(no title)
ranulo | 2 years ago
I have a theory in my head for years now. It is probably wrong, but here it comes:
In an infinite universe the total amount of gravity that affect us in one point in space is defined by the event horizon if we assume that gravity travels with light speed. Every atom in the universe has a very small influence on us. But this event horizon expands with light speed all the time. I wonder if this could lead to very small but permanent increasing gravitational pull from all directions at once. In other words, and increasing inflation.
pdonis|2 years ago
In our actual model of the universe, using the correct theory of gravity, the "total amount of gravity" affecting us (or any point) from the rest of the universe (i.e., once we factor out local influences like our solar system and our galaxy) is zero. That is because the average matter distribution in the universe is the same in all directions from us, so the "gravity" from it cancels out. The average matter distribution in the universe affects its overall rate of expansion over time, but this is not the same as the kind of "gravity" you are thinking of.
Also, while our universe does have a cosmological horizon (due to accelerating expansion), this horizon does not work the way your hypothetical "event horizon" does.
In short, your "theory" is not even wrong, because it doesn't even start from a correct underlying theory of gravity.
015a|2 years ago
I think this statement is really the crux of the counter-argument. Your statement that matter has average uniform density in all directions around us is obviously only correct in sufficiently large frames of reference; there are galactic voids, and galactic-super-strands, uniformity really only exists within the "mathematically and hypothetically infinite" frame.
You should expand on why the cosmological horizon does not function in the same way the GP's "event horizon" analogue does; and/or possibly, expand on how large the frame would have to be to achieve reasonable uniformity.
mxkopy|2 years ago
Can't gravity have an infinitesimally small effect, which means this matter distribution has to be perfectly balanced for its gravity to cancel out to zero at some point?
unsupp0rted|2 years ago
yodon|2 years ago
[0] https://en.m.wikipedia.org/wiki/Mach%27s_principle
kabouseng|2 years ago
pdonis|2 years ago
ReptileMan|2 years ago
pdonis|2 years ago
As I have pointed out upthread, the GP's "theory" is not correct, so it doesn't account for anything.
"Expansion of space" is just a consequence of the overall spacetime geometry of the universe, which is due to its overall average matter distribution (and to dark energy, which is what is causing the expansion to accelerate).
I_Am_Nous|2 years ago
jprete|2 years ago
pdonis|2 years ago
What would result in a contracting universe is a large enough density of matter (about a factor of 20 larger than the actual density in our universe if we just look at ordinary visible matter). But this does not mean "increasing gravitational force". As I have pointed out in other posts upthread, the "gravitational force" on a given piece of matter due to the rest of the matter in the universe (if we leave out local influences, like our solar system or galaxy for us here on Earth) is zero. This is true regardless of the current state of expansion or contraction.
_boffin_|2 years ago