Here’s why gravity pulls us down and not up

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to [email protected].

Why does gravity pull us down and not up? – Gracie, age 9, Brookline, Massachusetts

Gravity is the reason things with mass or energy are attracted to each other. It is why apples fall toward the ground and planets orbit stars.

Magnets attract some types of metals, but they can also push other magnets away. So how come you feel only the pull of gravity?

In 1915, Albert Einstein figured out the answer when he published his theory of general relativity. The reason gravity pulls you toward the ground is that all objects with mass, like our Earth, actually bend and curve the fabric of the universe, called spacetime. That curvature is what you feel as gravity.

What is spacetime?

Before getting into the complicated world of gravity, you need to understand spacetime.

Spacetime is exactly what it sounds like: the three dimensions of space – length, width, and height – combined with the fourth dimension – time. Using some very brilliant math, Einstein was the first person to realize that the laws of physics work in a universe where space and time are merged together.

What this means is that space and time are connected – if you move really fast through space, time slows down for you compared to someone who is moving slowly. This is why astronauts – who are moving very fast in space–age a tiny bit more slowly than people on Earth.