What is gravity?

The longer answer

You cannot see gravity, but you can see what it does. Let go of anything, a spoon, a sock, an apple, and it heads the same way every time: down, toward the middle of the Earth.

Everything has gravity, even you. But your pull is far too small to notice. It takes something as huge as a planet or the Moon to make a pull strong enough to hold people, oceans and air in place.

Gravity also reaches a long way. The Earth's gravity keeps the Moon going around us, and the Sun's gravity keeps the Earth going around the Sun, year after year.

Three things to know

• The Moon pulls on the sea, and that is what makes the tides. The Moon's gravity tugs the ocean toward it, so the sea creeps up the beach and slides back down about twice a day.
• On the Moon you would weigh much less. The Moon's pull is about six times weaker than the Earth's, so the same jump would carry you about six times higher.
• With no air, a feather falls as fast as a hammer. Air slows light things down. On the Moon, where there is no air, astronauts dropped both together and they landed at the same moment.

Try it at home: a drop test

1. Find two things that weigh different amounts but are about the same size, like a ball and a balled-up sock.
2. Hold them at the same height, one in each hand.
3. Let go of both at exactly the same time, and watch which lands first.
4. Now try a flat sheet of paper and a scrunched-up sheet of paper. What changed?

The ball and the sock land together because gravity pulls them down at the same speed. The flat paper is slowed by the air, not by gravity.