Gravity Facts

Gravity is what we call an ‘invisible force of nature’, but in reality, it exists throughout the universe.

It is one of the fundamental forces of nature along with electromagnetism, weak nuclear force, and strong nuclear force.

It keeps all of us on the ground, the planets in their orbits, and the galaxies spinning.

Without it, everything would be floating around aimlessly and nothing would be able to stay on the ground.

It is the attraction between objects with a force that is ‘proportional to its mass’.

Gravity Facts for Kids

  • Without gravity, we would float off into space.
  • Everything would float away if it didn’t exist.
  • The gravitational pull from the moon causes the tides of the oceans.
  • Isaac Newton formulated the Universal Law of Gravitation.
  • There is zero gravity in outer space.
  • Objects weigh a little bit more at the North Pole than they do at the Equator
  • It helps plants and vegetation grow.
  • If you travel to Mars you would weigh less than half your current weight

What is gravity?

Gravity is the universal force of attraction that draws objects towards the center of the earth. Additionally, it keeps the planets orbiting the sun. You have probably noticed that things fall back when you through them in the year.

For example, if you throw a tennis ball, it will come back after some time. It does not continue going up forever. The force that pushes the ball down is what we call gravity.

Isaac Newton, a renowned scientist, published the universal law of gravitation in 1687.  The law describes the movement of objects and explains why things fall on the ground. The acceleration of the free-falling bodies measures gravity. 

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In other words, all objects have a downward force or weight. On the earth’s surface, Objects have an acceleration of gravity of 9.8 meters per second. This means that the speed of the object increases by about 9.8 meters per second. On the surface of the moon, the gravitational force is relatively less at 1.6 meters per second. 

Who discovered gravity?

Isaac Newton

Isaac Newton was not the first scientist to show interest in how things moved.  Initially, greek philosophers believed that nature followed a natural motion as part of the gods’ realm until the 16th century. After 1500, Braghje, Galileo, and other astronomers discovered that planets revolve around the sun.

While Kepler showed that the planets follow an elliptical orbit, the question was why. However, it is until Issac Newton studied the force that the world got a clear picture. 

Sir Isaac Newton discovered gravity. The scientist was seated under an apple tree when he saw an apple falling to the ground. He realized that there was a force in play that moved the fruit toward the ground. Otherwise, it would stay with the rest on the tree. Newton called this force gravity and concluded that there exists a force between all objects. 

He was born in 1642 and attended Trinity College in Cambridge. Besides the law of gravity, he discovered laws of motion. The laws of motion are based on Kepler’s Laws of Planetary Motion. Newton’s law of gravity stuck unopposed well up until Einstein came up with the theory of relativity. He lived from 1642 through 1727. 

Why is gravity important?

It’s important in everyday life. Otherwise, we would be strapped on the surface or fly off. We can’t live without it. It enables you to walk to school. Without gravity, you would fly off haphazardly in the air.  On a large scale, it keeps the earth orbiting and holds it at the sun’s right distance. We require the sun’s warmth and light to survive.  

It helps keep our bones and muscles functioning. Here is an interesting thing. Our body cells can sense it.  The skeletal muscles are sensitive to load and mechanical stress. Due to this sensitivity, microgravity causes the muscle to wear away. 

 According to studies, the muscles’ strength reduces after traveling to space, making it difficult to perform physical activity. Astronauts have to perform physical activities after returning home. Also, an extended stay in bed, surgery, and illness cause muscle loss. 

Also, it enables us to retain the atmosphere, which is about 1/200000 of the earth’s mass. The only way to hold on to the atmosphere is through the force of gravity.  The atmosphere keeps the surface warm and reduces extreme temperature during the day and night. 

It has potential energy enabling us to harvest it. For instance, water in a river atop of the dam has potential energy. Gravity forces the water down to a dam enabling us to harvest electric energy from water falling in dams. 

Do objects fall at the same speed?

As mentioned, everything falls at the same acceleration. The acceleration value is 9.8 m/s and is known as acceleration due to gravity.

However, free fall assumes that gravity is the only force acting on the object.  This means that it’s not affected by the air resistance. 

Objects will fall with the same acceleration regardless of their mass if they are only influenced by gravity.

If a feather and brick are dropped simultaneously in a vacuum, they will hit the ground at the same time. 

Everything on the ground experiences gravitational field strength. Gravitational field strength on the surface of the earth is 9.8 N/kg. As things fall, they experience air resistance. Denser objects cut through the air resistance more easily, falling faster than less dense objects. 

The speed of the object and the cross-sectional area affect the amount of air resistance an object experiences. An object with large cross-sectional areas will experience more air resistance. Similarly, objects falling at increased speed will experience high air resistance.

Heavier objects have lower acceleration and greater gravitational force. This means that the two forces cancel each other out, resulting in terminal velocity. 

What is the acceleration due to gravity?

According to Newton’s second law of motion, the net force from gravity makes masses accelerate. The acceleration is constant for objects near large bodies such as planets.

In other words, the objects fall with equal acceleration.

Near the earth’s surface, the acceleration value is 9.8 m/s. Therefore any objects falling towards the center of the earth accelerate at 9m/s. This means that if you drop a pencil from a 1 story building, it will start falling at nine meters per second.

The speed will increase by 9 meters after every second. 

Where is gravity the strongest?

Mount Everest

While it’s assumed to be the same everywhere, It is not perfectly uniform on the surface.  It’s actually weaker at higher altitudes, such as Mount Everest and the equator’s peak due to centrifugal forces.

The highest gravitational acceleration is at the Arctic Ocean surface 9.8337 m/s, while  Peru’s Mount Nevado Huascaran has the lowest gravitational acceleration at 9.7639 m/s. 

What are the three laws of gravity?

Sir Isaac Newton the brains behind the three laws of motion and the law of gravitation. The three laws of motion state that:

1.  An object will remain in a constant state of motion or rest unless it is acted upon by an external force. This law means that the objects do not start, stop or change themselves directly. An external force is required to effect such change. 

2. The force acting an object is equal to its mass times acceleration. The momentum of the body is equal to the mass and velocity of a product. At the time of change, the momentum of an object is equal to its velocity and mass. 

3. The third law of motion states that for every action, there is an equal and opposite reaction. For instance, when a book rests on a body, the table applies an equal and opposite force to the book. 

Does the sun have gravity?

The Sun

The sun constitutes about 99% of the solar system’s total mass. For this reason, it exerts massive gravity on planets enough to keep the earth and other planets orbiting around it.

Precisely, the gravity of the sun is 27.9 times that of our planet. The bulk of the gravity of the sun is generated at the core of the sun. Also, the mass of the sun is about 333 000 times the mass of Earth. The gravity of the sun dwarfs the gravity of the rest of the solar system. 

To put this into perspective, diminutive Pluto is about 3.6 billion miles from the sun.  Therefore the sun requires massive gravity to keep the planet orbiting around it. The sun is about 1000 times heavier than Jupiter, which is the largest planet.

Fundamentally, light objects orbit larger objects. Sun’s gravity pulls the planets, and since it is the heaviest object on the solar system, it exerts the strongest gravitational force. 

Earth’s gravity

The gravity of the earth is the acceleration the earth exerts on an object on its surface. This acceleration is measured in meters per second. The particular gravitational strength varies in different locations.

It makes things fall straight down and determines all interaction. Gravity is different from that on other planets such as Jupiter and other objects such as the moon. 

Solar system

Solar system

Both the sun and earth are part of the solar system. The solar system consists of the sun, planers, and a colossal number of comets, meteoroids, and asteroids. While we can’t see the bodies with our naked eye, they are visible using strong devices such as telescopes.

Over the years, meteoroids have broken of the planets and moons. For instance, in 1969, The Allende meteorite fell and scattered over Mexico. 

The sun is the largest object accounting for about 99.8% of the solar system. It provides the energy that sustains life on our planet. Our solar system forms part of the milky way. 

A strange force

For many centuries, those that studied the sciences knew that there was ‘something’ that kept us firmly planted on the ground.

They would jump up and instead of flying off into space, they landed firmly on the ground.

Even Aristotle, the famous Greek philosopher, created a theory about this strange force.

In his time, he thought that the earth was the center of the universe and everything else floating around it.

The Greater the Mass

In gravity, the term ‘proportional to its mass’ means that the greater the mass, the greater the gravity.

Earth’s mass is greater than the moon’s gravity and so the gravity of the earth is more than that of the moon.

However, the moon has an effect on us as well, moving the oceans as the tidal movement.

There is an attraction between objects that have mass and that is the general definition of ‘gravity’.

Albert Einstein spent many years studying mass, energy and gravity and eventually developed his general theory of relativity.

Theory of Relativity

Did you know, gravity is actually different, depending upon where you are located on the planet.

An object that is at the equator weighs less than the same object that was placed at the North Pole.

The mass of the object remains the same, but the gravity would be different.

Gravity is also different on each of the planets.

On some planets, you would weigh considerably and on other planets, you would weigh less.