Question

Why does Gravity Exist? Why is any body able to attract another? Where does that energy emerge from? Is there anything like gravitational repulsion?

Answer 1

We don't really know. We can define what it is as a field of influence, because we know how it operates in the universe. And some scientists think that it is made up of particles called gravitons which travel at the speed of light. However, if we are to be honest, we do not know what gravity "is" in any fundamental way - we only know how it behaves.

Here is what we do know...

Gravity is a force of attraction that exists between any two masses, any two bodies, any two particles. Gravity is not just the attraction between objects and the Earth. It is an attraction that exists between all objects, everywhere in the universe. Sir Isaac Newton (1642 -- 1727) discovered that a force is required to change the speed or direction of movement of an object. He also realized that the force called "gravity" must make an apple fall from a tree, or humans and animals live on the surface of our spinning planet without being flung off. Furthermore, he deduced that gravity forces exist between all objects.

Newton's "law" of gravity is a mathematical description of the way bodies are observed to attract one another, based on many scientific experiments and observations. The gravitational equation says that the force of gravity is proportional to the product of the two masses (m₁ and m₂), and inversely proportional to the square of the distance (r) between their centers of mass.

We know from Isaac Newton and his law of gravitation that any two objects in the Universe exert a force of attraction on each other. This relationship is based on the mass of the two objects and the distance between them. The greater the mass of the two objects and the shorter the distance between them, the stronger the pull of the gravitational forces they exert on each other.

We also know that gravity can work in a complex system with several objects. For example, in our own Solar System, not only does the Sun exert gravity on all the planets, keeping them in their orbits, but each planet exerts a force of gravity on the Sun, as well as all the other planets, too, all to varying degrees based on the mass and distance between the bodies. And it goes beyond just our Solar System, as actually, every object that has mass in the Universe attracts every other object that has mass — again, all to varying degrees based on mass and distance.

With his theory of relativity, Albert Einstein explained how gravity is more than just a force: it is a curvature in the space-time continuum. That sounds like something straight out of science fiction, but simply put, the mass of an object causes the space around it to essentially bend and curve. This is often portrayed as a heavy ball sitting on a rubber sheet, and other smaller balls fall in towards the heavier object because the rubber sheet is warped from the heavy ball’s weight.

In reality, we can’t see curvature of space directly, but we can detect it in the motions of objects. Any object ‘caught’ in another celestial body’s gravity is affected because the space it is moving through is curved toward that object. It is similar to the way a coin would spiral down one of those penny slot cyclone machines you see at tourist shops, or the way bicycles spiral around a velodrome.