All the questions from the thread and the survey were put to Gemma (editor of the book) and the one she picked out was from NanSue's 6 year-old GS...
"What is a gamma ray"
The expert who provided the answer is science writer, journalist and broadcaster Marcus Chown - author of the excellent What A Wonderful World: One Man's Attempt to Explain the Big Stuff.
What is a gamma ray?
A rainbow is a beautiful thing. It's caused when falling raindrops split sunlight into colours. Those colours - the colours of the rainbow - are red, orange, yellow, green, blue, indigo and violet. Seven of them. But, actually, there are other colours that our eyes cannot see. For instance, beyond the red, is a colour known as infrared. It is given out by warm bodies. We cannot see infrared but snakes called pit vipers can. They use it to spot the warmth of mice in the blackness of night. And, beyond the violet, is a colour called ultraviolet. Ultraviolet is what burns your skin if you stay out in the sun too long. We cannot see it but bees can. Flowers often reflect ultraviolet from the sun and so look quite different to bees than to us. Why am I telling you this? Well, there aren't just two colours - infrared and ultraviolet - that we cannot see. There are MILLIONS. And gamma rays are simply another colour we cannot see, though scientists have built telescopes that can see them. Gamma rays are given out by violent events out in space like black holes colliding with each other or greedily swallowing stars whole. We can see these because astronomers have built artificial eyes that can see gamma rays. In fact, they have built artificial eyes that can see millions of colours invisible to the human eye. That's how clever they are!
