Sleeping on the blow-up mattress when your relatives come to stay may be a bit uncomfortable, but would you prefer a bed of nails? Actually, although they look like an instrument of torture, these favourites of fakirs can be a surprisingly pleasant place to take a nap. It may look kinda spikey, but you wouldn’t end up full of holes on a bed of nails because your weight is shared out amongst all the nails. Imagine if you tried to sit on one nail – ow! All your weight would push down on that nail, and it would definitely hurt. But a bed of nails is made up of thousands of nails. When you lie down (carefully!) you are spreading your weight over all of them. Each nail has to carry a lot less of your weight and with a bit of skill you won’t be hurt. Lying on a bed of nails can even be a pleasurable experience, especially the first time. If you are expecting something to hurt, your body releases natural painkillers, endorphins, to help you deal with the pain. If there is no pain after all, the endorphins are still flooding around your body, making you feel far better than you expected. Endorphins are also released after exercise, which is why some people feel great after going for a run or exercising at the gym.

	Egg-traordinarily strong
	Eggs are designed to provide a safe growing chamber for a developing bird, and are very strong. Their shape allows any pressure put on one area of the egg to be spread out over the whole egg, reducing the chance of them cracking.
	This might get messy, so do this investigation over a sink! Take an egg and squeeze it tightly in your hand – you’ll be amazed at how pressure it can take. Does the way you hold the egg affect how hard you can squeeze it?
	Now see how much weight you can support on four eggs. Pop an egg in each corner of a large egg carton, then place a strong board on top of it. Pile books on top of this until the eggs break. Using boiled eggs instead of fresh ones will reduce some of the mess when they eventually crack.