What is Gravity?
A force of attraction that acts between any two objects that have mass. The larger the masses involved, the stronger the gravitational force.
Gravity is one of the most important forces in the universe. It keeps your feet on the ground, holds the Moon in orbit around the Earth, and keeps planets orbiting the Sun.
Here is something surprising: gravity acts between all objects with mass — not just planets and people. Right now, there is a tiny gravitational pull between you and your desk, between you and your classmate, and between you and your phone. So why don't objects fly towards each other?
The answer is that gravity is only noticeable when at least one of the objects has an enormous mass — like a planet. The gravitational pull between two people standing next to each other is probably less than a millionth of a newton — far too small to feel or measure.
Think of gravity like a magnet. A tiny fridge magnet has a very weak pull. A giant industrial magnet can lift a car. Gravity works the same way — the bigger the mass, the bigger the pull. The Earth is so unimaginably massive that its gravitational pull dominates everything around us.
Gravitational Fields
Some forces, like friction or a push, require objects to be in direct contact. But gravity is different — it can act across empty space, without any contact at all. This is called a non-contact force.
To explain how this works, scientists use the idea of a field.
A region of space surrounding a massive object where any other mass will experience a gravitational force pulling it towards that object.
The Earth is surrounded by a gravitational field. Anything inside this field — a person, a ball, a satellite — experiences a pull towards the Earth's centre. Importantly, you don't need to be touching the Earth to feel this pull. That's how the Moon stays in orbit hundreds of thousands of kilometres away!
Gravitational forces act over very long ranges. The Sun's gravity reaches all the way to the outer planets. Saturn's gravity holds its rings and its moon Titan in orbit. Gravity truly is a long-range force.
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