Dave - You certainly can see satellites with a telescope. Definitely live satellites you can get quite good pictures of them. You can see the International Space Station and all the different bits of it with a large telescope. With your naked eye you can see stars which move across the sky very quickly and don’t have a red flashing light – those are normally planes. Anything moving across the sky very quickly is normally a satellite.

Chris - I saw the guys on the BBC website where they’ve got this tracking software which they’ve written themselves and some amateur telescope gear. They have got some amazing pictures of the International Space Station. It really looks like a computer game, how good the pictures are.

Dave - And also you can sometimes see satellites which aren’t supposed to be there. One of my housemates has got a friend who was taking photos of the sun – he’s an astronomer. Occasionally you see satellites going past the sun and you can see them in some frames of this video. There are lists of all the satellites which are supposed to be there and it was one which wasn’t supposed to be there. There’s definitely more satellites up there than anyone will admit to.

Chris - Also they fool people because some of them come down into lower orbits and then go back up again. You get these interesting Iridium flares where the Iridium network of satellites  which are telecommunication satellites come down low in order to communicate and then they go back up higher. They park them into higher orbits when they’re less in demand. It means they’re using less fuel in the long run because they’re not having to keep accelerating their orbit.

Helen - I want to know why you asked me that question, actually. I’m not really au fait, don’t have a dog myself and am not necessarily any the wiser for why this might be. It could be all sorts of reasons. We were discussing this before the show. Maybe it was something to do with marking his territory. Perhaps poo as well as wee and lots of other urine and other fluids like that are good for letting dogs know where they are and if that’s their territory or not. Perhaps a path where other dog have walked along and left their smells would be a good place to leave their mark. I was wondering if it thought it as a cat. Cats will be more likely to defecate on a path rather than grass. Cats like to try to cover up their mess. Perhaps on a sandy path rather than the grass. Maybe the grass is spiky and it doesn’t like the feeling of it.

Chris - A couple of people on our forum have speculated – Dr Beaver says using Occam’s razor the pavement doesn’t tickle its bottom when it squats, perhaps in the same way as the grass. A person who calls themselves Dent Student says I guess it’s because dogs don’t have the same social cues and don’t consider it to be antisocial to poo on the path. Someone points out saying, ‘are you saying that you do poo on the grass?’

Helen - I’d say it’s pretty antisocial to poo on the grass anyway. I hate treading in dog poo. I hope when the dog poos on the path you do clear it up afterwards!

Chris - Yeah, this is called liquid breathing. It’s been experimented on for a little while because also there’s some occasions when forcing gas into lungs is bad. If you’ve got an adult, for example, with respiratory distress syndrome. This can also affect young babies that are premature. The problem occurs when the lungs have a deficiency of a chemical called surfactant. Because the lungs contain lots of tiny airspaces called alveoli the linings of those  airspaces are kept saturated with water. Water makes something called a hydrogen bond. It’s a sticky molecule and one molecule tries to stick onto another. This would collapse the alveoli down and make them disappear if you didn’t have something there to break this water bonding and make it less sticky. This is what these surfactant molecules do. They help it to remain bigger. When people have some kind of lung condition – premature babies don’t have this stuff, adults can have conditions where they lack this stuff – you don’t have any surfactant. As a result the airspace is trying to collapse. As a result it becomes very hard to inflate the lungs and so you have to use very high pressures of gas being blown into you in order to keep the lungs inflated. This can do damage so scientists have been exploring the possibility of using fluids instead of gas under certain circumstances and also deep-sea-divers. Some of the fluids they’ve been exploring are fluids that don’t mix with water so they’re organic chemicals and per-fluorocarbons are the class of chemicals involved. They’ve done experiments with chemicals with six carbon atoms in a line: That’s per-fluorohexane. They’ve also done experiments with eight atoms linked together: that’s per-fluoro-octanes. They haven’t done experiments on humans. They’ve been done on sheep which is a good model for us because they’re also big mammals and have lungs similar to ours. They make a good model and what is special about these chemicals is you can persuade lots of oxygen and gas of any kind to dissolve in this liquid. You then pump the liquid into the lung and it then passes the oxygen into the blood, picks up the carbon dioxide and you pump the liquid back out again. The problem with this is that lungs are made to move gas, not liquid. It’s very difficult to move large amounts of liquid like this. Really the only time it’s practical is when you have someone mechanically ventilating you, in other words moving the liquid in and out for you. One place where it might therefore have a role is in things like intensive care. It might be possible to use it those setting and people with damaged lungs to get lots of extra oxygen and carbon dioxide out. Another situation where it might be useful is in the context of deep-sea-diving. When you go deep-sea-diving, something you’re well acquainted with, Helen, there’s a risk of the bends. As you go down underwater the pressure of gas you’re having to breathe in is increased from your tank by your regulator to overcome the fact that you’re under pressure under water. You’re now breathing gas which is at much higher pressure and density than gas at the surface. This forces a lot more nitrogen into the blood. Nitrogen does not dissolve well at all. It’s very insoluble in water unlike oxygen. As a result when you take the pressure off the person again the extra nitrogen that has dissolved in their tissues can come out as little bubbles. It forms bubbles in blood vessels and blocks them up. That’s why you get decompression sickness, the bends. If you used a liquid in the lungs instead of gas the liquid would not succumb to the increased compression of being down deep. Therefore it would not force extra gas into solution in the same way that air mixtures would. Therefore it might, in theory, be safer if we can overcome the other problems that are associated with it.

Helen - Have you seen the film The Abyss? It’s one of my favourites with a diver and I think they use liquid breathing. They put a mouse in a plastic bag and it’s fine but that would be fun if it could happen one day.

Dave - These two are actually slightly related. Light will carry on going for an awful long time. As far as the photons which were created at the end of the Big Bang that’s when there was a big soup of protons and electrons. As soon as the electrons got trapped by the nuclei of the atoms the universe went transparent. The photons have been travelling since then which is about 13.7 billion years ago. They reach us as part of the cosmic background radiation. They’ve carried on going. What they have done because the universe is expanding – one way to think about it – they’ve been stretched so their wavelength has got longer. They’ve moved further red. It’s called red shift which is the reason why the sky is black. If there was none of this effect then you’d see the effect of the Big Bang as incredibly bright gamma rays all around us. The sky would be bright white, bright x-ray really. Because the universe has expanded so much these photons have been stretched so they’re actually in the microwave region. The photons can go on forever but they can change their wavelength. Is there a limit to how bright light can be? The only one I’ve found possibly is you can get incredibly bright lights photons will start to scatter each other. People have suggested than in order to be able to see this effect you’d need an exowatt laser. That’s a billion watts of energy – a billion nuclear power stations being funnelled into the size of something a cubic millimetre. Then you’d need photons, instead of just going past each other, bouncing off each other at which point you won’t be able to get much brighter than that. There would be a limit somewhere with that.

Dave - The limit is this point at which the universe became transparent which is about 400,000 years after the Big Bang. Because before that the universe had free electrons in it. Electrons interact with light very strongly so the light would hit an electron very soon and essentially stops. That’s the limit.

Dave - In some sense it does. There is an antimatter equivalent to a photon. It’s not an antiphoton. If you have two photons you know are in exactly the opposite phase they can cancel each other out. As far as we know the photon is its own antiparticle.

Helen - Earwigs fortunately don’t eat our brains. That’s a bit of a wives’ tale. They eat all sorts of stuff. They can eat plants, they can dig out dead things. They’re omnivores essentially so plants, flowers  and other insects but I think we can rest assured they don’t eat you.

Lee E:  E=MC^2

Helen - My first one is that in the dot of a 12pt letter ‘i’ there are more protons than there are seconds in half a million years. That was quite mind-boggling.

If we made a scale-model of the universe and we made planet Earth the size of a pea the nearest star, Proximus Centauri would be 16,000km away.

I love the fact that when caterpillars munch on plants the plants have evolved to emit a smell that attracts other bugs that come and eat the caterpillars.

If you were to take Mt Everest and plonk it in the deepest part of the ocean you’d have to dive down 2km to reach the top of Mt Everest.

There’s all sorts of statistics associated with blue whales. I think the nicest one is that their hearts weigh half a tonne and that’s the same weight as a mini car.

Kevin, A12: A Pico second is to a second what a second is to 30,000 years. The moon is 400 times smaller than the sun but the sun is 400 times further away. So we get a perfect eclipse. What a fantastic fact.

Chris - The human heart will beat 40,000,000 times every year of your life. If you work out the weight of blood that it pumps around your body it’s lifting about 7 tonnes of blood a day and if you tot that up over a lifetime that’s about 2 very large aircraft carriers that your heart has lifted in terms of the weight of blood it’s pumped in a lifetime; which is pretty fantastic when you think of the work that nature’s polymers are doing. Evolution has given us a heart that can do something that can work for so long and so faultlessly in the vast majority of people.

The age of the universe. The universe we live in is about 13.7 billion years old. We can date that and know that was the moment when our universe popped into existence, begging the question what went before? What’s this universe is expanding into?

Scientists reckon conservatively there are about 10^22 stars in the known universe. That means there are 10^22 stars possibly a bit like our sun, many of them a bit different, of course. That means the prospect of finding another system like the system we’re in with our Earth, at the right distance from the sun, with liquid water and the right recipe for life doesn’t seem so unlikely when you think there are 1 followed by 22 0s after it opportunities for that to happen.

I share and everyone in this room shares 60% of your genes with a banana. Not because we’re particularly vegetable-prone but because of the ubiquity of the genetic code - it doesn’t matter whether you’re an E. coli bacterium or human, you have the same genetic code running in you. In other words you can take a gene out of a jellyfish, put it into E. coli and the E. coli bacterium will glow green like the jellyfish did because the genes that work in us work in bacteria. What this shows is that we all came from a common ancestor somewhere, probably about 3.9 billion years ago.

Can you guess what the fastest living creature on Earth is? Guinness book of records for the world’s fastest creature  is a bacterium. Its name is Bdello vibrio. It moves at 60 body lengths a second. It does it with a little propeller called a flagellum – tiny proteins that whip along and force the bacterium along. They’re actually predatory and eat other bacteria.

Dave - Light travels at 299,792km every second. Stuff which is hitting your eye is going ridiculously fast.

Light from the Andromeda galaxy has been travelling for 2.5 million years.

Some of the static the TV picks up – some of it is cosmic microwave radiation which has been travelling since 400,000 years after the big bang. For 13.7 billion years it hasn’t hit anything and then it hits your radio.

A typical hurricane uses the same energy as 8 billion tonnes of TNT.

A modern processor has got 580 million transistors. 35 years ago the first processor has just 2500.

Helen - Flies are difficult to swat for lots of reasons. Their eyes work much more quickly than our and they also have a clever way of lining themselves up before they get hit because they can hear where the noise of you coming at them is coming from. So they get ready to jump before they actually do jump. So they go in the right direction.