[12-Forces 视频] 一颗苹果引发的重力思考 | Gravity

Why don't we float off into space when we jump high?

There is an invisible force that pulls us back down. Without it, there would be no life on Earth.

It's called gravity.

We can see the effects of gravity all around us.

Every time we drop something or let something go.

If you jump into the air, gravity pulls you back to the ground... Unless of course, you're using a jet pack!

Gravity also acts in space. It keeps the Earth in orbit around the Sun.

Gravity is the force of attraction between any two objects in the universe.

It is only really noticeable when one of the objects is very large – like the Earth or Moon. The Moon's gravity pulls on the Earth as it orbits around us. This is the reason we have tides, as seas and oceans are slightly pulled towards the Moon.

Because the Moon is much smaller than the Earth, the gravity there is weaker. When astronauts walked on the Moon, they appeared to be bouncing!

The lower gravity meant the astronaut’s boots were pulled back towards the ground more slowly than on Earth – making it look like they were jumping around on a springy Moon surface.

Back here on Earth, we’d need a trampoline to jump that high!

Gravity affects everything we do.

What would happen if gravity on Earth was stronger? Or if there was no gravity at all?