​The reason the Earth revolves around the Sun is to do with what we call centripetal force. The Earth, believe it or not, is trying to move in a straight line. The force of the Sun's gravitational pull however keeps trying to pull it in. This results in a circular path round the Sun. It’s the same as when you play swing ball, except in that case it’s the string keeping the ball from shooting off.

On a similar subject Jasveer wanted to know Why do waves come on the shore from the Ocean? And
a Hector from Lewes wanted to know what would happen if there was no moon.
Well, we can combine these two as the tides are partially controlled by the moon. As the moon
circles the earth, the water in the ocean is pulled up towards it by the moons own gravity. Then as
the moon moves by, that water sloshes back down again and onto the shores of the Earth. If there
was no moon, that wouldn’t happen so much. There would still be smaller tides as the water in the
oceans bulges out as the Earth spins on its axis. But, also, there would be no more eclipses and
because the tides act as a brake, the Earth would spin faster so our days would be shorter.

Rymsha was wondering what gravity is made of. Blimey, that’s a huge question. As big as the
universe in fact because everything exerts a gravitational effect on everything else. The more
massive it is, the stronger the pull. Gravity is one of the fundamental forces that pervae the whole
universe. It’s known as a ‘weak nuclear force’. Its weak as it acts over distance, but slowly. There
are ‘strong nuclear forces’, such as the bonds between atoms. If you where, to say, drop a melon
from the top of a tall building gravity would take a good few seconds to accelerate it to its top speed
but when that melon hits the ground, the bonds between those atoms that form the ground stop it
almost instantly (and it splats). As to what it’s made of, no one is totally sure. Many scientists are
searching for what they call gravitons a quantum particle that’s been around since the big bang.
There are many theories as to how gravity works but Albert Einstein put it in what I think is the best
way. If you have a huge rubber sheet and put a selection of balls of different masses on it, the most
massive will make the biggest dip in the sheet and the smaller ones would roll towards it.

All these questions answered by Steve Evans.

We do an experiment that shows this well in our Space and Star Force shows, where you take a large stretchy plastic sheet, place the Sun at the centre and then spin a ball around it to represent matter curving around the fabric of space time. Here's a picture!

Good question, particularly as it snowed yesterday! 

​When snow falls onto water, or anything else not as cold as it, the heat energy flows into the snow and melts it.  If the ground is cold enough, the snow settles”

So, the light we see is part of what we call the electromagnetic spectrum. Scientists picture it as wavelengths.  Really energetic gamma rays have lots of peaks very close together.  At the other end, low energy radio waves are flatter with more distant peaks.  Our eyes have evolved over millions of years to be able to see just a small part of this spectrum. This is what our brains see as colour. Other animals can see into this part of the spectrum.  Some birds of prey such as hawks can see ultra violet which helps them track their prey as the preys wee show up in this part of the spectrum.  Bees can see infra red. Many flowers have patterns on them that shine in infra red helping the bees find the nectar.

Here are some links for you to find out more.. 
​http://www.dailymail.co.uk/sciencetech/article-473897/A-bees-eye-view-How-insects-flowers-differently-us.html
https://www.livescience.com/26994-how-birds-uv-vision.html

This is a prize-winning question, Yuvleen! Well done!

​Consider the basic principles. Actors moving around. Their actions being captured by a camera. Those images sent through the ether to a receiver. Receiver rebuilding the images,. Now, there are several ways to send the images. Satellite, terrestrial or cable. All three also carry the sound , hence AV, which means audio visual. Nothing can actually capture a moving object on camera. What happens is that lots of still photos are taken one after another and when they are replayed, it appears to the human eye that the object is moving. Thus, the TV camera takes thousands of pictures per second which are taken line by line and sent to the receiver which reconstructs them line by line on the TV screen. The tiny rectangles of light which this produces are called "pixels", and the greater the number of pixels, the clearer the picture. Hence 4K and 5K. Oh, by the way, 60Hz means the whole picture is refreshed 60 times per second. The picture is a diagram of a very early TV by the way! Modern televisions are more advanced than this, but thought it was an interesting diagram...

It depends on exactly what you're asking. The spontaneous radioactive decay of a nucleus involves only one atom. For example if you take an isolated uranium-235 atom and simply wait it will eventually decay without any interaction with anything else. You will have to wait for a long time.

However, in the case of an atomic bomb this cannot be done by relying on spontaneous decay. Instead  stimulated fission is used, where a uranium-235 nucleus is struck by a neutron from an external source and this triggers fission. The fission releases three neutrons and these strike other uranium nuclei and trigger their fission, and so on causing a rapid chain reaction and nuclear explosion.
​
Here is some info on this from https://en.wikibooks.org/wiki/Wikijunior:How_Things_Work/Nuclear_Bomb

There are two types of nuclear bombs, fission bombs and fusion bombs. Fission means to break apart and fusion to merge.
The fission bomb works on the principle that it takes energy to put together a nucleus with many protons and neutrons. Sort of like rolling a heavy cart up a hill. Splitting the nucleus up again then releases some of that energy. Some atoms have unstable nuclei which means that they tend to break apart with little or no nudging.
You may have heard of uranium and plutonium and that they are radioactive elements. These two have such unstable nuclei which causes their radioactivity. When a nucleus breaks into two smaller nuclei, a couple of neutrons shoot out. This is the radiation. Naturally occurring uranium and plutonium have atoms constantly undergoing radioactive decay. These are spaced sufficiently far apart so that the neutrons rarely bump into other unstable nuclei.
When a neutron, however, does hit an unstable nucleus, just like someone bumping into a cart at the top of a hill, it causes that nucleus to break apart and send out another couple of neutrons. By increasing the concentration of these unstable atoms, the probability that a neutron from one decay causes another one increases. The concentration where the reaction sustains itself is called critical mass and the reaction then called a chain reaction.
With each step of the reaction, energy is released and another step or two is started, and so an avalanche of reactions and energy release continues until the fissile (unstable) material is spent.

Basically atom bombs (which start with an atom exploding) are incredibly powerful and deadly weapons that are hugely destructive and very dangerous. However the theoretical science of atomic bonds and atomic fission is very interesting. So thank you for your interesting question!

​Dear Charlie, Brad here. Firstly, thanks for rocking up to the Fenwick's shows. We had a fantastic time in Newcastle. Met some great families and kids. It was a Blast. Secondly, thanks for taking the time to "Ask a Scientist". I ran your question past a friend of mine who is a marine biologist. Someone who likes this kind of science, like you. 

Now, your marine biology question is not only a very good question, but a very interesting one to boot. Growing up by the ocean, and having a father who worked on fishing boats, I've seen my share of big sharks up close. I also spent many years in the Florida keys, and was privileged to see some amazing sharks in thier natural habitat. Hammerheads. Mako. Nurse. Black tipped reef sharks, as well as rays, turtles, alligators and crocodiles. 

Sharks are truly amazing creatures, dinosaurs of the modern world. Unchanged for hundreds of millions of years. Sharks are perfect for how they act, and what they do. They are streamlined for stealth, speed and agility.  Hunting machines. 

That said, according to my research for your question, a sharks tongue doesn't seem to have much of a job to do. They rip and tear chunks out of fish, or eat them whole w replaceable teeth. A sharks tongue does, though, have a very cool name. It's called a basihyal. Remember that. 

So, Read up on all things marine biology, an important job for a young man like you. Learn all about  the seas and  oceans. We've  explored more of space  then the oceans of the world. 

Much to learn. Ask good questions, learn facts, do some field research, and have a blast with your scientific enthusiasm. Thank you for your question, Charlie. Well done.

Brad. 

Good question Mason – A chemical exists when you manage to combine 2 or more elements (stuff such as carbon, hydrogen, oxygen, iron etc, all represented on the periodic table of elements.  There are 92 elements which occur naturally on earth and some more made up by humans.  So, if you can these elements to stick together (bond), you have a chemical.  That’s a lot of combinations. According to a survey of the Society of Chemical Manufacturers, they estimate between 25,000 and 84,000 chemicals in use regularly in the US.  And that’s just the normal ones we know about. The answer is probably a lot higher.  A lot ​