We put this question to Dominic Ford from Naked Astronomy.

Dominic -   Well, it’s of course very hard to know what life there is out there.  People have looked for radio radiation from other civilisations using the Arecibo telescope in America and there are future telescopes that we’d hope to pick up radiation from aircraft radar and television transmitters on other planets.  So far, they haven’t picked up anything in the closest thousand, tens of thousands of stars around the earth.  So we probably think there’s not much life immediately close to the Earth but it’s very hard to know what is out there.

Chris -   A few years ago, in fact it was five years ago, I was in Washington DC at the AAAS conference and there was number of people at the conference talking about things like the SETI program looking for life.  Some of the world’s leading space scientists were right there and so we had them on a radio program, and I went along the table and said, “I’d like you all to guess or give any estimates as to the likelihood of us finding alien life within the next 50 years.”  Just out of interest, where would you put that number?

Dominic -   I think there were a number of very interesting space missions coming up in the next 10 or 15 years which have the potential to see earth-like planets surround other stars.  If we see those planets and we manage to see the light from those planets, we can take a spectrum of them and we can see what molecules are in their atmospheres.  And if we start to see organic molecules in those atmospheres, we will know there is almost certainly life on those planets.  It may not intelligent.  It’s very hard to tell whether it’s intelligent, but I think there is a lot of potential to see microbial life in the next 10, 15 years.

Chris -   Whether or not you'd call life on earth necessarily intelligent is also open to debate.  It depends where you look, I think.  Dominic, thank you very much.

Chris -  The answer is actually, yes, they can - because soap isn’t actually very toxic for bacteria.  The reason that washing your hands with soap and water works so well to decontaminate them is actually the physical decontamination.  When you rub your hands together, the soap helps to prise away various oils and other layers from the skin that the bacteria are clinging to and it therefore detaches the bacteria.  It’s not actually being necessarily antibacterial.  Now some soaps will kill bacteria.  The majority don't because the bacteria have got quite a tough cell wall around them, so they're resistant, but it’s the physical washing that gets rid of them.

One interesting thing though, when we’ve had lots of outbreaks of winter vomiting disease, the norovirus, you see lots and lots of these alcohol dispensers springing up all over the place, saying, “Clean your hands.  This will help to stem outbreaks of norovirus.”  Actually, norovirus doesn’t have around its outside an oily bag which can be attacked by alcohol.  It’s a very tough little protein husk that the virus is made of and as a result, the virus is completely immune to alcohol hand wipes, and therefore, all you're doing when you're using alcohol is you’re producing a pure culture of norovirus on your hands.  Soap and water on the other hand does work.  So the best thing to do, is always wash your hands.  Helen.

Helen -   Well that is rather lovely, but I just wanted to ask.  I've always wondered.  If you go to a public loo, there’s a nasty bit of soap sitting on the side and you think, “Yuck!”  Is it better to use that soap if it’s covered in bacteria and wash your hands and rub off your own bacteria, or should you leave it alone?  What do you think?

Chris -   This is a bugbear of mine actually because when you go to public conveniences, the first thing you have to do to get into them is open the door of course, and the door always opens inwards.  You can push the door open which means you don't have to touch any part of it.  But when you're coming out again, you have to touch the handle on the door of the loo then you got to touch all over the taps, and then you've got to touch the door handle to open it and pull it inwards again.

Now okay, lots of people will be good in the toilet.  They won't make a mess, but they will also wash their hands diligently afterwards.  You then go out, leaving the toilet with clean hands, but you touch the door handle that the one in a million people who haven’t washed their hands has just touched and decorated with a nice culture of bacteria, of faecal origin probably but also other things are possible.  It’s now on your hands - which were nice and clean, so there are no other bugs there to compete with them, so now you've got a nice pure culture of pathogens all over your hands.

Why are the doors are not organised so that you can push the door open on the way out or have some kind of automatic door?  More lavatories these days are getting themselves organised so that you sort of go around almost like a maze to get out.  But it means you don't have to physically open external doors to get out and touch surfaces because that’s how these bacteria spread – it’s touching surfaces. 

So to answer your question, you will pick up bugs when you touch surfaces including the soap dispenser and this is why in many places where medicine is done, doctors’ surgeries, nurses’ rooms and so on, you’ll see that the taps have these long wings on them.  This is so that you can actually close them off with your elbows, rather than actually having to physically touch them with the thing you've just washed.  So sorry Helen, despite your best ministrations to your hands, you're probably actually picking up bugs by using that grotty bit of soap, I'm sorry to say.

Helen -   I’ll just have to keep my elbows clean by the sound of it.

Helen -  That’s a really good question and it opens up an awful number of issues to consider, but we can certainly just get into that to some extent.

I think my first question will be, what do we mean by saving the species?  Are we talking about them persisting in the wild?  Do you want to keep them in captivity?  Those will require very different numbers of individuals within a population.  But also, we’re talking about genetic diversity and one thing you can think of is that when a population is cut down, when it declines, you do get the problem of inbreeding and that’s what we’re really hinting at.

If there’s not enough genetic diversity, you might get inbreeding and you might actually have the appearance of deleterious genes coming together and causing problems in the animals that are being born.  But that said, there have also been situations where we’ve thought that maybe genetic diversity is the reason why some wild species are not doing so well, when in fact, it isn’t, one example is the cheetahs.  

We think that historically they went through a very big bottleneck, these lovely, very fast running cats that run around in Africa, and there were various studies that pointed towards genetic diversity as the problem.  Things like, they could take skin grafts from any cheetah and put it onto another one and it wouldn’t be rejected.  So conservationists began to think, “Aha!  It must be this lack of genetic diversity which is why we’re not seeing enough new baby cheetahs surviving in the wild.”

In fact, this wasn’t true at all.  It was a glitch in the studies of those skin grafts that meant it wasn’t anything to do with genetic diversity.  It was because lions were eating the baby cheetahs and I think hyenas as well.  They were being predated upon by other animals, and when they were in areas where they weren’t, they were doing fine. 

So, it’s a tricky thing to think about.  You can also think about the island of Madagascar, which was colonised by just a handful of different mammals.  So they had very low genetic diversity.  It doesn’t necessarily mean a species is going to go extinct.  It’s all about lots of different factors that affect whether or not it’s going to survive in the wild which I think is what really we’re talking about - are they going to survive and can we try and stop extinctions from happening?  There are lots of things we have to consider.

Chris -   And as we heard last week when we were talking about Tasmanian Devils, actually being a bit inbred can be dangerous for another reason.  You can get something happening to a population similar to the Devils.  They have a line of cells which had become cancerous, and they can then go from one animal to the next, almost like an organ graft.  This is accepted and not rejected by the immune system of the recipient because they're so inbred.  There are dangers of a dwindling population.

We asked Dominic Ford from Naked Astronomy.

Dominic -   Yes, it certainly would be.  What’s important is whether the average density of the sphere plus whatever is inside it is greater or less than the density of the water that it will be floating in.  So for example, a ship floats because although a ship is made of steel and that’s very heavy, it’s got air in there as well and the air is much less dense than the water it’s floating in, so a ship as a whole floats.  Now if you take a sphere, the metal outside of the sphere will be much heavier than the water, but because it hasn’t got anything in it, that doesn’t contribute to the density.  So its average density be quite low.  So it will float.  It will actually float better than if you filled it with hydrogen or helium which, although they are lighter than air, they still have some mass to them, more than the mass of the vacuum which is nothing at all.

Chris -   Indeed.  It’s a good party question that, isn’t it?  Which is going to float more, a sealed barrel full of air, a sealed barrel full of hydrogen, or a barrel with a vacuum, and that most people will go for the hydrogen and actually, it’s the vacuum that floats the best.

Dominic -   Yes, of course.  You don't see barrels filled with vacuums very often because it’s so hard to suck air out of a barrel!

Helen -  Excellent question and it’s not actually anything to do with what they eat which is one thing you could think of - well maybe they eat something that’s white? but no.  They eat just the same stuff as all sorts of other creatures, but it’s about how they process that food and it’s all about proteins and nucleic acids, and how they break that down. 

We break down proteins and we all produce ammonia, but we make it into urea which we then dissolve in water and get rid of it in urine.  But we need lots of water to do that, so that means we have to drink a lot which means we don't really survive very well when there’s not much water around.

Birds and reptiles have a better way of dealing perhaps with low water, and the need to get rid of all that nasty toxic ammonia, and they create something called uric acid which is a solid or a mostly solid paste.  That is white, and that’s why their poo is white.  In fact, it’s very valuable stuff.  Guano has been mined in lots of parts of the world to be used as fertiliser and wars have been fought over it because it can be used to make gunpowder  - it’s got very high nitrogen and phosphorus in it.  So, there you go – white bird poo has lots of rather extraordinary applications.

Chris -  It sounds a bit bizarre, doesn’t it?  To think, could the sea be causing earthquakes?  But actually, the answer is, yes, it possibly could.  Now it’s a slightly indirect answer to this but there was a paper that came out.  It was in the journal Nature and it was last June, and it was by a US Geologist who’s called Selwyn Sacks and a researcher in Taiwan.  Taiwan is interesting because it’s got a very, very rapid rate of tectonic plate movement.  Plates there are moving and colliding at the rate of about 15 centimetres a year which is a huge amount of movement.  This means that where you have faults, you have enormous amounts of energy being stored up. 

So, Selwyn Sacks and his colleagues were measuring strain energy.  They were putting strain gauges into the ground there to measure how these faults are moving and storing energy over time.  What they were really surprised to see were some rather weird recordings on their strain gauges at certain points, and what they found is that they were seeing the arrival of typhoons – these big tropical storms associated with very low pressures.

Normally, when a low pressure moves in over land, what happens is that the low pressure makes the land swell up a bit.  So their strain gauges were recording that the land was swelling up.  But sometimes, instead of the land swelling up, they actually found the land shrinking and the only way they can explain this is if there’s been an earthquake – a so-called slow earthquake.

What’s going on, it turns out, is that when you have a very low pressure system, the air pressure drops, so the land swells, but where there’s sea, which is adjacent to the land of course, because the water doesn’t get out of the way, water doesn't swell, instead, more water comes in to fill the area with low pressure.  So this means the pressure on the sea floor is roughly the same, but the pressure over land is lower, and therefore, any faults open up for this reason because you've now got a pressure differential between the land and the sea, and this is more likely to unload faults and trigger earthquakes.

What they found is possibly happening in Taiwan is that you've got these so-called slow earthquakes which are earthquakes that happen over hours to days; they don't go all of a sudden.  They gently let go of the energy and this slowly dissipates the stored energy in the fault, but the thing that was triggering it, they found on their recordings was the arrival of these typhoons, and the typhoons are basically making the tide come in metaphorically. 

So, I guess you could say that the movement of large bodies of water can potentially trigger an earthquake.  So the answer is, yes.

Dominic -  This is interesting because of course, we normally think that light travels straight lines and so, when light comes into your eye, you know what direction it’s come from, so you know what direction you're looking in.  But light doesn’t always travel in straight lines.  For example when it goes through a lens, we know it’s bent and that’s because the lens is made of a glass which has different refractive index from the air around it. 

Air also has its own refractive index which depends on the temperature of the air.  So, if you have hot air, it has different refractive index to if you have cold air.  On a hot day, the sun will come down, it will heat the surface of the road and make the air close to the road very hot in comparison to the air above it.  That means that light rays are bent away from the road, and so, when you look down at the road, the rays are actually bending away from the road and back up into the sky, and you're seeing a patch of the sky in the road.  Water also looks like that because water is reflecting the sky, making the sky appear in the road.  So the mirage looks exactly like water.

We put this question to Dominic Ford from Naked Astronomy

Dominic -   Carol is absolutely right.  Whenever a planet orbits around the star, it exerts some gravitational force on that star and that force pulls the start back and forth and that produces a red shift in the spectrum that you can then observe.  You can observe it quite easily because the spectra of stars have quite narrow, well defined lines in them that you can see wobbling back and forth as the star moves.  By looking at the wobble of those lines, you can deduce both the radius of the orbit of the planet and also its mass.  The mass determines how far the features wobble and the radius determines the frequency of which they wobble.  If you've got several planets, they will orbit with different periods and that will produce a different period of oscillation in those features.  So for example, you might have an oscillation on a 10-day time scale superimposed on oscillation with 100-day time scale, just like a chord in music.  By taking apart those frequency components, you can work out how many planets there are and what radius orbits they're in.

Chris -   You basically have to build a model and come up with the only solution that satisfies the wobble that you're seeing.

Dominic -   Yes, that’s right.

Chris -   It’s interesting because we interviewed someone on this program called Dr. Christophe Lovis who was from the Geneva Observatory back in 2006 and he did precisely what you've just said for a star about 40 light years away from earth.  It was called HD69830 and in fact, there’s a very interesting interview with him on the Naked Scientists website, where you can hear a slightly different explanation for basically what you described Dominic.

Helen - Well it’s all about the types of UV (ultraviolet) radiation that you've got - both in the sterilising bulb that you've got in your setup, and that’s just all around us from the sun.  [Sunlight] comes down through the atmosphere and contains UVA, UVB, and UVC.  The most damaging form of UV is UVC, and that’s what’s in your sterilising bulb.  It will be at a very high intensity and your water will probably get sucked through a filter and fed past this UV bulb, and that will do a very good job of killing off all those bugs that you don't want, using this very powerful form of UV light.  But the UV light that’s around us naturally from the sun, or even from a light bulb above your tank, that UVC will be very easily blocked by the water.  Because it has such a short wavelength, it actually gets very easily disrupted and it won't actually make its way very far into the water.  That’s why nothing in the tank really gets affected by it.  So you need that very concentrated intensive burst of damaging UV to keep the water clean, but otherwise, we do fine with the UV that bounces around in the room.

Chris -   Because the stuff that we’re normally seeing is a little bit of UVA, a bit of UVB, and we have an ozone layer which is really good at excluding most of the UV, including that UVC.  So, in terms of sunlight, for the most part, we’re protected.

Helen -   Mostly protected.  We still can get burned by A and B and different sun creams can help to block that, but in terms of the life that’s in your tank, I think the water is enough to keep them safe from any bombarding UV light that’s coming in from the surface.

Chris -   Most filter systems have a little bioreactor in the bottom as well, where you have lots of bits of plastic and things with a high surface area.  Good bugs, ones that you like, grow on there and then after the water’s gone through the steriliser - which wipes everything out including the algal cells - it then goes through this bioreactor in the bottom of the filter which then re-seeds good bugs back into the water, as well as consuming some of the organic content which is how these filters actually work.

Helen -  Absolutely.

Chris -   That’s not strictly true that most things can repair if they're damaged.  Some tissues can replace lost cells.  So if you cut yourself or graze some skin, it will grow back.  But if you have a more catastrophic injury, then without the scaffolding of tissue there to support the growth and new stem cells there to provide a supply of new cells then tissues and complicated organs cannot repair themselves.  The key thing really is in the stem cells, and the heart does appear to respond very badly to injury.  If you have interruption to the blood flow of the heart by blocking a coronary artery, consequently, the muscle that’s supplied by that blocked artery is starved of oxygen and it does die, and the heart does not heal by repairing and replacing the lost cells in a human.  Instead, the heart heals by producing fibrous tissue and you get a scar.  That of course can't contribute anything to the pumping ability of the heart and so it increases the risk of things like heart failure. 

But not all animals are like that and in fact, researchers including Kazu Kikuchi who published a paper in Nature in January of this year, they found that zebra fish can regenerate almost a third of their heart if you cut away a third of the left ventricle, the main chamber of the heart, the equivalent of that in the zebra fish, then the zebra fish will regenerate a whole new heart, and they thought, “Well, if we can work out what they're doing, perhaps we can work out how to make humans better.” 

They then used a specific construct so that they could turn on a gene just in heart muscle cells that labelled those cells with a glowing green colour.  They then injured the heart and watched to see what happened as the heart repaired.  Their theory was, well if stem cells are coming out and repairing the damage and they're nothing to do with the muscle, then the heart will just make a new muscle, and they won't glow green.  If the muscle cells themselves in the zebra fish heart are repairing the damage, then you get a glowing green heart.  That’s exactly what they saw.

So what this tells you is that in these fish, when you injure the heart tissue, unlike in a human, the muscle cells respond to the injury by doing what’s called dedifferentiating.  They make themselves less specialised.  They become more stem cell-like.  They then divide lots and lots of times to make a big pool of cells that then go to the right places, wire themselves up and then turn back into muscle cells to repair the damage.

They have found some genes including one called GATA-4 which seems to be turned on to do this process and is also used when the heart is developing in an embryo in the first place and this suggests, if we can work out how to do this, it might be possible to trick human heart cells to do the same thing, and therefore, turn into stem cell-like cells in the heart that’s been injured and therefore repair a damaged area, not with a scar, but with healthy fresh muscle again.

Helen -   It’s extraordinary what we can learn from other members of the animal kingdom that will hopefully help ourselves in some of the problems that us humans have to deal with.

Chris -   Well, exactly and I think this shows you how useful having something like a little fish can be - because fish are very cheap, they're very easy to look at and these fish are transparent which means that you can grow lots of them in a little tiny dish and see exactly what’s going on inside them with simple microscopy.  This then informs the biology of much more complicated organs like rats and mice, and ultimately, humans.  So it’s making a very, very simple model of a complicated problem, and just distilling out what the crux of it is so we can hopefully find some answers.

Chris -  I've seen some studies where they have looked at children, and also young juvenile rats who are being fed sweeteners or normal sugar.  One suggestion that some people have made – I'm not sure whether the evidence for this is robust, but it sounds plausible - is if you feed juvenile rats on sweeteners, what happens is that the brain begins to misinterpret how many calories there really are in sweet things and it gets used to the fact that when you eat something which tastes that sweet and you don't get any calories for it, if you then do get into a situation where you can eat some sugary food, real sugar, sweet stuff, you then tend to over eat because the normal metabolic gate that would say, “I know how many calories I've taken in now because when I take in this level of sweetness, I normally get this number of calories.”  That’s been thwarted by eating the sweeteners and as a result, it can lead to overeating and weight gain, and there’s some evidence that people who are on these things for longer periods as children may then develop a habit or a sweeter tooth when they're older.  But as I say, I think it’s speculation.  I'm not sure how plausible it really is. 

Interestingly, there’s a paper that’s come out this week.  It’s by Jay Slack who’s over in America.  They're actually looking at the bitter taste associated with sweeteners because you know when you eat something like saccharin, it has an aftertaste, and they found a chemical that they call GIV3727.  The reason they call it that is because the real name of the molecule is 4-(2,2,3-trimethylcyclopentyl)butanoic acid.  This blocks the receptor for bitter taste buds, so you could call it a bitter blocker, and as a result, things that were bitter tasting now taste sweet.  So you can associate or accompany your sweetener with that molecule, and they've done it on humans, and people stop tasting the nasty bitter taste and they only taste the nice sweet taste.  Isn’t that nice?

Dominic -  Well yes, it could.  Among astronomical bodies, there’s quite a long hierarchy of bodies orbiting around other bodies.  Of course, the moon is orbiting around the earth and the earth around the sun.  But the sun itself is orbiting about the centre of the Milky Way galaxy and that itself we think is orbiting around within a local group of galaxies, and that we think is part of a larger super cluster of galaxies.  So you can certainly add another step to that hierarchy and put a body into orbit about the moon, and that is of course what we did when we went to the moon and we sent the Apollo spacecraft to the moon.

However, each step of the hierarchy tends to be less stable than the previous step.  It would take something quite catastrophic to take the sun out of the Milky Way galaxy but to strip the earth out of orbit from the sun would actually be scarily easy  - if a star were to pass too close to our own.  Stripping the moon off the earth, we think that will probably happen on a timescale of billions of years, naturally anyway.  So I think something orbiting about the moon will probably stay there for a matter of years before being shed into solar orbit.

Helen -  It’s a very nice idea in some ways, but first of all, you have to think about the scale of what you're trying to do here.  The oceans are absolutely enormous.  The numbers of fish we’re catching are absolutely enormous, and I just don't think we have the technology, if we even wanted to go about this if we thought it was a good idea.

We are doing some smaller scale things.  Some European eels for example are being “re-stocked” and I'm saying that in inverted commas because they aren’t actually being bred in captivity, they're just being moved around the place because in some areas, they're doing very, very badly, so tiny baby eels are being moved to try and restock rivers, to allow people to carry on fishing. 

There are things like genetic issues you might need to consider as well.  What sort of species?  Where are they coming from to restock them?  And I think we mustn’t forget that the oceans have an incredible ability to restock themselves.  We just have to give them a chance.

When we take away fishing pressure from certain areas, we do see an extraordinary recovery.  So we really have to focus on oceans healing themselves.  I think stepping in and doing it ourselves is not the approach.  It’s a case of letting the oceans do it themselves and giving them a chance.