[Ethos]

This concept has always given me trouble. On the one hand, we estimate the age of the universe to be approx. 13.7 billion years old. That translates into a universe with a total volume of fantastic size while beginning its existence as infinitely small. With expansion approaching the speed of light and increasing, by some estimates, one needs to ask; What is it that is expanding? We know that space is a structure and while some people wish to define it as nothing, most of us are aware that a structure can't be defined as nothing. This leads me to ask the question:

If space is expanding, does that mean that the space between particles is also following suit? Or; Is it only expanding where gravity and the electro weak and strong forces prevents it from doing so?

[MOD EDIT - please phrase your post titles as questions as this makes it easier for users to identify items of interest and also results in more responses over time. Thanks.]

[Soul Surfer]

Yes it IS space itself that is expanding.  That is why it is possible for things to "vanish over the edge"  by expanding away from us at faster rates than the speed of light.  This is why we do not yet (and may never know for sure)  the true size and shape of our universe. Currently this expansion with distance is too slow to show up at any distance less than that of large clusters of galaxies or affect the motions of planets stars and galaxies  although the theoretical expansion of for example the orbit of the earth is a small and not measurable but non zero amount in a year.

[Vern]

I suspect that the notion that nothingness, empty space, can expand was accepted when it seemed certain that Einstein's General Relativity was successful. The idea of variable space-time became popular because of Einstein IMHO, and still is popular among most folks who ponder the most basic realities of the universe. But that notion is a great obstacle to understanding the true cause of these same basic realities.

If you disallow variable space-time, the true cause of relativity phenomena quickly becomes obvious. H Ziegler explained this to Einstein in 1909. 

[Ethos]

The idea of variable space-time became popular because of Einstein IMHO, and still is popular among most folks who ponder the most basic realities of the universe.
 

If this is truly the case, then couldn't one also presume that the very space between particles themselves is also expanding? Even though this would be virtually nondetectable by current standards of measurement. If space is expanding, then one would have to assume that this space was also doing the same.

[ScientificBoysClub]

Yeah u can say space is expanding as distortion in space is expanding !!

[Raghavendra]

even the energy is spliting all the sides in the universe....They can be destructive

[irish del]

I wonder if the space between the stars ,planets and galaxies are expanding relative to there mass or does it expand evenly through out space irrespective of the gravity they exert?

[Ethos]

 The idea of variable space-time became popular because of Einstein IMHO, and still is popular among most folks who ponder the most basic realities of the universe. But that notion is a great obstacle to understanding the true cause of these same basic realities.

Absolutely Vern; It seems to me that if we limit this explanation to the effect that speed and gravity have on the volume or physical displacement of matter itself, one can clear up much confusion. Why it seems for the Physicist, less complicated to visualize space and time as variant, and then suggest that matter is invariant is like; Strainig at a knat and being willing to swallow a camel.

[Vern]

This is especially true Ethos, when we consider that we know the cause of the distortion of matter. There is no cause that can explain the distortion of space and time. The cause of the distortion of matter is that it is composed at its elementary level of stuff that must always move at the invariable speed of light.

 

[Paul25]

It could mean matter is shrinking for all we know

[Outcast]

I've seen no compelling evidence of space being created where there was none, or destroyed where there was some.

[Bogie_smiles]

I've seen no compelling evidence of space being created where there was none, or destroyed where there was some.

Agreed. I like the idea that space is infinite, and there are natural forces that cause big bangs and big crunches here and there, in pre-existing space. Time is the other factor, and in a universe where time and space are infinite (no beginning/no end), on a grand scale big bangs and big crunches could be explained by reasonable natural causes of expansion (big bangs) and contraction (gravity).

[Kryptid]

It could mean matter is shrinking for all we know

I want to say that we would know the difference, but it actually is eluding me at the moment as to how. More distant objects would look larger if this was the case, but apparently the same is true of an expanding Universe model as well. Perhaps processes that fall off non-linearly with distance would look different.

Presumably, Kepler's laws would still apply even if planets and stars were larger in the past (Newton's shell theorem would mean that the strength of gravity is the same when mass and distance are the same, despite the planet or star being larger). So if space was not expanding, the orbital rate of objects should look unchanged at large distances. If the Universe was expanding instead, then the rate that we receive photons from distant objects would be lower and thus the orbital rates of objects of the same mass would appear to be lower. However, now we have the issue of how to measure the mass of those same objects if we can't trust the orbital rates to be reliable...

Any ideas, anyone?

[yor_on]

I suspect you're correct Kryptid, presuming that all other factors, whatever they may be :) stays the same. You will get the same effect as long as the mass stays, I think?

What about a sun shrinking, would it change anything for its atmosphere? But it's a weird idea, I think maybe you need more than just mass changing for it to work out? How about all those constants, and chemical properties?

I know, I changed my mind here :) Maybe

[yor_on]

No, thinking of it again it should mean that you somehow avoid the Schwarzschild radius for mass https://en.wikipedia.org/wiki/Schwarzschild_radius

That doesn't make sense to me, how would you do that at the same time as you define it as shrinking? If someone have an idea I would be quite curious.