Q and A: Disney, Dark Matter and Deja Vu

You have questions, and our panel of super scientists have the answers!
12 June 2018
Presented by Chris Smith
Production by Katie Haylor.


What is déjà vu? Why do I get angry when I'm hungry? Why do I remember every Disney lyric, but can't remember how to set my oven? Materials physicist Jess Wade, neuroscientist Philipe Bujold, animal behaviour expert Eleanor Drinkwater and physicist Francesca Day join Chris Smith to answer a brilliant barrage of scientific questions...

In this episode

Goldfish in pond

06:51 - Can I train my goldfish?

Goldfish might be smarter than you think

Can I train my goldfish?

Chris Smith put the question from Liz to animal behaviour expert Eleanor Drinkwater, who explained there's more to goldfish than meets the eye...

Eleanor - The answer is yes you can train your goldfish. I had so much fun researching this question. And it turns out that there are How to Train your Goldfish kits available online if anyone does want to train their goldfish. And, even better, I’ve found out that in the 60s, 70s era of animal behaviour, they were using goldfish as a model to understand what effects alcohol might have on learning. So they set up an experiment which they tried to teach the goldfish to go into the darkest part of the tank, and they found that adding alcohol to the tank made them learn better. But, as is the way with some of these studies, it was unclear as to why this was the case.

Chris - Well, you know goldfish are quite well adapted to booze because they live in, especially freshwater environments, they live in ponds that freeze over the wintertime. And when they freeze, they run out of oxygen or they’re very low in oxygen so their metabolism shifts towards the same way as yeast. When you grow yeast in the absence of oxygen you get booze with your grape juice. Well, fish actually make their ponds a little bit alcoholic when the wintertime comes and they freeze in. And I interviewed the scientist who discovered this, and I said well could this be a useful way to make alcoholic beverages in the absence of yeast? And he said it would take a very long time. About 20 years for a goldfish in the tank to actually make enough. But that might be one reason why that research failed.

Elenore - Yeah. In fact, that’s one of my favourite facts about goldfish that you’ve just come up with. I just love the idea that under stress you start producing ethanol. Can you imagine how much better being stressed would be if that was the case in humans?

Chris - Life would improve enormously.


Philipe - I was wondering actually, you were mentioning over winter they have to survive for quite a few months I, unfortunately, have never had that much luck with goldfish. They’ve never really survived that long. I was wondering, how long does it actually take to train them? Because mine, on average, I would say about four or five months when I was a child. Does it take longer? Does it take a shorter amount of time?

Chris - And how do you train them?

Philipe - Exactly.

Eleanor - The scientific study is in the 60s and 70s, unfortunately, you electrocuted them to train them not to do things. But the nice kits that are available online, it seems to be a bit like clicker training in which they give them food rewards, which sounds a much nicer way of doing it than the 60s and 70s way of giving them electric shocks.

Chris - Because that’s a myth. Philipe was talking about myths earlier and people were only using 10 percent of their brain, people say goldfish have a five second memory of something but, actually, they have a really really good memory don’t they? Because people have done research showing that you can train them to find a hole in a net. This is Culum Brown, I think, from Australia. You can train a fish to find a hole in a net by using various visual cues, and then a year later come back and show them the same net and they immediately find the hole, so they’ve remembered. So they clearly do have very good memories. And if you think, fish have to live a long time and find their way over complex navigations and migrations in some cases, so they must have a pretty good memory so they ought to be trainable.

Eleanor - Yes, exactly. I think fish often get a bad rap just because we can’t see them. We tend to think about animals like dogs and cats just because we see them all the time; whereas we don’t really see fish so I think they’re often get a bad rap in our ranking of how intelligent animals are.

Chris - So, fish are clever. You’d batter believe it.

Jess - Can I just temporarily debate that. We put them in tanks so we can look at them all the time! I don’t think we don’t see them.

Eleanor. No, no. I’m not saying that we never see fish but I think that, in general, the kind of public awareness... For example, if you think about the ethics of animals, people are very aware of not causing pain to animals.

Jess - Oh yeah.

Eleanor - But it was only in the last few years that we proved that fish feel pain. And the fact that that was only discovered like a few years ago is just mind boggling you know. I think it’s perhaps due to the fact that some people are a little bit less connected to fish than perhaps terrestrial animals.

An artist's impression of a black hole accretion disk.

10:44 - What would Earth look like from inside a black hole?

Things get very strange indeed inside a black hole, but what would Earth look like?

What would Earth look like from inside a black hole?

Chris Smith put this question to physicist Francesca Day, who told us more about the weirdness that goes on inside one...

Fran - This is a really interesting question. The first thing I want to say is it is actually possible to survive for a short period inside a black hole. The entrance to the black hole would usually be defined by what we call the event horizon, which is the point where if anything, including light, crosses the event horizon it can never come out again because the black hole’s gravity is too strong.

Chris - That’s why it’s called a black hole, isn’t it? It’s bending space so much that not even light can escape.

Fran - That’s right.

Chris - The light falls into the hole and never comes out again.

Fran - Yes. Once we cross the event horizon we’re doomed to fall into the black hole. But, for all we know, we could be crossing an event horizon of a very large black hole right now and we wouldn’t necessarily feel anything. But, if you tried to look out of the black hole to other things, for example, the light would be so distorted and bent that you wouldn’t really be able to see a clear image of anything outside of the black hole.

Chris - So if I went in backwards and I’m looking at planet Earth as a blue marble in space in the distance. Let’s imagine I could see it that clearly. As I went over the event horizon of the black hole, because there’s still light coming in with me from the Earth that light would begin to stretch, would it, and I’d see a sort of distorted image?

Fran - Yeah. It would be warped, colours would be warped as well because the black hole sort of stretches the light.

Chris - So the answer to the question is then, is you would see it, but you wouldn’t see it clearly?

Fran - Yes.

Chris - Philipe?

Philipe - So would it be a bit like, going back to the goldfish, a goldfish looking at us through air?

Fran - Yeah, maybe. That’s nice how it all links up isn’t it?

Philipe - Definitely.

Chris - Anyone would think someone put this show together.

A brain sparking with electricity.

12:37 - What is déjà vu?

What exactly is déjà vu? Have we asked this before?

What is déjà vu?

Neuroscientist Philipe Bujold was asked this question from Marika by Chris Smith, and told us all some theories about déjà vu...

Philipe - I’ve had that question a few times. Actually, unfortunately, I can’t give you a hundred percent certain answer because we still don’t know what a deja-vu actually is. We have a few theories though and that involves a lot of the memory circuits. The hippocampus is involved in encoding the context in which memories are formed but right next to that there is a part of the cortex called the rhinal cortex. And that rhinal cortex is divided, but it’s main role would be to recognise what’s familiar. And so one of the big theories at the moment is that this rhinal cortex needs to fire inline with the hippocampus, which encodes context, and then that opens up a memory, so it will fire the network that’s associated with the specific memory. If, unfortunately, you don’t have that context firing, you just have that feeling of familiarity, then that might be why you have a deja-vu. So we’re not sure. The only really studies that have been done into that are starting to show us that that’s the case. The stimulation of these parts of the brain that also seem to create fake deja-vus, if you want, but we still don’t know why it would happen. It seems to happen more in young people, or it might just be that young people are more aware of it because we still have a lot of our brain intact because ageing hasn’t started.

Chris - It happens to me when I’m tired. Does that make a difference?

Philipe - Yes. So stress and fatigue actually are huge links to more deja-vu experiences.

Chris - I suddenly have a sort of flash or recollection and a feeling of oh, I’ve thought of this before and it’s a memory that’s fleeting. It’s there and then it’s gone and I can’t get it back. But it only happens when I’m really tired. After night shifts and things when I was a junior doctor, it would happen quite a bit.

Philipe - Yeah, exactly. So that’s probably when it would happen, especially for undergrads actually. I think it’s something like two thirds of undergrads seem to have experienced a deja-vu feeling.

Chris - Oh, don’t remind me.

Chris - Fran?

Fran - I used to be absolutely convinced when I was seven or eight that a deja-vu was something that I’d dreamt but I’d forgotten the dream, so I was sort of remembering from a dream. Is that at all plausible?

Philipe - I wish I could give you an answer. I don’t actually know. I would not think so because our brain seems to be very adapted to not remembering dreams otherwise we would have a lot of issues functioning in daily life. You already have to remember what’s happening for 12 to 16 hours every day, if you have to remember everything that’s happened overnight also that would be a big issue.

Chris - There are some people that do though aren’t there? These people who have some kind of savantic behaviour and can remember an excruciating episodic detail everything that’s happened to them throughout their lives.

Philipe - Yes. So it does happen for some people. That is fortunately not the norm because it is, like you said, excruciating for these people, but it happens in some cases. I wouldn’t be able to tell you why it happens but it does happen, yes.

NASA's Curiosity Rover

16:46 - Have NASA discovered alien food on Mars?

Organic matter has been found on Mars, what does this mean?

Have NASA discovered alien food on Mars?

The Curiosity Rover has found organic matter on Mars. Chris Smith talked to Naked Scientists Podcast panellists Jess Wade and Philipe Bujold to get their thoughts on the mission, and what is might mean for the future...

Chris - I just want to ask everyone. Did anyone catch the news recently that NASA think that they have got the best evidence yet that there may have been life on Mars, or at least they think they’ve found food for aliens? Did you see this, this paper in Science?

Fran - Yeah

Chris - The Curiosity mission which has found this interesting material?

Jess - I saw it so I’m hoping you guys saw it too!? NASA reported that they’ve actually found these organic small molecules on the surface of Mars. This is kind of crazily exciting because Mars has incredibly strong radiation. They have a really really thin atmosphere for whatever reason. They don’t have a magnetic field interestingly, and that is the cause of their very thin atmosphere. So they’re being bombarded by particles from the Sun and cosmic rays from Space. And what you wouldn’t expect in that kind of situation is for there to be any kind of organic material that could possibly survive. And Curiosity went up a long long time ago and it can only see so far. Curiosity can only dig about 5cm of the surface of Mars, so it’s particularly exciting that within that 5cm you have these organic materials. And kind of the future of space travel to Mars in 2020 there are going to be three big missions: NASA, ESA and China are going up. And the ESA drill, the European Space Agency one, can drill 2 metres into the surface of Mars. So everything we saw in this 5cm - wow crazy exciting, this is mind blowing - but imagine what we can see 2 metres further down where this radiation doesn’t hit, and that’s just so cool.

Chris - Philipe?

Philipe - Going back to the 2 metres down. Would it be possible basically that the tiny particles they’ve found now would be particles that were much bigger and got degraded over time, so more complex organic molecules?

Jess - Yeah, it could be. I mean these are kind of little segments of organic materials that we’re really interested in. I guess looking further down we’re interested in what kind of rocks are there and how similar they are to ones that are on Earth. But certainly the kind of science payload of all of these missions is so cool, right. They drill down, they collect this tiny amount of material. They take it into what looks to us like an egg box and then in there they have a raman spectrometer. They can do mass spectroscopy. They can do all these crazily precise measurements to work out exactly what that is.

And the funniest thing is there was a boy during my PhD, doing a PhD with me and he was looking at one particular small molecule, one particular part of a polymer. And the whole time he was looking at this and were were like, "you are so boring right! Get a new material, that is the most boring thing ever!" And now he’s working at NASA, at the Jet Propulsion Lab, programming for the new Mars rover and this particular molecule was the one they found!

A green laser

19:17 - How do lasers work?

They're the stuff of sci-fi, but how do lasers actually work?

How do lasers work?

Chris Smith asked Deirdre's question about how lasers work to materials physicist Jess Wade, who shined a light on the topic...

Jess - Oh, this is a great question Deirdre. Everyone loves lasers right, along with slime. They’re the second best thing in physics. Lasers work because we have atoms and inside an atom are some protons and neutrons, which is what Fran studies. We’re more interested in the electrons in material science, and what we need to do is in a laser is we need to excite one of these little electrons up to kind of excited state we call it, but it’s really unstable in this excited state. It’s like you give a child loads of slime to play with and they suddenly go ferociously energetic.

Chris - Loads of sweets!

Jess - And then really quickly it needs to stabilise, so it emits some light to get back down to its ground state. And you can do a really clever thing where you trap loads of atoms together so that when that one little electron jumps down and emits its light it excites another electron that’s nearby it and makes that emit its light also. And you have this kind of cascade affect where it keeps happening and you can do that by trapping these atoms between mirrors or something clever. What’s really exciting about laser light and why physicists like it so much is that little jump that the electron makes. That energy that it gives out is really specific to the atoms that you’re exciting. So laser light is only one colour, it’s only one energy and that lets us do all kinds of clever physics because we can then use that laser light to excite different atoms which absorb that particular energy, and it’s also super focused. You get these laser beams. You have a light bulb that gives out this really diffuse light but laser beams come at super focused, and we can keep them focused for a very very long time.

Chris - And, of course, by using different flavours of atoms you can get different colours of light that have different applications. Because if you want to do say medical imaging or you want to burn bits of tissue, you want a laser that will interact very well with tissue but not other things?

Jess - Exactly. And it’s very similar to fluorescence. So fluorescence is this thing where we excite an atom and very quickly they emit light and it happens over a very short timescale, and when it happens it’s gone. You can tune that fluorescence, you can tune that colour to whatever atoms that you are exciting.

Chris - Eleanor?

Eleanor - So talking of applications, something I’ve always wondered about lasers, taking this to a really highbrow level, I love Star Wars and one of the weapons they use is this kind of laser shooters. Is that ever going to be possible having kind of weapons that are lasers?

Chris - Do you have nefarious intent or something?

Eleanor - Of course not. I don’t know why you would suggest that.

Chris - When working with the ants becomes too much.

Eleanor - Well, you know.

Chris - It’s gone from burning them with a magnifying glass to a laser blaster!

Eleanor - I would never do that.

Chris - A laser blaster. Jess?

Jess - If you wanted a laser blaster you can make a laser blaster, right. If you get a very powerful laser you could fire it at something. You can pop balloons with certain lasers. You could certainly blind yourself with a laser. The majority of time spent at the beginning of your PhD in materials is trying to complete laser safety courses so you don’t blind any of your friends with a laser. So I don’t think you’re far off the Star Wars thing if you want one.

Box of Donuts

22:07 - Why do we get "hangry"?

We often get very angry when we get hungry, but why might that be?

Why do we get "hangry"?

Chris Smith put this question from Vy to Philipe Bujold, who gave us food for thought...

Philipe - Well Vy, that can be explained with science. Actually, the explanation is quite simple. When you get hungry your glucose level in your blood, goes what your brain would consider dangerously low. It doesn’t take much to reach that level because your brain, like I said earlier, actually used about 20 percent of your energy demand every day. So as soon as it senses lower blood glucose levels, it starts to release the same hormones that you would get when you’re angry, anxious, or stressed. So cortisol and adrenaline get released at the same time and these are surprisingly, or not surprisingly in this case, the same neuropeptides or neural transmitters that are associated with anger.  So there is actually a scientific reason for people becoming hangry, if you want. And fun fact: it’s actually worse for men. Usually the stereotype would be oh people, everybody gets angry but actually men have more of these receptors so, even though they might not show it, it actually affects men more.

Chris - And the cure is an easy remedy? Eat something!

Philipe - Exactly, yes. For sure.

Chris - And are some foods better than other because sugar is very rapidly absorbed isn’t it? So is that the best cure for hunger induced crankiness or are there better things?

Philipe - Well you see, for me I would go with chocolate.

Chris - Eleanor’s laughing.

Philipe - I’m not sure it works for everybody but yes, you want to get that blood sugar level really high, really quickly. You don’t want to crash however, so the solution I found is to just keep eating more chocolate.

Chris - Eating more chocolate.

Philipe - Exactly. And never stop.

Rusted Car

Why do some metals rust faster than others?

Val wanted to know why some metals rust faster than others, so Chris Smith put the question to materials physicist Jess Wade...

Jess - The technical term I think is corrode. Rust we only think about iron so iron rusts and goes that typical kind of rusty, bronze colour so that’s right. And corrode is when metals interact with oxygen, usually in the presence of water, and it’s because oxygen is super reactive; the oxygen that’s in the air. It’s a really hungry little gas. It needs to fill two electron spaces so it attacks these metals, which are kind of seas of electrons, and tries to pull them off that to react with it.

In some metals this seems to happen very quickly, so in things like iron. The interesting ones are the things where it doesn’t happen and aluminium actually super quickly, aluminum that we use in cans and in an awful lot of products, covers itself with a very very strong layer of aluminium oxide so that makes it look like its not rusted, but that layer is super tough and sturdy and no more oxygen can get through it. So we can do that.

We can do other kinds of clever things with metals where we blend them with other metals to stop them from corroding. I think the ones that are really interesting are things like gold and platinum, which have this sea of electrons. You know gold is really good at conducting electricity, which is why we use it so often and it’s beautiful if you buy expensive jewellry. But that doesn’t seem to rust, so the kind of interesting questions are why is that not happening? And I think that’s much much more complicated than we think. It’s a kind of quantum chemistry question why it doesn’t happen in gold.

But certainly all metals do seem to rust. They want to get back to their kind of state where we found them in these mountains and when we started refining them in the first place. So it’s a rate: you can look at a table to see which will rust faster.

Chris - You can make gold dissolve, but you need a mixture of all of the three sort of king acids, don’t you? Nitric, sulphuric and hydrochloric acid. Aquarega I think isn’t it to dissolve gold and it’s pretty horrible stuff?

Jess - Yeah. I don’t advise doing that at home.

African elephant

Quiz: Who's faster: Usain Bolt or an African elephant?
with Dr Francesca Day - University of Cambridge, Mr Philipe Bujold - University of Cambridge, Ms Eleanor Drinkwater - University of York, Dr Jess Wade - Imperial College London

It's time for Chris Smith to put our panel to the test. Team 1 is Jess Wade and Philipe Bujold, and Team 2 is Francesca Day and Eleanor Drinkwater...

Chris - Before we continue with your questions from people at home, we’ll first of all ask some questions of our panel here that we wrote earlier to test their mettle.

So we’ll have two teams: Philipe and Jess, you’re going to be team 1, and Eleanor and Fran, you're going to be team 2.

Because it is a World Cup year, we’re feeling pretty sporty, so we’ve got some speedy inspired questions to kick off with… Did you see what I did there?

Team 1, Philipe and Jess: And talking of round ball-shaped things - there’s the sport link: planets - which goes by more quickly: a day on Venus, or a year on Mercury? What do you think?

Philipe - You’re the physicist, I’ll trust you on this one.

Chris - What’s shorter?

Jess - You can take it. Okay, let’s go with a year on Mercury.

Chris - You’re going with a year on Mercury.

A: A Year on Mercury
A day on Venus is roughly 116 Earth days long, a year on Mercury is roughly 88 Earth days. Venus turns very slowly.

Team 2 - Eleanor and Fran : Which is happening faster, the growth of Mount Everest or the separation of the Earth from the Moon?

Eleanor - That is a great question which I’ve never thought of before.

Fran - I have no idea. I don’t even know if Mount Everest is growing. Is it growing?

Eleanor - I think it’s growing. Yes, it’s growing. I’m going to go with Mount Everest.

Fran - Yeah, my instinct is Everest. Mount Everest.

Chris - Okay, you’re going for Everest.

A: The Moon
Everest is growing by 4 mm a year, the Earth and Moon are separating by about 4 cm a year. That’s because the Moon is gaining angular momentum from the Earth because the Moon is going round the Earth and the Earth is turning inside the Moon. That’s why we have tides of course because the water on the Earth is being attracted by the Moon. But because the Earth is turning inside the orbit of the Moon. That bulge of water on the surface of the Earth close to the Moon is slightly ahead of the position of the Moon in its orbit and it’s dragging the Moon round with it giving some of the Earth’s spin energy to the Moon, accelerating the Moon so the Moon is, therefore, moving further away from the Earth progressively by up to 4cm a year. And we know that because of a laser, which Jess told us about earlier which is being bounced off a mirror which is on the Moon’s surface put there by the Apollo missions. Or, if you believe the conspiracy theory - it just got there.

Team 1: You’re in the lead at the moment team 1. Which is faster, Usain Bolt or an African Elephant? You can even try what happens if Usain Bolt is chased by and an African Elephant if you want to consider the question in a slightly different way?

Philipe - I was going to say, that might change the answer.

Chris - It doesn’t does it in the grand scheme of things. Unless he gets caught.

Philipe - I have seen many documentaries of elephants running.

Jess - I’ve seen Usain Bolt running. And he’s very fast.

Philipe - He is extremely fast.

Fran - You’re the elephant expert.

Chris - He’s a neuroscientist.

Philipe - I can tell you from their cortex that it’s quite heavy so they might go a bit slower than Usain Bolt who has a smaller brain to carry around. So I’ll go with that neuroscience answer.

Jess - Okay.

Chris - If I’m honest, I don’t think it’s the brain that’s the major mass contribution in an elephant.

Jess - Let’s go with Bolt. Let’s go with Bolt.

Chris - You’re saying bolt. Okay,here we go. You are correct.

A: Usain Bolt
Elephants can manage 25 km/hr, but Usain Bolt has been clocked at over 47 km/hr.

Team 1: You’re streaking into the lead.

Team 2 - Let’s see what happens with Eleanor and Fran now: Which moves faster, the electrons in a wire, or an F-18 jet.

Fran - By the electrons in a wire, that's quite a complicated question.

Chris - I know. You’re on a complicated show.

Fran - They’re not really just zipping through the wire, they’re sort of bumping into each other and their sort of pseudo particle motion.

Chris - So what are you going to go for? Which do you think goes faster, is it the electrons or is it the jet?

Fran - My instinct is the jet. It’s going to be very embarrassing if I’m wrong on this. What do you think?

Eleanor - I blow to your superior knowledge of electrons.

Chris - It sounds like you’re going for the F18.

Fran - I know there’s a lot of subtleties that make the question harder. I do not know the answer. I’m going for Jet.

Chris - Yep. It is the F18. You were quite right. Good to go with your instincts. Always trust your instincts

F-18s travel at 1915 km/hr, but the speed of individual electrons in a wire is just 0.2 mm/s. An electrical signal moves along a cable at almost the speed of light, that’s absolutely true, but the individual electrons that carry the current are actually moving very slowly. This is because electricity moves along a cable, a bit like if you had a tube full of beads, and you pushed in a bead, an electron at one end, it shunts along all the other beads inside the tube so another one comes out the end but the individual beads (the electrons) move incredibly slowly. So that’s why it’s only about 0.2 mm/s.

Chris - So it’s two plays one and let’s see what happens on the final round here.

Team 1 back to you: If you could drive vertically at motorway speeds and in a straight line, which would you reach first - space or the deepest point of the ocean?

What do you think?

Philipe - Oh, definitely space.

Jess - Yeah, let’s do it. I can’t drive so I’ll bow to your superior knowledge.

Chris - Let’s get this right. You reckon that driving at motorway speed vertically either up or down, you’re going to get to space before you get to the bottom of the ocean? That’s what you’re saying, yeah?

Jess - Let’s do a clever kind of Fran way of answering this. It depends on where you define where space begins. But yeah…

Philipe - Where do you start.

Jess - I’m pretty sure. I’m going to go with - I agree with you. The International Space Station is closer to us than Glasgow right, so I think we could go with that.

Chris - Okay. You’re going to go with space. No you’re not right. 

A: The Ocean floor
This is because the edge of space is about 100 km above the surface of the Earth, by our definition of where space starts. The Mariana Trench in the Pacific is, in comparison 11 km deep. So you’d get there a lot quicker. The International Space Station about 400 km up Jess. So Glasgow’s a little tiny bit further than that.

You didn’t get that right so now it’s all on you guys, Eleanor and Fran to see if you’re going to manage to equalise which will push it to a tiebreak situation. This is nasty. I’ll give you this, nasty this one.

Team 2 - Eleanor and Fran: Which unit of time happens faster, a shake, or a jiffy?

Eleanor - Can we answer the elephant questions? A shake or a jiffy?

Fran - I was unaware that either of those were actually a defined units.

Eleanor - It depends what you’re shaking. Because you say two shakes of a lamb’s tail. Maybe it’s another type of animal.

Fran - I don’t know at all. A jiffy sounds quicker.

Eleanor - Yeah.

Fran - Just a jiffy. Whereas a shake… you know. Maybe I like to shake for a long time.

Eleanor - Okay. Let’s go with jiffy.

Fran - Jiffy.

Chris - You’re going with a jiffy?

Did you know that Jess. You had your hand up.

Jess - No. I had my hand up because I liked the look of the Canadian while that was happening. He was like - what is a shake, what is a jiffy!

A: A shake
A shake is a top secret unit that was coined for the Manhattan Project: a shake is 10 billionths of a second. A jiffy is used in computer engineering, and is one hundredth of a second. An eyeblink is only about ten jiffies, or roughly ten million shakes

Chris - So you’ve got zero for that one.

Congratulations team [1] for winning, and if you got any of those listening.

Unfortunately, Eleanor and Fran, you didn’t win this week’s. So the big brains this week, Philipe and Jess with their amazing knowledge of elephants and Usain Bolt running. Very well done.

A bumblebee on a flower

33:56 - Why do bees die when they sting but wasps don't?

Bee stings hurt, but why do they hurt the bee even more?

Why do bees die when they sting but wasps don't?

James wanted to know why bees die when they sting you, but wasps don't. So Chris put the question to animal behaviour expert Eleanor Drinkwater...

Eleanor - This is a really good question. I recently started beekeeping so this is a question that we’ve been particularly interested in. But the answer…

Chris - Are the bees faring better than your ants?

Eleanor - Yes, they’re doing marvellously.

Chris - Are you putting RFID tags on them?

Eleanor - No, no, no. We’re looking after them brilliantly. They’re doing really well. They’re excellent. I’m very proud of them all.

Chris - So the bee proud of you.

Eleanor - Yeah, exactly. They are amazing. So what you're talking about is the fact that honey bees, in particular - there’s many types of bees but I’m guessing that in this case we’re talking about honey bees, they have a barbed sting. So if they sting something like a mammal that’s got nice fibrous tissues then they will actually pull out… If they stick their barb in it will get stuck, and so then if the bee is removed quickly, then it will pull out the sting and quite a lot of associated tissue as well, so they effectively disembowel themselves, which is quite sad. But the amazing thing about it is they can still live to - I think the study said up to 114 hours after effectively disemboweling  themselves.

Chris - Why have they evolved to do that though? Because Australian native bees don’t have barbs. They are stingless. They’re barbless.

Eleanor - This is the honey bees particularly. I was reading about this to try and answer this question because I thought that might come up, and there seems to be two schools of thought. One of which is suggesting that perhaps it’s maladaptive and it’s just that it was evolved to sting other insects which don’t have the fibrous tissues like we have.

The other school of thought, which I think I prefer, is the idea that if they have the sting in longer in causes maximum amount of damage to the mammal. Because there whole time it’s pumping the venom into the mammal and so, essentially, the worker is sacrificing herself for the colony. Then the fact that they can survive for up to 114 hours after they can still participate and help defend the colony.

Chris - So it’s all in the name of better persuasion against nest raiding.

Eleanor - Well, that’s one hypothesis. Obviously, it’s quite hard to…

Chris - You may not know this but do furry animal fare better? As in do bees manage to find it harder to sting things like dogs and bears and things that might go after their nest because they go to the exposed parts on us? My brother, who keeps bees, told me that when his bees get into your hair, because we watched a swarm arrive at a capture hive he’d set up the other day and we had them all buzzing round us, he said just watch out if they get in your hair because the tend to panic when they get in your hair and then they just sting you. None did sting us but do furry things fare better - or fur better?

Eleanor - I don’t know. I would guess it would probably depend on the type of fur. Because I guess if you could get like our hair, if you get tangled in it you’d have someone panicking. But  I would wonder whether on other animals, the fur is kind of thick enough that you can’t sting through, like us wearing our beekeeping suits.

hanging lightbulbs

Does light weigh anything?

Chris Smith put this question about light to materials scientist Jess Wade...

Jess - Yeah, this is great. I think firstly we need to think about light in two ways. We need to think about it as it being a wave which we’re all quite happy with, which reflects and kind of bounces off things and defracts and gives us great colours, and then we also need to think about it as being a particle. And then this is quite complicated and it comes from some great work done at the beginning of the 1900s to show that light comes to us as these tiny little packets of energy called photons, and photons move in waves and that’s exciting.

But these photons we define in physics, and I hope Fran agrees with me. We define that photons have no mass right?

Fran - Yes.

Jess - So photons don’t have any mass but they’re travelling incredibly quickly, at unsurprisingly…

Chris - The speed of light.

Jess - … the speed of light.

Chris - Is that why we say they have no mass because they couldn’t travel at the speed of light they wouldn’t have enough energy, because it would take an infinite amount of energy to travel at the speed of light if they weighed anything?

Jess - Exactly that. And it helps us out with an awful lot of equations that photons don’t have any mass.

Chris - So is it fudge, or is it that really the case?

Jess - I think the thing that makes everyone think photons should have mass is, we always say: E = mc squared. And photons have this phenomenal amount of energy (E) so therefore they should have some tiny amount of this m to give them this thing. But what we’re not actually thinking about is E = mc squared only really holds when you have no momentum, so = mc squared holds an invariant frame when the momentum is zero. So, in a photons case, all of its energy is coming from its momentum and that gets us round whether you think it’s fudging or not.What we can say, and what I think Fran might chip in with is photons behave like they have mass. So photons do - am I right?

Chris - They can give things a push can’t they? Because there’s this YORP (the Yarkovsky–O'Keefe–Radzievskii–Paddack effect) where light hits things…

Jess - Classic. Classic effect.

Chris - Well it’s well known. It pushes asteroids around in the solar system, and probably dislodged the asteroid that did the dinosaurs by giving them a nudge because that light falling on things gives them a push.

Fran - Yeah. So they have a momentum but they don’t have mass, which in general relativity is possible. I was just going to chip in on the is it a fudge question? People actually do experiments to try to work out if the photon might have a really really tiny mass. Because you can never rule out maybe it’s got a mass that’s just like one billion billion billionth of the mass of an electron or something. I think the limits lower than that now, and the limits are very very small at this stage.

Jess - It sounds like the beginning of your PhD: this is farcical, we don’t think it exists. Go and have fun for four years.

Fran - but it literally is in the beginning of my PhD.


39:53 - What is quantum entanglement?

The quantum world is strange, so what are entangled particles?

What is quantum entanglement?

Dan wanted to know what quantum entanglement was, so Chris Smith put the question to physicist Francesca Day...

Fran - Quantum mechanics describes the physics of how very small things work. And it turns out that the physics of how very small things work is super weird, and nothing like the physics of how everyday objects work. And one important point is that in quantum mechanics nothing is decided until we measure it.

Chris - Can I just clarify, when you say really small stuff, how small is really small?

Fran - The size of an atom or an electron, or a proton which are the particles in atoms.

Chris - Does that mean then if I could with a microscope start with something big and watch how it behaves, and get smaller and smaller and smaller and see progressively smaller things I would suddenly, at some point, see the behaviour switching and going into this quantum realm where things behave totally differently than bigger objects?

Fran - That’s a very interesting question whether you could do it gradually. No-one quite knows how the transition from quantum to classical physics works. It’s one of the really open mysteries because there isn’t a microscope that can do that whole range.

Chris - Ah. So quantum mechanics has thought of that and caught us out?

Fran - Yes. Quantum mechanics is very good at doing that kind of little trick.

Chris - Because Niels Bohr said if you’re not baffled by it you didn’t understand it, didn’t he? He’s saying look, you know I understand how it works, I understand the results I get but I don’t understand why I get?

Fran - That’s absolutely right. Quantum mechanics is a set of rules that’s very very good at predicting the results of experiments. So you have to sort of go with it but…

Chris - And just abandon all hope of actually understanding why? You just know it works?

Fran - We haven’t abandoned all hope. There’s a lot of scientists working on it.

Chris - Okay. So coming back to this idea of entanglement, what’s that?

Fran - As I said, we don’t decide things in quantum mechanics until we measure them. So, for example, photons which are particles of light have a property called polarisation and that describes the direction their electric field points in. And before we measure the polarisation of a photon, even the photon itself doesn’t know its polarisation.

Now it’s possible in an experiment to have say an atom emit two photons at once such that they have to have their polarisations pointing in opposite directions. When we do this, and say the photons travel to opposite ends of the world and then we measure one of them and it’s pointing in a particular direction. Then we measure the other photon and its polarisation will always be pointing in the opposite direction because those two photons are then entangled, and this happens instantaneously. So it’s very mysterious how the information can travel from our measurement of one photon instantaneously to our measurement of the other photon.

Chris - Now is it that the entanglement, the decision as to what polarity you’re going to have, that decision is made at the moment the two photons leave the atom or is that decision made only at the time when you measure one of them? Do we know?

Fran - It’s made only at the time when you measure one of them.

Chris - And how do you know that?

Fran - From the experiment I’ve described there isn’t a way of knowing that. So you might think well why isn’t it just decided at the source? But there are actually more complicated experiments you can do involving measuring things at different angles, and doing lots of different measurements that show that it has to be decided only at the point of measurement. They’re called Bell Inequalities if anyone wants to google further.

Chris - Over what sorts of scales can this operate? Or is it infinite as in if I had a particle which was generated at the time of the big bang, and another particle its pair, they’re now on opposite sides of the universe. As far as we know does the same rule apply?

Fran - Yes. As far as we know it is infinite. However, when I say a measurement, something like the photon interacting with a few other particles, interacting with its environment can destroy the entanglement. So you’d have to really isolate your photon somehow as it travelled across the universe.

Chris - But that also means that there is, in some way, information travelling over vast distances in zero time for this to hold. So how on earth is that happening?

Fran - We don’t know. It seems like it’s in conflict with Einstein’s theories which say that things can only travel at the speed of light, not infinitely fast. It’s actually possible to prove that it’s not possible to communicate this way in a way that violates Einstein’s theories. But it’s still very mysterious and people spend a long time worrying about it.

Chris - It certainly is. But it could hold the key, well it does hold the key to information protection, doesn’t it? Because basically, it’s a failsafe way of knowing if information has been tampered with if you entangle some information in this way, and you’ve read one bit of information it will change the other so you can tell? And that’s how online security works, isn’t it?

Fran - Yeah. So people are very interested in this for security purposes. It’s a lot better than anything you can do classically because it’s literally tamper proof from the very laws of physics themselves.

Baloo Toy

Why do I remember useless information over useful information?

Chris Smith put Nat's question about Disney lyrics to neuroscientist Philipe Bujold, who gave us advice on how to Let it Go...

Philipe - I was going to say, I think I sang “Let it Go” all morning, actually. Yes, that is a common problem that people have and it’s something that’s really great for humans because, until quite recently, we didn’t have written language, right. So songs would have been a really good way to transmit information and there’s a really good reason why they are so good. Memories are a bit like networks. You can think of them in the brain as different neurons linking and showing specific patterns, so two similar memories might have similar patterns but differ in a few final roads, if you want. What happens is that a lot of these networks, the more neurons are involved, the easier it is to remember something. So while your oven might only have a specific network, you can think of the network as like a tree and you would have a trunk, and you can’t think of the trunk. What happens with other memories is that you would have multiple trunks going into that memory, so in music you have rhythms. You have what you were feeling when you were listening to it, you have what was happening when you were younger. So all of these things happen and, at the same time, you’re happy and you always try to reward yourself with things that make you happy so your brain will try to make you remember these things much more.

Chris - The Ancient Greeks, for example, and the Romans - Latin classicists - had poetry. And I put this to a classicist and said, "is that why poetry and the rules of the language became so rigid and were rigidly imposed?" Because, if you have a rule to go by, then you have to make the language fit the rule and then it helps you to remember. Because you’re remembering what the rule should be, you make the words fit that rule, and therefore it’s easier to remember what the message should be so you don’t distort your message...

Philipe - Exactly. And rhymes are a really good thing for this. Actually, there was a study done recently on can you remember more textbook information if you make it rhyme? And there’s a reason for ‘yes’ to be the answer. Basically you know what the rhymes going to be so your network is activating. You already know that the sentence is going to end with ‘ing’ for example, so you can fill that in with the rest of the information you have in your brain.

It’s actually quite clever and song is probably the best way to remember things.

Jess - Are there then mathematical formulas to create a song that has the most lasting impact on our memory? I know this word ‘earworm’, is that right? You make a pop song that people are going to like hearing it and then you sell an awful lot.

Chris They might be memorable for all the wrong reasons and actually more comes into it. I hate it so much!

Philipe - Exactly. There’s two things that can make you remember a song a lot more on that front. If you really like it you’ll remember it a lot; if you hate it yo will also remember it a lot.

Chris - Yeah, we’ve had that.

Philipe - Because you’re getting a lot of emotions involved. As for the perfect songs: I know there’s a lot of machine learning techniques being used at the moment to try and compose fake songs or songs that are not created by humans. I don’t know how that’s going. But pretty much every pop song uses the exact same four chords. There’s a reason for that: we keep remembering them a lot better. It’s a lot easier to sing let’s say Rihanna than sing some Frank Sinatra. I’m saying that, they might use the same four chords, but for me I can’t remember.

Chris - You should make that rhyme.

Philipe - I should really try, but yeah. So basically, songs that you hear a lot more you will remember. So even though there’s no necessarily perfect formula, although there might be right now I just don’t know that field enough, you might remember things that you hear more in public, so when you’re listening to the radio you have that.

gravitational lensing

48:40 - Is dark matter really there and how do we know?

Dark matter exists all throughout the universe...right?

Is dark matter really there and how do we know?

Chris Smith put this question to physicist Francesca Day, who definitely didn't keep us in the dark...

Fran - First I should quickly explain what dark matter is in case anyone doesn’t know. Dark matter is matter that we think is there because we can see the effects of it’s gravity on other matter like stars and galaxies in space, but we haven’t detected it any other way than its gravitational effects. So then you might think well, maybe it’s not that there’s extra matter, maybe we just haven’t quite understood gravity. And, indeed, there are physicists that work on modified gravity as an alternative dark matter.

Chris - What’s modified gravity?

Fran - It’s where you take Newton’s laws of gravity or even Einstein’s theory of gravity and you tweak it to try to fit the observations better.

Chris - That’s called fiddling, isn’t it? Isn’t that called adding a fiddle factor to make the observation fit the fact?

Fran - Yes, absolutely.

Chris - It sounds iffy to me.

Fran - Dark matter is much much more popular because based on just having one more particle in our model of particle physics, and having there be some of these particles around we can explain all the observations. But there are observations that dark matter can explain very easily but modified gravity can’t; for example, dark matter is required to explain how structures like galaxies form in the universe in the first place. You need the gravity of the dark matter to be the seed that hold the galaxies together, whereas modified gravity can’t explain this. So dark matter really explains a lot of different astrophysical observations with only one addition, which is what makes it a very appealing theory but, of course until we detect it we can’t know for sure.

Chris - Why would all the dark matter stick together and be in a big halo round a galaxy for example? Because if it’s gravitationally active, why isn’t it all sort of mixed up with the other material we have, the stars and the planets and so on?

Fran - It is, but it’s more the case that the stars and the planets are mixed up with the dark matter. We think that dark matter probably only interacts significantly via gravity and it’s other interactions are very weak, so the dark matter falls in on itself because it’s gravitationally attracted to the other dark matter and forms these big blobs of dark matter.

Chris - So dark matter is attracted by gravity to other dark matter but it doesn’t interact with dark matter in any special way apart from via gravity we think?

Fran - We think. It might interact with other dark matter using some other forces that we don’t know about yet, but there’s no direct evidence for that.

Chris - And we think it was there what as a product of the big bang? Has it been around since the birth of the universe?

Fran - Yes. In the same way that all the regular matter that we see every day was produced in the big bang, dark matter would also be produced in the big bang at the same time.

Chris - So when scientists talk about there being particles of dark matter whizzing through us all the time, one physicists at UCL in London put it to me that if I had a pint glass, I’d have at least a couple of dark matter particles in there right now. Why is that there? Why isn’t it out aggregated around with the dark matter in a halo then? Is that just a reflection on how much dark matter there is all over the place, all the time?

Fran - Yeah. It’s best to think of the Earth as being in a dark matter halo. The Earth is situated in the Milky Way galaxy, and the Milky Way galaxy is situated in a big sphere of dark matter. So because we’re in this big sphere of dark matter there are dark matter particles around everywhere.

Chris - Will the dark matter go where the matter goes? Is that why we’ve got our galaxy, there’s a mixture of matter and dark matter in the same place in space and time?

Fran - Yeah. They’re gravitationally attracted to each other. But it’s better to think of it as the matter going where the dark matter is.

Chris - Philipe?

Philipe - Because dark matter is then a form of matter, would there be something as an anti-dark matter particle?

Fran - That’s a very interesting question. In some theories of dark matter there is anti-dark matter particles but in some theories there aren't. In the same way that an electron has an antiparticle which we the positron, but a photon is its own antiparticle, it doesn’t have a different antiparticle. It’s the same for dark matter, so some dark matter wouldn’t have an antiparticle but some could.

Tree in Concrete

53:20 - Can trees grow in concrete?

Is it good for trees to be boxed into the pavement?

Can trees grow in concrete?

Do trees get enough water in city pavements? Chris put this to Eleanor Drinkwater, who got to the root of the problem...

Eleanor - That is a really good question. Trees, and plants in general, can be amazing in adapting how they grow to the different environments in which they are. So you can think about something like a willow tree, and if you plant it by a river it might not put down very strong roots because the water’s right there. It can be a problem with willow trees that they might flop over because they just don’t have the support structure there. Perhaps with the trees that you’re talking about, they have much more in depth root structures that’s adapted to the environment so they can spread out and find what they need.

Chris - Do you also think that it could be a factor that if you have concreted over the ground, actually what you’re doing by doing that is trapping water in the ground? Because the Sun’s not hitting the Earth’s surface and therefore evaporating water so the Earth might be losing a bit less water, so the tree might not actually have to try so hard to get at ground resources as it normally would. There’s less competition and there’s less evaporation.

Eleanor - Yeah, that’s a very good point.

Chris - In my experience, lots of trees that are grown in that way end up solving the problem for themselves by basically turning the pavement into a trip hazard, don’t they? You just get this massive load of dislodged paving stones and the tree says, I don’t care get these out the way. Because it’s testimony to the power of water really, isn’t it? Because these trees grow and then they’re using water for hydraulic pressure to split rocks and concrete out of the way so the tree can grow. Thank you Eleanor.


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