I don't think space is expanding.

[jonesdave116]

And by matching the evidence, you mean predicting the birth and fate of the universe and the abundance of the elements in it, right?

No, you are getting confused between redshift observations and the BB cosmology. Redshift is an observation that supports that cosmology. Hence why we have had various crackpots, who don't want to believe in the BB cosmology for whatever reason, coming up with silly tired light hypotheses. They realise how fatal it is to their beliefs. Unfortunately for them, the evidence supports the consensus view, and basic science and observation rules out their tired light woo. Hence why nobody bothers with said woo anymore.

 

[Reformed Offlian]

I haven't forgotten.

This is actual one of my favorite falsifications of the idea, because of how perfect it is.

Do you think that right now, we've observed the bulk of the universe while only the tip of the proverbial iceberg is concealed?

JWST goes up soon. We will either see something that looks like our models, or we're in for a shock.

This is the time to make predictions. Heck of an opportunity.

I've already told you what the prediction is. And it isn't even much of a prediction, because the relevant observations have already been made.

Astronomers have already measured how much infrared light is reaching us from the cosmos. JWST isn't going to find a big pot of IR energy that's previously gone unnoticed, just as Hubble didn't find a lot of light that had previously gone unnoticed. The most that will happen is that we'll be able to resolve some of the background we've already measured into individual sources. And those sources *won't* be able to suggest a different explanation for the CMB, because they will be tiny, discreet point sources. Of infrared, not microwaves.

 

[Mike Helland]

I've already told you what the prediction is.

Quantitatively? I don't have it in my notes.

And it isn't even much of a prediction, because the relevant observations have already been made.

If you say so.

My guess is the "large scale structure" of the universe might end up looking kind of small.

 

[Mike Helland]

It is. That is why it is called the cosmic microwave background. Any alternative explanation will have to explain why we see it at that wavelength, and not any other/s.
The properties of the CMB tell us that it comes from one place at one specific time. If the radiation had travelled further in time (and therefore distance), then it would be stretched to longer wavelengths. If it was from closer in time and space, it would be at shorter wavelengths.

Ok.

So let's take an empty volume of space.

Now say five photons enter that space, and while they're there, they redshift.

Then they leave that space.

Do we have the exact same empty space we had before.

The conservation of energy says to me that space contains the energy the photons lost before they left the volume.

Is that unreasonable?

 

[RecoveringYuppy]

The conservation of energy says to me that space contains the energy the photons lost before they left the volume.

We've been over this. Where's the momentum?

 

[Mike Helland]

We've been over this. Where's the momentum?

Since energy and momentum of a photon are intimately tied together, E=pc, the most obvious thought is that the energy that's redshifted away from the photon has that momentum.

It would be pretty small, assuming photon's don't redshift in giant quantized steps.

 

[Reformed Offlian]

Quantitatively? I don't have it in my notes.

If you don't, it is only because you haven't been taking notes.

 

[RecoveringYuppy]

Since energy and momentum of a photon are intimately tied together, E=pc, the most obvious thought is that the energy that's redshifted away from the photon has that momentum.

It would be pretty small, assuming photon's don't redshift in giant quantized steps.

So you've forgotten everything from before.

 

[theprestige]

So if that energy is being transferred into spacetime or whatever, what should that look like? Is it heat? We should see heat blooms across the sky, obscuring all but the closest objects in the infrared wavelengths.

Is it momentum? What happens if shove momentum into spacetime? I think maybe space would have to expand, to accommodate it.

Is it bonus photons? Then we should see a similar photon bloom across the sky. We should see more distant objects emitting more, redder photons. But we don't. As our resolution improves, we don't see blurrier and blurrier distant objects. We see crisply resolved distant objects, emitting exactly the numbers of photons we predicted.

 

[Mike Helland]

So if that energy is being transferred into spacetime or whatever, what should that look like? Is it heat?

I know this was shot down before, though I don't understand exactly why, but I would suppose it contributes to the background energy:

https://en.wikipedia.org/wiki/Vacuum_energy

"Vacuum energy is an underlying background energy that exists in space throughout the entire Universe.[1] The vacuum energy is a special case of zero-point energy that relates to the quantum vacuum.[2] "

Ok, maybe not so much that second part, but "underlying background energy that exists in space throughout the entire universe" sounds spot on.

 

[theprestige]

It would sound spot on, if it weren't already accounted for in the second part.

 

[Mike Helland]

It would sound spot on, if it weren't already accounted for in the second part.

It also says this:

" In particular, the second law of thermodynamics is unaffected by the existence of vacuum energy "

Do you know anything about that?

Because if the redshifts in standard cosmology don't respect the conservation of energy, and the background energy doesn't respect the 2nd law of thermodynamics, my idea is basically the opposite.

The energy is conserved, by going to the background, and the background energy tries to be at thermal equilibrium with its environment, producing the CMB.

 

[theprestige]

It also says this:

" In particular, the second law of thermodynamics is unaffected by the existence of vacuum energy "

Do you know anything about that?

Because if the redshifts in standard cosmology don't respect the conservation of energy, and the background energy doesn't respect the 2nd law of thermodynamics, my idea is basically the opposite.

The energy is conserved, by going to the background, and the background energy tries to be at thermal equilibrium with its environment, producing the CMB.

That would put the CMB in front of the objects producing it. The CMB would be between us and all but the nearest objects. But in reality we observe that the CMB is coming from beyond the redshifted sources you're trying to explain.

What's more embarrassing? That your idea is predicts things we don't actually observe? Or that it fails to predict things we do observe? Is the embarrassment the juice?

 

[theprestige]

Mike, do you even know what "background" means?

 

[theprestige]

Honestly I think you should keep proposing crazier and crazier hypotheses. Sooner or later, you'll get to, "guys! Guys! What if - hear me out - what if... space is *expanding*?! Crazy, right? I know! But what if?!"

 

[Mike Helland]

Honestly I think you should keep proposing crazier and crazier hypotheses. Sooner or later, you'll get to, "guys! Guys! What if - hear me out - what if... space is *expanding*?! Crazy, right? I know! But what if?!"

What if... like, the photon doesn't move through time and space, but the motion of the photon defines time and space.

 

[Mike Helland]

So you've forgotten everything from before.

Oof. I hope not.

So we're talking about a vector, a direction?

https://socratic.org/questions/how-do-you-calculate-the-momentum-of-a-photon

"The momentum of a photon is given by En/c where n is the unit vector in the direction in which the photon is moving, E is its energy, and c is the speed of light. "

I would assume n (or hat n) stays the same in this event. Otherwise, there would be the blurring and such.

 

[Ziggurat]

Ok.

So let's take an empty volume of space.

Now say five photons enter that space, and while they're there, they redshift.

Then they leave that space.

Do we have the exact same empty space we had before.

The conservation of energy says to me that space contains the energy the photons lost before they left the volume.

Is that unreasonable?

The volume of space increased. You need to take that into account.

 

[theprestige]

What if... like, the photon doesn't move through time and space, but the motion of the photon defines time and space.

Like, it's the photons themselves that are making space expand? I like where your head is at!

 

[Mike Helland]

Like, it's the photons themselves that are making space expand? I like where your head is at!

Exactly.

Alternatively, they could make time expand.

In a non-relativistic model, this would mean the photon's experience of time in the model does something like this:

And then it moves like this:

Now it's frequency (v, nu) can be computed two ways, and both equal:

That produces the identical redshifts to a simple expanding universe.

If the first step is not a simple line, but instead this:

Then we can explain the so-called "acceleration" of the universe pretty naturally.

This "acceleration" here is based on the non-linear motion of the photon, which produces a warped time which we observe as redshifts.

In relativity, if we are sticking with the idea that the motion of a photon defines space and time (rather than the other way around), if the photon's path is not defined by v=c, but something else, than that's how space and time would be defined.