Expansion of the universe or contraction of scale?

[katahiromz]

They say the Universe is expanding since the big bang.

However, relatively thinking, is it possible that we and our scale are shrinking?

 

[exchemist]

4 minutes ago, katahiromz said:

They say the Universe is expanding since the big bang.

However, relatively thinking, is it possible that we and our scale are shrinking?

 

S u r e l y    n o t. 

[Genady]

12 minutes ago, katahiromz said:

They say the Universe is expanding since the big bang.

However, relatively thinking, is it possible that we and our scale are shrinking?

 

No, it doesn't work.

The universe expands only on a very large scale, hundreds of millions of parsecs. Solar system, Milky Way, galactic clusters do not expand. The expansion is not a matter of scale, but a matter of physics.

[Intoscience]

5 minutes ago, Genady said:

The universe expands only on a very large scale, hundreds of millions of parsecs. Solar system, Milky Way, galactic clusters do not expand. The expansion is not a matter of scale, but a matter of physics

Am I correct in thinking that the expansion only affects areas where gravity is too weak to overcome the expansion (dark energy)? 

[Genady]

3 minutes ago, Intoscience said:

Am I correct in thinking that the expansion only affects areas where gravity is too weak to overcome the expansion (dark energy)? 

The expansion is result of gravity. It appears when the gravity is homogeneous and isotropic. If gravity is, for example, spherically symmetric, like around massive bodies, there is no expansion.

[studiot]

1 hour ago, katahiromz said:

They say the Universe is expanding since the big bang.

However, relatively thinking, is it possible that we and our scale are shrinking?

 

A very reasonable question.
Have you thought about possible tests ?

 

Interestingly this is made possible because of the finite speed of light.

We can look back over much longer timescales than our own lifetimes or even our civilisations'.

 

So we can compare the configurations of matter over very long timescales and we find that the further back in time we look the smaller the gaps are and the average density is diminishing, when directly comparing one with the other so we can say with confidence that the correct interpretation is expansion not contraction.

[joigus]

31 minutes ago, katahiromz said:

However, relatively thinking, is it possible that we and our scale are shrinking?

You mean shrinking space?

Or also time?

What about mass, electric --and other charges-- etc? Would they be shrinking in your picture?

 

x-posted with @studiot

[katahiromz]

13 minutes ago, studiot said:

Have you thought about possible tests ?

Nope yet.

 

13 minutes ago, joigus said:

You mean shrinking space?

Or also time?

I thought on the scale of space only.

[Markus Hanke]

I think one should also mention that none of the other fundamental interactions (strong, weak, EM) are invariant under rescaling, so a “shrinking matter” type of model is not compatible with known physics. 

[joigus]

8 minutes ago, katahiromz said:

I thought on the scale of space only.

Just stretching/shrinking space without time being involved... I see this difficult to reconcile with known physics. Physics with matter --massive-- is not invariant under scale transformations. Time-dependent scale transformations would make this even worse.

I don't see how you could save conservation of charge, for example, if space is actually shrinking at small scales...

3 minutes ago, Markus Hanke said:

I think one should also mention that none of the other fundamental interactions (strong, weak, EM) are invariant under rescaling, so a “shrinking matter” type of model is not compatible with known physics. 

Exactly!

[Intoscience]

1 hour ago, Genady said:

The expansion is result of gravity. It appears when the gravity is homogeneous and isotropic. If gravity is, for example, spherically symmetric, like around massive bodies, there is no expansion

Has this been proven? I was under the impression that it was still unclear why space expands, thus why "dark energy" is inferred? I'm only asking because I'm a layman when it comes to this subject.

Thanks.

[Genady]

4 minutes ago, Intoscience said:

Has this been proven? I was under the impression that it was still unclear why space expands, thus why "dark energy" is inferred? I'm only asking because I'm a layman when it comes to this subject.

Thanks.

It is proven in GR that homogenous isotropic space is unstable. It has either to expand or to shrink. Which one and for how long, depends on initial conditions. Why the initial conditions, aka Big Bang, were what they were, is unknown.

The dark energy is inferred not to explain why space expands, but rather to explain why the expansion accelerates. 

[Intoscience]

17 hours ago, Genady said:

It is proven in GR that homogenous isotropic space is unstable. It has either to expand or to shrink. Which one and for how long, depends on initial conditions. Why the initial conditions, aka Big Bang, were what they were, is unknown.

The dark energy is inferred not to explain why space expands, but rather to explain why the expansion accelerates. 

Ah, ok thanks for clearing that up.

Much appreciated.

[Sensei]

Only what is known for sure is that photons emitted in the distant past are redshifted i.e. have much lower energies/frequencies than in modern times.

Edited March 7, 2023 by Sensei

[Genady]

4 hours ago, Sensei said:

Only what is known for sure is that photons emitted in the distant past are redshifted i.e. have much lower energies/frequencies than in modern times.

I think there are more things we know for sure, such as patterns of the redshift, CMB radiation and its patterns, gravitational lensing, elements content, evolution of features, etc.