This question has been asked before under other guises. I am not a scientific profesional however i have some schooling in pyhsics and mathematics and have a keen interest in these subjects.

It seems plausible to me and was a thought i had my self many years ago whilst at college, that the universe could possibly be expanding from within itself. Ie matter and space were expanding at the same rate as each other.

I observe there is no relative distance increase between the objects i see on a day today basis and as such this type of expansion wouldn't change our perception of this relatively speaking. Everything we observe would remain the same and we would be unaware of the expansion..

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    $\begingroup$ Duplicate of physics.stackexchange.com/q/2110/50583 $\endgroup$ – ACuriousMind Apr 21 '15 at 20:35
  • $\begingroup$ As noted, this is a duplicate. Second, if we can not observe any changes to anything, than it isn't physics or science of any type - it is merely belief with no backing. $\endgroup$ – Jon Custer Apr 21 '15 at 21:11
  • $\begingroup$ This is not belief. Belief is faith that something is the truth even though it cannot be proved to be so. Are you suggesting that my observations are just my own reality and what i observe is without doubt dependent upon my own perception or can my observations be similar to another and thus be given a degree of fact. I trust my observations i have nothing else to believe in and i observe no difference in the space around me quantifiable or not $\endgroup$ – 8Mad0Manc8 Apr 21 '15 at 22:07
  • $\begingroup$ My question is a duplicate of another however this was several years ago admitidly I did not look to see if there was a post on this before i posed the question. I'am not sure of the mathematics involved but could it be that the expansion surrounding us is not detectable simply because of the vast distances we are dealing with and from a relative point of view here as an observer we cannot detect the expansion. $\endgroup$ – 8Mad0Manc8 Sep 17 '16 at 21:12

Because near matter spacetime isn't expanding, and if it isn't expanding it can't be stretching the matter.

The expansion of spacetime is a prediction of general relativity for the special case of a matter distribution that is homogenous and isotropic. If we feed in this condition we find that the geometry of spacetime is described by an equation called the FLRW metric, and this tells us that spacetime is expanding.

But in the real universe the distribution of matter in not homogenous and isotropic. For example as I type this I have about six trillion trillion kilograms of Earth below me and nothing a few thousand kg of my house and the atmosphere above me. That severely distorts spacetime away from the FLRW metric, and the spacetime in my vicinity is not described by the FLRW metric and is not expanding. Near me spacetime is approximately described by the Schwarzschild de Sitter metric, though actually the deviation from the Schwarzschild metric is tiny compared to, for example, the gravitational field created by my house.

On very large scales, i.e. around the dimensions of galaxy superclusters, the FLRW metric is a pretty good approximation so on these large scales spacetime is expanding. However on the scales we encounter in everyday life it is not.


General relativity deals with equivalence classes of maps. If you take one map of space-time, put it through a continuously differential equation, and alter the metric accordingly, you get an equivalent map. You can't talk about one or the other being right. They're equivalent. Either they're both right or they're both wrong.

To be fair, that's just a mathematical model. I don't know how the universe actually works, but I suspect that it doesn't actually carry around an infinite number of equivalent maps. Maybe there's one map that's actually fundamentally true. Or maybe they're just all equally good maps of the way the universe actually works, and none of them are more right than any other.

But even if there really is a correct map, general relativity doesn't give us the slightest clue what it is. Space randomly expanding in no way violates the laws of general relativity. It's not clear how you could prohibit that but still allow pieces to expand and contract like we know they do.

  • $\begingroup$ Could it be simply that the reason we don't observe any notable difference in the distance of objects here on earth be accounted for by the fact that small differences caused by the expansion simply add up to great distance changes over the vast expansion of the universe and these small changes between objects add up to great amounts and large velocities along the gap between them those objects $\endgroup$ – 8Mad0Manc8 Feb 18 '17 at 19:41

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