Q&A: How did we outpace the big bang?

Why do black holes spin, and what makes glue so sticky?
22 November 2022
Presented by Chris Smith
Production by Will Tingle.


Big Bang


This week, it is time to put your questions to a panel of excellent experts in one of our Q&A shows! We are going to be investigating how we track disease outbreaks, why our ears go pop, and why neanderthal DNA makes some of us more susceptible to diseases like COVID. Plus, we have a science quiz based on the World Cup. See how you fare against our experts...

In this episode

A microphone and mixing desk

Meet the Q&A team!

Chris - The World Cup starts this week, and we will kick off the show with a look at our lineup. Emma Pomeroy is an archeologist at the University of Cambridge. She has worked on our close relatives - those are the Neanderthals. And she's also interested in how susceptibilities to different diseases that we see today evolved in the past. Hello Emma, welcome to the programme. It's been a huge year for people interested in Neanderthals, hasn't it? Especially in the last few months because we've seen a Nobel Prize for the sequencing of the Neanderthal genome, we also saw that amazing paper where genomics had been brought to bear against people living in two adjacent caves in Russia - those Neanderthal communities where they showed there was society there. Also, we've seen the first amputation of a person from about 30,000 years ago who survived. It's been a big year for your field.

Emma - Absolutely, and I think it always is. There are so many discoveries and new techniques. You might think of Neanderthals, of fossils. We are discovering new species, new things that we could never have imagined studying. Like you said, the relationships between individuals found in particular caves. So it's really exciting stuff.

Chris - Jonathan Kennedy is also here. Jonathan actually works for the global health team at Queen Mary University of London. He's got a book coming out next year. It's going to be called Pathogenesis. It's absolutely brilliant actually, Jonathan, I've really enjoyed reading this book. It's a beautiful exploration of some of what Emma's saying about our evolutionary origins and how diseases play out in the past and really take shape in the modern era as well. In your book, do you actually see how our past leads us to the risk of diseases and the way that they manifest in the modern era?

Jonathan - I think the whole narrative of the book is arguing that viruses, bacteria, and other pathogens have just had a fundamental role in not just the evolution of complex life and humans, but social, political and also economic life. So the meta argument is that we can't understand the world that we live in without looking at these pandemics that have affected humanity for over the last few thousand years.

Chris - In your book, you talk about going back a couple of thousand years, to Athens and the plague of Athens, and you can now begin to piece back together what that probably was. We think that was a flu pandemic?

Jonathan - Possibly, but this has been one of the tough ones to decipher. There was, about 10 years ago, a study that thought it was typhoid, but there were various problems identified with that paper. So it ended up not being accepted. Still the best evidence we have is the description by Thucydides of the disease and scientists have gone by that.

Chris - So we think that Covid was a big problem for us in the modern era, but our ancestors were also grappling with pandemics even thousands of years ago. Also here is Rosemary Williams. Now Rosemary's a budding astronomer and astrophysicist. She's been an intern with NASA not once, not twice, but actually three times. And she's also worked with the Griffith Observatory in California. She's now over here at the University of Edinburgh where she's studying for a masters in science communication. So you've slewed sideways from pure science into how to get science across to the general public. Why the transition?

Rosemary - I think I realised that I loved talking about science more than I loved actually being in the lab and studying it. And so I realised I should probably transition out of that unless I wanted to be writing grant proposals for the rest of my life.

Chris - It's a big year for people interested in space science as well, isn't it? Because we are embarking on trips and forays back to the moon where we haven't been for nearly half a century.

Rosemary - Very exciting.

Chris - Space continues to appeal to people very much. It always grabs attention straight away. When we put the call out for this programme saying there's going to be a space scientist along, about 4/5 of the questions, straight away, astrophysics, black holes. Andrew Morris, now. Andrew's a physicist by training and background who then became a teacher and now he still teaches but in a slightly different way because he has written a book. It's called 'Bugs, Drugs and Three Pin Plugs'. I've got a copy of that in front of me. I really enjoyed reading this as well, Andrew. And the reason I enjoyed it is because what you've tried to do is put into plain, simple language a lot of the questions that grownups probably get asked by kids and and currently say, "ask your teacher."

Andrew - Well, I used to be a regular teacher in a sixth form college, in a further education college teaching physics and maths. But I always felt, going back to my own teen age, that I was just interested in asking questions about the world around me. And I've always felt sure that most people are like that. They are curious even though they might find science at school difficult. So I set up this experimental idea of trying to run groups, teaching in an adult education centre in London, in which I took the risk of just inviting people to ask questions. They might be outside my field or they might not, and to see if a discussion could evolve. And without necessarily having the answer to their precise question, I could use this as an entry point into some of the basic ideas about science: molecules, cells and so on.

Chris - I always make the case when we're doing shows like this, if people ask us a question and we don't know the answer - because at the end of the day, the reason scientists are employed as scientists is because we don't have all the answers - often the answer "I don't know", is as valuable because you can then use it to explain to people how we might go about working it out. We did this show up in Edinburgh. Someone in the audience went to this Q and A show and said, "how many protons are there in a star?" And I don't know if they thought they were being funny. The person they put it to was initially a bit scared, and then I said, "well, we could work this out actually."

Andrew - I mean I think that's a very detailed example, but I think that approach of modelling, trying to not exactly answer precisely a question, but to think of the process by which you would get at an answer, estimating, is a particularly important aspect of scientific literacy.

Aerial view of Earth from space

07:51 - Where does outer space begin?

where does our atmosphere end and outer space begin?

Where does outer space begin?

Rosemary - Yeah, that's a great question. The issue with astronomy and all things in general is there's very rarely a black and white answer. The atmosphere, it doesn't have an edge, so to speak. It kind of fades out. So scientists have categorized the atmosphere into a few different layers. The one that's most valuable to all of us, I guess the one that we're gonna be interacting with our whole lives, is called the troposphere. That's where 75% of all of the atmospheric particles lay. And it goes all the way out to the exosphere, which actually reaches about halfway to the moon. So it's this very large range for the atmosphere. But most people think that space probably starts a little bit before halfway to the moon, you know? So in the 1900s there was a scientist named Theodore von Kármán, and he basically calculated the highest point that an aircraft could function within the atmosphere, right? So planes rely on air to provide lift. And so he calculated about 84 kilometers, around there, was the highest point that a plane could fly, relying on lift. Now, he ultimately decided that a hundred kilometers is just a nicer number. There wasn't a lot of science behind that. But a hundred kilometers also happens to be about where a satellite can no longer stay in stable orbit because then you have to take into account the atmosphere interfering with that orbit. So it might destabilize. So the general consensus is around a hundred kilometers. It's not super important, space is space. The only reason that it was kind of concerning is politics. You know, who's controlling what aspects of the air and all that. So, great question. Thanks Emma.

Chris: So 100 kilometers is currently accepted but it's a bit of an arbitrary number because the atmosphere doesn't stop there, other aspects don't stop there, and the International Space Station that's about 400 kilometers isn't it up? So it's about four times further than that. But that's still in the atmosphere because I was talking to a space scientist and they were saying they have to periodically give it a boost because it is experiencing drag from the wisps and tendrils of the atmosphere that progress and progress even up there.

Rosemary: Yes, that's true. Yeah.

Chris: There you go. Now you know about the Kármán line. Thank you for that, Rosemary.

Ancient hunter gatherer skeleton from the Balkans. These people were already gathering cereals before farming arrived in the region

10:21 - How can you tell the age of a skeleton?

What clues do bones have as to the age or sex of a skeleton?

How can you tell the age of a skeleton?

Emma - That's a great question. And assessing sort of sex and age at death are two of the fundamental things we do as bone specialists. I should perhaps start out by saying that if you did find a skeleton, you should leave it where it is and not touch it and let the police know just in case it's of forensic relevance. But let's assume you are volunteering on an archeological dig and you come across some skeletal remains. Well, for babies, children, and teenagers, actually it's very hard to tell what sex the individual was because a lot of the sex differences in the skeleton only really appear at puberty. But in adults there are two areas of the skeleton that we typically look at most. So the pelvis, the hip bones and the skull. The pelvis or the hips are a functional characteristic if you like, because they tend to be broader and ha ve a wider birth canal for the baby to pass through in women. So we can see sex differences there in the skull, they're mainly secondary sex characteristics. So things like males tend to have slightly heavier musculature because of higher levels of testosterone and that leaves all marks on the bones that we can then pick out. And things like the brow ridges above the eyes tend to be more developed in males as well.

Chris - What about the age question?

Emma - In terms of age at death, it's almost the other way round. So actually for babies, children and teenagers, we can get a much more precise and accurate idea of age at death. And that's based on the development of the teeth, so the formation of the teeth and also their eruption, but also on the formation of the skeleton and the bones. Whereas for adults, actually it's much harder to be really precise and accurate about how old someone was when they died because once the skeleton and the teeth have all finished forming, we have to rely basically on wear and tear on the skeleton and trying to figure out how old someone was based on this wear and tear. And obviously many factors affect that. I mean, how active you are, whether you have a good diet, how healthy you are all affect how much wear and tear your skeleton will show. So it becomes really difficult, especially for older adults.

Chris - I was very taken with that piece of research that showed that amputation in that 30,000 year old early human ancestor was reported a couple of months ago. And the fact that they were able to say this individual would've had that injury aged about 12 and they died about age 16, how would they have known that, for example, that that person survived for four years after that injury and didn't die from it?

Emma - I mean it was a really remarkable study and one way you can tell, so basically once your bone has had some kind of injury, so that could be an amputation or say you break your arm or something, the bone goes through a healing process. So we can see that if someone died about the time that an injury happened or an amputation happened, there won't be much healing. And if they survive for a while afterwards, then there will be evidence of healing and the bone smooths over that kind of thing. So particularly in that case, because in a younger individual we can be quite precise about how old they were when they died and then we know it must have taken approximately that period of time for that level of healing to occur. We can then work back and say, okay, if they were 16 when they died, they must have been say 12 when that injury or that amputation happened in this case.

A map of the world showing hotspots of an infection.

How do we trace back disease outbreaks?

Jonathan - Well, I think it's not just viral outbreaks. I think we can look at epidemics and pandemics as one category, and perhaps it helps if we go back to the first epidemiologist, John Snow. So in about the 1830s, Europe was hit by cholera for the first time. And people didn't know what was causing this, this horrible disease. Some people thought it was due to my miasma.

Chris - Bad air.

Jonathan - Bad air, literally bad air. Other people thought that it might have been some kind of plot by the rich to poison the poor because it was poor people living crowded in sanitary urban slums that were being most affected. And John Snow had a hunch that this was a waterborne disease, which was revolutionary at the time because germ theory hadn't been accepted at all. And this made sense, or it makes sense in hindsight because for example, London, where John Snow lived, was a city of about 3 million people in the middle of the 19th century, but it had no kind of integrated sewage and water network. Enormous amounts of human waste just flowed into the Thames. And London inhabitants got their drinking water from that very same river. So when a cholera epidemic broke out in 1854, Snow ran to Soho in the center of London where the outbreak was occurring. And he undertook what's probably the first epidemiological study. He went around and he interviewed people that were affected and he tried to work out what linked them together in their working life and in their kind of everyday life. And he realized that it must be related to this water pump on Broad Street, which is still in Soho if you happen to happen to go there.

Chris - Amazing insight to think that he, because we take this for granted these days, don't we? That something must cause something. There must be a connection between all the individuals. We ask all the people what their common exposure is, and that must be the reason that they've got the problem. But for him to do that in that era where we didn't even know that germs existed, and that therefore they could be contained in a water supply and transmitted via water, that was really a big leap.

Jonathan - No, it was absolutely revolutionary. And sadly, his ideas weren't accepted in his lifetime. So he died about four years later and there was a 33 word obituary in the Lancet, the prestigious medical journal. And it didn't mention it.

Chris - But did they take him seriously at the time? So when he said, 'look, there is this water pump, there are all these cases that seem to be connected to it'. Did people take it seriously at the time, stop using the pump and the disease went away, thus proving he must have been right?

Jonathan - Yes and no. So the local authorities, they looked at his evidence and agreed to remove the handle of the pump, and then the outbreak stopped. But the broader scientific community, in particular the commissioners that were charged with looking into the causes, looking at the causes of the 54 outbreak, rejected his idea. And they kind of doubled down on the miasma theory and in this obituary to Snow a few years later, there was no mention whatsoever of his work on epidemiology. It was all about his work on anaesthetics, which was the other thing that he was known for. And it wasn't until the next outbreak, which occurred in 1866, so this was after the sewers had been built in London and the last remaining place in London to not have sewers connected, around Bethnal Green, had the big outbreak. And that finally convinced people that this was the waterborne disease. But to come back to the question, if we look at Covid now, and the way that that's traced back to the wet market in Wuhan, it's pretty similar. Epidemiologists have worked out that a large number of people that had the disease early on had been at the market. And so that's a very likely point at which it jumped over from animals to humans. But still, we're not a hundred percent certain that that's the case. It's just this circumstantial evidence.

Chris - It's interesting that there is that historical route to this aspect of epidemiology, but like many amazing leaps in science, it was too early, too soon and people didn't take it seriously and it took more convincing. I suppose it's kind of good in some respects that science is robust enough to defend itself against arguments and wants to be convinced, but we mustn't be too dogmatic in our thinking. We must be open to new arguments and new evidence, I suppose is the moral of that story.

Jonathan - I think that's a fair point. Although I'd like to think hopefully science has advanced quite a lot since the 1850s. The state of medical understanding then was pretty rudimentary and it hadn't changed much since the ancient Greeks, to be honest. So there's been a massive revolution in understanding.

Chris - Although I mean you make this point that germ theory, the idea that there were germs that could be transmitted between individuals, had yet to be born at the time that all this was going on. And I was having this same conversation with someone the other day where we were pointing out that in fact, if you look at the mortality rates and how long people were living and so on in that period in London, they were plummeting well before we even discovered what germs were. Or for instance, deaths from tuberculosis were plummeting well before we even knew what caused it. And it was all about cleaning up London, giving people better living conditions, giving people fresh water, sewage, better food. So public health did all that well before modern medicine came along.

Jonathan - Exactly. And I think it shows the importance of politics to public health. The fact that there were political reforms in the UK and in the 1860s, 1870s, that made it politically viable to basically borrow money and spend it on public health because the electorate had been expanded so much that the people that were benefiting could actually vote for that, but didn't have to pay for it.

Chris - Sounds nice. And many governments are accused of eventually running out of other people's money to spend and that's when they get voted out. Thanks for that, Jonathan.

painkiller pills

How do painkillers know where the pain is?

Andrew - Yes. A very interesting question. You might imagine that pills must have some kind of destination board on the front saying, I'm headed for the liver, or I'm going to sort out that headache. But it ain't like that. Really the clue to this is in the fantastic discoveries that different molecules have got different shapes, different structures. Actually where we are in Cambridge is one of the great centers for discovering the structure of molecules. Originally, people used to look at the structure of rocks and minerals through shining x-rays and doing crystallography on them. And then people hit on the idea that we could do this with biological substances. If we could only make them into crystals, we could work out what the structure of these molecules is. And indeed the famous Nobel laureate, Dorothy Hodgkin's, work used x-rays, made crystals of penicillin and later on insulin, and discovered the precise structure and what that means, of course, just to make it clear, molecules are assemblies of atoms that are all bonded tightly to together, and they make an overall shape. And in the body, a huge number of molecules are very large, extremely large. They're called macromolecules. In fact, proteins are one example, DNAs another. And proteins are constructions of hundreds or often thousands of atoms into one gigantic molecule, which wraps up into a kind of globule. They're called globular proteins. And on the surface of these proteins, they have, and little hills and valleys and proteins in the body distributed often on the surface of different cells, have different shaped crevices and different shape hills and valleys. Now, when we take a drug, like a painkiller or any other drug, a beta blocker or a statin, these are small molecules, much, much smaller, and they've got a particular shape as well. So what happens when you take them, they course through the body, through the fluid systems, through the blood in particular bloodstream. And it's only when the shape of this little molecule happens to pass by a crevice or a little niche on a protein. And it fits, it's like a lock and a key. The drug molecule fits the crevice on a protein that it sticks. Basically the small molecules, the drugs and the medicine are passing by almost everything until it reaches a specific receptor. It's called a receptor because that's where it receives the drug.

Chris - A bit like triggering a landslide in your valleys discreetly in just the right valleys because the drug is addressed to the right parts of the body that have the right shape valley to happen

Andrew - I mean, I've emphasized shape there, but I should also for accuracy say that there's an electrical issue as well, that molecules have a, tend to have a positive end and a negative end, and they have to match up. So the positive end of a drug molecule matches up with a negative place on the receptor molecule

Chris - So there's a well known slogan for one brand that it hits pain where it hurts. Yeah. And so in some respects, that's not wrong. It's that the drug does kind of know where the problem is because the problem only exists where it hurts, so it binds to the right place. Absolutely. Andrew, thank you very much.

Coronavirus particles

23:56 - Do viruses prey on other viruses?

If there are so many viruses on Earth, what do they use to reproduce?

Do viruses prey on other viruses?

Jonathan - Yeah. So I think that number is correct. I saw it quoted in nature microbiology too, and I found an interesting fact that if you lay all of the viruses on earth end to end, they would stretch for a hundred million light years.

Chris - I mean, that's really saying something when we're talking about a flu virus which is one 10,000th of a millimeter across. So that's a lot of viruses, isn't it?

Jonathan - Yeah, I think it's so hard to get one's head around both the size of viruses, but also the enormous number of viruses in the world. So, you know, for example, it might be easier to conceptualize. If you take a liter of seawater, it's a hundred billion virus particles in that liter. Or if you take a kilogram of soil from the earth, there's about a trillion. So that's a million million virus particles in just a kilo of soil. It's just absolutely mind blowing. But I think the thing to remember is that animals and plants and fungi, although they dominate our view of what the tree of life is, they only actually kind of represent a tiny, tiny amount of the tree of life. The vast majority of species are bacteria and archaea. So kind of single celled organisms on the whole, and only a few twigs of the tree of life really are made up of complex life like animals, fungi and plants. So I saw some studies where it says that there's less than 10 million species of complex life, but there's about 1 trillion types of bacteria and archaea. So it's really, it's really mind blowing. And you might say, oh, well these are just tiny little insignificant things. But actually, if you took all the bacteria on the planet and weighed the mass of them, they would weigh a hundred times more than all the humans on the planet. So they're still really, really significant. But to come back to the question, the vast majority of viruses are viruses that infect bacteria. So what we call bacteriophage, phages from the Greek to devour. And these actually play an enormously important role in the way the whole ecosystem works because they kill an estimated 20 to 40% of bacteria on the planet every single day. And this allows the world or the ecosystem to maintain its balance. So yeah super important. But viruses can play positive as well as kind of disease carrying roles.

Chris - Well, we talked the other day in our program about tuberculosis, about the use of these bacteria phages to kill those TB bugs. But returning to the question which was are there viruses that prey on viruses? They have been discovered, haven't they? There are so-called viral phages. There are viruses that piggyback on other viruses and infect viruses. So when a virus is growing in a cell, you can get another virus that comes in and gets into the process and steals some of the resources the other virus is making for itself. So it can basically parasitize a parasite. Yeah, so viruses are incredible things, aren't they?

Jonathan - Mind blowing, mind blowing stuff.

Chris - Yeah. Thank you very much, John.


27:42 - The Q&A Quiz!

Who will win this month's big brain award?

The Q&A Quiz!

Chris - Right it's quiz time. I knew you were all eagerly anticipating this. We do this whenever we have a Q and A programme. It's our opportunity to test the mettle of our panel, but also you can play along at home. We've got four people here in the studio. So logically that breaks down into two teams. And I'm gonna divide you up into Emma and Andrew as team one and Jonathan and Rosemary are gonna be team two. You're actively encouraged to confer between you, please. Now we've got three rounds for this, and the first round is the World Cup. Don't worry, this is not actually, I'm told, about football. We've got two questions based around the competing teams. Question one, for Emma and Andrew, which of these previous World Cup host nations have been awarded the most Nobel prizes for science? I'll give you three options, and by Nobel Prizes for science, it's physics, chemistry, or the physiology or medicine prize. So is it A) Switzerland, B) France, or C) Germany? Which of those World Cup host nations has had the most Nobel prizes for science in the past? What do you think? Do confer.

Andrew - France had a lot in the early days with the Curies and everything, didn't it? Germany industrialised very early, right? And did an awful lot of science.

Chris - Switzerland, France, or Germany?

Emma - Yeah, let's go for France.

Chris - Unfortunately, it's a miss. No, the answer is Germany. It's got the third highest number of scientific Nobel prizes, 79 across all categories. And they're behind us, the UK on 90. But of course the leaders out in front are the USA, big country - 273. You were right to point the finger at France who have 35 Nobel prizes in science. But Switzerland so far have only got 18. I'm afraid that's a miss for you guys.

Chris - Question two is going Jonathan and Rosemary's Way, and again, another world event happening right now. COP 27, very much in the news at the moment. This is the climate conference. They've got a focus at COP 27 on preserving biodiversity. So what we want to know, Jonathan and Rosemary, is which of the following nations at this year's World Cup has the highest biodiversity index ranking? And if you want to know what one of those is, a biodiversity index is defined by what percentage of all of the world's animal species are found in that country. So which of these countries has the highest biodiversity index? Is it Mexico, Australia, or the United States? What do you think?

Rosemary - The US is so broad. There's so many different biomes within the US.

Jonathan - I know Australia is a lot of desert, but it also has some rainforest, but yeah, an enormous amount of the outback as well where there doesn't seem to be much. Maybe the best way to work it out is: biodiversity seems to increase as you get closer to the equator. There's more sun, there's more vegetation.

Rosemary - So, maybe Mexico?

Chris - You've scored a goal. Well done it is indeed Mexico. Brazil would be far too easy. That was the highest. Mexico sixth in the world for biodiversity. 10% of the total world species are found there. Australia's seventh place and the US is in position number 10. We are a small island. The UK is down the bottom of the world rankings.

Chris - Right over to round two. Back to Emma and Andrew. So this round is which came first - we are asking you which invention of these three came first? Is it the raincoat, the hot air balloon or the photograph. The raincoat, the hot air balloon or the photograph? Which of those inventions came first?

Emma - The one I have really no idea about is the raincoat.

Andrew - Well I was thinking the macintosh.

Emma - How are we defining raincoat? That sounds a very boring, scientists answer, but if you were talking about using skins, or some kind of fabric that was impregnated with something that would help make it waterproof, that could actually go back quite a long way in terms of archeology, you know, using fats or something like that on skins or tanned hides.

Andrew - I see hot air balloons as quite a bit later.

Chris - Unfortunately, you've hit the bar again. The hot air balloon was the answer. Would you have got that? The raincoat, you were quite right, Andrew, was invented by a Scottish architect, Charles Macintosh. That was in 1823. The first photograph was taken in 1814 by the French inventor Joseph Nicephore Niepce. But in 1783, following tests with a rooster, a duck and a sheep, followed by a human pilot who is the frencher Pilatre de Rozier, he successfully ascended to the dizzy height of 25 metres in a hot air balloon that was built by the Montgolfier brothers. So unfortunately you didn't score on that one. So at the moment, team two are in the lead. They have one point. Let's find out if they can cement their lead. Rosemary and Jonathan, we want to know which of these was discovered first. A) the planet Uranus B) the element Hydrogen or C) the cell. What was discovered first?

Rosemary - Okay, so William Herschel discovered Uranus in, like the 1800s. I don't know about the cell or hydrogen.

Jonathan - I'm not sure about the cell. The first person to use a microscope was Anthony Von Loevenhook, a Dutch haberdasher who ground lenses because he wanted to look at the quality of his curtains that he was buying and selling. But I'm not sure if he would've identified the cell. But that was back in the late 1600s.

Chris - I'm gonna have to hurry you.

Rosemary - Maybe the cell.

Jonathan - Okay, let's go with that.

Chris - And you score another goal. Very good. You're quite right to choose the cell. I'll give you the reasoning and the argument behind this. All of them were discovered a long time ago, but Uranus, you're quite right, was Sir William Herschel, 1781. Hydrogen, Henry Cavendish, Cambridge man, 1766. But the earliest of all was the cell. Robert Hook described the cell in 1665. His collaborator was Loevenhook, who was sending, to the Royal Society, reams and reams of drawings of things he had seen with his tiny little blast droplet lenses. Do you want to have a go at the last one? Because it is quite funny. So if you can redeem yourselves and get off the ground team one, because it will be about time if you do so. And that is the name of the next round: It's about time. Emma and Andrew, our planet's rotational speed is gradually slowing. This is because of friction effects associated with the tides which are giving energy to the moon, speeding it up. So that means the length of a day on earth was shorter in the past. How long was a day about one and a half billion years ago. Was it A) 12 hours B) 18 hours or C) 23 hours long?

Emma - I have even less idea than I had about the last 2. We didn't do particularly well on those.

Andrew - Go with the 23 hours.

Chris - Sorry, you haven't redeemed yourself. You scored three misses. I don't know who you are taking penalties for, but you are not going to be on their team for the World Cup. It was actually 18 hours long. At the formation of the earth, the day was as short as 12 hours. But on average, because the length of the year increases by a second every 65,000 years or so, if you wind the clock back it was about 18 hours back then. Do you want to have a go you two and see what you would've won? The average human lifespan across the planet is about 73. But there are members of the animal kingdom that achieve this many times over, and one of the oldest living vertebrates is believed to be the greenland shark. One individual got carbon dated. In fact, they looked at its eyeball for various reasons and they found that it was the longest living vertebrae that had ever been discovered. How old did the scientists think that she was? Was it A) 191.5 years? B) 301 years, or C) 401 years?

Rosemary - I feel like I remember reading something about a shark being older than the United States. I could be pulling that out of nowhere, but I feel like I read that.

Jonathan - I think it's really, really old. I mean, they're a funny species, aren't they? I believe they get these parasitic worms in their eyes that they obviously can't get rid of because they don't have fingers or hands to take them out. And they go around for hundreds of years with these parasitic worms in their eyes. But I'd probably go for the longest, the oldest.

Rosemary - So old I I'm going to stick to 301.

Chris - You're gonna go 301?

Chris - Okay. You've missed your first shot on goal. It's actually 401 years. The way they proved it was with radiocarbon dating. The eyeballs, because they contain tissues that are not replaced during the lifetime of the animal, those are the crystalline proteins that form the lens. They are not replaced as the animal ages, and so you can look at the age of the carbon atoms in there and how many of them are radioactive and work out how old the animal is. And when this was done, 401 years is the average because it could be between 272 or perhaps even as old as 512 years. Isn't that amazing? Isn't nature an incredible thing? Anyway, the winners of the Naked Scientists Big Brain of the Week award this week are our astronomer Rosemary Williams and our expert in global health. Jonathan Kennedy. I think they deserve a round of applause, don't they?

An aircraft in flight

39:22 - Why do my ears go pop?

What about being high up makes your ears pop?

Why do my ears go pop?

Andrew - I've got a friend who's in my discussion group who asked a similar question once. She loves going to the Canary Islands, and she went, she had a cold and her whole head was blocked. And when the plane took off, she found that her ears got unblocked again. And it was wonderful. So she had lovely hearing on the flight, and then when it descended her ears all blocked up again. What it seems is that there's obviously a difference in air pressure in a cabin. The air pressure is raised by taking air from the engines, bleeding it off into the cabin, but the air pressure in the cabin of an airplane is still slightly less than it is at ground level. In fact, it's about the same pressure as the top of a mountain, and that's to make sure that the stresses on the fuselage don't lead to the plane exploding. So you've got slightly lower pressure than normal, but of course, the other side of your eardrum inside your middle ear is still got the air pressure that you've got when you, when you took off. So there's an imbalance between the air pressure on one side of very drum and the other side of the eardrum. And of course, this happens when you walk up a mountain, you get similar effects going into a tunnel on a train. But your ear got a brilliant mechanism for balancing out, equalizing the pressure on both sides, and it's called the eustachian tube. The eustachian tube vents, as it were. It vents the middle ear out, back to the normal atmospheric external pressure through your nose. So, when you yawn or the experience of walking up a mountain and feeling the pressure change, or in an airplane, what's happening is the middle ear is venting itself through the eustachian tube - a little burst of air to make sure that the pressure on both sides of the eardrum is the same

Chris - And if you get a cold and it clogs up, that's why it can take a bit longer for that to happen. Thanks very much.

An artist's impression of a supermassive black hole

41:54 - Why do black holes rotate?

The answer involves zooming in on the singularity at their centre...

Why do black holes rotate?

So in order to understand why black holes rotate, we have to understand how they form. Black holes essentially form when you have a star that collapses under its own weight. There's two main processes happening inside a star. You have gravity that's pulled all of this hydrogen and helium together, and then you have a nuclear fusion at the core that's essentially forcing all of these hydrogen atoms together to form helium and then three heliums together to form a carbon. And that's providing a lot of energy that's stopping the collapse. But eventually stars are going to run out of this fuel at the centre and you no longer have a big force outward due to nuclear fusion. So you just have gravity forcing itself inward, and that star starts to collapse on itself. Now, all of the stars that we have observed have had some sort of spin, they've all rotated. And, in physics, just like there's conservation of energy, you have this thing called conservation of angular momentum. You have to keep the same momentum over time, over everything. You have to maintain it. So when the black hole is collapsing, it's going to keep that momentum of the star that existed before it. So you have a star that's spinning much like you have an ice skater that's spinning: they bring their arms in, they spin faster. That's the same thing that's happening. You have a star that's spinning, it collapses in on itself. It still has to spin. The question of what exactly is spinning, well, you have a singularity at the centre of a black hole, and we usually say it's this infinite density thing. You have a lot of mass in this infinitesimally small space, but in reality it does have some volume. It's just so small that we can just kind of say that it doesn't. And so it is that tiny, tiny volume of mass at the centre of a black hole that's spinning. Now, we don't exactly know what is happening at the centre of a black hole and we may never know. So it's important to say that, but that's what we've theorised to have happened based off of equations and physics and all of that. But physics gets super wonky on these small scales.

Pot of glue

How does glue work?

Andrew - I mean, glues are sticky only really when they're connecting two surfaces. It's not a kind of magic property that they have. And they only stick when the right surfaces and the right glues meet each other.

Chris - Hence the old joke, you know, how do they get the glue to come out the tube then if it's so sticky, why doesn't they stick to the tube?

Andrew - Exactly. We've all probably got examples from our woodwork classes of glues that never worked and so on. And it's back to this story about the forces between molecules: adhesive forces and cohesive forces. Because if you look at two surfaces in contact through a high powered microscope, it is extraordinary to see that they're really, really rough. And it's like this kind of top of a mountain range on one surface meeting the top of a mountain range on another surface and grating against each other. So actually, when two surfaces are in contact, it's mostly empty space in between them and just the peaks, one peak meeting another peak where they're actually physically in contact. So the job of glue is to get in there into the space between two surfaces. And it might penetrate through cracks or it might just get absorbed into the surrounding material, or there might even be a chemical bond. But once the glue penetrates one way or another into the two surfaces, that would be bonded. The question is, do the forces that hold the glue molecules together, that's called cohesion, are they less or greater than the forces of attraction between the glue molecules and the surface, which is called the adhesion. So glues have to adhere from the glue surface to the surface they're connecting, but they also have to cohere so that the glue doesn't fall apart itself.

Chris - Can you help me out then, and tell me why I can't get Weetabix off of a bowl that's gone dry.

Andrew - <laugh>. Well, there's a new one.

Chris - I mean, it's a similar thing to wallpaper paste, I presume, isn't it? Because it's starch. And I presume because that's a stringy molecule. It's doing exactly as you say, and threading the tendrils of starch into the rough surface of the ceramic in the same way as the wallpaper paste gets into the back of the wallpaper and the wall.

Andrew - Very good point. And at the fundamental physics level, it's electrical attraction. To make it simple, it's the fact that one molecule electrically is attracted to another molecule.

Chris - I have a lot of electrical attraction. I'm sure you can sympathize with that.

Artist's impression of the Big Bang.

46:36 - How can we see the big bang?

How have we travelled faster than light to see the big bang?

How can we see the big bang?

Rosemary - Yeah. To think of this question, you have this big explosion and going away from the explosion, you have a lot of light, you have a lot of energy that's turning into mass, right? E = mc2. You can turn that energy into a mass. We actually did go faster than the speed of light but it's a tricky question. There's a lot of caveats to that. Imagine you have a stretchy sheet. Objects on the sheet, which represents space time - let's say marbles, are constrained to move below or at the speed of light, 300,000 kilometers per second. But the sheet itself can stretch faster than the speed of light. It's not constrained to this 300,000 kilometers per second. So although particles and things within this sheet have a speed limit, the sheet doesn't. So you can kind of get around this, it's kind of like you can walk on a train, right? You have your speed on a train. Maybe you're walking four kilometers per hour or something. But the train itself could be moving 90 kilometers per hour. And so because of that, we're still getting light from the Big Bang because we've kind of outrun it and now it's catching up to us. So now we're able to see this light, this energy temperature, the cosmic microwave background from all around us coming from the Big Bang, which is super, super cool.

Chris - In summary, then you are saying the universe is born, there's all these particles together sharing the same energy at that moment in time, which is what's going to ultimately give them the cosmic microwave background radiation as it is today. That bit of the universe, the sheet they're all sitting in, gets much bigger very, very promptly and much bigger than the speed of light. And drags the particles with it effectively. They haven't moved, but because the space between them has got much bigger, much more quickly. When we appear, we are seeing those things all over the place. In the observable universe. So we are seeing as though that light is coming to us for the first time.

Rosemary - Yeah and I think the really interesting thing about this is if you could see through this kind of fog, we call it recombination, around us, you would be able to see the big bang happening all around you if you had a super powerful telescope. Because when you're looking through space, you're looking back in time. And so in theory, if you looked in any one direction far enough, you'd see the Big Bang. And if you turned around and looked really far in that direction and you'd see the Big Bang. So the Big Bang would be happening all around you. Which is so incredibly weird.

Chris - Yeah, it is a bit mind boggling, isn't it? But the way you've put it very, very clear. Thank you for that.

Taking a child's temperature with a digital ear thermometer

49:23 - Why do we get a temperature when ill?

What does raising body temperature do to help fight illnesses?

Why do we get a temperature when ill?

Jonathan - I think the answer to this is quite simple, right? It's just the body's immune response to being infected and many viruses, many bacteria that infect humans are very temperature sensitive. And so the body's immune system increases its temperature in order to make it less hospitable for these pathogens.
Chris - You're Basically cooking them into submission, is that what you're saying?

Jonathan - Yeah. Or at least kind of discouraging them from reproducing and making us even more sick.

A paleo diet meal

50:09 - Are there any benefits to the paleo diet?

What is the paleo diet, and is it better than any other diet?

Are there any benefits to the paleo diet?

Emma - So the idea of the paleo diet is that the optimal diet for humans to eat and the one that we probably ate for most of our evolutionary history as a species, which is something like 300,000 years is what hunter gatherers would eat. So you would think of wild hunted game. So they have low body fat compared to domesticated species, for example. So very lean meat, not eating things like pulses and grasses, things like that. Going for wild foods. Not the kind of domesticated things that are the foundation of our diet today.

Chris - But it still would critically contain meat.

Emma - Yes and I guess there's different versions of the diet depending on who you ask. The big problem here, well there's various big problems here. So one is that there is not a single diet that even contemporary hunter gatherers eat, let alone hunter gatherers in the past. There's been climate changes, we find hunter gatherers everywhere from the tropics right up into the Arctic, and of course they're eating very different diets. So there is no one diet that humans are adapted for. It's also the case that we are adapted to eat some of the foods that we have domesticated since the adoption of agriculture. We can see evidence for adaptation to consuming milk, for example, and also changes in our carbohydrate metabolism that are linked to that. And equally we know if we look in the archeological record, we can see evidence of even Neanderthals gathering grasses and wild grains and eating those. So it's not so simple as there's one diet that humans are adapted for, or that certain types of food are necessarily good or bad. And really we have to take a much more pragmatic and holistic approach to our diet and think about other factors as well, like exercise, the amount of energy we are using. That will affect how much food and what kinds of resources our body needs. So we can't really single out diet on its own to really know what's going to be healthy and best for our bodies.

A representation of the evolution of the universe over 13.77 billion years.

What shape is our universe?

Rosemary - Oh, this is a tricky question. So this is addressing a part in astronomy that is the observable universe versus the universe itself. So the observable universe being, when you look up at the night sky, when telescopes are looking at the night sky, what they can see, the amount of light that they're getting in from all different directions. And we know that that is a sphere because when we look up around us, we can see stuff in all directions. Now, the universe as a whole, there's three different possibilities for what it could be. It could either be a sphere, it could be kind of a saddle shape, or it could be flat. The sphere is a positive curvature in every direction, a saddle shape being this negative curvature, and then flat, obviously being no curvature. And I believe this is taken from measurements, from the cosmic microwave background, which is so rich in information. That's why studying the cosmic microwave background is so important in astronomy because it gives us so much information about the universe and how we started and the composition of our universe, how much dark matter there is, how much matter there is. And it is one measurement where I believe if it is one, it is that the universe is flat. If it's above one, it's curved. And if it's below one, it means that our universe is kind of negatively curved, this saddle shape. And the current measurements are around this one value. And we haven't gotten it exactly precisely, which is exactly why it's important for us to keep studying the cosmic microwave background. But it's hovering around one, which means that it makes me very uncomfortable to say, but that the universe is kind of flat, which I don't like at all. I want it to be like a sphere. But that's kind of what the science is saying right now. But continuing to study this is very important and it'll give us a great understanding of the universe beyond our observable Universe.

Chris - You obviously like the idea that you can start and go on forever, come back where you started eventually.

Rosemary - Yes, I do.

Chris - Very comforting for you.

A model of a neanderthal.

54:30 - Why do neanderthal genes make COVID worse?

How do certain genes affect our susceptibility ot illnesses?

Why do neanderthal genes make COVID worse?

Jonathan - Well, I think Emma should be able to help us with this as well, so maybe you can chip in. But I think to begin with, we have to remember that Homo sapiens and Neanderthals perhaps had a common ancestor between 500,000 and 750,000 years ago. So a long, long time ago, Neanderthal ancestors managed to leave Africa and end up in much of western Eurasia. And I think evidence has been found everywhere from Gibraltar all the way to the Altai mountains in Siberia right?

Emma - Yeah, absolutely.

Jonathan - So from a kind of epidemiological perspective, Neanderthals and Homo sapiens were growing up in, or were evolving in very, very different conditions. So you had Neanderthals evolving to adapt to the challenges posed by a temperate climate. And you had Homo sapiens evolving to adapt to the challenges in tropical areas

Emma - Sub-Saharan Africa. So quite a different environment.

Jonathan - And because biodiversity's much higher in the tropics, you don't just have more vegetation, you have more animals, you have more parasites that live on those animals. So the disease burden carried by Homo sapiens was different.

Chris - They're evolving in different environments, so they're therefore facing and responding to different challenges, which is gonna select for different sorts of genetic endowments, as it were, to resistance to different diseases. So how does that then address the question of the Neanderthal genes changing our risk of Covid?

Jonathan - So let's do another step as well because I think it's really fascinating and builds on what we talked on before, but 15 years ago, we didn't know whether Homo sapiens and Neanderthal had actually met, but after the genome of Neandertals was kind of restructured, we realized that humans have about 2% of Neanderthal dna. And this isn't just random DNA, this is gene variants that help Homo sapiens adapt to the environment that they face when they're migrating out of Africa 40,000 years ago. So quite a few of these gene variants are to do with the immune system and maybe Emma wants to take over

Emma - Yeah, and so actually you're absolutely right. There's these different variants that are associated with different aspects and different functions of our immune system, and it has been shown by one paper that there's a certain variant that we can track back to Neanderthals that increases susceptibility to covid. On the other hand, we've got another variant that actually offers some protection as well. So it's a balance and it's not clear Neanderthal genes are bad or good, so to speak in terms of covid susceptibility.

Chris - It's still extraordinary to think that running around in about 2% of our genomes are genes that would've been carried by this other group of our ancestors dating back more than 50,000 years.

Archaeological artefacts recovered from Pompeii

57:21 - When does grave robbing become archaeology?

Is there an amount of time that has to pass? Or is it more nuanced than that?

When does grave robbing become archaeology?

Emma - It's extremely interesting and I think it's not necessarily about time because you can actually do archeology on very recent sites, and people do that. It's more about the motivations and how you do it. So grave robbing is usually inquisitive, so it's to get remains or to get the grave goods to keep or to sell. Whereas archeology is actually about finding information about the past and in some senses preserving the past. So taking meticulous records and doing everything in meticulous detail to really preserve the knowledge about how people lived in the past

Chris - So it's the intent that matters, isn't it? Thanks Emma for that.


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