Actually. we do not understand the why or the how of gravity, but we can and are able to accurately predict the results of its effects through two modelling procedures, Newtonian: the attraction between masses that falls off as the inverse square of the distance between them. General Relativity: A more accurate model that describes gravity as the effects of mass/energy on the geometry of spacetime, summed up beautifully by the John Wheeler quote: "Mass/energy tells spacetime how to curve: Spacetime tells mass/energy how to move".
Gravity is the name given to related phenomena where free (unattached) masses without significant electrical charge tend to accelerate towards one another. Galileo studied how objects fall and recognized that if there was no air resistance, small bodies moving much slower than light near the Earth fall at the same acceleration, regardless of their composition or size or speed. A high speed bullet of lead shot from a rifle falls 9.8 meters in one second of flight just as an egg dropped out a window does. Kepler studied the planets and said they all move in ellipses with the Sun at one focus. Newton recognized that rain falling from clouds and the moon moving about the Earth were the same type of phenomena and called his precise mathematical model Universal Gravitation. This explained that Kepler was slightly wrong. Newton's Universal Gravitation works very well in predicting the motion of planets and describing escape velocity and lets us aim rockets and hit the moon and distant planets. But Newton's theory of gravity did not work well enough to describe everything we can measure because the planet Mercury's orbit was changing in a way about 1% different than Newton's equations predict. Between 1905 and 1916, Einstein came up with new ways to think about time, motion, space and gravity. In Einstein's thinking, falling is much more natural a motion than not-falling. Even light falls in Einstein's theory. And the evidence shows that Einstein is more right about gravity than Newton. The motion of the planet Mercury is explained better, the path of light near stars and big clumps of matter is explained better, the way clocks in high buildings and in orbit is explained better. Also Einstein's gravity predicts black holes from which no object may escape are possible, and that gravity can even send momentum and energy across the universe in the form of waves. Today we have evidence that black holes exist in lots of places, that orbiting stars send out their momentum and energy in gravitational waves and that they can be measured. We also have evidence that gravity, operating very close to how Einstein predicted, has been shaping our universe for billions of years. Gravity is very important to the behavior of the universe, and Einstein's theory is our best current understanding of gravity-related behavior.
What exactly is gravity? Given what has been posted in response, the consensus of the scientific community is that we don't exactly know. There is a search underway for a quantum solution to gravity, and that would be great for a lot of reasons. Quantum gravity would have some basic characteristics. We start with the quantum nature of particles; when talking at the quantum level, it can be said that particles would be composed of wave energy in quantum increments. That said, then a particle, composed of wave energy could be characterized as a complex standing wave pattern; complex because the standing wave pattern would vary depending on the type of particle; the pattern must represent the presence and mass of the particle. The standing wave pattern would have two fundamental components, directionally inflowing wave energy, and spherically out flowing wave energy, and the standing wave pattern would "contain" the energy of the particle. The directionally inflowing wave energy would be the spherically out flowing component from surrounding particles and objects. Then there are two things, presence which relates to location as well as mass, and motion which is the effect of quantum gravity. The presence of a particle is the complex standing wave pattern, and the mass of the standing wave pattern can be quantified by the finite number of wave intersections within the pattern. Wave intersections come into play because they form momentary high energy density spots (quanta) within in the pattern as the inflowing and out flowing wave energy components intersect and overlap. (The freeze frame concept is a useful thought experiment to help with understanding the mass of a quantum particle, which is proportional to the number of high energy density intersections (spots) in the count taken during the freeze frame.) Motion of the particle is the result of quantum gravity, and occurs when there is a directional imbalance in the inflowing wave energy sources. Particles move in the direction of the net highest directional wave energy inflow. The reason for that is because the highest wave energy density inflow causes more high density spots to form in that direction within the complex standing wave pattern. The spots are momentary, and are continually refreshed by the inflow, and so the net highest directional inflow is the direction in which the preponderance of new internal high energy density spot form. The location of the particle at any instant is represented by the current configuration of high energy density spots, and that location is continually changing as the new spots are continually forming in the direction of the highest net wave energy inflow. All of that is speculation though, and is only mentioned because everyone agrees that the scientific community does not yet have a solution to your question, "What exactly is gravity". Beside there being outrageous layman level speculative ideas like the above, there is a lot of activity in the professional community to do much better at characterizing quantum gravity, and the are expectations that a consensus solution can be established.
We have tried and looked for source of gravity inside the mass, we think that may be one day will get Quantum Theory of Gravity, which may tell us, which fundamental aspect of matter is responsible for Gravity. So our search is inward, are we looking at the wrong place ? Why not look outward...
Can't as on date, working on. But rough idea is like this, you are in deep ocean, shrink some water and somehow make it denser than the water, so what will happen ? A space will be created around this and if it is spherical, near by water or objects will appear to fall towards it......do we need QGT if we look outward?
Please do not post your pseudoscience rambling in the science section, that is what the fringe section is for. Reported.
