At its simplest, Newtonian gravity is based on what Newton could observe. Einstein gravity is based on the broader principals that Newton had no way of grasping when he was doing his work. Each has its specific applications.
Yes, any two particles of matter mutually attract. But when we consider a large amount of matter — all the matter in a given chunk of the whole Universe — it’s not all going to collapse into a black hole, any more than all the air in a room will spontaneously collect in one corner. Think of it this way: any particle in the midst of a diffuse cloud of particles will be pulled in all directions at once, so the gravitational force will tend to average out to zero. (Now if the particles are more compressed for some reason, that’s another story! Mutual gravitation can bind them into clouds, galaxies, stars, or even black holes.) {
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If we could just find that pesky little magnetic mono-pole, we could.
Of a sort, yes. But science has discovered everything yet.
Its not a concept, it is a theory (please, take the time to look up the definition of a
scientific theory before spouting the typical nonsense that it is just a theory) We have observed it and tested it. We have tested Einstein's predictions and found them to be true. We have seen that in zero-g environments liquids form perfect spheres. Keep in mind that particles, even very large "particles" such as asteroids, act is a liquid in the vast reaches of space so they form spheres when they begin to compress.
