Naked Science Question and Answer and Polonium Poisoning

Answers to all your questions on science, technology and medicine, including why spiders don't run out of silk, what is the universe expanding into, what a flame looks like...
03 December 2006


Dr Chris, Dr Dave and Dr Phil answer all your questions on science, technology and medicine, including why spiders don't run out of silk, what is the universe expanding into, what a flame looks like in space, and what happens when the brain is cut off from a supply of oxygen. We also talk to Dr Mark Peplow from Chemistry World about polonium 210, how much was needed to kill former Russian spy Alexander Litvinenko, and where the perpetrators could have acquired it. Sticking with nasty substances, Derek Thorne and Dave Ansell make a mess with milk and vinegar in the name of Kitchen Science.

In this episode

Longest Ever Golf Shot

Russian cosmonaut Mikhail Tyurin has just hit the longest golf shot ever. He did have a slight advantage over Tiger Woods though, as he was 390 km up and travelling at 7.7 km per second outside the International Space Station. The whole stunt was sponsored by a Canadian golfing company who paid the Russian space agency an undisclosed fee for the publicity and supplied a gold plated golf club for Tyurin to use. Unfortunately for Tyurin, despite being very well qualified for space walking, he'd only ever played golf twice. The pressure of being tethered to the space station and only holding the club with one hand due to the bulk of the space suit meant he sliced the shot off to his right. The shot was supposed to be sent backwards, ensuring that it quickly descended and burnt up in the Earth's atmosphere. NASA scientists have analyzed the trajectory of the sliced shot from video footage and estimate that it would have burned up on re-entry in 2-3 days after travelling about a million miles. As it happened, scientists had expected the shot to be less than accurate so had provided a super lightweight golf ball to ensure no damage would be done if it hit any space station structures. But the spacewalk was not just about a golf gimmick. While outside Tyurin and his partner Lopez-Alegria also moved an external antenna and attempted to release a jammed antenna on a docked supply ship.

Hubble Given a New Lease of Life

The fifth and probably final service mission to the Hubble Space Telescope has been approved to keep it running to around 2013. Hubble was designed so that astronauts could visit the telescope to make repairs and swap old instruments for new updated versions. However, the latest mission scheduled for 2004 was cancelled after the Columbia shuttle was destroyed on re-entry. Now that recent shuttle missions have performed well it is thought that it is safe to send astronauts to Hubble again, however because Hubble is farther from the Earth than the space station, it is unlikely that a rescue mission could be launched if there is a problem with the shuttle. The mission itself will concentrate on replacing gyroscopes and batteries and adding two new instruments. The gyroscopes are spinning weights that keep Hubble stable and three are required. Hubble has six in total with three being spares. Currently two are too worn to use so only one spare is left. Batteries also have finite lifetime as anyone out there with a mobile phone will know. A new phone will stay charged for days but an old one may only last hours. Hubble's batteries are now 16 years old so they don't charge up from the solar panels very well any more. The new instuments are called the wide field camera 3 and the cosmic origins spectrograph. The wide field camera is essentially a new updated digital camera with a 16 megapixel CCD sensitive not only to visible light but also to UV and also an infra red detector. The spectrograph is built to look specifically at long strands of galaxies that have previously been discovered separated from each other by vast voids of empty space. The new improved Hubble should then last until at least 2013, by which time the new James Web telescope should have been launched into space to take over.

- Science Update - Biomimetics

The Naked Scientists spoke to Chelsea Wald and Bob Hirshon, AAAS, the Science Society

Science Update - Biomimetics
with Chelsea Wald and Bob Hirshon, AAAS, the Science Society

Bob - This week for the Naked Scientists, we're going to talk about biomimetics, that is, a type of engineering that aims to imitate biological systems. I'll tell you about a new robot snail that could soon be crawling through your intestines, but first, Chelsea tells us what engineers are learning from rats.

Chelsea - In the future, autonomous robots could use artificial whiskers to help them sense their surroundings. In fact, engineers Mitra Hartmann and Joseph Solomon of Northwestern University have built a prototype of robotic whiskers that may work a lot like those on rats. Hartmann says the key is to measure how much the whiskers bend as they sweep across an object.

Mitra - And suppose an object is in close and the whisker rotates into it fast. Well, then the whisker's going to bend a lot very quickly. If the object is far away, and it's rotating at the same speed, then it's not going to bend as much.

Chelsea - Using this system, her team was able to re-create a 3-D image of a face. Aside from helping autonomous robots navigate, the whiskers could check parts on an assembly line, generate 3-D models, or feel for obstructions in pipelines..

Bob - Thanks, Chelsea. And speaking of pipelines, robotic snail may someday crawl through the human intestine to diagnose diseases. According to biomedical engineer Dimitra Dodou at the Delft University of Technology in the Netherlands, such a device could provide a more comfortable alternative to colonoscopy. She says the challenge is finding a way to navigate the intestine's uneven, slippery terrain.

Dimitra - Imagine that you have to move inside a deflated balloon, and it is covered with a lubricated material.

Bob - Rather than fight the lubrication, Dodou and her colleagues sought to imitate the snail, which both sticks to and slides on its trail of slime. They found that chemicals called muco-adhesives created enough friction for a simple device to walk across a pig's intestine. They're also fine-tuning patterns of motion, in order to create a sure-footed prototype robot that still treads lightly on delicate tissue.

Chelsea - Thanks, Bob. We'll be back next week to tell you about the space telescope NASA has planned to replace Hubble. Until then, I'm Chelsea Wald.

Bob - And I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists.

- Polonium 210

The Naked Scientists spoke to Dr Mark Peplow, editor of Chemistry World from the Royal Society of Chemistry

Polonium 210
with Dr Mark Peplow, editor of Chemistry World from the Royal Society of Chemistry

Chris - It's been a week or two that's really recreated something that I don't think Ian Fleming could have recreated in the James Bond series; stories about KGB agents knocking off ex-Russian agents and Alexander Litvinenko dying from polonium 210 poisoning. But what actually is polonium 210 and how does it actually do away with people when it gets inside your body? How do you get hold of it and how do you get it inside your body? The editor of Chemistry World from the Royal Society of Chemistry, Mark Peplow, joins us to tell us. What is actually is it, and if I wanted to get some, where would I get it?

Mark - Well this is one of the most bizarre things about this case. It's a very very rare element; a silvery sort of metal. When it was first discovered by Marie and Pierre Curie back in 1897, they did it by trawling through uranium ore, but you only get about 100 micrograms of this stuff in every tonne of uranium ore. So these days you make it by bombarding an element called bismus with neutrons. Now the only way you can do that is in an experimental reactor.

Chris - So that means that somebody must have had access to some pretty high class technology to be able to do this. It's a well-planned and orchestrated attack.

Mark - Absolutely. This is something that you can't just go out and set up yourself. There are maybe only forty facilities around the world that are capable of making this stuff. Funnily enough, Russia actually exports about eight grams of polonium 210 every month, and all of it to the US. It does have a very small use to help discharge static that builds up in certain types of machinery. But other than that, it's not really made very much at all in the world.

Chris - So how much would you need to get inside your body to be harmful?

Mark - The maximum safe dose you could get away with is seven trillionths of a gram. That's a minuscule amount. According to the doctors, the sorts of doses Litvinenko took or was given was substantial enough to cause this very rapid onset of radiation poisoning. That might only be micrograms or milligrams though, so it's the sort of amount that could constitute something smaller than a pea.

Chris - Why do you think someone would have gone for such an exotic way to kill someone? Wouldn't something like lead poisoning in the form of a bullet have been more effective and probably easier?

Mark - Yes, it's very bizarre. This now gets into the realms of a spy thriller and something that is really speculation. From one point of view, it sends out a very powerful message that whoever has done this does have access to some very serious pieces of kit and is able to move radioactive material around the world almost certainly. On the other hand, it may have been a geniuine attempt to try and disguise the mode of poisoning of this guy. Obviously he was sick for quite a few weeks before people realised exactly what had poisoned him, despite the fact that experts at University College London had been testing him and looking at him to treat him. This may have been one of the reasons to use the polonium. It's simply so rare and there's no other documented cases of deliberate poisoning by this metal, that it may have been to cover up the fact that this guy had been poisoned in this way.

Chris - You don't think for instance that this is a KGB calling card. They're saying that you can't prove anything, but it's obvious who's done it.

Mark - Well like I say, it may be a very obvious way to say 'look, we have the technology and we can get to you with some really bizarre stuff that you need serious contacts and power to get hold of.' So yes, that may be one explanation.

Chris - And once you've got this stuff inside your body, why does it actually make you unwell?

Mark - Because it gives out radiation, the type of radiation it gives out is called alpha particles. It's a bundle of two protons and two neutrons; the little particles that make up all the atoms that make up all the different elements in the universe. These alpha particles can work in two ways. Because they're positively charged, they can rip electrons away from the molecules that are found in your body cells that are responsible for doing all the biochemistry needed to keep you living. In doing so, they make things called free radicals, and that can help to break down all the different biochemical reactions that are going on. That can cause you illness. In the longer term, the alpha radiation can damage DNA in your cells. It can damage the DNA to such an extent that the cell realises how badly warped its DNA has become and that can actually make it shut down. The cell will kill itself in a process called apoptosis because the cell has undergone such rapid damage.

- What's a flame made of?

What's a flame made of? Is it made of carbon, and if so can substances that don't contain carbon actually burn?

What's a flame made of?

It depends what colour the flame is. What's happening with a flame is you're reacting something with oxygen. You have a gas coming up which is reacting with oxygen and giving off lots of heat. If that's reacting very cleanly you tend to just get a plain blue flame, or possibly white. If you get little soot particles in there, they glow very brightly yellow. So if you see a very yellow, sooty flame, that is the carbon you're talking about glowing. You can put other things into flames which is how they make colours. So if you have copper salts you get blues and greens, and strontium makes nice red colours.

- What would happen if you lit a match in space?

What would happen if you lit a match in space? Considering there's oxygen in the air on a space station but no up or down, what would be ...

What would happen if you lit a match in space?

A flame goes upwards because of convection. The hot gas created by the flame rises. As you say, there's no up or down in space so the gas just forms a sphere around where it's burning and you just get a sort of circular flame. But actually stuff doesn't really burn very well in space. This is because the process of the gas going upwards (as happens on Earth) gets rid of the carbon dioxide formed in the burning process and sucks in more oxygen to keep the flame stoked. This keeps everything burning quickly. As there's no upward movement of gas in space, you don't have much oxygen getting into the flame and it's quite a poor flame that is formed. So essentially it chokes itself in its own waste products and just goes out.

- What is the universe expanding in to and how far can it expand?

According to the Hubble space telescope, the known universe is expanding. What is it expanding in to and how far can it expand?

What is the universe expanding in to and how far can it expand?

If I'm quite honest no one really knows the answer. However, there are a lot of interesting ways to look at it. My favourite way is to imagine that the world was two dimensional, so you and the Earth are stuck on a flat bit of paper. Now imagine that that piece of paper is part of a giant globe (you can also think of it as a flat spot of ink on a balloon). As the balloon expands, it's expanding in three dimensions, but the surface area you can see as a two dimensional human being will be getting bigger and bigger and bigger. Now if you can imagine that we see the world in 3D, if you can imagine that was maybe just the surface, as it were, of a four dimensional shape, (I really struggle to imagine it) then that would be one way that you could imagine it. There are more dimensions that we can actually see and we are expanding in these other dimensions. A lot of people ask what is it expanding into, because there must be something. But of course if the universe is everything, then as soon as it expands it just makes the thing that exists bigger. There are also ideas that there are millions of different universes all competing for space and going at different speeds. Like little bubbles, all crowding each other out. And actually, maybe the black holes in our universe go through to other universes that are being created. It's really one of those questions that's more philosophy almost, than science. Everyone's really only making guesses. Everyone's trying to get the evidence to prove that it's one way or another and that evidence just isn't here yet.

Why don't spiders run out of silk?

Spiders are really actually quite clever. Ancestrally they go back a couple of hundred million years, we think. They have glands at the back end of the spider and now it turns out also on their feet that make silk. And what scientists think, is that the glands on the back of their abdomen that make silk are just adapted limbs, where they used to have some legs. Silk is the reaction of proteins. So you have a chemical reaction going on at the back end of the spider that literally spins silk on demand. The spider eats something that has got protein in it. So when it goes and catches something in its web, it injects a venom into that insect that kills it by paralysing it. The insect is paralysed and doesn't die instantly so it remains fresh, the spider injects digestive juices which liquify an insect. And because an insect is like a husk, with a hard skeleton on the outside with the soft bits in the middle, the spider can literally suck the good bits out of the inside leaving behind a dry, wizened up shrivelled skeleton. That's why you see these sort of husks of insects left under spider webs. All the protein and goodness from inside the insect ends up inside the spider, the spider digests that, absorbs it, and then the proteins go to the back end of the spider. And they get turned into new web, amongst other things a spider needs to make. And some spiders have taken this a step further. What they've done is to make the process even more efficient, by eating their own web. This doesn't do them any harm because web is just protein. By eating their own web they're getting the proteins back into their body and they can then reuse them. Spiders' web is incredible stuff and it can absorb immense amounts of energy. It's got the tensile strength of steel. Scientists are now looking at ways of using it for bullet-proof vests, for example. If you can make this artificially in enough quantities you've got something with the tensile strength of a piece of steel, and the ability to stop bullets much better than a bullet-proof vest. Which means rather than police having to go around in these very thick outfits which restrict movement, if you could make it out of spider silk it would be a) lighter, b) a breatheable fabric, so it wouldn't make you so hot and uncomfortable, and c) it wouldn't restrict your movement so much.

- What happens when the body is cut off from oxygen?

What happens physiologically when the body is cut off from oxygen?

What happens when the body is cut off from oxygen?

The body has an incredibly high metabolic rate, so you're burning off oxygen really, really fast. The brain has the highest metabolic rate and in fact the retina is the part of the brain with the highest metabolic rate. So that's why when you stand up out of a hot bath very quickly you get a very brief dip in blood pressure, because all the blood is in your legs. The result of that is the retina gets slightly less blood for a fraction of a second and that's why you see those funny lights and you feel a bit woozy. But then as your blood pressure comes back up again the brain gets a good supply back. That's evidence of how oxygen dependent your brain is. If you cut off the supply for a fraction of a second, the reduced blood flow just makes you lose consciousness. Tissues like the brain are incredibly sensitive to just a minor interruption in their oxygen supply. And that's why you faint. When I was at medical school we did an interesting experiment where they simulated going to the top of a mountain. So I said "oh I'll be the subject". I was laying on a table and breathing out of a bag which was 10% of oxygen instead of 20% you normally find in a room. They were trying to see if my blood would get slightly less oxygen dissolved in the blood stream. But it didn't actually work very well. I breathed this bag for about 20 minutes and it didn't actually reduce my oxygen capacity terribly much. If you do go mountaineering what you do to compensate is you just breathe more. So you pack more breaths in and your haemoglobin's very good at grabbing oxygen out of the lung and putting it in the blood stream. A red blood cell takes about 0.8 seconds to go through the tiny blood vessel through each of the air sacks in the lungs. But it only takes about 0.3 seconds for the oxygen to get into it. So there's a safety factor of at least threefold. It's got three times longer to pick up oxygen that it needs, so if you breath a bit harder and shove more oxygen into the lung, you can pick it up. This is also why you've got to be careful breathing helium balloons, because there's no oxygen in that helium. I did it a while ago and it made my head go incredibly dizzy.

- Can RFID strips be reactivated?

Can magnetic anti-shoplifting strips get reactivated after your purchase, causing alarms to go off? How do they work?

Can RFID strips be reactivated?

The way most of these work is by having a tiny little electric circuit in it. They've got an aerial around the outside of that, and when you walk past one of those detectors, that puts radio frequency energy through you. This powers up the circuit. The little circuit sends a code back to the detector and says "Help, help I'm being stolen" and then the alarm goes off. There are also the solid ones you find in clothes, which are attached, and the reason you might think they're magnetic is the way you deactivate them by using a magnet which allows them to detach without spreading dye all over your nice new clothes. However, the tag will still activate the alarm. The ones which are actually stuck to the things you're buying are deactivated in a slightly different way. What they do is they have a little an electronic thing which puts in such a huge amount of power that it basically melts something in the circuit and causes it to break.

- If the universe keeps expanding will it hit itself eventually?

If space has a curvature and is expanding outwards, how long before it goes around in a circle and kicks us up the backside?

If the universe keeps expanding will it hit itself eventually?

That's a really good question that no one quite knows the answer to. You're right in saying that there have been theories that space has got a curvature, but the most recent results show that it hasn't got a curvature at all. It might be completely flat, or it's so close to flat that we can't tell the difference between curved and flat. How do they work this out? It's pretty tough but it's all to do with the speed at which that things are flying away from us. If you can imagine measuring the angles of a triangle on a flat piece of paper, they add up to 180 degrees. On a curved space that's not the case. So we use these geometries to work out what exactly this curvature is. As I said, at the moment it looks like everything's completely flat, or at least very very close to it.

- What limits the length of the human life?

What limits the length of the human life?

What limits the length of the human life?

There are a number of things that can determine how long we live. The first thing is the rate of your metabolism. If you compare a mouse with a human, then we're very very genetically similar. But if you look at the heart rate of a mouse it's running along at several hundred beats a minute, whereas our heart's beating at 50 times a minute. So a mouse, in order to survive because it's so small, has to run it's body very very fast. It's almost like you being whipped along by a slave driver. In a mouse, the cells are growing faster, they're dividing more, they're doing everything more quickly, and so the mouse burns itself out more quickly than a bigger animal, like a human. If you compare animals like tortoises, which are cold-blooded, they're big, they're cold blooded, and their metabolism is running much more slowly. Giant tortoises can live for 100, maybe 200 years. So it's down to the speed of your metabolism. Scientists have found whales in the ocean which might even be several hundred years old. There are harpoon tips which have been recovered from the blubber of whales that date back historically to the types of harpoons that haven't been used for several hundred years. Leading scientists to conclude that they really are quite old. The second thing is something called a telomere.These are structures on the ends of each of your chromosomes that are almost like the pieces of cellophane you find around the end of your bootlaces to keep the lace from fraying. Every time a cell divides, it erodes a little piece off of the telomere so it gets shorter and shorter and shorter. If you look at cancer cells that seem to live forever, they have switched on an enzyme that makes telomeres get longer and longer and longer. That seems to be what gives the cells the ability to divide forever. But in a normal cell, the problem is that eventually the telomeres get so short that they run out, and that seems to determine how many times a cell can actually divide. It's called the Hayflick number so there's a limited number of times a cell can divide. But that's not why someone dies. They usually die because something has damaged their DNA and that causes the cells to work less well, and so you get things like cancer.

- How does a fly land on the ceiling?

How does a fly land on the ceiling? Aren't its wings beating in the wrong direction?

How does a fly land on the ceiling?

Flies are quite cunning. They have little grappling hooks on the end of their feet, and when they're going towards a surface, they literally have to throw themselves straight upwards towards the ceiling so their head points towards the thing they want to hit. They reach out with their front legs and they grab hold of something spiky or rough that they can latch these miniature grappling hooks onto. They then switch off and fold their wings away, and swing their body under them in order to lock onto the ceiling. Now they're hanging on upside down. When they want to drop away again, gravity does the work for them. They can just let themselves go, but they hang on with some feet first so that one part of their body drops away and then the rest of their body drops after it so they're in the right position to begin flying again. People know this because they wondered that very question and someone clever invented a camera that could take pictures fast enough, called time lapse photography. You can get pictures now at 4000 times a second so you can see individual wing beats of insects and things. Now they were able to work out exactly how they're doing this.

- What happens if you fire a bullet from a plane?

What happens if you fire a two bullets from an aircraft moving at 1000mph? One is fired forwards at 1000mph and the other backwards at 10...

What happens if you fire a bullet from a plane?

This is moving relatively slowly so this isn't complicated by the problems of relativity. All you have to do is add up the speeds. The one going forwards will be going at 1000mph plus 1000mph so 2000mph. The one going backwards will be going at 1000 minus 1000, so not at all it will fall straight down.


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