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!