Gravity
Any two objects have a force pulling between them called gravity. How much an object pulls on another object depends on the distance they are apart and their mass.
Mass means how much stuff (matter) is in an object.
Gravity is what pulls people down toward Earth. When you jump, gravity makes you come back down. When you are walking, it holds you on the ground. The Earth's gravity pulls you to towards its centre. Wherever you are on the Earth you are pulled 'down' towards its centre.
You only notice gravity when at least one object is massive such as a moon or planet or star.
Is There Gravity in Space?
There are small amounts of gravity everywhere. Far out in space (thousands of miles away from the Earth), astronauts would float around inside their spacecraft. That is because of microgravity.
"Micro-" means "very small". Microgravity is when the pull of gravity is not very strong. In microgravity, it is easy to move heavy objects. Astronauts can move heavy things with just the tips of their fingers.
Is there gravity in the International Space Station (ISS)?
Yes. You do not have to be on the Earth to feel Earth's gravity. The ISS is 200 miles above the Earth but Earth's gravity is still very strong there. So it is not microgravity that causes things to float on the space station.
There are small amounts of gravity everywhere. Far out in space (thousands of miles away from the Earth), astronauts would float around inside their spacecraft. That is because of microgravity.
"Micro-" means "very small". Microgravity is when the pull of gravity is not very strong. In microgravity, it is easy to move heavy objects. Astronauts can move heavy things with just the tips of their fingers.
Is there gravity in the International Space Station (ISS)?
Yes. You do not have to be on the Earth to feel Earth's gravity. The ISS is 200 miles above the Earth but Earth's gravity is still very strong there. So it is not microgravity that causes things to float on the space station.
Why do things 'float' in the ISS?
The ISS, its crew and all the objects inside are falling around Earth. As they are all falling together, the crew and objects seem to float.
How can things fall around the Earth?
Earth's gravity pulls on the space station. So it is falling toward Earth's surface. But the station is moving very fast. It moves so fast it matches the way Earth's surface curves.
If you throw a ball, gravity will cause it to curve down. It will hit the ground. But a spacecraft that goes around the Earth moves at the right speed so that the curve of its fall matches the curve of Earth. The spacecraft keeps falling toward the ground but never hits it. Instead, it falls around the planet.
The ISS, its crew and all the objects inside are falling around Earth. As they are all falling together, the crew and objects seem to float.
How can things fall around the Earth?
Earth's gravity pulls on the space station. So it is falling toward Earth's surface. But the station is moving very fast. It moves so fast it matches the way Earth's surface curves.
If you throw a ball, gravity will cause it to curve down. It will hit the ground. But a spacecraft that goes around the Earth moves at the right speed so that the curve of its fall matches the curve of Earth. The spacecraft keeps falling toward the ground but never hits it. Instead, it falls around the planet.
The sun's pull is the strongest.
The sun is the biggest thing in our solar system and it has the most mass. So the pull of its gravity is the strongest. This is why the planets circle around the sun. The planets are falling around the sun. If they weren't moving very fast they would fall into the sun.
The Earth and the moon both have a gravity. Their gravity pulls on each other but the Earth is bigger and has more mass so it pulls more on the moon. So the moon falls around the Earth.
The Earth and the moon both have a gravity. Their gravity pulls on each other but the Earth is bigger and has more mass so it pulls more on the moon. So the moon falls around the Earth.