Chris - Yes we do, because we speak to them. Scientists have shown that men who have deep voices tend to be more attractive to women who fancy men, obviously.  Voice is down to the level of testosterone – the more testosterone you have the lower your voice and so it can be a sign of a well-testostero-genised man.  Also there was a study recently that showed women who are at their peak fertility tend to use higher tones in their voice than at other times of the month.  Women speak with a high pitch when they’re more fertile.  This is maybe another subtle clue that women are using to give away their fertility to men.

Kat - This is an interesting one but my prime suspect in this case would be birds. There is some evidence that worms can crawl but I doubt that big earthworms can crawl that far. I reckon that a bird has got mud on its beak or is maybe carrying another earthworm that’s got mud on it that’s got tiny earthworm eggs and they’ve got deposited up there. It’s a nice environment, it’s nice and damp. If you’ve got soil, organic matter up there then those dropped worm cocoons, the eggs in a bundle have started to grow. I reckon they’ve been dropped up there by birds.

Chris - I agree because when I was little I got into trouble with my parents for putting a worm in my brother’s hair which I absolutely did not do. Because he reached into his hair and found a worm and got told off for it. Actually a bird had just gone over and I think a bird dropped the worm on my brother’s head. I didn’t do it honest.

Dave - It is very hard to balance when a bike’s stationary. There’s two effects. One of them is if you tip a bike to the left you’ll see the front wheel tends to turn into the left as well because the front forks are leaning forwards. It’s more stable if the handlebars tip to the left. Once the handlebars tip to the left then you tend to steer into the corner and the wheel works its way back underneath you.

Chris - So it’s like if I give you the old trick of a broom handle you can balance the broom handle in the palm of your hand. Just by moving your hand around you can hold the broom handle vertically. It’s because when the broom starts to fall in one direction you can move your hand to go effectively into the direction of fall and that’s what keeps it stable. The bike’s doing the same thing.

Dave - The bike’s doing the same thing automatically. There’s also a gyroscopic effect that can help.

Chris - Because the wheels are spinning and so because the wheels themselves are turning they have a gyroscopic moment. It’s obviously difficult to make it deviate. Given that it’s most unstable when it’s moving slower you can still balance. You probably get more stable when you speed up?

Dave - You do and it’s easier to ride when you’re going faster. If you imagine a spinning top it starts to fall over it starts to rotate round and round in circles and the same thing starts to happen to your bike wheel. As you start to turn over it starts rotating and turns into the corner as well.

Chris - The answer is we don’t 100% know.  Clouds are made of billions of tiny particles, ice crystals.  They’re called hydrometeors and these particles rub against each other in the cloud because the clouds are full of big currents of air.  There are big ones and small ones.  In exactly the same way as you take a balloon or a comb and run it through your hair it will transfer charge from one thing, your hair, to the balloon or comb.  This enables you to have static electricity. 

The same thing happens with these particles in a cloud.  By a mechanism that no one understands that well for some reason the big ones get a negative charge and the small ones get a positive charge.  The small ones get pushed to the top of the cloud and are upcurrents, more than the bigger ones.  That’s how you get this distribution of charge within the cloud.

Some people speculate it might be something to do with the solar wind which is this charged stream of particles coming from the sun, past the Earth’s magnetosphere. That aside, what you end up with is a big aggregation of static energy within the cloud which is separated, according to its charge.  The bottom of the cloud is very negative.

The Earth, therefore, feels an electric field pushing towards it and this repels any negative charge in the surface of the Earth because the negatives can move away, leaving the surface of the Earth net positive.  This intensifies the electric field and the result is that eventually the potential difference that builds up overcomes the natural insulation or the inherent resistance of the air and it begins to ionise.  This is where you strip electrons away from gas molecules in the atmosphere and because electrons can move they can conduct.  You begin to carry a current and so you get a few feelers come down. 

When you’ve got a sufficient and contiguous connection between cloud and ground you’ll get a full-on strike.  The lighting comes zipping down.  The actual discharge is only about the size of a five pence piece and it lasts for a billionth of a second, microseconds at best.  The actual current that flows down it is something like 20,000 Amps and it’s discharging between 1 and 10 billion joules of energy which is, in fact, enough to light a 100W bulb for 100 days.  It’s not a huge amount but is enough to make a big bang.  The reason that the lightning’s nice and bright is that, as the electricity goes smashing though the air it causes the electrons in the atoms to get very excited.  They then fall back to their original energy positions, giving us some light in the process.  They also get very hot and because of the thermal expansion you get a shockwave.  It’s like a gun going off.

Kat - I’ve been doing a life time of research into chocolate and yes,  you’re right. Bloom on chocolate this kind of white stuff you see in it is not harmful. You get two types of bloom on chocolate. You get cocoa butter bloom which is when the cocoa butter comes to the surface of the chocolate. You can tell if you’ve got cocoa butter bloom because it kinda feels a bit oily and greasy.  You can get sugar bloom and that’s when sugar crystals come out of your chocolate and that feels kind of granular. What’s causing it? Well, chocolateers think that what causes bloom is when you get temperature changes, big changes in temperature to chocolate. As it’s been hot in Australia and now you’ve put your chocolate that’s been in the fridge to keep it cold you’ve put it through quite a big temperature differential and then got it back out of the fridge again. That’s caused the bloom. It’s probably best to keep your chocolate at a cool, stable temperature – not necessarily in the fridge.

Dave - What’s happening when your car windscreen mists up is you’ve got lots of moisture in the air inside your car. If the car windscreen is cold enough then it will be below the dew point and below the temperature at which water can condense on it. You will get condensing on the windscreen until eventually you get little droplets making it hard to see through. There’s various things which will affect this. One of them is the amount of moisture in the air. If you’ve got rain it’s very humid and you’re probably wet. You’re probably heating up water and it’s evaporating off you so it makes the air very moist. The other big one is how cold the glass is. If it’s raining then rain’s probably hitting the glass, taking a lot of the energy out of it and cooling it down. Probably two reasons: one is that there’s more moisture in the air and the other is that it’s cooled down.

To try and stop this from happening, you should try this Kitchen Science Experiment! - www.thenakedscientists.com/HTML/kitchen-science/exp/stopping-fogging/

Chris - Cramp is a muscle spasm and we don’t actually know what cramp is.  We just know that if people have regular cramps – and it tends to happen quite often at night and it tends to happen in younger people more often than older people and it tends to be relieved with quinine, the same stuff that makes tonic water taste nice. A muscle spasm is when some of the muscle fibres – because a muscle isn’t just one homogeneous giant thing. It’s actually made up of lots of individual little muscle fibres. Some of those muscle fibres go into a spasm. In other words, the contract more than they should and they lock in a contracted state. Surprisingly, muscle actually takes energy to relax, not to contract. When a body of a person dies, they go into rigor mortis because the cells in their muscles run out of energy and their muscles can’t relax and they stay rigid. That’s why a person gets rigor mortis. If you leave them a bit longer then the rigor mortis goes away again when the muscle breaks down and starts to relax. What cramp could be is for some reason that clutch of muscle fibres don’t have enough energy in them, perhaps because there’s been a reduction in blood flow that’s insufficient for the muscles needs. Therefore the muscle runs a little bit short of energy and this trips its inability to relax properly and you get a cramp. Rubbing a muscle and massaging it to get the blood through it can make it better.

Zanzibar Rothschild, in Second Life - Bananas are good for cramps. Could it be down to potassium?

Chris - could be but I don’t know for sure. I know that if you don’t have enough potassium then you can end up with excitable cells in that way and this can lead to muscle spasms so that’s a possibility.

Chris - I think what you’re thinking of is a hypnic jerk. When people fall asleep and you can notice this yourself you suddenly jerk violently. Often enough to wake you up again and certainly anybody who’e sleeping next to you. If you’re on a bus with someone and you don’t know them it scare the hell out of them because I’ve done that to people. This is a hypnic jerk and it’s to do with the part of the nervous system that paralyses you when you go to sleep. When we go to sleep and we dream you don’t want to be acting out your dreams because that could have unfortunate consequences. There’s a region of the nervous system called the sub-cerulean nervous system in your brain stem which receives information about when you’re going to dream and it also has the ability to switch off the flow of motor systems going down to your spinal cord. It can paralyse your body when you’re going to sleep. When you’re switching in this system, sometimes it gets a bit carried away. You get these jerks as the system is turning on.

Dave - Basically, does a burn up on the way down but not the way up? The amount of heat you’re generating is all to do with how fast you’re going and how thick the atmosphere is. The thicker the atmosphere and the faster you’re going the more heat you generate. Although space rockets can go several times the speed of sound they do get some heating on the way up. It’s not that much because they’re going fairly slowly while they’re near the ground and the air’s fairly thick. They get faster up in much thinner air so there’s less heating. On the way down they’re going really fast and they’re still going fast through the thin air. As the air gets thicker they’ve still got lots of energy.

Chris - The escape velocity’s 13-14,000 miles an hour or something ridiculous, isn’t it? They have to have a way of dissipating heat.

Dave - They can’t dissipate all that energy in the upper atmosphere. They have to dissipate it lower down.

Chris - The yellow colour is because of the stuff that makes your blood red. When we break down red blood cells which last about 120 days the haemoglobin makes a protein which has a iron atom at the centre. That protein gets broken down into something called bilirubin. Bilirubin is dumped  out of the body by the liver. The liver metabolises the bilirubin bit by adding sugar to make it dissolve in water, puts in bile and your bile then gets squirted into your small intestine to help it reabsorbs fats. The bilirubin, because it has sugars stuck on it becomes broken down by bacteria. The bacteria metabolise the molecule and they turn it into something which is called urobilinogen. Urobilinogen gets reabsorbed further down the small intestine. Unlike bilirubin, which is not very soluble in water urobilinogen is very soluble but it’s a brown colour. The urobilinogen goes round the blood stream again but when it goes round in your blood stream again but when it goes through you kidney, because it’s soluble in water, it moves out through the kidney in the same way as the other things that go into urine do and it goes into your urine. Because your urine is a concentrate of plasma you take water back but leave the products that have got filtered behind and it builds up in the urine and adds this brown colour. So urine goes darker and darker. The more dehydrated you are the darker it is because the concentration is higher.

Kat - It may be a bit of it’s riboflavin as well because if you take a lot of B vitamins you just wee them out. I think, riboflavin, when it’s dissolved in water is very yellow as well.

Dave - The only way that actually adding music to your iPod could increase its mass could be if you were somehow increasing the energy of it. The way modern iPods tend to store music is in what’s called flash memory. This has lots of tiny cells inside it. You tend to trap the electrons, maybe a few hundred electrons in the little gap. That affects how current will flow through a wire until you can read it again. This is going to store some energy and maybe a miniscule amount. Probably 1/1000^th of a joule at most inside your iPod.  That’s for the 1s so the 0s wouldn’t store any energy – so half of that.  According to E=MC² it will increase the mass ever so slightly. That’s a tiny amount but that’s far less that the increasing mass. Perhaps when you charge up the battery but that’s less than the mass of a greasy fingerprint you put on top of it.

Chris - So the answer is yes if you put some energy into the iPod – if whatever you do to it means it gains some energy because Einstein says E=MC² it has to go into mass but the amount is going to be tiny.

Kat - Absolutely not at all. Then screening wouldn’t work. Things like the breast screening and the bowel screening that we have now. Some cancers, yes, they are advanced and that’s why the government’s trying to do a lot through an initiative called the early detection and awareness initiative to try and catch cancers earlier. Bowel cancers you can spot them when they’re just a little polyp. You can take them away and cancer will not have grown anywhere. In the case of breast cancers, breast screening picks up very small tumours that really haven’t spread far so it’s not necessarily true for all types of cancers that they will have spread around the place.

Chris - Could she mean that cancer’s a multistage process where you slowly build up and acquire changes of your DNA which eventually mean you get cancer and you could have spent a lifetime building up those changes?

Kat - That’s kind of true because we do pick up all kinds of damage to our DNA just in the hurly burly of life within our cells. Cancer is a disease that usually takes a very long time to happen. There is also and idea that we do, everyone has tiny cancers all over us but it’s our immune system that’s constantly patrolling our bodies and keeping these under control. What happens when cancer really starts to grow is that it started to evade this immune suppression and really start going for it. There’s a lot we don’t understand about how cancer really gets going.

Chris - Goose bumps or goose pimples are the bulges produced by your piloerector muscles. These are the muscles that can make your hairs stand on end. In other animals like mice, cats, dogs; making your hair stand on end is a good thing. If you’re cold you trap more air next to your body and it thermally insulates you. If you’re scared it makes you look much bigger. If you look much bigger then you’re scary to other animals and they’re less likely to attack you. We’re obviously derived and related to all these other mammals that do this but have less hair. It doesn’t serve a useful purpose in us, it’s just a sort of evolutionary vestige.