Why Isn't Everyone Ambidextrous?

13 July 2018
Presented by Chris Smith.

What is a near-death experience? How do you stop mosquitoes getting into water tanks? Why isn't everyone ambidextrous? What is Schrodinger's Cat? Why does elephant urine take so long to dry out on roads? How do we measure the distance to far away stars? Plus, finding a far flung source of neutrinos...

Eusebius - Now today's science story that we're going to start with, I can hardly even say it. Normally, I can at least fake gramatically reading the sentences on my page. But it does sound really fascinating and ghostly: subatomic particles that can travel, unhindered at that, for billions of light years.

Chris - Yeah, this is a pretty interesting paper. What scientists in Antarctica, using an appropriately named detector called the Ice Cube Observatory, have detected are neutrino particles issuing probably from about 4 billion light years away and possibly a giant black hole. Now let me wind you back a bit.

In the 1930s scientists proposed that these particles called neutrinos must exist. They're absolutely tiny, they're subatomic. They are massless, they don't weigh anything. And they travel at nearly the speed of light. They're also uncharged. And what this means is that they can travel through space, across time, at blazingly fast speeds, and they don't interact with anything. That means that they're unhindered and unfettered in their passage through space by other stuff, like gas and dust. In fact there are probably trillions of neutrinos whipping through every single one of us every day. So how do you detect them then?

Well that's where the Ice Cube Observatory comes in. And what this group did, a number of years ago, is that they drilled holes which are nearly three kilometers deep in the ice in Antarctica. And this pattern of 86 holes, which are nearly three kilometers deep, have dangling down them cables, and these cables are arranged in a hexagonal pattern and they have detectors on them for light. Now, when neutrino particles come streaming in from space, and they pass through the nice, clear ice of Antarctica where these detectors are, occasionally very very occasionally, they interact with a particle in the ice. And that interaction gives a brief flash of light and these detectors can therefore plot what the direction of the flash of light is and therefore infer from that the trajectory of the incoming particle. So that's why Ice Cube, which is built in a cubic kilometer of ice in Antarctica, that's what its job is to find these neutrinos.

Why they're interesting is we've proposed them since the 1930s. They were first detected in the 1950s and now we're trying to work out actually where they're coming from, because we know that the sun produces them. We know that radioactive decay produces them but there are also very high energy particles streaming in from space. Where do they come from? What's their source? Could they open up a new vista in astronomy for us because, because they dont get absorbed by things and they're hard to detect can they tell us about distant things going on and therefore we can understand more about how space works. And that's what this announcement this week is, they found a very powerful energetic neutrino some million times more energetic than anything we can make on Earth in one of our particle accelerators. It seems to have come based on its trajectory from a blazar which is a structure in the universe about four billion light years away where there's a very active star forming region, where there's a supermassive black hole. And what the researchers think is that these particles are being produced when black holes get, sort of, cosmological indigestion. They ingest material they burp up lots of jets of material and that jet material going so fast them rams into itself and produces collisions that then produces neutrinos. So this is an interesting proof of concept, it's announced this week in the journal Science by a big team and it gives us a new insight into possibly what this structure out in deep space is doing but also really how the universe works.

Eusebius - Fascinating. Bahcausy, good morning to you. Welcome to the show.

Bahcausy - Good morning gentlemen. My question concerns near death experience. I have read books on this and was quite taken aback by the similarities that I personally experienced back in 1965.  And I just wondered how true, or if science has actually explored that terrain?

Eusebius - Okay. Chris?

Chris - Well this is a well trodden path. People have been speculating and investigating the science of the near death experience for decades. And in fact for a long time it wasn't really subject to proper scientific scrutiny but in recent years it has been. And scientists have done a number of experiments by doing things like putting written pieces of paper or objects in places where patients in operating theatres wouldn't be able to see them unless they did what they said they did, which was to float off the operating table when they died, look down from the ceiling of the room why they'd go up there when they died, don't know, but there would be objects that they could see from that vantage point but not on the operating table. When patients have incidentally reported near death experiences and said they floated up to the ceiling of the room, the researchers have asked them well did you see anything and they didn't. So this argues that they weren't really up there on the ceiling of the room they were just having the view or the perception that they were. Now what we think is going on when people have near death experiences is that because you are near death or you have physically died for a short while perhaps, for instance, you've had a cardiac arrest, and so the blood flow has stopped your brain temporarily. Perhaps when this happens to you because you're so unwell this affects the neurochemistry of your brain. And so in the same way as when you dream you create an alternative reality inside your head perhaps this state of illness, this state of hypoxia, low oxygen, creates a temporary state of, sort of, dreaming or alternative reality created by your brain just like you dream. And when you then wake up in the same way as if you're woken up in the middle of a dream you can remember glimpses or snatches of that dream perhaps that's what's happening in this circumstance but we dont think there's really any good strong evidence for people who have near death experiences. They're real experiences to those people but we dont think there's anything spooky going on. We think this is a phenomenon created by the unwell nervous system.

Eusebius - Mike, good morning.

Mike - Morning. My question is that I dont have gutters on my house, so the rain when it does rain pours off. Now in the winter we haven't had any rain recently, but in the winter if rain falls, it falls into open containers that I keep to water my plants. However in the summer the mosquitoes breed in this water. I want to ask Chris is there something I can put into this mosquito breeding water to kill the mosquitoes but to make the water still safe to put on my plants.

Chris - Yeah, it's a really good point. You can hear Eusebius doing his emails in the background there. Or are you checking up on me again, Eusebius?

Eusebius - I am indeed.

Chris - It's a really good point this, because in many countries where mosquitoes spread not just malaria but they spread other things like yellow fever, dengue, zika virus, there are police forces and members of public health who will go round and they look for containers that mosquitoes can breed in and they can fine people if they do this. So this is a big issue because mosquitoes especially Aedes mosquitoes are very good at finding pools of stagnant water even if it's a small amount and laying eggs in them. Now it's also very important to conserve water and no one knows that better than the residents of Cape Town at the moment for example. So how do we sort of satisfy those tensions? Well one sensible approach because, believe it or not in Britain, people have also got mosquitoes breeding in their water butts. So one thing that people are doing is being encouraged to put a fine mesh work over the access point to the bucket. So you buy some thin muslin where, obviously, water will go through that no problem but mosquitoes won't. And if you can keep the mosquitoes from having access or contact with the water surface they can't lay eggs in the water and therefore they can't breed. So my advice to you would be to put the containers there because collecting the water is very important for just use of water but keep the mosquitoes out with muslin.

Mike - Oh okay. Thank you. Thank you very much.

Eusebius - Thank you Mike much appreciated. Maurice, Good morning.

Maurice - Good morning. Eusebius, I would like to ask Chris: Why aren't all human beings ambidextrous?

Eusebius - That's a lovely question. Chris?

Chris - Yeah, I'd give my right arm to be ambidextrous. That's an old chestnut, isn't it?

You know, I asked Chris McManus this, who literally wrote the book on this subject. Chris was professor for medical education at University College London and won the Wellcome Trust Book Prize for his book 'Right Hand, Left Hand' and won the Novartis Prize for the same title. It's probably the best book I've ever read on a, sort of, general science topic but it explores handedness, not just as humans but from the ground up. Handedness of particles and atoms and molecules right up to us. It's a really excellent science book 'Right Hand, Left Hand'. I'll tweet out a link to it after the program for anyone wants to follow us on Twitter at NakedScientists. I'll tweet them out because it really is an exceptional book. And I asked him this a number of years ago and he said well actually the interesting thing about humans is that while we do have a dominant hand, and we dont know why we have handedness but what we do know is that it's all to do with which side of your brain is dominant. And because one side of your brain controls the opposite side of your body, the dominant side of your brain seems to be the part of your brain where language is based and in the vast majority of humans, 90 percent of us, language is in the left side of our brain. And that means the dominant hemisphere of our brain is the left side and therefore your dominant hand that you prefer to use is your right hand. That's not to say though that you can't become very good at using the opposite hand. And we probably become very good at doing things with our right hand because we practice because we prefer to use it, but actually in people who have a disability or can't use their preferred hand and they have to use the other hand. A friend of mine broke her arm for example, and because she couldn't use her preferred hand she had to learn to write because it was exam term at the university and she had to learn to take lectures and do exams with the wrong hand and she said although it felt terrible to start with, she actually became quite good and could write quite neatly with the wrong hand, quite quickly, and until it became okay to be left handed were you know in 100 years ago people with left handedness were regarded as grossly abnormal or something wrong with them and we used to punish these people and tie their hands behind their back and stop them from using their left hand. Then, in the modern era we now know that people who are left handed actually because they were forced to become quite adaptable to a right handed world because they were in the minority, they actually became quite good at using the wrong hand their right hand to do things to fit into our world. So actually we are very very much ambidextrous, that was Chris McManus' view but we just have a preferred hand to use when we do most things and we're not alone. There are many animals that do have a preferred side. Horses prefer to run round the track with one leg going as their outer leg compared to the other. Some birds prefer to use one particular claw or set of talons to pick apart their prey.Hangaroos and wallabies have a preferred hand to use. Scientists have done experiments watching them in the jungle in the bush in Australia to see which hand they prefer to use. So there are lots of species that have a preferred side but humans seem to be the most extreme, and it's mostly 90 percent of people are right handed and they have been ever since cavemen were wandering around on Earth because we know this from cave paintings from studies done in France that people were painting with one hand and using the other as a template to hold on the cave wall. So it's not a new phenomenon either.

Eusebius - Theo, good morning.

Theo - Morning. I just wanted to find out more about Schrodinger's cat expiment and what exactly that has to do with cats?

Chris - Okay, well this is that sort of uncertainty situation where, the thing about quantum mechanics is it's really weird. And Niels Bohr, who is one of the forefathers of quantum mechanics, said if you're not baffled by this then you didn't understand it. Because the thing is when you shrink things down to the very very small they begin to behave very unusually and we think we understand the world on the scale that we are, the size of a human. But when you shrink down to the size of individual atoms and molecules things don't behave themselves. They behave in a very strange way. And there's a phenomenon called entanglement where, if you can imagine experiments, say I have an atom, and that atom can issue two photons one going in one direction, and one going in the opposite direction. Now that atom had made those two particles but by some strange phenomenon that we don't understand, they become inextricably bound together. So even if they end up on opposite sides of the universe, if I examine one of the photons I immediately know something about the other photon and if I change the photon that I can see, I immediately change the behavior of the other photon on the other side of the universe. So there's something weird that's connecting these entities together and that's entanglement. Now the whole thing about Schrodinger's Cat is that if you have a cat in a box, until you measure the cat in the box you dont know if it's alive or dead. So the cat is therefore in both conditions; it's both alive and dead until you look, you don't know. But then when you actually open the box you seal the fate of the cat. And if the cat has a counterpart which is entangled with it on the other side of the universe you also change the fate of that cat. Are you confused yet?

Eusebius - I'm suitably baffled, therefore, I comprehend

Chris - Therefore you understand. Exactly my point.

Eusebius - Julie out in Stellenbosch, good morning to you.

Julie - Good morning. I have a weird question. In Kruger National Park, you have tarred roads. If there's a sudden downpour of rain the road is dry within a few hours. But if an elephant passes and urinates on the road, wees on the road, that stays there for a long time, even though the dung is dry. Is it the tannins in the seeds they eat, or why would that be?

Eusebius - Okay. Chris, did you manage to hear that question?

Chris - Yes, I did. I'm not a coprologist or someone who's an expert on urine on roads, especially from large pachyderms, but I'll have a go. I think you're probably heading in the right direction. I mean there's a range of different things in urine and faeces and so it's possible that they do get onto the road surface, the heat of the road surface then bakes these chemicals and makes them into a very hard insoluble material which glues itself onto the road surface, and when the rain comes down it doesn't actually wash those things away so you leave a residue there. I suspect that's the reason, you got things which are poorly soluble and things like tannins as you say which are bound up with that and they probably are not easily washed away. If you were to go along and scrub them and get them away from the road surface with a scrubbing brush, not that you're going to bother doing that in the Kruger Park, something would come and eat you. But then that probably would get rid of them but I suspect that's the reason but it's the speculation if anyone knows better. Do please tell me.

Eusebius - Mark, good morning.

Mark - Hello. Yes, I need to understand Chris, how they do manage to measure the distance between, for example, our planet and our star, which is you know, light years away?

Eusebius - How do they measure the distance between stars.

Chris - There's a number of ways to doing this and in the old days people did this by something called parallax and you can demonstrate this for yourself how they did it very simply; if you hold out your arm in front of you straight out in front of you with your thumb pointing outwards like you're trying to be a hitchhiker, and if you close one eye and use your thumb to cover a distant object, and then you open the other eye and close the first eye, you'll see that the object is no longer covered by your thumb. So it appears to have moved. Now the amount it moves is proportional to how far away your object is. So how do we do this on the scale of the Earth? Well what the astronomous would do is they'd look at a distant object and they'd make a measurement when the Earth was on one side of its orbit. That's like you looking with one eye. And then they would wait till the earth was on the other side of its orbit and look at the same object and it would appear to move, and the amount it's moved is proportional to how far away it is. So that's one way of doing it. The other ways of doing this are that we can use what's called Stellar Candles. An interesting observation made by a lady called Henrietta Leavitt in the late 1800s, early 1900s. She was working at Harvard, and she helped Hubble actually discover that the universe was expanding. She discovered these things called Cepheid variable stars. And what we understand is that different stars of different sizes puff up and shrink at a very predictable rate. And that tells you how big they are, and if you know how big they are you know how bright they are. And if you know how bright something is you know that because light spreads out as it comes from the source to us, the further away something is, the brighter or dimmer it is. And so you can use the regularity of the star puffing up and shrinking to work out how big it is. So you know how bright it is and if you measure the intensity of the light you can work out how far it is. So when you see distant smudges in the sky you can use those stellar yardsticks as well to work out the distance to the stars so those are two simple ways of doing it.

Eusebius - Thank you so much for sharing your knowledge with us.

Chris - It's a pleasure.

Eusebius - We'll do it again next week, of course.


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