Research on gravity

Quantum mechanics and relativity was two of the most successful theories of how the world works. Quantum theory describes how a matter behave at subatomic level(Which is slightly insane). Quantum objects can simultaneously be in two locations, or moves at different directions.

The problem is that no one has figured out how quantum theory and relativity fit together to make quantum theory. Einstein was one of other scientists who try to combine gravity with other physics theories and formulas, other than Newtom. Quantum gravity theory seems to be fundamental problems that not solved yet.

It's the force we all know about and think we really understand. Gravity seems keeps our feet on the ground and our world is circling the sun. You jump up, and gravity brings you back, down to earth. You reach the top hill and gravity accelerates you down into lower land. It behaves as Newton's-like. It's a force which affects and changes the motion of something else.

Einstein came with his relativity theory, that gravity is not as simple as Newton's Law. Relativity provides a framework which the laws of physics look the same for everyone at every moment, regardless of how they are moving. Einstein achieved this by making gravity a property of the universe, rather than individual bodies.

General relativity describes gravity as geometry. The fabric of the universe, 4 dimensions of space and time, is full of lumps and bumps created by the presence of mass and energy. This wrapping is unavoidable : a photon of light - tries to travel through the universe in a straight line, it is actually follows a trajectory that is curved by any mass and energy in the vicinty. The result of this curvature is what we think of as gravity. To look at it in slightly different way, gravity is not what one body does directly to another, but what a body's mass does to the surrounding universe.

Gravity is somekind like straightfoward force, as Newton did too. It still allowed us to send rockets out from our planet to the moon and then chart out the orbit of the planets with astonishing accuracy.

Eistein's description has stood up well to scrunity in situations when high speed and accelerations are involved. Yet, neither Newtonian model nor relativity is a fundamental explanation for gravity. We still don't know how the fundamental quantum properties of mass, energy and space-time. At most basic level, the other three fundamental forces if nature, the electromagnetic force, the strong and weak nuclear force. The electromagnetic force is delivered by photons, also known as quantum field theory.

However, when quantum field theory is applied to gravity, it is prone to give nonscence answer to gravity where it still fundamental obstructions have to be overcome. All other forces in nature have opposites, in case of electromagnetic force, it can repel and attract, depending on the charges of the bodies involved.

According to quantum field theory, the particles which transmit strong and weak electromagnetic forces have various types of charges. It can be positive and negative. No one really know what is gravity, whether it's force or dark energy, which seems to be accelerating the expansion of the universe, meanwhile, it may indiate that gravity work both ways, dark energy and fundamental force.

The differences between gravity and other fundamental forces poses a problem for physicsist, wanting to create the 'theory of everything' that provides single explanation for all. Most theorist expect best route to such theory to lie through hidden symetry of nature, known as supersymmetry. Supersymmetry suggests that every particle has much heavier twin waiting to be discovered though it might no be the final answer.
Gravity is actually weaker than electromagnetic forces. Although the other forces act on different ranges, and between very different particles, they seem to have different kinds of particles which roughly comparable with each other. There is no other possible explanation rather than the 'string theory', which lead to theory of everything.

String theory requires that the universe has more than three spartial dimensions that we experienced, an it might as many as 10 dimensions. The string theorist's best idea is that gravity is so weak unlike other forces.

The moment of the universe's birth created both matter and expandind space-time in which matter could exist while gravity pulled the matter together, the expansion of space drew particles of matter part and the further apart they drifted, the weaker their mutual attraction became. It turns out that the struggle between these two was balanced on a knife-edge. If the expansion of space had overwhelmed the pull of gravity in newborn universe, stars, galaxies and human would never have been able to form. On the other hand, if gravity had been much stronger, stars and galaxies might have formed but also quickly collapsed on themselves and each other. The gravitational distortion of space-time would have folded up universe in a big crunch.

Gravity might both fundamental force and dark energy, theorically. Practically, no scientist have proven it so far.