The Science of How not to break an egg!
Eveybody knows that eggs are fragile and break very easily. However, as you can see here, they are very difficult to crush.
To show that this is not a trick, the egg is first spun to show that it is fresh and not hardboiled (see how to tell fresh from hardboiled eggs).
Then the egg is put into a plastic bag - this is just in case it does get crushed, which can be a bit messy! As you can see, the egg cannot be crushed, although it can be "cracked" very easily.
This is because, although the shell is not very thick, the shape of the egg is a very strong one. Being nearly a sphere, all the pressure from the fist is spread evenly over the whole shell, so the thinness isn't important.
When you "crack" the egg, however, all the impact is on a small bit of shell, which breaks.
If you try this yourself, make sure you take off any rings as they can crack the egg