What is Gravity? (Quick Answer)
Gravity is the invisible force that pulls objects towards each other. Here on Earth, gravity pulls everything down to the ground. Drop something and see!
Gravity in one sentence: Gravity is the force that pulls things together. That is why we stay on Earth instead of floating in the air!
Gravity: Mass vs. Weight
- Mass is how much ‘stuff’ is in something (this doesn’t change)
- Weight is how hard gravity pulls on a mass
Note: this is why an astronaut has the same mass on Earth and on the Moon. But they weigh less on the Moon than on Earth.
Who Discovered Gravity?
People have always been able to notice that things fall to the ground. Isaac Newton was the first to write rules for how gravity works.
Albert Einstein took it a step further! He explained that really big objects warp time and space, and that warping acts like gravity.
Is There Gravity in Space?
Yes! There is gravity in space. There only seems to not be gravity when astronauts float because they are in continuous free fall. This is also called microgravity.
What is the Acceleration due to Gravity on Earth?
At Earth’s surface the acceleration of gravity is about 9.81 m/s2 (32.2 ft/s2).
This means that the speed of an object falling freely will increase by about 9.81 metres (32.2 ft) per second every second.
Does the Moon have Gravity?
Gravity is experienced on the Moon. The acceleration due to gravity on the surface of the Moon is approximately 1.625 m/s2.
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 Moon!
High and low tides in the ocean are caused by the Moon’s gravity.
Gravity and Tides
High and low tides happen mostly because the Moon’s gravity pulls water towards the Moon, causing a higher tide. Then away from the moon has a lower tide.
More Info About Gravity
Did you know that gravity is the reason we stay on Earth and why a ball comes back down when you throw it into the air instead of just traveling higher and higher?
Or that without gravity, we would fall right off of the Earth’s surface and float away?
But, Earth is not the only planet with gravity. All planets and stars have gravity. This is how the Sun keeps all the planets in our solar system in orbit.
What exactly is this mysterious force of nature? Keep reading to find out.
What exactly is this mysterious force of nature? Keep reading to find out!
What is gravity?
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 Earth, but we stay on Earth’s surface instead of being pulled to the Sun because we are much closer to Earth. The gravity of the Sun keeps Earth in orbit around it, keeping us at a comfortable distance.
What More About Discovering Gravity?
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.
Why is gravity important?
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 traveled 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.
Weight and Gravity – How are they related?
As we mentioned earlier, the larger the mass of an object, the more gravity.
This is why planets and stars have a stronger gravitational pull than other, smaller objects, like moons. This is also why all humans, animals, and plants stay on Earth – because of the Earth’s strong gravitational pull toward these objects.
Did you know that the Earth’s gravity is so strong that it even keeps the Moon in orbit around it? Yes! Earth’s gravitational pull determines our Moon’s orbit around our planet. Similarly, other planets, too, have gravity, which keeps their moons in orbit around them.
Gravitational pull of a black hole
First off, a black hole is the result of a collapsed star. Its gravitational pull is so strong that even light cannot escape it!
This makes black holes the only objects in the universe with the strongest gravitational pull.
As mentioned in this article, for anything to escape the gravitational pull of something else, it must move faster than its “escape velocity”. Earth, for example, has an escape velocity of seven miles per second. So, for an object to leave Earth’s gravity, it has to travel at that speed or more.
This is how rocketships leave Earth’s orbit to travel to other parts of the solar system.
Since a black hole’s escape velocity is faster than the speed of light, nothing that goes inside it can come back out! How fascinating!
How is Gravity Measured?
Gravity is usually measured in units of acceleration. The standard unit of acceleration is meters per second squared, m/s^2.
20 Facts about Gravity
- There is still gravity in outer space, but astronauts float because of microgravity.
- 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 scientist who discovered gravity.
- Objects weigh a little bit more at sea level than they do on the top of a mountain.
- This is because the more distance you put between yourself and Earth’s mass, 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 kilometers) per second.
- This number is called Earth’s “escape velocity.” 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 in a vacuum (no air).
- Gravity even helps guide the growth of plants!
- Gravity is everywhere, everything with mass is affected by gravity.
- On Earth, gravity pulls at 9.81m/s².
- In a vacuum (no air), a feather and a rock fall at the same speed.
- The moon has about 1/6 the gravity that Earth does.
- You can jump higher on the Moon than on Earth.
- Gravity causes planets and stars and galaxies to form over time.
- Ocean tides are caused by gravity of the Moon
- Astronauts float in space even though they are pulled by gravity, the gravity is just really weak
- The further away you are from some mass, the less the gravity affects you
- Two objects with mass exert gravity on each other!
Now you know gravity is a major force in the universe. It keeps us from floating away, controls the ocean’s tides, guides plant growth, keeps Earth and other planets in orbit, and more!
Frequently Asked Questions
Why is gravity a force?
Gravity is a force because it is caused due to the interaction of two objects with masses. The object with the larger mass (e.g., Earth) attracts an object with a smaller mass (e.g., a ball) toward it, which causes a force between the two. This force is called gravity.
What type of force is gravity?
Gravity is a non-contact force. This is why everything stays on the surface of the Earth.
Why isn’t there gravity in space?
There is gravity in space. It may be undetectable as you move further and further away from Earth and other planets, you don’t feel their gravitational pull, but it exists.
Is gravity caused by mass or energy?
Gravity is caused by both mass and energy. This is why objects like both light (has energy) and Earth (has mass) cause gravity.
Can we create gravity?
Although we may not be able to create gravity exactly, we can generate a kind of artificial gravity. This can be done using accelerations (like a centrifugal force) and a vehicle that is strong enough to spin at a rate equivalent to gravity.
