RE: How is the Universe Expanding?
June 17, 2017 at 8:26 pm
(This post was last modified: June 17, 2017 at 8:50 pm by Anomalocaris.)
The way I visualize it is if you start with two point particles that are some distance apart but at rest with each other, then somehow cancel out all the effects of all the fundamental forces upon the each of them, including any forces acting between them, you would still find these two particles would not stay at rest with respect to each other, but would somehow gradually accelerate away from each other.
What is more, you would find this rate of acceleration is completely independent of any attributes of these particles, but increases in direct proportional to the distance between these two particles.
So it is like negative gravity is acting on these particles, except it is not proportional to mass, nor does it decrease with inverse square law, Instead it increases in proportion to the amount of space between any pairs of particles. So it is not localized, and permeates all space. Hence it is as if space is stretching.
Now put fundamental forces back in. If two particles are sufficiently close to each other such that their gravitational acceleration with respect to each other surpasses the acceleration away from each other caused by expansion of space, then they will not draw apart. So the ants, the earth, the solar system, the Milky Way, or perhaps even the local cluster of Milky Way, andromeda and M33 are probably safe from being ripped apart by expansion of space. But as distance increases force of gravity decrease while acceleration by expansion of space increases, there could be defined a radius from any concentration of mass and gravity such that the aggregate gravity of all mass within a spherical region of that radius about this mass concentration would produce an inward acceleration exactly equal to the outward acceleration of expansion of space at the surface of this sphere. Anything outside of the sphere that started at rest with respect to The sphere will inexorably be torn away faster and faster from everything inside that sphere by expansion of space, whereas everything inside that sphere that started at rest with respect to the sphere will be drawn towards the center of the sphere.
What is more, you would find this rate of acceleration is completely independent of any attributes of these particles, but increases in direct proportional to the distance between these two particles.
So it is like negative gravity is acting on these particles, except it is not proportional to mass, nor does it decrease with inverse square law, Instead it increases in proportion to the amount of space between any pairs of particles. So it is not localized, and permeates all space. Hence it is as if space is stretching.
Now put fundamental forces back in. If two particles are sufficiently close to each other such that their gravitational acceleration with respect to each other surpasses the acceleration away from each other caused by expansion of space, then they will not draw apart. So the ants, the earth, the solar system, the Milky Way, or perhaps even the local cluster of Milky Way, andromeda and M33 are probably safe from being ripped apart by expansion of space. But as distance increases force of gravity decrease while acceleration by expansion of space increases, there could be defined a radius from any concentration of mass and gravity such that the aggregate gravity of all mass within a spherical region of that radius about this mass concentration would produce an inward acceleration exactly equal to the outward acceleration of expansion of space at the surface of this sphere. Anything outside of the sphere that started at rest with respect to The sphere will inexorably be torn away faster and faster from everything inside that sphere by expansion of space, whereas everything inside that sphere that started at rest with respect to the sphere will be drawn towards the center of the sphere.
