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I'll go into a bit more detail below but, basically, Einstein discovered that space and time can't be separated. They are part of the same thing, and gravity is actually produced be bending and warping this "spacetime," like a heavy ball sitting on a sheet of elastic. Classical (or Newtonian) Physics Time can be considered as a dimension, just like ...


3

The stress-energy tensor is a local property. Its value at a point is determined by the properties at that point and not by the surroundings of the point. Consider a hypothetical object with a sharp edge i.e. the density changes discontinuously from a finite value to zero at the edge. In that case the stress-energy tensor will also change discontinuously. ...


2

When we use the terms "bending" or "warping" with respect to spacetime and gravity, you have to keep in mind that these words are not being used in a literal way. Since the majority of concepts in General Relativity are far beyond what our experiences allow us to comprehend, we have come up with a few ways of picturing these concepts in our minds, none of ...


2

No. Take any 3 bodies, the sun, earth, and moon, for instance. Let's say that the sun is positive and the earth is negative. Then the sun and earth attract. But that means that, since the moon and earth also attract each other, the moon must be positive and be repelled by the sun. This does not happen - in fact, the gravitational attraction between the sun ...


1

As said in the comments, there are only 4 known fundamental forces, gravity, strong and weak interaction, and electromagnetism. Since we are restricted to low energy classical mechanics, we can ignore two of them, and we are left only with gravity and electromagnetic forces (which includes, among others, magnetostatic and electrostatic forces). Moreover, ...



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