There was a time when the movement of planets and other celestial bodies was shrouded in mystery and was the subject of numerous stories. Attempts to discover the scientific principles behind the same were attacked with criticism and considered heresy by many. In 1633,1 Galileo was forced to recant his view that the Earth revolved around the sun.

The principles behind these natural phenomena became clear when Sir Isaac Newton discovered gravity.2It is said that he stumbled upon the idea of gravity in the year 1665 when he saw an apple falling from a tree. He suggested that the force that made the apple fall was the same force that kept planets and their moons in orbit. Newton suggested that any two objects feel a mutually attractive force that is directly proportional to their masses and inversely proportional to the distance squared. The mathematical formula for the same is F=GMm/r2. 3

## How Gravity Changed our Perception of the World?

Years before the discovery of the gravity equation, Kepler had deduced that Earth and other planets revolved around the sun in an elliptical orbit and not a circular one. But the reason for this was unknown until the discovery of gravity. Gravity helped prove the fact that the Earth revolves around the sun. It also paved the way for the rethinking of multiple scientific phenomena that were previously unexplained.

●  Discovery of Calculus:

Newton attempted to quantify the speed of a falling object. He found out that the speed of a falling object keeps on increasing every second. But there was no mathematical method to analyze this change. He began working on this issue and incorporated planetary movements into his theory. He discovered that he could explain the movement of planets in elliptical orbits using calculus.

●  Laws of Motion:

Gravity led to many important discoveries. Newton went on to discover the three laws of motion. He discovered the concept of force. He stated that force is a phenomenon that makes an object move. He explained uniform and accelerated motions, which form the basis of the first and second laws of motion. He also stated that forces act in pairs. Equal and opposite forces act upon any object at any given time.

●  Gravitational Waves:

In 1916, Albert Einstein predicted the existence of gravitational waves.4 They are produced when massive stars or black holes collide, causing disruption in spacetime. At the speed of light, undulating ripples of spacetime propagate in all directions away from the source.

●  Planets Orbiting Around Sun:

The mass of the sun is enormous, at around 333,000 times that of the Earth. 5As seen from the gravity equation, the larger the mass of the object, the greater is the force of gravitation between them. Due to the gigantic mass of the sun, the gravitational force exerted by the same on planets is also huge. This force pulls the planet towards the sun. Thus, the straight-line motion of the planet changes to a curved path. It is because of this gravitational force of the sun that planets orbit around it.

●  The Orbiting of the Moon:

Newton observed that if no force was acting to pull the moon towards the Earth, it would simply fly away from the Earth in a straight line tangential to its orbit. Thus, the moon’s orbit around the Earth is caused by gravitational force.

●  Discovery of Neptune:

The concept of gravity was used to determine the existence of the planet Neptune.

Astronomers U.J. LeVerrier and J.C. Adams6 are credited with the prediction of the

position of Neptune. They noticed that the position of the planet Uranus did not correlate with its mathematically predicted position. They deduced that there must have been a planet that was exerting a gravitational force on Uranus.

●  Formation of Tides:

Large tides are caused by the moon’s gravitational pull on the water present in the oceans. If the gravitational force was absent, the oceans would be calmer, and tides would be approximately one-third of their present height.

●  The Shape of the Earth:

Earth’s mass is huge. Hence, the gravitational pull of the interior portion of the Earth forces it to assume a shape that has the least surface area, that is, a sphere. The vertical differential of the Earth’s surface, that is, the difference in height between the highest point (Mt. Everest) and the lowest point (Mariana Trench), is around 19.8 kilometers. 7 Though this distance might seem huge, it is nominal when compared to the radius of the Earth (6378 kilometers). 8

●  Orbiting of Satellites:

To launch into orbit, a satellite has to be launched on a rocket that has a very high velocity. Once the satellite reaches the desired location above the Earth, the rocket lets go of the satellite. The momentum of the satellite gives it a tendency to fly off the Earth.

But, Earth’s gravitational pull still acts, even though the satellite is thousands of miles from the surface of the Earth. This gravitational force perfectly balances the momentum of the satellite. Thus, the satellite stays in orbit.

●  Gases in the Sun:

The sun is chiefly composed of various gases and vapors. Due to the enormous mass of the sun, its gravitational pull is also very high. It is due to this pull that the gases remain within the atmosphere of the Sun. If gravity was absent, the gases would simply leave the sun’s surface.

●  Black Holes:

Most scientists believe that massive aging stars, which have used up all their fuel, fail to resist the force of their own gravity. They collapse inward, thus creating a black hole. A black hole’s gravitational pull is so huge that not even light can escape from it.

Gravity keeps us grounded, quite literally. It maintains the Earth’s atmosphere’s stability and is responsible for precipitation when water droplets become too heavy to float.

Isn’t it amazing how gravity has helped to explain so many previously unknown concepts? How it has helped to unfurl the mysteries of the universe! To read about more such fascinating facts, go through other articles on BYJU’S FutureSchool blog.

## References

1. Galileo was forced to recant — Adam Smith Institute. (n.d.). Retrieved January 16, 2023, from https://www.adamsmith.org/blog/galileo-was-forced-to-recant
2. Gravity. (n.d.). Retrieved January 16, 2023, from https://web.stanford.edu/~buzzt/gravity.html
3. Newton’s Law of Universal Gravitation | Boundless Physics | | Course Hero. (n.d.). Retrieved January 16, 2023, from https://www.coursehero.com/study-guides/boundless-physics/newtons-law-of-universal-gravitation/#%3A~%3Atext%3DThe%20mathematical%20formula%20for%20gravitational%2CG%20is%20the%20gravitational%20constant
4. What are Gravitational Waves? | LIGO Lab | Caltech. (n.d.). Retrieved January 16, 2023, from https://www.ligo.caltech.edu/page/what-are-gw#%3A~%3Atext%3DAlbert%20Einstein%20predicted%20the%20existence%2Chis%20general%20theory%20of%20relativity.%26text%3DThese%20cosmic%20ripples%20would%20travel%2Cthe%20nature%20of%20gravity%20itself
5. How big is the sun? | Space. (n.d.). Retrieved January 16, 2023, from https://www.space.com/17001-how-big-is-the-sun-size-of-the-sun.html#%3A~%3Atext%3DThe%20total%20volume%20of%20the%2Cthe%20mass%20of%20the%20Earth
6. Le+Verrier’s+planet | Article about Le+Verrier’s+planet by The Free Dictionary. (n.d.). Retrieved January 16, 2023, from https://encyclopedia2.thefreedictionary.com/Le%2BVerrier%27s%2Bplanet
7. Our Amazing Planet Top to Bottom: Mountaintop to Ocean Trench (Infographic) | Live Science. (n.d.). Retrieved January 16, 2023, from https://www.livescience.com/27551-our-amazing-planet-top-to-bottom-mountaintop-to-ocean-trench-infographic.html
8. How big is Earth? | Space. (n.d.). Retrieved January 16, 2023, from https://www.space.com/17638-how-big-is-earth.html