Can we Create Artificial Gravity?

Chris Smith put this question to Danni Green.

Danni - Well, although most people think it’s the blue whale and they can get to about 30 metres. The longest animal in the ocean, and indeed in the world, is actually the humble worm called the bootlace worm or Lineus longissimus, which it’s quite aptly named. It’s the longest recorded animal ever found and it washed up in about the mid 1800s after a big storm at St. Andrews, and it was about 55 metres long...

Chris S - This is just a worm?

Danni - … and about 10cms wide. And the thing about these ribbon worms is they a toxic proboscis that whips out and it has a neurotoxin in it that it uses to get its prey. So I don’t know what a 55 metre worm was preying on, but we don’t know what’s out there and how many more of these massive worms there are. It’s actually found
all round the UK as well these ribbon worms.

Chris B - I was wondering, does it have a nervous system that travels the whole lengths, so a nervous system that’s 55 metres long?

Danni - The smaller ones do yes, so I believe it would have. It’s amazing. Chris B - Wow! I wonder how long it takes for potentials to go from one end… Chris - Nerve impulses? Danni - That’s a good question.

Chris S - Because you’d think the sensory nerve information travels about one metre per second in small nerve fibres, doesn’t it? So it might take up to a minute to get your sensation. But motor information is 100 metres a second so movements might go a little bit faster. But that’s intriguing isn't it? Where do these worms hang out, they sound terrifying?

Danni - You find them all around the UK.

Chris S - Really?

Danni - Yeah. The bootlace worm - if you look it up there’s some really cool YouTube videos of them wriggling around. They awesome.

Chris S - What about land animals though Chris? You’re our Zoology/animal expert - biggest land animals?

Chris B - It would have to be a snake of some kind. So I wonder about the reticulated python

Danni - Was the question animal? Because if it was an organism it could be fungus. You know they those massive like - what are they called again?

Chris S - A mycorrhizal.

Danni - That’s a word a can never say, yeah. Those can be like hundreds and hundreds of metres, can’t they?

Chris S - They are literally hectares. I think they’re the biggest moving organism. It lives in America and it is a giant subserve fungal network which is hectares in size so that’s true. But in terms of land animals - how big is a giraffe in terms of its actual mass and that kind of thing? How much does one of those weight because they
don’t look like they would weigh much but they’re I guess actually quite big?

Chris B - Yeah. They vary from about 800 tons up to 1.2 tons sometimes. In terms of height, really, really tall giraffes are about 5 to 6 metres high. Chris S - Is this true Chris that they have special adaptations so they don’t explode their brain with their blood pressure becoming too high if they put their head down to drink? Is that true?

Chris B -Yeah, it’s a bit of problem. You’ve got to be able to push all this blood up to the head so you’ve got to work against gravity. But when giraffes lower their heads to drink, for example, they’ve got this problem of how do they actually stop their heads from exploding, their eyes popping out of their skulls? We think it’s because they’ve got a network of really find blood vessels that acts like a sponge. So it mops up this excess blood pressure when the head it is down and release it when the head is up.

Chris S - I was having a conversation, because medical people do this kind of thing, the other day about animals throwing up and we were speculating this might be a challenge for a giraffe. But then someone pointed out that they were ruminant animals, aren’t they, so they have a very good mechanism for regurgitating what’s in their stomach and chewing it back over again. So, in fact, they should be able to throw up without a problem.

Chris B - Yeah, it’s crazy. You can see food going down the neck and you can see it going back up as well. It’s really creepy when you watch it.

Chris S - Because someone said to me that you have to be careful with cows because if cows eat rhododendron this is very powerful as a mitogenic agent for them - it makes them throw up. And if you think the cow is the size of an oil drum, and a cow is an oil drum of liquid basically, just throwing up all in one go. And if a big field of cows eat rhododendron you can have a lot of cow vomit everywhere.

Chris B - If you see ruminants throwing up then you know something is seriously, seriously wrong. I’ve never seen a giraffe throw up and I hope I never do.

Chris Smith answered this question from Adel, after first asking the team.

Richard - Well, it’s that great philosophical question, isn’t it, that if we regenerate our cells are we still us anymore? It’s a question you could apply to the Flying Scotsman, for example, to bring it round to trains.

The Flying Scotsman locomotive, built in the 30s, rebuilt so many, so many times. Completely rebuilt recently - is it still the same engine as was originally built because so many pieces have been replaced?

Chris - In that great comedy “Fools and Horses,” I remember Trigger saying - he shows Del Boy his broom and says “this is my Great Grandfather's broom.” And Rodney goes “what the real one?” And he says “well it’s had one or two new handles and heads since then but yeah, yeah, it’s the original broom.”

Danni - do you want to speculate how many of your atoms are the ones you were born with?

Danni - Killed a lot of mine off in the first few years at university I think. But I think what you’re saying about the brain accounting for about 5 percent of your weight, and your eyes and all the rest, I’d say about 3 percent.

Chris - So we’ve got a 3 percent from Danni. Tim any thoughts?

Tim - I think it has to be a low percentage. We know quite a few different cells die and then you replace those cells, and this happens at different rates throughout your body. I think this happens for most of your cells, so by the time you’re dead, I’m thinking you’ve replaced quite a few of them.

Chris - I think it’s actually quite a difficult one to know the precise answer to this. But making it into the simplest question possible, you could argue how much does a newborn baby weigh? About seven and a half pounds or in new money, three and half kilo or so. How much does the average adult human weigh? Seventy kilo. Therefore your birth weight as a proportion of your grown adult weight is 3.5 divided by 70 times 100. That means you weigh about 5 percent at birth of what you will as an adult. Therefore, if you’re growing from 5 percent to your full size, only 5 percent of the atoms in your body can, by definition, be the ones you're born with. Therefore, if the answer to this question cannot be more than 5 percent, I would argue. Therefore, it’s got to be less than 5 percent but it’s not zero percent.

Now we know that things like your brain and the nervous system, those cells, and some muscle cells are also there for life. Your heart cells, for instance, last you a lifetime. Therefore, the answer probably is what proportion is the brain of your total body mass? It’s a couple of percent. So it’s probably somewhere between 2 percent and 5 percent of the atoms that you are born with last you a lifetime. Because you’ve got literally cells in your brain that are lasting you a lifetime, and the DNA in those nerve cells because the cells are not dividing, the DNA in those cells is not being replaced. So I’d say the numbers close to about two and a half to three percent. That would be my guess.

Richard - Yes. I like the way you show your workings there.

Chris - You get marks for that.

Richard - Excellent. Very good.

Chris Smith put Stella's query to Tim Revell...

Tim - To answer Stella, she doesn’t have to use a set of keys if she doesn’t want to. I have a friend, for example, who has a really cool setup. When he’s on his way home his heating slowly starts to heat up because his phone knows he’s on the tube on his way back home. And then, as he slowly starts to get towards his door, his lights come on automatically because he’s starting to get inside his wifi zone. Then as he gets to his front door, of course he doesn’t have a standard key turning lock, he’s got a number pad that he just types in the number and opens up the door.

This stuff is already here but the reason why a lot of people still have keys is because they’re installed on a lot of doors. How many people do you know that have actually bothered to change the locks on their doors? And these things are still a bit more expensive. A lock is a very simple mechanical device that you turn and a bolt goes through the door.

A lot of office buildings have these sorts of things where you can use a retina scan or you can use a fingerprint so this technology is here. So if Stella really wants it, she can have it.

Richard - What about power cuts or the wifi going down? I have a stereo system round the house which is brilliant. You show off to friends and everything - look what I can do on my phone - I can do all this. And then the wifi goes down and then it’s rubbish.

Tim - This is a problem but it depends to what extent. So, if this is actually for the lock on your door probably that doesn’t consume that much power anyway and you would expect it to have a battery that can backup the system should you need to still get in. Quite often these systems also have a lock that you can use with a key as a backup if you need it. A bit like car keys - a lot of car keys are beepers but there’s normally a way to get into the side of the car (a keycard or something) and there’s a little key that you can use somewhere. Yes, we need electricity for this stuff, but it’s not normally much so it’s not too bad if the system goes down.

Richard - It’s not zombie apocalypse-proof?

Tim - No… but neither are regular locks! The thing with all of these things is doors and locks are reasonably secure, but if someone wants to get in your house they’re probably going to break a window. There’s no fingerprint sensor on those so most people don't bother. And a lock is often made of steel and your door is probably made of wood. So you can just saw straight through past that.

Chris Smith put this question to Space Boffin Richard Hollingham...

Richard - We know that space is bad for you. Being in space, being in microgravity causes loss of muscle, loss of bone really quickly. You only have to be there a matter of hours before these things start happening.

Chris - Really?

Richard - Yeah. Very, very quickly. Problems with the nervous system, problems with the immune system and we are adapted to gravity, that’s how we evolved. We live around gravity.

Chris - Those nervous system problems and immune problems, are they down to a lack of exposure to gravity?

Richard - They are still being investigated but it would seem certain. There are other things going on in the space environment when you haven't got gravity. You’ve got, for example, with the immune system because you’ve not got gravity, bugs, bacteria, viruses won’t sink so they are around you all the time - there could be things like that. We haven’t got that many astronauts to study at any one time so you’ve not got a great group of people to look at and to study.

Chris - They’ve gone on to live a fairly long time those these astronauts.

Richard - Yeah. They’re doing pretty well. We’ve just had a year long mission but the problem is going to be not so much a year is fine. But a trip to Mars is going to be at least nine months out. Then you are actually on Mars and then you’ve got to come back nine months. You know the ‘giant leap for mankind,’ you don’t want to be coming down the bottom of a ladder and fall off and break you leg or something, which could happen if you’re not adapted, so, at the moment, in space they have various resistance machines. Treadmills for Tim Peake when he was in space he ran the London marathon on the treadmill. So there are adaptations but artificial gravity, that’s the thing we would love. And you look at those fantastic images 2001 Space Odyssey where you’ve got this big rotating spacecraft. The amazing images from the 60s and 70s of these massive space stations that rotate. Because they’re really big, they’re very difficult to make but people are looking at those sorts of options.

Chris - Would it work?

Richard - It would work, absolutely. You could get it to rotate - it’s not artificial gravity it’s centrifugal force. In 2001 that’s a great example. Can everyone remember the 2001 Space Odyssey? Even if you didn’t look through the whole film, it’s a brilliant opening where he’s doing this running. He’s basically running round the inside of the spacecraft. The Martian - the Matt Damon film recently. Again it had artificial gravity with this spacecraft spinning.

Chris - What does it feel like Richard? Do you feel like you’re actually experiencing gravity or do you just feel like you’re on that fairground ride that sort of does the same thing?

Richard - The trouble is no-one knows because we haven’t done it yet. It should feel like real gravity and they are doing some experiments on a much smaller scale. For example, the German space agency actually has a mini centrifuge that they’re looking at putting in the space station.

Chris - Can you put your wife on that?

Richard - No. I put her on a much bigger centrifuge actually. She was really good at it - I was rubbish. I was absolutely rubbish - I really squealed. So it is something that the space industry is seriously looking at. They’ve got to do something so a large spinning spacecraft would be the answer. The problem is launching a large spinning spacecraft. I mean, it’s taking since 1998 to build the International Space Station and you need something a lot bigger. So it’s a huge undertaking.

Chris - So right now you just have to keep up the exercise in space and hope for the best?

Richard - Yeah.

Chris Smith put this question to mathmetician Timothy Revell...

Tim - That’s a really good question. So what is pi, let’s start with that? You grab your favourite circle and we call the distance around the outside the circumference. And we call the width, making sure you go through the middle the diameter. If you divide the circumference by the diameter, then you end up with pi, which is just this number 3.14159ish.

But the thing is, I don’t think we take the time to realise just how crazy pi really is. If you take a circle that is the size of a pin prick, or that you take a circle that is the size of the moon and you divide its circumference by its diameter, you get the same number.

This is like some sort of universal conspiracy. This is why mathematicians study this so much. This is why we want to know pi so precisely. Because it’s a conspiracy, how does this happen?

Chris - Why should we be surprised though Tim that that’s the case because a circle, if you make it bigger, then all those things increase in proportion? That’s exactly what pi is so why is that a surprise?

Tim - Well, for me it’s a surprise. Why should there be a particular relation between the way a circle looks round the outside versus going straight through the middle? These seem to me to be rather different things but, obviously, the right answer is they’re not different things because pi is what links them.

Over the years there’s been lots of attempts to try and work our pi to the most number of digits, but the truth is pi is actually a rather tricky beast. You’re never going to work out all the digits of pi because it’s what’s called an irrational number. What this means is that if you write it out after the decimal point you are never going to stop. There are an infinite number of digits after that decimal point.

Over the years there’s been lots of different ways to try and calculate pi beyond just measuring it - various formulas and things, and the current world record is 22 trillion digits which was calculated by a guy called Peter Trueb in 2016, in November.

Chris - Why?

Tim - That’s a good question why? At the moment it just seems to be to show off how good is your algorithm and your computer.

Chris - I was going to say how good is your computer because that’s a lot of memory you’re going to need to handle all of that?

Time - And a lot of time that it takes to actually compute these things. You need a big computer and you need to leave it for a long period of time. In terms of how useful is that? It’s not very useful. NASA, they only use 15 digits of pi, and if you wanted to measure the whole universe down to a precision of a single atom you would only need 40 digits of pi. So to get to 22 trillion is a lot.

Chris - So when we have this question from Hannah which is: how do we keep finding extra digits? Because it’s an irrational number, if you just keep cranking the handle, you will keep churning out numbers as long as you keep turning the handle. It will never end.

Tim - Yeah. We know ways of getting closer and closer to this idea of what is pi? This sort of number but writing down those digits will take an awfully long time so it’s about finding the time and the energy and the people to want to do it.  So we will be able to do that for the rest of humanity.

Chris Smith put William's question to Richard Hollinham.

Richard - Nice question Chris. As Chris said the Goldilocks zone which is the area we inhabit, the Earth inhabits. We are the perfect distance from the Sun, we have gravitational stability so Earth doesn’t wobble around on it’s orbit around the Sun thanks to the Moon sitting there orbiting around the Earth. We have a magnetic field and this is very important for life. The magnetic field gives us this magnetosphere which is like a protective magnetic bubble around the Earth which protects us from charged particles from the Sun, stops us from getting zapped. And we’re pretty much the right size. So everything about Earth is great. That doesn’t necessarily mean…

Chris - Not everything.

Richard - Well no. We haven’t got time to go into all the things that are wrong right now. Let’s talk about all the things that are great physically with the Earth. It’s great for life.

That doesn’t necessarily mean that other places aren’t great for life it’s because life might be different there. I’m firmly of the view there is a lot of life out there. It might not be like us and I don’t think it’s going to be intelligent life. But I think if you look at places like hydrothermal vents deep underwater, and very toxic environments, where you can find particularly bacteria, and viruses, other microorganisms that we thought no way life could be there. You just need some source of energy and probably water but not necessarily.

So the argument with Jupiter’s moons which may have liquid water, energy there won’t come from the Sun, energy there will come from the gravity of Jupiter. So you’re looking at all these places that could have life but it won’t necessarily be us.

Chris - I was very fortunate to go down one of the world’s deepest gold mines in south Africa. And, in fact, in these operations there are microbiologists working because there are seeps of water and you can prove chemically that the water has been cut off from the rest of the world for millions of years, maybe 100 million years plus. You can tell that from the chemistry of the water. And yet when you look in this water which, in some cases is 60 degrees centigrade, you can find it’s thriving with bacterial life. So people said “well where do they come from?”

When scientists unpicked this, and this was a paper in Science about ten years ago, what they find is that there is uranium present in the ore. The radium is spitting out radiation, and the radiation is doing things to water molecules and giving them some energy. The water molecules then attack minerals in the rocks and release them for these microbes to live on, and the first layer of microbes eat those and then other microbes eat those first microbes, and you’ve got this whole ecosystem growing powered by radiation. So once people found that they said well look, it’s not so unlikely that you could have this somewhere else in our solar system, in a very inhospitable place but it’s got a nice warm interior because it’s radioactive and there’s life there.

Richard - Yeah. We can’t answer the fundamental question of how life gets there in the first place, but there does seem to be life in the most unlikely places.

Chris Smith put John's question to marine biologist Danielle Green...

Danielle - When lightening strikes the sea it spreads out horizontally rather than vertically so it would spread out along the surface. And because most fish and marine organisms tend to live at deeper depths they’re likely to avoid being struck by lightning but it doesn’t mean that they can’t be. There have been cases where people have observed lightning strikes and then seen dead fish floating on the surface. So I think they can be but it’s not something that is a huge problem because it’s not like it’s going to radiate across the whole earth.

Chris S - Because it’s spreading out and, as it spreads, it’s going to weaken quite considerably isn’t it? So the electric field to which the fish is going to be exposed is going to diminish really quite rapidly.

Danielle - Yeah. And in terms of marine mammals as well, there’s been some observations, sort of fisherman’s tales - I’m not exactly sure if it’s true or not - witnessing a whale being struck by lightning and things like that. If a human gets struck by lightning they don’t always die - I think it's 20 percent or something like that. It’s not a good thing. You wouldn’t go out of your way to get it but they’re not always going to die from it anyway. So I think it is something that’s possible but it’s not a huge problem because they’re usually deeper.

Chris S - Tim?

Tim - One of the first things I ever did for the Naked Scientists was piece about a person who’d been struck by lightning and wanted to know about it. The thing I most remember about this is we interviewed someone in the US who was all about lightning safety and he came up with this great phrase that I will remember till the day I die which is “when thunder roars, stay indoors.”

Chris S - Good quote. Farmers, Chris say they sometimes find animals that have died in fields. They sometimes argue that lightning hits the ground or something and then travels across the ground and if you put a long animal like a horse or a cow, it could go up the front legs, along the body killing the animal enroute, and then out the back legs. Do you think that’s true?

Chris B - Yeah. I definitely think it’s possible. Imagine the setting… you’ve got a nice open field with livestock - it seems like a good recipe for lightning strikes. I often wonder are giraffes particularly sensitive to this problem? They tend to hang out in open spaces.

Chris S - But they’ve also got an inbuilt lightning conducter, haven’t they?

Chris B - Exactly.

Chris S - And is that the case because you get some pretty vicious thunderstorms over the areas of Africa where these animals live

Chris B - Again, you hear lots of stories of people saying they’ve witnessed lightning strikes in giraffes. Yeah, I don’t know.

Chris Smith put this to zoologist Chris Basu...

Chris B - The question of which apes did human beings evolve from? That’s a big, big, big question and that’s the reason why this area of science, the study of human ancestors, is such a big and active area. That’s because the honest answer is we don’t yet know.

We do know little pieces of the puzzle. So we know that by looking at DNA the last common ancestor between human beings and chimpanzees lived about 7 million years ago and when we look at fossils from around this time we do find that these fossils do have things in common with human beings.

So fossils from West Africa are starting to show the really early signs of things like bipedalism. But one of the challenges of this area is, when we look at these fossils, we’re not looking at our direct ancestor. It’s like if I’m studying a photograph of my great uncle and I’m trying to imagine what my great grandfather looked like. So it’s one of these challenges that we’re trying to work out what our ancestors looked like from our distant relatives.

But going to the question of the eye colour yes, our early human ancestors likely had brown eyes. And the diversity in the eye colour that we see today comes from mutation in our genome. So, for example, the mutation that give us blue eyes, we can pin down to about six thousand years ago. And perhaps one of the reasons we do see a lot of variety in eye colour in humans is because of our white sclera. So the whites of our eyes really makes our eyes really stand out, really punch out when you look at them and that’s probably because of things like non-verbal communication, so facial features, are really important in our society. That’s we’re drawn to look at eyes.