Your Science Questions

14 June 2009

On this Naked Scientists Question and Answer show, we discover how storms create slow earthquakes and how a local star, betelgeuse, could explode very soon. We also hear of an accurate way to date pottery and explore the physics of helicopter seeds. Plus, why hurricanes rotate in opposite directions either side of the equator, the ultimate fate of stars and how to boil your fishtank without harming the fish. All this and in Kitchen Science we snap some spaghetti to seek the physics of pasta!

In this episode

Why does water go the opposite way in the Southern Hemisphere?

Dave - Okay, this is an effect, which theoretically would work in certain circumstances. It definitely works with big weather systems or low pressure areas. Essentially, if you're a low pressure area or anything which is sucking liquid in from a long way away, the stuff which is to the North; because the Earth has a smaller radius out there is moving, going round the Earth once a day, but it's not going very far so it's not moving very fast. But, the stuff nearer the equator, you're further away from the axis of the earth. So, the distance you travel everyday is further so you're travelling faster. If you then suck the stuff in towards the central point, the stuff which is going faster, from the South will overtake stuff from the North and it will sort of start to spin around into the center. Now, this is an effect which does happen, cyclones go anti clockwise in northern hemisphere and clockwise in southern hemisphere. But, when you start talking about emptying basins and sinks, the problem is this effect is there, but it's absolutely microscopic, it's tiny.Chris - People have measured it.Dave - People have measured it, yes. Americans did make a huge bath, several meters across. They put a little bit of water in it and left it to sit for a fortnight and they pulled the plug out in a very controlled manner. If you do that, it does always get out anti clockwise in northern hemisphere. Problem is in a normal sink, it's much more affected by which tap you use to turn it on. How you move your hands in it within hours before you left it to pull the plug out, and exactly how you pull the plug out. And so, we did this experiment on the Naked Scientists a while ago and we found it's essentially random in both northern, southern hemispheres.Kat - You mentioned about cyclones going different ways. What happens to the cyclones moves across the equator? Does it suddenly stops and start going the other way?Dave - They generally slow down and I don't think they normally do - I've never seen one.Chris - It wouldn't be energetically favorable probably for it to do that.Kath - So it wouldn't do it, it would grind to a halt. Crazy.

Why don't we choke when we drink through a straw?

Kat - Okay, I have done extensive research into this question myself last night with some rum-based cocktails. So, this is..Chris Smith: It would have to be rum or can it be anything?Kat - Anything would work, yes, but I'd like Margaritas. But, you can't really drink them through a straw and I will be publishing my results in the journal of Inebreology very soon. But, basically, the reason is, is that when you're drinking a drink that's a full drink, you create a vacuum in your mouth and that's basically what forces the liquid up the straw. You're not really kind of sucking it up. You're actually dropping the pressure in your mouth and that causes the liquid to go up the straw. What happens when you get right down to the bottom of your drink is that there's very little liquid there. So, if you start there's not really a lot of liquid that's gonna go up into your lungs even it was to get there. The other thing is that fluid is a lot heavier than air and when you actually do the motion of sucking something up from the bottom of your cocktail glass or your milkshake, you kind of form a barrier at the back of your throat with like soft palate or things like that. So, the dregs of fluid come up the straw, they get into your mouth, they kind of go 'phleh' into your mouth while the air gets..Chris Smith: How it go again?Kat - 'Phleh'Chris Smith: Just checking.Kat - That's the scientific term I think you'll find. It sort of goes 'phleh' into your mouth. They don't really make it to the back of your throat to go down your lungs, but if you are a clumsy or a very enthusiastic drinker. It is possible to inhale fluid into your lungs up a straw, but most of us have kind of learned how to drink so we don't do it.

How can I boil water without killing the fish that lives in it?

Chris - I love that question. What is he doing? It's basically fish bowl.Dave - He's apparently got a live fish swimming in the fish bowl and he wants to boil the water without harming the fish.Chris - He wants to boil the water without harming the fish. Well, thinking about it. I mean, what we know about the boiling point of water. You can make water boil by raising the temperature that gives the water molecules more energy so they can escape from the body of water against the force being applied to the water surface by atmospheric pressure. You can also make water boil at the same temperature by reducing the pressure above the water. So, I suppose if you put the fish bowl into a very large space that he could evacuate very abruptly - so in other words, take all of the air out so the fish bowl is sitting in a vacuum, the water would boil without getting hot and therefore, wouldn't harm the fish through heat. The problem is all the dissolved gases would presumably boil out instantly so the fish would asphyxiate very quickly unless you did it transiently, just quickly make it boil and then stop again. Just as a party trick to prove that this is possible.Dave - I guess the other problem is if the water is boiling around the fish even if its not damaging the proteins because it's not hot. the fish is probably going to get the bends because any water or gases...Chris - Indeed because fishes have swim bladder, don't they? This is how they regulate their buoyancies like a diver's BCD, which makes them buoyant, neutral buoyancy in the water. So, if you had a fish that has a swim bladder, it could explode. I presume under those circumstances.Dave - Even if you have a little shark or something which didn't and then it's gonna get the bends, so it's probably not going to be a happy fish.Kat - Horrible people.Chris - But, it may not die straight away. So, there you go, there is the solution to your problem.

Why do my eyes take time to adjust to the dark?

Chris - You've got two important questions there. First of all, getting used to the dark. We'll have to think John Gamel for this, who is an ophthalmologist over in America and he sent me some ideas. One of the most important points with eyes getting used to the dark is actually how your eyes see in the first place. Which is when that you're looking at something, There are beams or rays of light of certain wavelengths or colours coming into your eye and they interact with the photo pigment. A chemical which is sensitive to certain wavelengths which is in your retina. When the light waves hit that pigment, they cause the pigment to change its configuration. It is so called bleach. When it changes its configuration, it then signals the cell to change its behaviour so that's basically how the retina turns light waves into brain waves. It's turning the information into pulses of nerve activity the brain can understand. For a period of time, when that pigment has been bleached, it can't to respond to light again until its regenerated, until its shape goes back to its original starting confirmation. So, when you go from a very light area where on average many of your pigment molecules in your retina will be being bleached out any given time and then you go into the dark; Many of those bleached-pigment molecules will slowly turn back into unbleached pigment molecules, they're sensitive again. So, in other words, the longer you spend in the dark, the more pigment molecules becomes sensitive and therefore, the more sensitive your eyes become. That's the first point. The second one is also that the retina is a very dynamic electrical organ. There are two different ways in which the retina responds to light. There are cone cells, which are not very sensitive to light. They need a lot of light to activate them, but they see in colour and then all the rod cells which are very sensitive to light. But, they can only see in black and white, and what the eye can do is at low light conditions, you can connect via electrical coupling called a gap junction some rod cells to the cone cells and what this means is that the rod cells trigger the cones at a lower amount of light and they otherwise would need to turn them on. So, as a result, you can actually see in colour at much lower light than you would otherwise. It takes a little while for these gap junction connections between the different classes of rods and cones to actually get activated. So, there's also that process of adaptation.Now, in terms of what happens when your dog goes out into the dark. The reason dogs can see so well at night is because in common with many animals that are nocturnally active, dogs have a structure at the back of their eye called a tapetum lucidum which is Latin for bright carpet. If you look at the back of the dog's eye also sheep have this, cows have this, horses have this. The back of the eye is very, very reflective and shiny. This means that any light that comes into the eye that misses the retina the first time can bounce off the back of the eye and back on to the retina. The benefit then is that it makes the eye much more sensitive to light, but slightly less able to pinpoint precisely where the light is coming from. So, there's a small loss of acuity which comes at the cost of increased sensitivity. So, that's basically how your dog can see much better in the dark than you can.Dave - So, is this tapetum lucidum the reason why if you try to light the dog's eyes they bright up so brightly?Chris - When you shine light into a person and you see this when you do flash photography and you see red eye. The human retina looks red to the camera because the light illuminates the very dense rich blood supply at the back of the eye because the retina has one of the highest metabolic rates of all the tissues in the whole body. But, in the dog or one these other animals, because the back of the eye has this tapetum lucidum, this bright carpet. The light that goes into the eye immediately turns around and bounces straight back out again in that very demonic way. It's because it's like reflecting at the back of the eye that makes your dog's eyes look very bright, but the same thing doesn't happen with the human.Dave - Also, I think the lens focuses the light straight back where it came so all the light which you shone into the eye comes right back at you standing next to the torch.

What is the ultimate fate of a star?

Dave - Very good question Jim.

There are lots of different types of stars and what happens depends upon how big the star is to start with.

If you've got a very small star - for instance what's called a Brown Dwarf, which is a minute star maybe 8 percent of the mass of the Sun - it collapses, forms something like a "big Jupiter".

It starts to warm up, but it doesn't even warm enough to start nuclear fusion. It doesn't fuse any hydrogen. It just sit there and slowly cools down and ends up as a very cold planet.

Slightly bigger, and you get stars in which the gas collapses, they heat up and start burning (fusing) hydrogen. These are small stars, less than about half of the mass of the Sun.

They burn all the hydrogen, but they never get hot enough or dense enough to start burning helium so they then cool down again.

A star is basically just hot gas, the only thing that is supporting it under gravity is its temperature. So, it slowly cools down and shrinks and shrinks and shrinks and forms this very big lump of helium as sort of helium White Dwarf.

Normal mass stars, like the Sun, burn their hydrogen away but then they've got enough mass to collapse down further and begin burning their helium to form carbon; then that will burn away. As it does so, the core of the star collapses.

It gets very, very hot and blows the outer layers of the star out to form a red giant. It's got a very small core with a great big kind of diffuse, warmish red star outside it.

This core is not massive enough to burn the carbon to form anything else. So, the core can make an explosion, it blows away the gas to leave a cold, carbon core.

Some of these, as they cool down, can crystallize and form diamond-type things.

If you get a bit bigger than this white dwarf, that's got enough mass to collapse and form a neutron star, that explodes and forms a huge supernova. If you get even bigger than that, it's so massive that the neutron star will collapse to form a black hole from which nothing even light can escape.

39:11 - The Science Museum - Science Icons

2009 marks a 100 years since the opening of London Science Museum. To mark this special anniversary, the Science Museum is launching its centenary journey trail, which identifies ten...

The Science Museum - Science Icons
with Chris Rapley, Science Museum Director; John Liffin and Katie Maggs, curators of the Science Museum; Lord Peter Mandelson

Kat -  Now it's time to join Meera Senthilingam.  She's been in the Science Museum in London this week to celebrate its 100th birthday and to mark the occasion, as with all great parties, the museum has launched a special exhibition showcasing ten iconic inventions from the history of science such as Stevenson's rocket, the Pilot Ace computer, the Apollo 10 capsule and the DNA double helix.  So, Meera went along to find out more.

A real representation of StephensonMeera - 2009 marks a 100 years since the opening of London Science Museum.  So, this week, I've come down to the museum in Kensington for the launch of centenary celebrations.  Now to mark this special anniversary, the Science Museum is launching its centenary journey trail, which identifies ten scientific icons. In addition to this trail there's a public vote to identify the most significant object in the history of science.  Today's event was launched by the Secretary of State for Business Enterprise and Regulatory Reform, Lord Peter Mandelson.   Here's what he had to say about the importance of science and Science Museum in society today.

Lord Peter Mandelson -  The road from late night brainwave to scientific breakthrough then commercial success is a long, hard and rocky road. But it does start with the thirst for knowledge and a love for innovation. Over the last 100 years the Science Museum has helped feed and nurture that spirit for countless British innovators.  It has helped explain and show the role of science in our lives in all its glory.

Meera -  That was Lord Peter Mandelson discussing the importance of science in society today. Now, today's centenary celebrations were also launched by the museum's director, Chris Rapley.  So, Chris, tell me a bit about the origins of the Science Museum.

Chris Rapley -  We can trace our origins right back to the 1851 Great Exhibition, which was a celebration of Victorian industrial design and production. In fact, Prince Albert, Queen Victoria's husband was really one of the driving forces behind that.  It was hugely successful something like the equivalent of about 1/3 of Britain's population at the time visited that exhibition. They had 6 million visitors in 5 months and they set up an organization called the South Kensington Museum so that's what we trace our origins to.

Meera -  What would you say the original kind of role of the Science Museum was?

Chris Rapley -  Okay, it was really important that you always find historic champions and the historic champions at that time were the astronomer, Norman Lockyer in particular who actually established Nature magazine which is still, you know, the premier science magazine.  He and others saw the science collection as hugely important to both the scientific, cultural and industrial benefit of the nation and our view of course is, you know, plus ca change. It's exactly the same today.  We're using those objects not just to engage people with something interesting but hopefully to engage them we're thinking about how they can change the future because ahead of us lie great challenges. Science and technology will play an enormous role in either solving those or not. We want everybody to play a part in that.

Meera - Chris Rapley, Director of the Science Museum discussing the origins of the museum and the role it plays in inspiring science in society today.  Now, two people showcasing some of the scientific icons on display here are John Liffin, the curator of communications and Katie Maggs, the curator of medicine.  So, John which icon are you representing?

John -  As a curator of communications, I suppose I really have to go for a Cooke and Wheatstone five-needle telegraph.  This really represents the beginning of electrical communication.  The world exists today on communication.  For the last 150 years, it's been part of what's been making the world as a smaller place. It all started back in London in 1837 with the demonstration of a simple device where magnetic needles pointing to different letters.  You could send a message over a distance.

Meera -  And Katie, you are here supporting the x-ray machine so what makes this the most important icon?

Katie - Well, x-rays have absolutely changed the way we visualize and understand the world and our bodies.  Before the discovery of x-rays, only surgeons could really sort of understand the mess inside our bodies. It's revolutionized medical diagnosis and also it changed science in the way we understand materials.  We wouldn't even know about other icons on the list such as the structure of DNA without x-ray crystallography.  Also, unlike all the other icons which were made by adult scientists and expert engineers this was made by precocious 15 year-old and his father.just a matter of days they're inspired after they first heard about Roentgen's discovery when he was publishing it in 1896. I'm voting for it on behalf of all sort of amateur scientists performing cutting-edge research at home.

Meera - Katie Maggs and John Liffin, both curators here at the Science of Museum.  Now, back to Chris Rapley.  Chris, why were these items chosen above the so many other inventions in the history of science?

Chris Rapley - Well, of course we went through an exercise here with our own staff saying what do you think had the biggest impact on the last 100 years. So, you can see why Stevenson's rocket which completely transformed  expectation of transportation around the country both with goods and people. The Apollo 10 module, you know the pinnacle of human achievement in many ways. It's still marvellous that humans manage to send small numbers around the moon and indeed on the surface of the moon. Penicillin, how many people's lives had been changed, you know, saved by penicillin.  So, there a lot of different ways of looking at this but of course, we're open to debate and discussion. If somebody listening to the program thinks they got it wrong and thinks they should have chosen something else.  We'd be very happy to enter that debate.

Kath - You can look through the remaining icons chosen by the museum by visiting thesciencemuseum.org.uk/centenary.  You can vote for your favourite or even suggest something you think they've missed.  That was Meera Senthilingam there talking to Katie Maggs, Lord Peter Mandelson, Chris Rapley, and John Liffin.  Now, I personally think in the top ten should be pasteurization, DNA sequencing and the jet engine.  How about you Chris?

Chris - Do you want the list? The list that they've got on there is steam engines, Stevenson's rocket, electric telegraph, x-ray machine, Model T-ford, penicillin, V2 rockets, Pilot Ace computer, the double helix and the Apollo 10 capsule.  So, ..

Kat - None of mine then?

Chris Smith - No, they didn't pick up on your one.  What about you, Dave?  What would be on your icon list?

Dave - I think for me the biggest thing would be the printing press because the only way science can keep on going forward is if you can learn from other people and the rest of the world on what they've done until you got a printing press that's very, very difficult.

Chris Smith - Well, I sort of thought in the same vein and I thought modern-day impact on people: similar sort of idea, I go for the internet.  I felt that everyone thinks the museum should have old things in it but that's not necessarily the case. The internet, I think has been the greatest leveller and the biggest communications tool and the biggest conduit for information that we've ever seen in the history of mankind.  Well, I definitely put that as an icon. I also had radio and the radar and transistors because without transistors, we couldn't have an internet, connect computers and we don't have anything so William Schottky's transistor. I had on my list as well.

Does fog have a dampening effect on sounds?

Chris - It definitely does. Yeah, great question, Charles. The reason for that is the fog consists of tiny particles of water, which are suspended as little blobs in the air down at ground level and sound is the compression wave that travels through air. So, when the compression wave goes through the air, it's making air molecules vibrate and they're passing those vibrations from one to the next like a hand shake. If you put water molecules into air, it means that the water blobs can soak up the droplets or soak up some of the vibrations and this will attenuate or damp down quite literally (excuse the pun) the transmission of that sound through the air. So, fog does have a sound attenuating effect and the other reason why it might that when it's foggy, people tend to slow down too. So, people don't go out as much. They don't play games as much. They don't drive as much and as a result, you might see a reduction in the overall sound..

Would our Solar System survive in intergalactic space?

Dave - I think if you managed to pick up our solar system and somehow magically transport to the middle of intergalactic space. There might be slightly high levels of really high energy intergalactic cosmic rays because the galaxy does have a magnetic field which will shield us from very high energy cosmic rays slightly. Again, a lot of cosmic rays are being made inside our galaxy so it probably cancels out a bit. I think the real thing is that you can't really get the solar system out into the middle of a big void like that. It doesn't get formed there because you need enough gas to form stars and there's just nothing out there. So the only way you could get a star out there that would really something quite violent happening so you'd need to have three stars coming very close to each other and the other two dumping most of their energy into the third one and shooting it out into the galaxy or something.Chris - There is an errant star, which is currently on its way out of the milkyway. I think it's even left the Milky Way. It's destined to in the next, I think literally in hundreds of thousands or few thousand years. It's actually gonna completely leave the galaxy and it was exactly as you said it was part of a binary system where the two were twirling around each other near to the central black hole. They've got very, very rapidly accelerated and it was as of a sling shot where one spun away and the other one got trapped into potentially a trajectory to intergalactic space.Dave - Yeah, and if it's done that, you know rip off, you know a planet is gonna be ripped off and held somewhere entirely different. It might also end up in intergalactic space but probably nowhere near the original star.Chris - So, life as we knew it on those sorts of planets, that would be curtains, wouldn't it?Dave - And also, you couldn't form a star which could support life as we know it outside of the galaxy because we depend on heavy elements, a lot heavier than iron. These were formed in the supernovae we we're talking about earlier so you then get to the hydrogen helium and you can't really make a planet out of hydrogen helium and a little bit of lithium. So, although I think you could probably sustain it life out there, I can't see in any way of achieving it.

How is caffeine extracted from whole coffee beans?

Chris - I have to say until he raised the question, I haven't even considered it but it's a very good question.Kat - It is. I am a decaf coffee drinker. I'm caffeine-free so this actually intrigued me as well. In fact, there's a number of different ways that people get the caffeine out of coffee. They do it on the whole beans. It's not when you brew up the coffee and then take the caffeine out of it. You decaffeinate the beans before they're even roasted because that helps preserve as much flavour as possible when they're finally roasted and then ground up. So, there's a number of ways you can do it. You can do it the nasty way, which is to bung a load of solvents in there. Caffeine dissolves in certain solvents, some of the ones kind of slightly related to things like dry cleaning fluid (not very nice way of treating a coffee). So people try and develop other ways of doing it with things like water. You can basically just try and wash the caffeine out by washing the beans and then filter out the the caffeine. There's another really clever way that people do it is by washing the coffee beans with a very, very strong solution of coffee that's sort of saturated with all the coffee flavour molecules.Chris Smith: But presumably decaf.Kat - But not caffeine.Chris Smith: Right.Kat - So, basically it's using, I guess it's osmosis isn't it, sort of. Chris Smith: Diffusion. It's the diffusion gradient.Kat - That's the one.Chris Smith: If there's no caffeine in the solution and there's lots of caffeine in the bean there'll be a net movement into the solution.Kat - Exactly, the caffeine goes out the beans into this coffee-flavoured solution, but you don't lose any of the flavour from the beans because there's already loads of these flavour molecules in the water so they don't want to move out of the beans. That's another way of doing it using carbon dioxide as well, high-pressure carbon dioxide which kind of forces the caffeine out without losing the flavour. So, that is apparently how they do it.

When I have a good hand in poker why does my heart rate go up and my vein pulsate?

Chris - Well, this is your sympathetic nervous system. We have two arms to our autonomic nervous system. The thing that controls our unconscious bodily systems. We have the sympathetic nervous system, which you activate when you need to fight or when you undergo flight, you wanna run away, and you have the parasympathetic nervous system when you rest and digest things. When you get excited, your sympathetic nervous system turns on. This makes your pupils big, it makes your heart rate go up., your blood pressure goes up, you start sweating. You also might get slightly trembly and as a result you give yourself away because you're obviously getting excited. So, trained people know how to slightly damp down that reflex so that they don't actually display those innermost feelings. So, it's a question actually of probably self control and training yourself not to get too excited.

Are humans now de-evolving?

Chris - What he means by that is we keep giving people caesarean sections to help get babies out does this mean that we're evolving so that women get a narrower and narrower pelves so that in the future they won't gonna have babies normally. Kat - It's an interesting one. There's no such term really as de-evolving because we're all constantly evolving. Humans are changing in result of environmental pressures that are on us. I guess, many, many, many thousands of years if we do carry on medicalising humans so that we don't die of conditions caused by our biology then we might evolve to kind of get round them. For example, I'm not sure about if there is evidence that our appendix is vanishing gradually or not because that's a common cause of illness. I don't think we really have enough time to tell how the impact of modern medicine which only been around for about a hundred years or so is actually affecting our evolution. Chris Smith - Undoubtedly, there will be an effect because of course fewer people would die, who would have died otherwise. So, evolution may run more slowly. It may be that we evolve in a different way. One of the pressures has been removed but there are new pressures we have to compensate for the fact that we take less exercise. Actually, we eat more and perhaps not as good for us.Kat - We're constantly evolving. It would be interesting to see how it goes.

57:46 - Is the Earth losing water into space?

Is the Earth leaking? Could water evaporate into space? Given enough time could the Earth end up like Mars: a desolate wasteland with not a drop of water to be found?

Is the Earth losing water into space?

We put this question to Luca Montabone, Atmospheric, Oceanic and Planetary Physics dept., Oxford University...

On the Earth, water can exist in all three forms namely as a solid, liquid, or gas. Evaporation transforms liquid water into water vapour which can then freely move in the atmosphere as a gas.

Now, atmospheric molecules, including water vapour molecules, are in perpetual motion in all directions. Without the gravitational field of the Earth, those moving away from the planet would be lost. Even with the gravitational field, in the upper thin part of the atmosphere, a molecule moving outwards has little chance of colliding with another and would therefore be able to escape if it has sufficient speed.

The average speed of the gas, for example water vapour, depends on its temperature. The conditions of temperature at the altitude from which water molecules are able to escape indicate the earth can retain water vapour over geological time scales, that is, over several billion years.

The retention of water vapour on our planet is also favoured by the fact that it can condense, form clouds at an altitude well below the one from which water molecules can escape and precipitate back to the ground as rain or snow.

Adding to all these, we have to remember that water is also introduced in the hydrological cycle from the interior of the planet, for example, every time that a volcanic eruption occurs.

So, to summarize, even if a few water molecules are continuously lost to space, the average level remains fairly constant over geological times, which is what we want!

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