How to Explain Gravity

People often think that there is no gravity in space; they get mixed up because there is no air in space. There is gravity in space. It gets less the further you go from the Earth or any other planet, but it is still there. It is gravity that keeps the planets in orbit; otherwise they would all float away!

Astronaut on the Moon

Spacesuits worn on the moon allowed astronauts to walk around the lunar surface far from their lander.

Courtesy of NASA

Astronaut on the Moon
Courtesy of NASA

Astronaut on the Moon

Spacesuits worn on the moon allowed astronauts to walk around the lunar surface far from their lander.

Courtesy of NASA

Enlarge image

People often think that there is no gravity on the Moon; they see pictures of astronauts bouncing around on the Moon. There is gravity on the Moon, but it is not as strong as on Earth because the Moon is not as heavy as the Earth. People often get confused also because there is no air on the moon (and therefore no sound).

Gravity is not just a force which pulls us down to Earth – everything in the Universe exerts a force of gravity. So why do the table and chair not jump towards each other? Because their force of gravity is so very tiny compared with the huge gravity of the massive Earth.

We have all seen images of astronauts floating around inside their spacecrafts, weightless, and people often think that this is because gravity does not exist there. This is not the case. Even 300 km above the Earth’s surface, where most spacecraft travel, the force of gravity is still 90% as strong as it is on land.   See the section on ‘Weightlessness’ which is also called ‘Microgravity’.