There are four different types of force in the universe. These are in order of strength:

Gravity – the one we might think is the strongest, is actually the weakest. But the more stuff you have, the stronger it becomes, and the Earth is made of a LOT of stuff, so the gravitational pull of the Earth feels very strong indeed.

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The weak nuclear force – this one has a bit of a lame name and frankly, it’s a bit complicated. It’s involved in some types of nuclear radiation, but as it turns out, the weak force is related very closely to the much more well-known electromagnetism. Which leads me nicely to the next force…

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Electromagnetism – This is what light is made of. No, really. I promise. And it is one million million million million million million times stronger than gravity. Seriously. Don’t believe me? Tell that to your sunburn on your next holiday. You don’t feel the sun’s gravity pulling on you as it moves through the sky, but you definitely feel its light blistering your skin. Or tell the floor that holds you up (through electromagnetism), despite all that gravity that’s trying to pull you through it. It is pretty tough stuff, but not quite as tough as…

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The strong nuclear force – this is the strongest known force and it does a very special job. The nucleus of an atom is made of protons, which all have a positive charge. But similar charges repel each other. Positive pushes away positive and negative pushes away negative. So what stops them flying apart and from each and every atom and molecule of your body exploding into smitherines!?!?! The strong nuclear force does. It’s basically the glue that holds nuclei together, but it only works over very, very small distances.

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You should probably thank it. Your life depends on it.