Questions about Physics, Biology and perspective

[bennyboy]

Okay, a kind of relativity question:

If the forces in the universe were the things changing and distance being constant, rather than vice versa, such that everything was actually shrinking, couldn't this give the exact some sense of redshift and the illusion of motion? It seems to me that if the receptor has shrunk in size, it will sense light as being longer in wavelength, and therefore lead to the inference of motion due to red shift, though perhaps none has occurred. Would there be anyway to differentiate experimentally between these two possibilities?

[Alex K]

Okay, a kind of relativity question:

If the forces in the universe were the things changing and distance being constant, rather than vice versa, such that everything was actually shrinking, couldn't this give the exact some sense of redshift and the illusion of motion? It seems to me that if the receptor has shrunk in size, it will sense light as being longer in wavelength, and therefore lead to the inference of motion due to red shift, though perhaps none has occurred. Would there be anyway to differentiate experimentally between these two possibilities?

Yes, when you do the math of the Standard model living in an expanding universe, you have to make a choice. Either your stick the change of scale which you get from the Friedman equations into the coordinates, which gives you the usual expansion picture, or you absorb it into the fields, forces and masses, which gives you shrinking matter
The latter is much more complicated mathematically, but should be physically equivalent.

As far as I see it, it's a matter of convention without observable differences.

[Alex K]

But if my maths doesn't fail me, one has to scale time as well when one wants to do that, but that's not surprising. So if the universe "grows by a factor of 10" in the usual picture, you can either stretch the space coordinates by a factor 10, giving you the usual interpretation, or you increase the masses by 10 and shrink time by 10.

But I think this all fits together. This can be seen best with a hydrogen atom as a test system giving you measures of length and time:

We now want to take an alternative view of a situation where the universe has expanded by a factor of 10 in a given timespan:
The size (the bohr radius) of a hydrogen atom goes with 1/(effective mass of the electron). So if we increase the electron mass by a factor 10, the hydrogen atom shrinks by a factor 10, which gives us the desired effect of the universe seeming bigger to any observer made of matter. The frequencies emitted and absorbed by the hydrogen transitions are proportional to the mass, so they will rise by a factor of 10. This is exactly what you want, because if you let a hydrogen atom emit a photon in the past, and then we raise the electron mass as a substitute for cosmic expansion, when we receive the wave later it will only have one tenth of the frequency of our reference hydrogen atom, and will thus seem red-shifted. It wasn't really redshifted from this perspective, but all physical rulers shrunk.

[bennyboy]

Okay, a kind of relativity question:

If the forces in the universe were the things changing and distance being constant, rather than vice versa, such that everything was actually shrinking, couldn't this give the exact some sense of redshift and the illusion of motion?  It seems to me that if the receptor has shrunk in size, it will sense light as being longer in wavelength, and therefore lead to the inference of motion due to red shift, though perhaps none has occurred.  Would there be anyway to differentiate experimentally between these two possibilities?

Yes, when you do the math of the Standard model living in an expanding universe, you have to make a choice. Either your stick the change of scale which you get from the Friedman equations into the coordinates, which gives you the usual expansion picture, or you absorb it into the fields, forces and masses, which gives you shrinking matter
The latter is much more complicated mathematically, but should be physically equivalent.

As far as I see it, it's a matter of convention without observable differences.

It seems to me there would be at least one important difference: the view on the Big Bang Theory.  If you virtually reverse time, even if you scale all matter to an arbitrarily large size, causing overlap, you'd never arrive at a singularity, since that would require an infinitely large scale.

[Alex K]

Yes, when you do the math of the Standard model living in an expanding universe, you have to make a choice. Either your stick the change of scale which you get from the Friedman equations into the coordinates, which gives you the usual expansion picture, or you absorb it into the fields, forces and masses, which gives you shrinking matter
The latter is much more complicated mathematically, but should be physically equivalent.

As far as I see it, it's a matter of convention without observable differences.

It seems to me there would be at least one important difference: the view on the Big Bang Theory.  If you virtually reverse time, even if you scale all matter to an arbitrarily large size, causing overlap, you'd never arrive at a singularity, since that would require an infinitely large scale.

The past singularity (which is an artifact of using classical theory, but let's run with it for now) would manifest in the masses going to zero and matter and everything tending to grow to infinite size. There would be a singularity in the time coordinate though, I believe. The fact that space isn't "vanishing" in this picture would already tell you that the naive picture of a singularity is not to be trusted - it is an artifact of the maths at a point where the theory is invalid.

The point of the singularity is not so important for Big Bang theory, because we don't have a theory there - all that goes under the name of Big Bang theory and is of a scientific nature, concerns itself with times after the singularity. The thing with the singularity should never have been brought up, there likely is none and we don't know the physics back then.