The panel



John O'Farrell Writer

Author, broadcaster and comedy scriptwriter.



Iain Stewart Geologist

Stewart presents a new TV series, Earth: The Biography, this autumn.



Will Self Writer

Novelist, short-story writer, critic and broadcaster.



Susan Greenfield Scientist

Author of several popular science books about the brain.



Kirsty Wark Broadcaster

Political journalist and presenter of BBC2's Newsnight.



Marina Warner Writer

Novelist, critic and cultural historian, in particular of female myths.



Robert Winston Scientist

Human fertility expert and science TV presenter.



Daisy Goodwin TV presenter

TV producer and presenter, editor of several poetry anthologies.



Q: Why does salt dissolve in water?



Iain Stewart Er, I guess the sodium ions get taken up... oh, gosh, I suppose the sodium and chlorine dissociate. The chlorine joins with the water and the sodium ions float free. Something like that.

Will Self It doesn't completely dissolve, of course. It must be because it absorbs water to the point at which it disintegrates. Is that right? I couldn't describe it scientifically.

Daisy Goodwin It forms another compound. The only reason I know any of this is because I've been testing my daughter on her GCSEs.

Marina Warner The molecules join with the water molecules. The sodium molecules join up with the hydrogen and oxygen molecules.

Susan Greenfield Because sodium and chloride disassociate and H20 is hydrogen and oxygen.

Kirsty Wark Because it's less dense.

Robert Winston It's to do with ions isn't it? Let me just work it out. It's to do with the way sodium and chloride ions, um. Do you know, I'm not sure I can really explain it. I can't remember now from my physics years ago.

John O'Farrell No idea.

Answer: Sodium chloride is an ionic substance that contains alternating sodium and chlorine ions. When salt is added to water, the partial charges on the water molecule are attracted to the Na+ and Cl- ions. The water molecules work their way into the crystal structure and between the individual ions, surrounding them and slowly dissolving the salt.

Q: Roughly how old is the earth?



John O'Farrell I'll have a guess. About 100 million years?

Will Self I'm completely winging this. A couple of billion years? No? Give me right on that. Mark me up.

Iain Stewart This I am sure of: 4.5 billion - no, actually 4.6 billion years.

Daisy Goodwin Pass. This is embarrassing.

Marina Warner That I don't know. (I did actually just hear Melvyn Bragg's programme this week about very ancient worlds.) I'm not very good at figures.

Robert Winston Well, the universe is 13 billion or 14 billion and the earth is between 4 and 5 billion years old.

Kirsty Wark More than 5 billion years.

Susan Greenfield Oh blimey. Well, I know that human beings have been going for about a million and a half years, so ... I'm just grasping here. Something like 60 billion years or something like that, but that's a grasp. I'm not a physical scientist and it shows. I'm probably not scientifically literate.

Answer: 4.5 billion years.

Q: What happens when you turn on a light?

Will Self In my house, very little, because I never get round to changing the bulbs. You complete a circuit?

Iain Stewart This is taking me right back to school physics. It's the kind of question I always pray a nine-year-old won't ask me. I think the switch closes a loop for the circuit.

Kirsty Wark It gets brighter. There's a current... that connects between two prongs.

Marina Warner The energy is conducted along the wire to the filament.

John O'Farrell I'm running out of steam here. I really don't know.

Susan Greenfield There's a flow of electrons called a current, and it's that flow which is the energy and generates heat and light.

Robert Winston Well you fall in love, don't you? Isn't that what it is? No, Okay, when you turn on the switch you make a circuit.

Daisy Goodwin You connect a circuit.

Answer: The switch controls the flow of electricity through a circuit - a complete, unbroken loop through which electric charges can move. When the light switch is on, these electric charges can move in an endless loop. This loop begins at a power station where the charges pick up electric energy. They then flow through wires to the light switch, then to the light bulb where they deliver their electric energy, and finally back to the power company to obtain more energy.

Q: Is a clone the same as a twin?

Will Self No.

Iain Stewart Yes, er, I think... oh God, it's probably not. But I think it has to be, doesn't it?

John O'Farrell No. How could it be the same? That's not how cloning works, is it?

Susan Greenfield Yes. An identical twin.

Daisy Goodwin As an identical twin? That's quite interesting. No. Well, I'm not sure about that. I'd say no. But maybe yes. I'm baffled.

Kirsty Wark No. But there's two different kinds of twin. You have to give me a point for that!

Robert Winston Well, not necessarily. It's not genetically the same actually, no. You see, it depends on the kind of twin. Do you mean an identical twin? Identical twins are different in all sorts of ways. It's different epigenetics and there's different mitochondrial DNA, so it's a different organism. Actually, what we're beginning to understand is that the epigenetic aspects of cloning are fundamentally very important. And twins are rather more dissimilar than people imagine, too. For example, they have different fingerprints from each other, so there are quite interesting and subtle diff erences.

Marina Warner Yes it is. Well, identical twins are clones, not non-identical twins.

Answer: Yes, up to a point (see Robert Winston's answer).

Q: Why is the sky blue?

Susan Greenfield That was discovered here at the Royal Institution [of Great Britain] by Tyndall. Sorry, I can't articulate that entirely because I'm half asleep.

John O'Farrell My daughter explained this to me the other day. She is in Year Seven. It's to do with blue being the dominant colour in the colour spectrum.

Will Self It's because of the diffusion of light from the sun through oxygen, through the air.

Iain Stewart Because of 'Rayleigh scatter', the diffusion of blue light molecules.

Daisy Goodwin I have no idea. I have looked it up because I've been asked the question by my children and I've explained it to them and now I've forgotten. It's the colour of the atmosphere or something. It's the gases or whatever.

Marina Warner It's a refraction of the light.

Robert Winston Oh bugger, I can't remember now. Um. Oh Jesus. It isn't really blue actually. It doesn't actually have a colour at all. It just simply appears blue.

Kirsty Wark Because it's a reflection of the oceans on the planet. No idea apart from that. I think the sky is blue because... the rain clouds obscure the blue, and the blue is a reflection... because of the sunshine. Fuck! I don't know! Why is the sky blue?

Answer: A daytime sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light.

Q: What is the Second Law of Thermodynamics?

Will Self It's either the conservation or the dissipation of energy, isn't it? It's everything tending towards entropy, isn't it?

Iain Stewart It's about the conservation of motion, I think, but I'm not sure. Different field from mine, you know.

John O'Farrell Let me think. Is it to do with heat conductors? Metal is an effective heat conductor and wood is not. I remember that from metalwork classes.

Marina Warner Is it that mass cannot be... that no energy can be lost? The first law is conversion. Is the second law that there is no loss... that energy must go somewhere?

Susan Greenfield That everything degenerates to entropy.

Robert Winston I've always refused to answer that question on a matter of principle, simply because of C P Snow, and you can report that. But it is in one of my children's books.

Daisy Goodwin Don't know. I'm scientifically illiterate.

Kirsty Wark No idea.

Answer: It is the Law of Increased Entropy. It states that in any system the quality of energy deteriorates gradually over time. 'Entropy' is defined as a measure of unusable energy within a closed or isolated system (the universe for example). As usable energy decreases and unusable energy increases, 'entropy' increases. As usable energy is irretrievably lost, disorganisation, randomness and chaos increase.

· Click here to read 'The new age of ignorance'