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Webb and Hubble confirm Universe's expansion rate

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Re: Webb and Hubble confirm Universe's expansion rate

#291

Post by michaelsbradley »

pigpang wrote: post #230
denton-scratch wrote: post #223

Earlier quoted context omitted.

> (photon is a wave, so it waves something) That sounds suspiciously like postulating the 'ether'. Surely what a photon 'waves' is the electromagnetic field, which is not a medium, and which fills the whole of spacetime. There is no 'end of the medium'.

"Field" means 3d array of numbers. Spacetime means 4d array of numbers. You are talking about mathematical model of Universe, while I'm talking about physics. Mountain is not just an excitement in a height field. If photon is not waving something, then it's not a wave. Physicists prove that photon is a wave.

> If photon is not waving something, then it's not a wave.

No, you’ve simply hit the limits of needing/wanting to understand something in terms of something else similar or more familiar.

Makes the same point on a related matter: https://youtu.be/Q1lL-hXO27Q

Re: Webb and Hubble confirm Universe's expansion rate

#292

Post by nashashmi »

justsid wrote: post #290
dexterdog wrote: post #241

Earlier quoted context omitted.

But I believe he was the winner for many years under price is right rules.

Can you claim to be a winner under the rules of a game that won’t be invented yet for hundreds of years?

Yes. The fact that even this was a thought and he was charting the space bodies and trying to establish distances between them. The rules were invented. The players just were not famous.

Re: Webb and Hubble confirm Universe's expansion rate

#293

Post by throwawaymaths »

sebzim4500 wrote: post #250
throwawaymaths wrote: post #104

Earlier quoted context omitted.

No. According to the standard big bang theory the CMB should look like black body radiation. As for smearing, IIRC black body curve has the central limit property

> According to the standard big bang theory the CMB should look like black body radiation. Yes, that's my point. >As for smearing, IIRC black body curve has the central limit property Surely that can only be true for a very specific distribution of temperatures? To go to an extreme, if you combine the spectrum of two objects of different temperatures you do not get anything like a black body curve.

> if you combine the spectrum of two objects of different temperatures you do not get anything like a black body curve.

Also true for two normally distributed variables and yet the normal distribution has the central limit property.

Presuming the hypothesis, do you suspect that you'd be looking at exactly two grains of dust, one of which has a crazy high temperature and the other has a crazy low temperature in any given pixel of the CMB?

Re: Webb and Hubble confirm Universe's expansion rate

#294

Post by throwawaymaths »

raattgift wrote: post #268
sebzim4500 wrote: post #250

Earlier quoted context omitted.

> According to the standard big bang theory the CMB should look like black body radiation. Yes, that's my point. >As for smearing, IIRC black body curve has the central limit property Surely that can only be true for a very specific distribution of temperatures? To go to an extreme, if you combine the spectrum of two objects of different temperatures you do not get anything like a black body curve.

I agree with you; you can't build up a perfect blackbody spectrum by superposing different near-blackbody spectra, and that led to the cosmological thermalization problem. Furthermore, baryonic intergalactic dust isn't like dark matter: we see redshifted spectral features of components of such dusts imprinted on all sorts of backgrounds from quasars to the CMB. The dusts tend to be greybodies. (I'm ignoring the warm-…

I am not a physicist, but iirc the idea of the alternative explanation of the CMB is that if you time evolve backwards intergalactic dust over expansion, you reach a point where the dust gets really dense and effectively opaque.

So this isn't summing all of the dust you go through, but rather the redshift all the way back to an era when the universe was super dusty (with the expected thermal signature of that era)

Re: Webb and Hubble confirm Universe's expansion rate

#295

Post by munksbeer »

effingwewt wrote: post #274
munksbeer wrote: post #251

Earlier quoted context omitted.

Well yes, but did you read my post in detail? I asked what the difference was between "space expanding" vs "objects moving away from each other". And secondly, what is the mechanism for "space expanding"? What is "space" in this context? What actually is expanding?

Let me try to explain- galaxies moving would be like balls floating in a pool. The galaxies are moving across the water. Space moving would be like balls placed on a bed sheet and the sheet expanding. The galaxies aren't moving- the sheet is. What's actually happening is more like galaxies moving around on a sheet that's being pulled further at all sides.

How can you tell the difference?

Re: Webb and Hubble confirm Universe's expansion rate

#296

Post by munksbeer »

pigpang wrote: post #257
munksbeer wrote: post #251

Earlier quoted context omitted.

Well yes, but did you read my post in detail? I asked what the difference was between "space expanding" vs "objects moving away from each other". And secondly, what is the mechanism for "space expanding"? What is "space" in this context? What actually is expanding?

Spacetime is 4D array of points. It's like a movie file, but with 3D frames instead of 2D frames (pictures). Expansion of space means that coordinates of points in a frame changed to move away from us, to match movie (model) with reality.

An array of 4D points implies some sort of construct upon which the points exist. As far as I know, the that was the concept of "the ether" and that fell out of fashion long ago.

So again, how can you tell the difference between space expanding or two things actually just moving away from each other (to keep it to a very simple example of two bodies).

Re: Webb and Hubble confirm Universe's expansion rate

#297

Post by munksbeer »

tvshtr wrote: post #264
munksbeer wrote: post #220

Earlier quoted context omitted.

What does "space is expanding" mean? That the distance between objects is increasing? How can you tell the difference between "space expanding" and "objects moving in a non-expanding space"? Is there any way to tell the difference or is it just that all objects are moving away at the exact speeds that satisfies the "space expanding" explanation and nothing else? But then, I'm back to what does "space is expanding" me…

Imagine a deflated baloon with two dots drawn close to each other. Now inflate it; the dots didn't move but the plane that they were drawn/positioned on did.

I understand that concept. I'm asking, how can you materially tell the difference?

Re: Webb and Hubble confirm Universe's expansion rate

#298

Post by pigpang »

pdonis wrote: post #285
pigpang wrote: post #207

Earlier quoted context omitted.

It's just an interpretation. Your interpretation is similar to the Big Bang model of visible Universe expansion. If you can convince us that your model is better than other models, then we will use your model, but nobody can prove than a model is correct, unless we will find a hidden recorder somewhere which was turned on for few dozens of billion years. Photon will hit something, or will travel until it will be reds…

> It's just an interpretation No, it's not, it's our best current model's description of the actual physical reality of our universe. > nobody can prove than a model is correct That's true, but it's also true that we can show models to be incorrect , as in, falsified by the data. For example: > Photon will hit something, or will travel until it will be redshifted to obvilion, or will travel until end of the medium Fo…

> No, it's not, it's our best current model's description of the actual physical reality of our universe.

OK, it's our best model, but it doesn't invalidate other models, less complete or less popular, it compete with them.

> That's true, but it's also true that we can show models to be incorrect, as in, falsified by the data.

Yep. The article is about the Huble Tension, which invalidates Big Bang model. We still use it.

> the second is known to be false because there is no "gravitational redshift" of light in the universe as a whole (because models in which there would be such a redshift are known not to correctly model our data on the universe as a whole)

The Big Bang model is incomplete too: galaxies with FTL speeds, different speeds of expansion, no center of bang, no flows, no source of energy, it stretches time and space, etc.

I assume that the only infinite thing in infinite Universe is Universe itselft. All other things are finite. Thus, a photon has finite life, like any other wave.

> there is no "end of the medium"

The right-hand rule in EM suggests that we are in north hemisphere of something, so south hemisphere will have symmetrical rule, unless you believe that God chose right-hand rule for the whole infinite universe. If we are in a sphere, then that sphere rotates and have a boundary.

> what "waves" is the electromagnetic field.

"Field" is an array of numbers. You are mixing model and reality.

Re: Webb and Hubble confirm Universe's expansion rate

#299

Post by SkyBelow »

swamp40 wrote: post #289

I cannot for the life of me understand how you look at the cosmic background radiation - which appears equally in every direction you look, for as far away as you can see - and say this is evidence of a "big bang", originating from a single spot at a single point in time. And the universe just "expanded faster than light" to cover everywhere with the same consistent drab layer of cosmic background radiation. It seems…

>originating from a single spot at a single point in time

That's based on a simplified model of the big bang which isn't what scientist use. It is everywhere, and time itself isn't defined. One major result of this is that many people treat the visible universe as the universe, but those are two different concepts and while the visible universe is finite, the universe might not be (it might be infinite, finite unbounded, or finite unbounded).

Also, science isn't saying "This is what happened". It is saying "Our best model to date says this is happening". In the end it is only a model and the model is still open to being refined and there is always the possibility of data resulting in the entire model being overturned, though often this leads to an ever more complex model that is harder to work with but better fits the experimental data (such as the wave/particle nature of light which is hard for a person to conceptualize).

Re: Webb and Hubble confirm Universe's expansion rate

#300

Post by BunsanSpace »

arandomusername wrote: post #160
lagrange77 wrote: post #109

Earlier quoted context omitted.

Interesting, thanks! Out of curiosity: Can we actually differentiate between the expansion of space itself and the drifting of objects within it in the same direction?

I think we observed some of the galaxies moving away from us at rates faster than speed of light, multiple times faster, which wouldn't work with objects drifting away if we hold by that speed of light is max speed matter can move at.

The speed of light, or C, is the max speed information can move through our 3d space.

Having objects moving away from us at a speed greater than C, isn't weird. The observable universe is a 3d subspace of a higher dimensional object. A good analogy is a balloon, where there's a 2d subspace on a 3d object that's being inflated. Even if you can only move at a certain velocity, the balloon can inflate such that the 2d surface expands faster than the max velocity we prescribe for it, and would grow faster at the beginning even if we pumped a constant amount of air into said balloon.

Great analogy for gravity too! because you could create dimples in the balloon (gravity wells) which would curve a straight trajectory, while being unnoticed to an observer on the 2d subspace.

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