Did you know that without gravity, we would fall right off of Earth’s surface and float away?
Or that gravity is the reason a comes back down when you throw it into the air, instead of just travelling higher and higher?
Gravity is a force of attraction that pulls together all matter (anything you can physically touch). The more matter something has, the greater the force of its gravity.
That means really big objects like planets and stars have a stronger gravitational pull.
The gravitational pull of an object depends on how massive it is and how close it is to the other object.
For example, the Sun has much more gravity than , but we stay on Earth’s surface instead of being pulled to the Sun because we are much closer to Earth.
For a long time, scientists knew that there was some mysterious force that keeps us on the surface of the Earth.
It wasn't until 1666 that Isaac Newton first mathematically described the force of gravity, creating Newton's laws of universal gravitation.
It is said that his ideas about gravity were inspired by watching an apple fall from a tree. Newton wondered what force made the apple fall downward instead of simply floating away.
Another scientist you may have heard of, Albert Einstein, later added to Newton’s ideas about gravity with his theory of relativity.
We already mentioned that we wouldn’t be able to stay put on Earth’s surface without gravity. Objects would simply float away if gravity didn’t exist.
Gravity is also the force that keeps the Earth in orbit around the Sun, as well as helping other planets remain in orbit.
And did you know that weight is based on gravity? Weight is actually the measurement of the force of gravity pulling on an object.
For example, your weight on Earth is how hard gravity is pulling you toward Earth’s surface.
If you travelled to other planets, you would weigh more or less depending on if those planets have more or less gravity than Earth.
Since gravity is related to mass, you know that you would weigh less on smaller planets and more on larger planets.
High and low tides in the ocean are caused by the moon’s gravity.
The moon’s gravity is 1/6 of Earth’s gravity, so objects on the moon will weigh only 1/6 of their weight on Earth.
So if you weigh 80 pounds (36 kilograms) here on Earth, you would weigh about 13 pounds (six kilograms) on the !
There is zero gravity in outer space, so you would be weightless if you were floating out in space!
In physics, weight is described as a force and can also be measured in Newtons. Guess who this unit of measurement is named after? That’s right—Isaac Newton, the who discovered gravity.
Objects weigh a little bit more at sea level than they do on the top of a .
This is because the more distance you put between yourself and Earth’s , the less gravitational force Earth exerts on you.
So the higher you go, the less gravity pulls on you, and the less you weigh. However, the difference is very small and barely noticeable.
If you wanted to escape Earth’s gravitational pull, you would have to travel seven miles (about 11 kilometres) per second.
This number is called Earth’s “escape .” To travel that fast, you would have to be a superhero!
Even if two objects are different weights, the force of gravity will make them travel at the same speed.
For example, if you dropped balls that were the same size but different weights out of the same second-story window, they would both hit the ground at the same time.
Gravity even helps guide the growth of plants!