I don't think space is expanding.

[Samson]

That's not implied by my theory.

The universe is indefinitely large, like 10^100 bigger than you can think times another trillion.

We're at the center of our observable part, but beyond that, there's nothing to indicate the universe's size from our vantage point.

That is indeed my understanding.
We are either in the exact center or it is unknowable the size, but I read that it is likely to be at least 256 times bigger than our observable universe.

 

[Mike Helland]

That is indeed my understanding.
We are either in the exact center or it is unknowable the size, but I read that it is likely to be at least 256 times bigger than our observable universe.

If space isn't expanding, there would be no evidence of a size limit, and it should be considered indefinitely large.

 

[Ziggurat]

I guess there is something to the black body thing I'm missing, because it seems obvious to me that when there is no body, it'll appear black.

Yes, you are missing a considerable amount. What it appears as isn't relevant here. A blackbody radiator can in fact appear white.

In thermodynamics, a black body is an object that absorbs all incoming radiation. This requires that it also thermally emit radiation, otherwise thermal equilibrium would not be possible. A black body emits the maximum amount of thermal radiation because it absorbs the maximum amount as well. Anything which is reflects or transmits radiation will thermally emit correspondingly less radiation, again as a requirement of thermal equilibrium being possible. The amount of thermal radiation, not only in total but also as a function of wavelength, is also something that we can calculate theoretically and observe experimentally for a blackbody emitter, all based on the requirement that thermal equilibrium is possible. The peak of that emission spectrum scales with temperature, but the shape is constant. If a blackbody emitter is sufficiently hot, it will glow in the visible spectrum, and may even appear white. If an object either reflects or transmits some fraction of incoming radiation at a particular wavelength, it will thermally emit that fraction less at that wavelength than a blackbody emitter at the same temperature would. Since objects in nature are almost always not actually black (ie, they either reflect or transmit some radation at some wavelengths), they are almost always not blackbody emitters.

The sun is roughly a blackbody emitter. But like all stars, it has very noticeable deviations from a perfect blackbody spectrum. The CMB has no observable deviations from a perfect blackbody spectrum. It is quite remarkable in that respect.

 

[Mike Helland]

Thanks for the replies and the information.

The CMB has no observable deviations from a perfect blackbody spectrum. It is quite remarkable in that respect.

So if space just has stray energy kicking it around, wouldn't that be a black body since it's at equilibrium with itself?


Also, doesn't the cold spot in the CMB cast some doubt on what it really is?

We see the cold spot to the south. Which direction do the other observers see the CMB cold spot?

 

[Ziggurat]

So if space just has stray energy kicking it around, wouldn't that be a black body since it's at equilibrium with itself?

If the universe were at thermal equilibrium, everything would look one color. The fact that it's black with spots of white is proof that it's not at thermal equilibrium. This should be obvious since space is cold but stars are hot.

So no, the universe won't look like a blackbody. Our galaxy certainly doesn't. The interstellar dust that we can observe doesn't.

Also, doesn't the cold spot in the CMB cast some doubt on what it really is?

No. Variations are to be expected. If there were no variations, the universe would not have coalesced into galaxies, but should remain a uniform expanse filled with diffuse gas.

We see the cold spot to the south. Which direction do the other observers see the CMB cold spot?

I don't know.

But I think you may be a bit confused, because the question is less meaningful than you think. The cold spot is to the south of us. That means that the part of the universe to the south of us that's ~13 billion light years away was colder than the parts of the universe ~13 billion light years away in other directions. But the north oberver on your diagram doesn't see those same places when he looks at the CMB. His south CMB originated around where we are now, but ~13 billion years ago. He isn't seeing through us, it's not like south is a cold direction, rather it's the direction to a specific cold spot. The spot 7 billion light years away in the south direction may have been a hot spot, but we can't see the CMB from that anymore, it's already passed us by. Was our current location a cold spot ~13 billion years ago? I don't know (my suspicion is no), though professional cosmologists probably have an idea.

 

[Mike Helland]

No. Variations are to be expected. If there were no variations, the universe would not have coalesced into galaxies, but should remain a uniform expanse filled with diffuse gas.

True, but not too this degree:

https://sci.esa.int/web/planck/-/51...-cold-spot-in-the-cosmic-microwave-background

"Two Cosmic Microwave Background anomalous features hinted at by Planck's predecessor, NASA's Wilkinson Microwave Anisotropy Probe (WMAP), are confirmed in the new high precision data from Planck. One is an asymmetry in the average temperatures on opposite hemispheres of the sky (indicated by the curved line), with slightly higher average temperatures in the southern ecliptic hemisphere and slightly lower average temperatures in the northern ecliptic hemisphere. This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look. There is also a cold spot that extends over a patch of sky that is much larger than expected (circled). In this image the anomalous regions have been enhanced with red and blue shading to make them more clearly visible."

But the north oberver on your diagram doesn't see those same places when he looks at the CMB. His south CMB originated around where we are now, but ~13 billion years ago. He isn't seeing through us, it's not like south is a cold direction, rather it's the direction to a specific cold spot. The spot 7 billion light years away in the south direction may have been a hot spot, but we can't see the CMB from that anymore, it's already passed us by. Was our current location a cold spot ~13 billion years ago? I don't know (my suspicion is no), though professional cosmologists probably have an idea.

Yeah, that seems reasonable to me.

The cold spot is because, off in that direction, there isn't as much hot stuff.

Those are anomalies in the standard model, but if space isn't expanding, then the CMB isn't an echo from it, and there's nothing particularly anomalies about it.

 

[MRC_Hans]

We know what it absorbs based on what it reflects.

No. Something that passes through is neither reflected nor absorbed.

Hans

 

[Mike Helland]

No. Something that passes through is neither reflected nor absorbed.

Classically, perhaps.

At the quantum level the photon is being absorbed and emitted by atoms of the medium.

 

[catsmate]

I don't think space is expanding.

Why should we, or indeed anyone, care about you opinion, contradicted as it is by vast amounts of observational data?

 

[Ziggurat]

Those are anomalies in the standard model, but if space isn't expanding, then the CMB isn't an echo from it, and there's nothing particularly anomalies about it.

You're asking about minor anomalies (these temperature variations are actually quite small), but you still can't address the biggest feature, the CMB shape. This is much like electric universe folks debating the nature of the solar wind, even though they can't even account for the far more significant fact of the sun's power output itself. Don't bother fiddling at the edges if you can't even get the main features right.

 

[Ziggurat]

Classically, perhaps.

At the quantum level the photon is being absorbed and emitted by atoms of the medium.

That distinction isn't relevant for thermodynamic purposes. Absorption and instantaneous re-emission is no different, from an energy flow perspective, from transmission. And energy flow is the basis for black body analysis.

Plus, your claim was about space itself, and space itself doesn't absorb and re-emit, even at the quantum level. It doesn't absorb at all.

 

[Mike Helland]

Why should we, or indeed anyone, care about you opinion, contradicted as it is by vast amounts of observational data?

Because current observation data doesn't fit the standard model nicely either.

A new physics is needed. That's become widely apparently to those in the field.

https://phys.org/news/2019-10-crisis-cosmology-universe-rapidly-believed.html
https://www.space.com/universe-standard-model-hubble-constant-new-measurements.html

More:

https://duckduckgo.com/?q=cosmology+crisis

My theory is that Hubble's Law is actually the photon's velocity.

Space doesn't expand at H * D, light slows down at H * D.

This fits the new redshift very well.

Here is an interactive demonstration:

https://mikehelland.github.io/hubbles-law/

And here is a testing page to fiddle with values:

https://mikehelland.github.io/hubbles-law/test.htm

 

[Mike Helland]

You're asking about minor anomalies (these temperature variations are actually quite small), but you still can't address the biggest feature, the CMB shape. This is much like electric universe folks debating the nature of the solar wind, even though they can't even account for the far more significant fact of the sun's power output itself. Don't bother fiddling at the edges if you can't even get the main features right.

If the CMB is supposed to look the same in all directions, and it doesn't, and this warrants conjecture such as "parallel universes must have hit us":

https://www.independent.co.uk/news/...cosmic-microwave-background-cmb-a7743216.html

Then I would gather it's not something you can just sweep under the rug.

The evidence for the Big Bang looked WAAAY better last century.

What is the CMB in my theory? Probably just derelict energy left by photons as they decelerate over long journey's.

 

[Ziggurat]

If the CMB is supposed to look the same in all directions,

Who said that?

and it doesn't

Yes, it doesn't. But I don't think you understand how small the variations are.

Then I would gather it's not something you can just sweep under the rug.

Nobody is.

What is the CMB in my theory? Probably just derelict energy left by photons as they decelerate over long journey's.

That wouldn't produce a blackbody spectrum. Nor do you have any way of calculating what the variation should be, so it doesn't really make sense to criticize a different theory for what your theory doesn't actually do either.

 

[Mike Helland]

Who said that?

The ESA, in the article I gave: This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look.

Yes, the CMB does have fluctuations. The cold spot is outside what those were predicted to have likely been.

That wouldn't produce a blackbody spectrum. Nor do you have any way of calculating what the variation should be, so it doesn't really make sense to criticize a different theory for what your theory doesn't actually do either.

I think if anomalies show up, and the field uses words like "crisis" and "rewrite" liberally, then I think being skeptical of the standard theory is fair game.

If a random photon, scattered from its buddies hits you, and wouldn't really have a spectrum, would it? It's just a single photon with a single frequency.

Is a single photon a black body?

 

[Ziggurat]

The ESA, in the article I gave: This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look.

Yes, the CMB does have fluctuations. The cold spot is outside what those were predicted to have likely been.

The fluctuations are larger than expected. That's very different than fluctuations not being expected at all.

I think if anomalies show up, and the field uses words like "crisis" and "rewrite" liberally, then I think being skeptical of the standard theory is fair game.

Sure. But again, if you want to replace the standard theory, then you have to be able to address the big stuff AND the little stuff. It doesn't work to explain the little stuff but fail on the big stuff. That's what I was referring to when I mentioned the EU folks. They're obsessed with little stuff like the solar wind, but they can't even get the big stuff like the power output of the sun right. It makes no sense to worry about the fluctuations in the CMB if you can't explain why there's a CMB in the first place. And you cannot. Your ideas don't produce a CMB, not even close.

Very often in physics, if a theory can explain the big stuff, then successor theories which go on to explain the little stuff build off of that original theory, they don't have to overthrow it completely. That's where we are most likely at: the standard model and big bang cosmology are broadly accurate, but need some refinement.

If a random photon, scattered from its buddies hits you, and wouldn't really have a spectrum, would it? It's just a single photon with a single frequency.

Is a single photon a black body?

You aren't making any sense. Of course a single photon isn't a black body. No photons are black bodies. Black bodies are sources of photons, not the photons themselves. And photons do not scatter off of each other, so I'm not sure what "its buddies" is supposed to refer to. And it doesn't matter that single photons aren't a spectrum, we still observe a spectrum. It's out there.

 

[Mike Helland]

Black bodies are sources of photons, not the photons themselves. And photons do not scatter off of each other, so I'm not sure what "its buddies" is supposed to refer to.

Stars emits lots of photons constantly, right.

So if those photons are traveling, and there happens to be some dust or something, some of those photons scatter.

Most of the photon continue on together, but some are bounced around, randos.

What would the spectrum of those photons look like?

Faint and in all directions, I would think.

 

[Ziggurat]

Stars emits lots of photons constantly, right.

So if those photons are traveling, and there happens to be some dust or something, some of those photons scatter.

Most of the photon continue on together, but some are bounced around, randos.

What would the spectrum of those photons look like?

Faint and in all directions, I would think.

Again, the issue isn't that the light would be faint in all direction. The issue is that it won't be a blackbody spectrum. Starlight isn't a blackbody spectrum. When it bounces off stuff that also isn't a blackbody, it doesn't turn into a blackbody spectrum. It doesn't matter how diffuse the signal is, it won't be a perfect blackbody, not even close.

You still don't seem to understand how big a deal this is, but it's a really, really big deal. A far bigger deal than the temperature variations. We aren't still talking about it because the problem of why it's a blackbody spectrum in the first place is already considered solved. But it was a really god damn big deal when it was discovered.

 

[Mike Helland]

The issue is that it won't be a blackbody spectrum.

What is the difference between a black body spectrum, and a random photon?

 

[Ziggurat]

What is the difference between a black body spectrum, and a random photon?

What's the difference between a note and a symphony?

And what's your point? We measure not just individual photons, but an entire spectrum. The spectrum has to come from somewhere. BBT offers an explanation of where it comes from, and why it's a perfect blackbody spectrum. No other theory, including yours, does.