Gravity. Its what keeps us on the ground and makes things fall when you drop them. Simples Right.
Newton and Einstein spent ages looking into it in great detail and sussed it surely. Well yes they worked out very well HOW it works. Essentially, Mass Attracts Mass, Bigger Mass = Stronger Gravity, Distance Matters. BUT we don't know how it works at the deepest level. In fact we have no idea what exactly creates gravity.
We live with gravity every second, but it's still one of the biggest mysteries in physics. Gravity affects everything, apples, planets, stars, black holes, even light, space and time. Amazingly gravity has an infinite range unlike the other fundamental forces in nature.
All of Newton's and Einstein's theories apply perfectly to apples and planets, but completely and utterly break down when we zoom into the tiny world of atoms and particles. The study of Quantum Mechanics does not include gravity in any of its theories. This contradiction between General relativity and quantum theory is one of the biggest unsolved problems in physics.
Gravity is not a force; it is the curvature and warping of spacetime fabric itself. We learn in school that gravity is a force pulling objects together. However, Einstein's theory of General Relativity revolutionized this idea. It states that massive objects, like stars and planets, create a dimple or curvature in the fabric of spacetime, a single entity combining the three dimensions of space and the dimension of time. When Earth orbits the Sun, it isn't being pulled by an invisible force; it is simply following the straightest possible path along the curve that the Sun has created in the spacetime fabric, much like a marble rolling around a bowl.
Scientists suspect a hypothetical tiny particle called a graviton might be behind it. Nobody has found or detected a graviton and there is no scientific experimental proof of its existence yet.
So here are some searching questions:
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If gravitons are massless then they travel at the speed of light. How are they able to escape a black hole and influence the surrounding space outside the black hole's event horizon when photons which are also massless cannot escape?
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Is there a material that might block gravity similar to how lead can block radiation?
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Is there such a thing as an anti-graviton and therefore Antigravity?
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Given that gravitons are possibly responsible for gravity, could they also play a role in Einstein's general relativity theory? Could an anti-graviton speed up time?
A working theory of quantum gravity must explain extreme environments like black holes and the Big Bang, where both quantum mechanics and general relativity are crucial. An alternative leading candidate is String Theory and that's for another discussion.
