The invisable force school series 13

 Gravity — The Invisible Force

We learnt in school that gravity pulls everything towards the Earth. We dropped a stone, watched it fall and moved on to the next chapter.

But gravity is much more than that.

Gravity is the invisible force of attraction between objects that have mass. The Earth attracts us, which is why we remain on the ground instead of floating away.

But the same force works on a much larger scale.

The Sun's gravity holds the planets in their orbits. Earth's gravity holds the Moon in its orbit. The gravity of the Moon contributes to the rise and fall of our tides.

Even the stars and galaxies are shaped by gravity.

There is something particularly fascinating about Earth's gravity: it gives us weight. Our mass does not change when we travel to the Moon, but our weight would be much less because the Moon's gravitational pull is weaker.

And gravity does something even more extraordinary.

According to Einstein, gravity is not simply an invisible pulling force in the old-fashioned sense. Massive objects curve space and time, and objects move through that curved spacetime.

We don't notice this extraordinary structure in everyday life.

We simply drop a ball—and it falls.

So the lesson we learnt as children was only the beginning:

The same invisible force that makes an apple fall also keeps the Moon around Earth, the Earth around the Sun, and the stars bound together in galaxies.

Gravity is invisible.

Its effects are everywhere.