality rate in the people who were taking certain antioxidant vitamins like vitamin A and vitamin E, compared with people who weren't taking those supplements. What we can conclude from this is that, as I was saying, food is the best source of micronutrients. As long as you have a healthy balanced diet and you don't have a deficiency state, this is probably the best way to be healthy. Trying to adjust that with special kinds of supplements is probably not useful for the average person. Now, if you are a performance athlete and you have particular demands and you're placing particular demands on your body, or you have a particular disease then this is different. But for the average person, a good healthy diet which means a good balance between proteins, fats and carbohydrates, it means a good source of fibre in the diet and so on, all those things add up to making your body healthy. If your body is healthy, your brain will be healthy because at the end of the day, your brain is your most precious organ. It's also your most metabolically hungry organ. Your brain burns off 20 per cent of the energy that you get through any seconds. The amount of energy being burned off in your brain is equivalent to a 20 watt light bulb running above your head. It's a very metabolically hungry organ. But it's living tissue and it runs on exactly the same cellular mechanisms and biochemistry that the rest of your body does. It needs all the same things that the rest of your body does. So, a healthy body does actually make a healthy brain...

Comet 67P-Churyumov-Gerasimenko - image from the European Space Agency - ESA

33:58 - Good morning Philae

The Philae lander, deployed onto the surface of comet 67-P-Churyumov-Gerasimenko in 2014, has begun to to send back data...

Good morning Philae

The European Space Agency's Philae lander, deployed onto the surface of the comet 67-P-Churyumov-Gerasimenko in November 2014, has begun to transmit data Comet 67P-Churyumov-Gerasimenkofrom the comet surface, as Cambridge astrophysicist Zephyr Penoyre explains to Chris Smith...

Zephyr - Some fantastic news came through I think this morning to everyone which is that Philae, the probe that is on the Rosetta mission on a comet that we'd lost for the last few months has turned back on. I don't know how many people remember, but when it first hit the comet, the plan was to harpoon it and stay in place. The harpoons may or may not have worked. They certainly didn't work fully because it bounced, almost enough that it was lost from the comet and settled back down in a deep dark crater. It's just now got - because the comet is orbiting the sun - got far enough rounds that light is reaching the probe and it's turned back on and is transmitting again. This is fantastic because this may well - we weren't sure if this was going to happen or not. We were hopeful, but it's really gratifying to see and we will hopefully get all the data that the mission could've found back to Earth now.

Chris - It's pretty impressive to have managed to land a tiny object on another tiny object so far from home and that actually, it is now sending that data back. What do they hope to learn about the comet that it's on? Why is it important that they've gone there?

Zephyr - So, the really important thing about comets is that most of the water on Earth which obviously, we wouldn't have life without, has come from comets. Working out what kind of form that water is in, what chemicals are in it, which could also be helping to make life. Even possibly if there could be life on a comet itself. There are theories that life has come to Earth via a comet. This will help us probe all these kinds of things, actually being there on a comet, taking some readings...

Water bear (tardigrade), Hypsibius dujardini, scanning electron micrograph by Bob Goldstein

How did insects evolve?

We put this question to Georgia Mills and Zephyr Penoyre...

Georgia - Insects are very strange-looking sometimes. But if you look across the whole animal kingdom, there are some really, really weird ones. Look up water bears, if you get a minute, they're some of the strangest creatures you'll ever see. There's also.

Chris - What's one of those?

Georgia - They're these tiny little creatures that can basically just survive anything. they look like something from a studio Ghibli film. They're like really, really creepy tiny things. but insects did almost certainly are in the same tree of life as all other animals. The reason we know this is from things like DNA sequencing and also from the fossil record. Insect fossils are very hard to come by but there are a few that look like transitions between insects and their close relatives, the other arthropods. And did insects come from a comet? Well, like you mentioned Zephyr, there's the theory that all life came from a comet. This is panspermia. This is an interesting debate but if it did happen like this, it's likely that all life came this way. If a comet arrive now with some exciting new microbes on it, it's likely that the current biology of the planet which is gobble it up.

Chris - Zephyr.

Zephyr - They actually sent some tardigrades - water bears - up into space!, not really planning to get them back down, and they got them back down and found that they were fine! They'd survived the vacuum of freezing cold space absolutely fine!

Coral reef fish

Do fish get thirsty?

We put Jason's question to zoologist (and fish specialist) Max Gray:

Max - The short answer is no. The long answer is that you've got to consider three different types of fish. You've got fish that live in freshwater and then a fish that live in saltwater, and then also in saltwater in the oceans, you've got a separate type of fish. So, sharks and rays, they don't have bones. Their entire skeletons made of cartilage. So, we've got these three groups. Freshwater fish don't actually drink at all. They absorb all the water they need through their gills. So, they're fine. They don't ever get thirsty. Marine fish are what's called hypertonic to the seawater. So essentially, they lose water through their gills to the seawater. The seawater is saltier than their blood. in order to replenish that water, they have to drink seawater and process the salt out. But they live in seawater constantly. They can drink whenever they like. So really, they're never going to get thirsty because they're going to drink tiny amounts of seawater as and when they need it and keep themselves topped up. Sharks and rays are what's called isotonic with seawater. Their blood is exactly as salty as the water around them. All they need to do is adjust the iron concentrations in blood and so, that all happens across their gills and other permeable membranes and they're fine.

Chris - Can I chuck a spanner in the works?

Max - You can.

Chris - What about fish like salmon that are born in freshwater in the river, they go out into the sea, do their thing - eels do this as well - and then they come back to the river they were born in to spawn? How do they cope then?

Max - They're no exception either, but they just have very sophisticated gill membranes that can switch essentially from what is needed in a saltwater environment to what is needed in a freshwater environment. The various proteins and ion membranes involved in their gills will shuffle things around depending on which environment they're in. there is however one possible exception to the idea that fish don't get thirsty and this is fish that breath air. You may have heard of things like the lung fish or the most well-known one I think is mudskippers. They live in very, very poorly oxygenated ponds, shallow muddy ponds and they actually breath better with a very rudimentary lung that they have and they crawl out of the water, splash around in the mud and can breathe air for several days at a time. so in theory, they could spend long enough out of the water that they need to be driven back into the water by a thirst. Whether or not they feel thirsty starts to get into the realms of animal consciousness and that's an entirely separate question.

A pair of In-N-Out cheeseburgers

Would my weight change if I ate a burger while standing on some scales?

Chris - I would argue that, actually, the burger is already mass in your hand on the scales and therefore, if you put it into your mouth, it just turns into mass in your body. There would then be some metabolism, obviously, because you've got to exert some energy to work the muscles of mastication to chew up the burger. And to produce some saliva; you've got to warm your body which means you're burning some energy doing that as well and you presume the burger is going to be a bit lower than body temperature probably by the time you've done your experiment. So there's a little bit of a loss of energy there. So, that means you're going to lose a little bit of mass. Metabolism that's going to carry on as you digest the burger as well, because you got to break it down into its component parts and absorb it. I reckon in the short term, no change. In the long term, there'd be a modest small reduction in mass... Max - How accurate your bathroom scale is?

Chris - Well, that was going to be my bottom line, if you excuse the pun, because I was going to say that actually, you're talking about trivialities. Once the burger goes in, the burger becomes part of you. There will be some losses to the toilet though and so, a certain amount will be absorbed and a certain amount won't be absorbed. And so, you won't get all of the energy turning into mass. But let's assume that none of the burger is wasted. It would all get converted either instantly into sugars that you would burn or fat that you would store, so your body mass would reflect the increase in weight gain owing to the burger...


Why is incest an issue for some animals?

Naked Scientists Chris Smith and Georgia Mills considered William's question:

Georgia - Well, to start with, the reason incest is an issue is because of your DNA which is your internal code. So, your DNA is made from both parents. So, half is from your mum, half is from your dad. When these two pieces are put together, so every gene you have - so for example, let's say my eye colour gene, I have one bit from my mum, one bit from my dad. Say, my dad's one is a bit rubbish and codes for a bad eye, but my mum's is good, I still have a good eye. I don't know why I'm using myself as an example here, but then if I breed with someone from my family, they're likely to have the bad gene too. So, when this assortment of genetics happens in the next generation, they're more likely to have two copies of this bad gene. And therefore, exhibit this terrible trait. If you think about it, there's so many genes across throughout your DNA, the chances of this happening are quite high. Another reason why incest is in general a bad idea for animals is because if populations have quite similar DNA, something like a disease can come along and wipe them all out because there's not enough diversity. I was interested in this question, and I did a little research because I had some pet mice and I remember they were meant to be all brothers. One of them was a sister and then suddenly, I had hundreds of mice. I remember thinking that they just didn't care. But apparently, mice do care. They can actually smell whether they're related to each other. But if there's no other opportunities to mate with someone who's not related, they will just take what they can get. So, incest is an issue for pretty much all animals that breed sexually for the reasons I outlined. Most animals do have ways of telling if they're kin or males get trucked out of group. So, it's less likely to happen. But it does happen more often in nature sometimes.

Chris - I suppose it's worth mentioning that if plants don't have sex and exchange genes and by this, I'm thinking of plants like bananas where they're all clones - if you look at where we get our banana plants from, a sucker comes up from the root or you get a cutting, you make a new plant, but it's genetically identical to the parent plant. We've seen with potatoes as well. They're all genetically clones of each other. All it takes is a pathogen or a bug to come in and exploits or finds a loophole in the defences of these particular plant species and it just wipes out the population. We saw this with the Irish potato famine where a fungus evolved the ability to attack a certain strain of potato. And now, the banana is under threat because we've seen the loss of the Gros Michel banana which are very sweet and very nice little banana to Panama disease and now, the Cavendish banana - the big yellow ones we all buy in the supermarket that we're all very fond of - they're under threat too for exactly this reason. So, sex isn't just important to animals. It's important to plants too.

Georgia - Yup! Anything that breeds sexually which does include plants although they might not look like they do.

A sailfish hunting a group of sardines off the coast of Mexico

Can animals forecast danger?

We put John's question to zoologist Max Gray.

Max - So, John is in good company here. People have been asking this question apparently since the 4th century BC. It's the first recorded documentation of dogs being able to sense earthquakes in ancient Greece.

Chris - When you say sense earthquakes, do you mean predict, almost presage their arrival?

Max - So, this is the question that people have been asking and it's not really very clear. People think that dogs can sense earthquakes way before we can and then if we could somehow tap into that, we might be able to predict earthquakes which are notoriously difficult to predict. So, people have looked at this. People have looked at studies of dogs and other animals going missing. I think it was in San Francisco before an earthquake in the 80's and there were some anecdotal evidence that more animals go missing in the week before an earthquake. Then people have gone away and done a research into this and realised that actually, the robustness of that claim is very weak indeed. But in the early 2000's, somebody did actually get some concrete data about this, a man called Stanley Coren who was doing a completely separate study at that time about hearing in dogs, had a set of kennels with 200 plus dogs in and then as an earthquake happens to happen. He managed to get data on how many of those dogs responded in the certain timeframe beforehand and it was a vast majority. And most of the dogs.

Chris - Responded how? Barking or.

Max - Yeah, they get very stressed. They get nervous, mostly barking, whining, hiding in the corner, that kind of thing. but some of the dogs didn't and it was mostly the dogs that were in some way impaired in their hearing or dogs with big floppy ears that kind of obstruct their ears that way. So, it seems to me that dogs may have the ability to kind of hear the deeper rumblings that precede an earthquake. However, that's not really going to be very useful diagnostically. We have this one piece of evidence. There is again, more anecdotal evidence about it. Maybe cows appear to reduce their milk production slightly before an earthquake. Sharks migrate away to deeper water before tropical storms which seems to be based on a prediction due to the lowering of atmospheric pressure. But we have much better ways at measuring that through meteorology and so, all of this kind of stuff is very, very anecdotal so we don't really have the evidence. Even if we did, is it in any way useful? You can't really use a kennel of 200 dogs as an earthquake predictor. It's a little bit inhumane and you can't tell for sure. I mean, most animals are aversive to things they're not familiar with. They don't like new sensations, new sounds, loud noises, unfamiliar smells, anything. It's called novaphobia [sic], the fear of the new. This is present in most animals. So, there's no way we would know whether it's a prediction of a natural disaster or whether you know something unfamiliar and pungent happens to be nearby that was entirely harmless to us.

Chris - I've heard Novas are quite good cars but there we are.

Industries causing air pollution

How do greenhouse gases warm the planet?

Chris Smith answered this question...

Chris - One has to first of all think about why does the Earth have any kind of temperature in the first place? Well, energy comes to the Earth from the Sun. It does that in the form of heat given out by the sun which is invisible light - infrared and also, visible light because light is energy. That light reaches the Earth. It hits everything on the Earth and the energy in the light is absorbed by the things it hits and those things, because they now have more energy, have a higher temperature.

What normally happens is that the energy is then re-radiated as long-wavelength infrared light back into space. So, what comes in goes out and the Earth stays stable. But if something gets in the way of that re-radiation back into space then the amount of energy in the system goes up. In other words, the temperature goes up. It turns out that certain gases in the atmosphere are very good actually at interacting with long-wavelength infrared light. Things like carbon dioxide; things like water are very good at doing that. So, the rays of infrared come bouncing off the Earth's surface - and off of you - going skywards, but they see a molecule of carbon dioxide, and the bonds in that molecule soak up the energy and stop it going skywards.

As a result, you retain more of the heat close to the ground, which means that things on the ground are more likely to stay warmer. In other words, the overall global temperature has gone up by just a tiny amount but it's a significant amount in energy terms over a long period of time. Therefore, you will begin to shift the balance of energy distribution on the planet because the temperature is on average higher. So, just a tiny whiff of carbon dioxide in the atmosphere - and some more water - will make a difference in a global scale.

Georgia - That's really surprising. I would never expect water in the atmosphere to make this kind of a difference.

Chris - Water is a very, very powerful greenhouse gas. In fact, everyone maligns greenhouse gases but remember that greenhouse gases are good too, because were it not for our atmosphere - were it not for the ability of water and carbon dioxide to retain heat in the atmosphere - then we wouldn't be on a watery warm planet Earth - we would be on "snowball Earth".

It's down to the fact that we have this atmosphere that does retain some of the energy and keeps Earth cushioned and cocooned in a higher temperature than it will otherwise be that we do have this lovely balmy environment that's ideal for us to live in. So, we do need a greenhouse effect, but we don't want to exacerbate or exaggerate the greenhouse effect in an uncontrolled way, because that means the environment that has kept us nurtured us and nourished us, will begin to go off kilter and that could have unforeseen consequences...

 Artist's concept of what a future telescope might see in looking at the black hole at the heart of the galaxy M87. Clumpy gas swirls around the black hole in an accretion disk, feeding the central beast. The black area at center is the black hole...

What is it like to fall into a black hole?

We put this question to Cambridge astrophysicist Zephyr Penoyre...

Zephyr - That is a very difficult question. What a black hole is, is an object that's just so heavy that light itself can't escape from it. Now, we're often told that light isn't affected by gravity. As far as things on Earth are true that is completely true. The amount of gravity, the amount of mass needed to actually affect light is huge. But black holes are remnants of massive stars that have collapsed into a very small space, and they're so dense, they're so heavy, that even light cannot escape. What actually happens when something passes, what we call the event horizon - the distance away from the actual body which light can't escape from - is very, very unclear and we may never know because it's impossible for anything that we send through, past that point, to ever come back because light - the fastest traveling thing - even that, cannot escape. Likely, it wouldn't be a particularly pleasant process. Even as you approached it, you get stretched and stretched, and stretched.

Chris - Would you feel that though? Would you actually feel yourself being pulled?

Zephyr - You'd be pulled by potentially, depending on how fast you approach the black hole. You might be pulled kind of string-thin, you might be torn.

Chris - Over what timescale would it take as you felt yourself - because literally, you're feeling a force on your legs. It would be like being put on a medieval rack then? Is that what you're saying? You would literally feel yourself being drawn out.

Zephyr - Yes. The quicker you go into the black hole, the better it is for you in the process of going in.

Chris - [Laughs] - That's one way of putting it...

Zephyr - The quicker you go in, the less stretching the time you're stretched.

Chris - So, a really agonising approach would be a really slow journey into the black hole? 

Zephyr - If you spiralled around for years and years, you will slowly get longer and longer.

Chris - And then what would happen?

Zephyr - Then that is where it gets really unclear because there are things like absence of a black hole, it doesn't seem like there's any force to stop the mass at the centre collapsing more and more. And so, you'd expect the density at the centre to go up and up, and up, faster and faster and faster, and become infinite. And that must be impossible, because if there was infinite density, it would have an infinite force and everything, everyone in universe will be sucked in. So we're very unclear on what exactly is stopping that happening in the centre of the black hole. There are theories even that time must slow down and stop at that centre, so that we can't reach this infinite density...


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