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The cosmic microwave background radiation didn’t appear until the universe was about 380,000 years old.

https://en.m.wikipedia.org/wiki/Cosmic_microwave_background



So CMB is just 14B years old? Then why we see objects older than CMB? Moreover, why these older than CMB objects appearing in front of CMB?


There were no objects before the CMBR. The universe was so hot that atoms couldn't even form. Once it cooled to the point where hydrogen atoms came into existence, the CMBR became possible. I'm talking at the limits of my knowledge, so allow me to refer you to this video by Fermilab that's pretty good.

What is the Cosmic Microwave Background? -- https://youtu.be/AYFDN2DSVgc


I think OP's question related to the observable universe vs what is beyond. We see the CMB (and thus our limit of light) only to a point, but that doesn't mean there's nothing beyond that - otherwise we'd be the literal center of the universe (I recall an old minutephysics video[0] on this).

[0] https://www.youtube.com/watch?v=W4c-gX9MT1Q


We ARE the center of the universe. Just like any other point!


We dont see galaxies older than CMB.


Yep. This is the problem. Why CMB is emitted at the edge of our Universe only? Where are atoms, which produced the CMB?


Because the “edge” of our universe where we see the CMB is not a point in space we are viewing in real time that is currently emitting the CMB.

That edge is a sphere in space that was far enough away when the CMB was emitted in the past that we only see the light from it now.


Yep, but this sphere must have radius up to 14Bly, to be part of BB.


The observable universe has a diameter of about 47 billion light years!

https://imagine.gsfc.nasa.gov/educators/programs/cosmictimes...


Then we need to move the time of BB to 47/2 = 23.6By. Moreover, we should do that every time when we improve our telescopes.


Correction... I meant radius of 47 billion light years. It's about 94 billion light years across!


> Why CMB is emitted at the edge of our Universe only?

I thought CMB was emitted everywhere.


The CMB is everywhere, but it was emitted by the initial formation of neutral hydrogen (from plasma) in the early universe. When people talk about the CMB being far away they're really talking about the last scattering surface, which is that early plasma as seen 13+ billion years later.


CMB is produced by atoms, right? We see darker/lighter regions in CMB, so we should see a transition somewhere. 300M years is very short period of time, unless everything cooled very very uniformly, which is not the case. Sometimes, somewhere there must be a galaxy past CMB.


> 300M years is very short period of time, unless everything cooled very very uniformly, which is not the case

~300M years is the time between the Big Bang singularity and the CMB, but not really relevant. The entire universe was everywhere as hot as the surface of a star at the time of the CMB, so any evidence of galaxies forming before that is surprising.

The surprisingly high uniformity of the temperature of the CMB — isotropic to roughly one part in 100,000 — is one of the reasons the Big Bang model replaced one of the older competing hypotheses (continuous creation IIRC).

So it is in fact the case that everything cooled very very uniformly and I'm not sure why you think otherwise?

I'm also not clear what you're saying with

> so we should see a transition somewhere

Given the CMB is itself the transition that we see.

> Sometimes, somewhere there must be a galaxy past CMB.

I think here you're mixing up space and time.

It's reasonable (please permit my use of conventional language rather than 4-vectors) to assume that a galaxy exists on the other side in space of the CMB as we see it now, but that happens at a point in time after the recombination epoch began and space became transparent, and light from that event hasn't reached us yet; when it does, the apparent distance of the CMB will be large enough for the galaxy to appear on this side.

Are you familiar with light cones and the convention of one space axis and one time axis? It might help you visualise it if you draw what's going on.


https://en.wikipedia.org/wiki/GLASS-z12

GLASS-z12 is 33.2Bly away from us. It should be behind some of the CMB produced by BB, isn't?

> Given the CMB is itself the transition that we see.

In BB model, CMB emitted by hot plasma. Where it is, that plasma?

In steady universe model, CMB is light with z=1000, emitted by distant galaxies, in range of 4Tly. It explains high uniformity of temperature. It's like the temperature of a water stream from underground: it's uniform across a climate area because underground temperature averages seasonal temperature shifting.


> It should be behind some of the CMB produced by BB, isn't?

A reasonable mistake, but no.

If you look at the info box on your link, you'll see there are two different distances:

≈33.2 billion ly (10.2 billion pc) (present proper distance)

≈13.6 billion ly (4.2 billion pc) (light-travel distance)

The latter is what we're talking about when we say the CMB is about 13-point-whatever billion years old.

The difference with the other number is that the universe got bigger in the meantime, and that's where we recon it is now.

> Where it is, that plasma

The plasma itself?

Everywhere. The whole universe, including here.

The bit we see?

An echo made of light emitted at the last moment in time that it stopped being plasma — the light from the plasma that was here is now as far away from us as the plasma that caused the light we can see.


These numbers means that nothing can travel at FTL speed except this galaxy. It travelled 20Bly in 13By at the speed of 1.5 c. Extraordinary claim requires extraordinary evidence. Where is the source of energy for this FTL galaxy? Why this galaxy is not ripped apart into ball of gluon plasma?

Echo requires something to reflect of. Moreover, echo will be an order(s) of magnitude weaker and will have a stamp of the reflective surface on it properties.


> These numbers means that nothing can travel at FTL speed except this galaxy

Nothing including this galaxy can beat light locally.

Look up the balloon (or raisin bread) analogy.

> echo will be an order(s) of magnitude weaker and will have a stamp of the reflective surface on it properties.

It does. That's in the CMB.


> Look up the balloon (or raisin bread) analogy.

In bread analogy, sugar is the source of energy and CO2. In balloon analogy, new air is added to balloon (with lot of turbulence). What is added to our Universe, which causes the inflation? Where we can see it?

In case of Steady Universe model, light just changes it's properties over time, for example, because gravitational waves are stretching photons and photon beams. Gravitational waves are produced by massive objects, which are orbiting each other.


> What is added to our Universe, which causes the inflation?

It's a free parameter in the equations, just like the initial value for the energy in the space or the baryon number.

Or the number of space-like and time-like dimensions.

Or their inherent topology.

Not that it matters, as the point of what I suggested is that it's an analogy for all objects within the space observing the same relationship, and the implications thereof.

> Where we can see it?

In the relationship between distance and redshift. More distant objects move away faster, the further away the faster they move on average, and that relationship best matches "accelerated expansion" than any other model.

Or, more locally, it's (perhaps by coincidence) about the right level to explain the moon's orbit slowly getting bigger.

> In case of Steady Universe model, light just changes it's properties over time, for example, because gravitational waves are stretching photons and photon beams. Gravitational waves are produced by massive objects, which are orbiting each other.

Great!

Unfortunately for you, those gravitational waves can't act anything like the ones predicted by GR which we've actually observed, because those are far too weak (or spacetime too 'stiff', IIRC).

GR has known weaknesses, to be sure, but they're all annoying beyond any observations we've been able to make, and people really are looking as it's considered both important and prestigious to find a way to tie it and quantum physics together properly.

In the meanwhile, the same equations for GR describe the (just about) detectable gravitational influence your body has, and the various demonstrations of gravity influencing the flow of time and path of nearby light.

IIRC, the best atomic clocks are just about at the level where an extra 100kg sitting next to them can change the last digit relative to another otherwise identical clock, but I'm not sure how long you have to sit there.

They're definitely good enough for it to matter which floor of a building you put them on.


> Unfortunately for you, those gravitational waves can't act anything like the ones predicted by GR which we've actually observed, because those are far too weak (or spacetime too 'stiff', IIRC).

Let's play with numbers. Two kinds of gravitational waves are claimed to be observed: 1) HF waves by LIGO/Virgo and 2) LF ones by NANOgrav[1].

I assume, that the meter is defined as c1s/299792458 in steady vacuum*. Same for the second. I assume, that speed of light can go down only, in other words, speed of light cannot be higher than c.

Gravitational wave background strain amplitude calculated to be ~ 2.4E-15 y-1. For simplification, I assume average slowdown (stretching) of light to be 1E-15 per year.

LF gravitational waves are quite powerful, with strain amplitude 2.4E-15 y-1, but their low frequency does almost no impact to the wave length of light. In 1 billion of years, wave length will be enlarged by up to 1,0000024.

HF gravitational waves are much weaker, say 1E-21, but their high frequency, say 20kHz, may increase wave length up to 1.88, which is much closer to expected Red Shift of 7.

[1]: https://iopscience.iop.org/article/10.3847/2041-8213/acdac6


24 kHz gravitational waves are made by…

a pair of objects orbiting 24 thousand times per second.

This happens when black holes or neutron stars merge and that's it; this means you don't have enough of them to do what you're claiming, not even if I trusted what looks suspiciously like you blindly asserting without evidence how much they should alter wavelengths.

The effect of gravitational waves is barely anything even on the LIGO detector, and they need to use a squeezed quantum state to even notice because it's much smaller than the wavelength of the light even over the length of the entire beam-line.

Also, gravitational waves don't redshift the photons, they change the length of the path the photons take.

-

And as LIGO, NANOGrav etc., are relying on a prediction of the exact same GR equations that also lead to the big bang etc., you trying to shoehorn that in is roughly analogous to a Young-Earth Creationist talking about carbon dating.


Or by 24 thousand pairs orbiting 1 time per second, or by 24000*365*24*60*60 pairs orbiting 1 time per year.

> Also, gravitational waves don't redshift the photons, they change the length of the path the photons take.

Yep, more length to travel - larger wave length. :-/

> And as LIGO, NANOGrav etc., are relying on a prediction of the exact same GR equations that also lead to the big bang etc

I had a discussion about that recently. I have no power to repeat the discussion. You can find it in my comment history.


> Or by 24 thousand pairs orbiting 1 time per second,

no, and for the same reason you can't use the output of a quarter million 2.45 Ghz microwave oven magnetrons to produce monochromic teal light (612500 Ghz).

The maths is basically equivalent for EM and gravity waves, except for the constants.

Well, that and the fact it's changing the space-time through which the waves themselves propagate, but the effect is usually small enough to be barely detectable even when you want to.

> Yep, more length to travel - larger wave length. :-/

no, same wavelength, going further on one half of the cycle, then not as far on the other half of the cycle. Same wavelength within the space, it's the space itself which changes.

> I had a discussion about that recently. I have no power to repeat the discussion. You can find it in my comment history.

TBH, that would be a colossal waste of my time. I'm only even bothering to reply to this this now because discussion is supposed to be helpful while I learn things.


> no, and for the same reason you can't use the output of a quarter million 2.45 Ghz microwave oven magnetrons to produce monochromic teal light (612500 Ghz).

Why we need monochromatic light? Gravitational wave background is just noise. A lot of orbiting objects in a galaxy will produce steady noise, due to interference. It's easy to check just by putting a bunch of wave generators with different frequencies in a same pond, and then move. Interference between waves will create noise with higher frequencies than original.

Even small effects are producing significant results over large periods of time. 1 billion years is 31.5E15 seconds.

If we integrate over all frequencies of gravitation noise floor, then we may have a number, which will explain a part of red shift.

More over, gravitational noise is important for Pilot Wave theory, because it may explain the source of energy for the pilot wave.

> no, same wavelength, going further on one half of the cycle, then not as far on the other half of the cycle. Same wavelength within the space, it's the space itself which changes.

It implies FTL speed at the second half of the cycle, which is impossible. If wavelength of light will be enlarged, then it will stay enlarged, because light traveling at c, so c-delta is possible, but c+delta is not.

> TBH, that would be a colossal waste of my time. I'm only even bothering to reply to this this now because discussion is supposed to be helpful while I learn things.

I have the same filling. I only reply because my pleasure to talk with you overcomes the inconvenience of Hacker News.

Maybe we should switch to email, or to a wiki with a proper set of tools for scientific discussion.


GLASS-z12 is way in front of the CMB.

You have to be careful with what you mean by "distance" at cosmic scales. Space is expanding with time, and there are several different definitions of "distance" that give very different results at cosmic scales.

The best "distance" measure here is simply redshift. GLASS-z12 is at redshift z=12, as the name suggests. The CMB is at redshift z=1100, so it's father away.

In fact, for very straightforward physical reasons, no light can reach us from beyond the CMB. The universe was opaque before the time of the CMB, because it was ionized and dense. Before the CMB time, photons could not travel very far at all before they hit an electron and were scattered.


Nobody pointed to a source of energy for this "expansion" of "space". Usually, coordinate system doesn't expand with time. An extraordinary claim requires extraordinary evidence.

Yes, CMB emitters are much further away, at a distance of about 4Tly, while BB claimed to be just 14By ago. Your claim, that CMB is produced by BB, requires a lot of stretching.


There's no point in arguing about this here. There's a very well defined, mathematical theory called General Relativity, which explains gravitational phenomena from Mercury's precession all the way to the expansion of the Universe.

If you take the time to learn General Relativity, and to learn how to apply it to cosmology, you will see that there are rigorous mathematical answers to the various questions you're raising.

I want to point out that this isn't esoteric stuff that only a few people understand. General Relativity and cosmology are part of a standard undergraduate physics curriculum. It only takes a few years of study, starting from Physics 101, to get to the point where you can derive the answers to all your questions from scratch.


Doesn't even need that much — their questions so far are at my level, and I keep messing up the much simpler special relatively questions on brilliant.org


How GR explains claimed FTL speed of GLASS-z12? (20Bly travelled in 13By, 1.5c).

I'm listening with both ears.


You've already got the answer: space expanded.

Spacetime being dynamic is kinda the point of GR.

"How" this specific expansion happens is an open question — not because nobody has any idea, but because we can't distinguish between three of them and a forth leads directly to the unsolved challenge of combining GR with quantum mechanics.


No, this is not an answer, because it breaks number of laws of physics, such conservation of energy. It looks like an excuse that an answer. It's just heavy stretching of the evidence until it fits the BB model of evolution of Universe.

Static Universe model of evolution doesn't requires such stretching: CMB is just light of distant galaxies. End of story.


>No, this is not an answer, because it breaks number of laws of physics, such conservation of energy.

THE WHOLE POINT of GR is that it explains things that "classical" physics did not, while also explaining everything that classical physics did. Nothing in GR "breaks the laws of physics" because GR largely IS the laws of physics now.

If you want to throw away GR by using a "Static Universe" theory, you have to re-derive a hundred different solutions to problems you bring back into physics by doing so. Einstein literally TRIED to put a static universe into GR because he thought it felt better, and turned out to be dead wrong!

In terms of "what drives the expansion", to us, within the universe, it's just what we see. It could very well be that it's a property of whatever "substrate" or "Stuff/emptyness" that a "Universe" exists in, if "exists" even makes sense in that context. It could be a completely unknowable to us thing. There are very likely phenomena and questions that we cannot ever answer, because we simply have no way of probing them.

All we know is that the way GR says to do the math works out really well for like 99.99% of things, and if you want to come up with a model that doesn't allow space to change "size", you have a shitload of math left to do at a minimum. If you want to understand how we got here, you have 400 years of physics history to read up on. None of this is about the "correctness" of GR either. It just makes the best predictions so far, and in science, all that matters is who makes the best predictions. Want to supersede the GR model? Just predict something correctly that GR cannot, while also predicting everything else correctly.


> If you want to throw away GR by using a "Static Universe" theory, you have to re-derive a hundred different solutions to problems you bring back into physics by doing so.

GR will be a special case in a new theory, which will explain laws of Universe better, which may join together GR and QM. If a formula does a good job, then it will be used anyway. We are not throwing away Newton physics just because GR does a better job in some cases.

> In terms of "what drives the expansion", to us, within the universe, it's just what we see.

Are you talking about a "light sail" effect? Yes, EM radiation creates pressure on dust particles, which pushes them away, but gravitation doesn't let it go. The same effect happens at size of galaxy. I'm not sure about superclusters, but it looks like we are falling into Great Attractor then into Shapley Attractor with all that dust.

So yes, this is possible, but EM radiation must be stronger than gravitation.

> It just makes the best predictions so far, and in science, all that matters is who makes the best predictions.

Predictions are very important, because they allow to prove or falsify a theory, but this is a game for theoretical physicists only. There is only one reality, which can be describer in many ways. Many different formulas can fit the same data. Many different techniques can be used to achieve the same result.

Moreover, every formula works in a range, then it doesn't work. Pi is an irrational number, which cannot be reproduced correctly in reality, thus every formula or path, which contains the irrational number, can be reproduced by physical reality with limited precision only. Multiply the error by many iterations, and new physics will emerge in the same place.

The only way to prove a theory, as I see it, is to make physical demonstrations at human scale, an analog, and then study it.

Hydrodynamic quantum analogs allows us to see pilot wave at work, so no mysteries in double slit experiment anymore: it just self-interference of the pilot wave. The same can be done for space effects.

It's easier to make computer model, to make predictions, but to make a correct model, we need to understand physics first. Egg and chicken. In case of a physical demonstration, nature performs all these calculations for free, automatically. Even when they are partially correct, they are still helpful.


> this is not an answer, because it breaks number of laws of physics, such conservation of energy

GR doesn't conserve energy. What follows is a bit beyond my level so I may be misremembering, but IIRC Noether's theorem is that conservation laws are always identical to some symmetries, and the symmetry for energy (time?) just isn't true in GR.

(I don't think it's even true in SR because space and time are observer dependent, but at least in SR you can get a different conserved quantity because all observers agree on a space-time interval; but as I implied in a different comment where I mentioned brilliant, this is my hobby not my profession).


> CMB is just light of distant galaxies. End of story.

The CMB is a perfect blackbody. Galaxies are far from a blackbody. Your explanation fails if one knows even a tiny amount about astronomy.

Before you criticize Big Bang cosmology, you should learn the theory. That means studying General Relativity, learning to derive the Friedmann Equations, learning about the (utterly overwhelming) observational evidence for the theory, etc. Then you'll be in a position to ask intelligent questions about the theory.

I promise you that if you learn the theory, you'll understand that the questions you're asking either don't make sense or have obvious answers. For example, conservation of energy does not hold in General Relativity. You keep saying that expansion is an ad hoc assumption that breaks physical laws. However, if you solve the Einstein Field Equations, you'll see that the universe must be either expanding or contracting. This fact bothered Einstein so much that he tried to modify General Relativity to get rid of it, something he regretted when observational evidence firmly established that the universe was indeed expanding. This was all the way back in the 1920s, and the evidence is so overwhelming now, a full century later, that it's impossible to deny.


> The CMB is a perfect blackbody. Galaxies are far from a blackbody.

CMB is not emitted by a single galaxy or even group of galaxies. It's light of trillions of supeclusters, like our Visible Universe, averaged. I expect that almost any local unevenness should be polished out when averaged over such large area and distance. We are not seeing stream of photons from individual emitters, we see random photons from extremely huge range of emitters at extremely huge range from us.

If clump together all radiation from all our Visible Universe into single stream of photons, then we will see something very similar.

> For example, conservation of energy does not hold in General Relativity.

Then something is wrong.


If you average a bunch of different types of galaxies, you do not get a blackbody.

Do you know what does give you a blackbody? An optically thick medium with a uniform temperature, which is what the CMB "last scattering surface" is.

I just have one question for you: do you think that physicists are all a bunch of dunces? You're doing extremely simple questions. Do you think that physicists haven't worked out the basics of the theory? Again, instead of raising extremely simple objections, your time would be better spent understanding the theory first.

>> For example, conservation of energy does not hold in General Relativity.

> Then something is wrong.

Energy conservation only holds locally, when space is nearly flat. The true conservation law in General Relativity is more complicated (energy-momentum conservation).


> If you average a bunch of different types of galaxies, you do not get a blackbody.

Black body averages emission of trillions of trillions of atoms. Why it will not work for emission of trillions of trillions of galaxies? Can you prove that?

> Energy conservation only holds locally, when space is nearly flat.

Space is flat in all directions.


> Black body averages emission of trillions of trillions of atoms. Why it will not work for emission of trillions of trillions of galaxies? Can you prove that?

No, that's not what a blackbody is. A blackbody is an optically thick medium in thermal equilibrium. Galaxies are not blackbodies (not even close), and when you average a bunch of non-blackbody spectra, you don't get a blackbody. You'll get a spectrum with all sorts of atomic and molecular features. There is actually something called the "Cosmic Infrared Background," which is caused by distant galaxies, but it's not a blackbody and it has much larger amplitude variations than the CMB (because galaxies are distributed in a clumpy way).

> Space is flat in all directions.

Globally, spacetime is not flat (i.e., it is not Minkowski). Spacelike surfaces of constant coordinate time are flat, but the whole manifold is not flat. If this is all a bunch of gobbledygook to you, then you need to learn the basics of General Relativity.


> A blackbody is an optically thick medium in thermal equilibrium.

Black body can be simulated by a cavity with small hole, so incoming light will be scattered and fully absorbed, with zero reflections. In case of CMB, light from our Visible Universe will never return back to us, because it will be too weak and too stretched.

Moreover, this is really big journey for a photon, with very high probability to hit something on the way to us, so we may see a large portion of re-emitted EM radiation instead of the original light.

What is the difference between black sky and black body?

> Galaxies are not blackbodies (not even close), and when you average a bunch of non-blackbody spectra, you don't get a blackbody. You'll get a spectrum with all sorts of atomic and molecular features.

Emission from multiple random objects can be approximated as black body radiation, even when they are not in thermal equilibrium with their surroundings.

Moreover, we use statistic to distinguish between different emitters. In case of CMB, years may pass until we receive second photon from a same galaxy. Statistic doesn't work in such extreme cases, unless we will point an antenna in the same direction for a millennia or even longer.

> There is actually something called the "Cosmic Infrared Background," which is caused by distant galaxies, but it's not a blackbody and it has much larger amplitude variations than the CMB (because galaxies are distributed in a clumpy way).

CIB emitted mostly by stars and dust particles, which are hit by the star light, which are much closer to us than CMB emitters. We may get different picture from outside of our galaxy, or when we filter out local emitters.

> Spacelike surfaces of constant coordinate time are flat, but the whole manifold is not flat.

You are talking about model. Can you map your model back to physical reality, please? As I understand, you are trying to tell me that a point in the non-flat space-timecan have less or more neighbourhood points that in flat space time. In other words, wormholes or space-bubbles are possible in your imagination.

> then you need to learn the basics of General Relativity.

I'm too stupid to understand this great theory. I need simple explanations.


> Moreover, this is really big journey for a photon, with very high probability to hit something on the way to us

Wrong. The universe is remarkably empty, and photons can easily travel across the entire visible universe without hitting anything.

> Emission from multiple random objects can be approximated as black body radiation

Wrong. There are very specific conditions for blackbody radiation. Other conditions give rise to different types of spectra, such as synchrotron radiation, Bremsstrahlung, etc.

You're making a lot of claims about how physics works that are simply false. Before making up your own alternate theories of physics, you should learn physics as it is presently understood.


> The universe is remarkably empty, and photons can easily travel across the entire visible universe without hitting anything.

The universe is remarkably empty, but any small probability can be multiplied by a really big number, to get ~1.

For a simplified example, the lowest density of interstellar space is 100 molecules per m3. The number of water molecules in water is 3.3E28. If a photon travel 3.5E10 light years (35Bly), then it's roughly equivalent to passing a 1m3 of water (by density, regardless of optical properties of the medium). 4Tly is a rough equivalent of 113 meters of water for such space. Most of this mass will be hydrogen molecules, of course.

> There are very specific conditions for blackbody radiation. Other conditions give rise to different types of spectra, such as synchrotron radiation, Bremsstrahlung, etc.

Dark sky is the perfect absorber. Bremsstrahlung spectrum will approach black body spectrum anyway as density increases.

Gray body is not real, as I see.


> Then something is wrong.

Yes, you.

(I suspect also GR, but not for any reason you give — the maths presumes no singularities from what I've been told, and yet they happen anyway with easy initial conditions).

For the broader point, if there were galaxies trillion of light years away whose light had time to reach us, they'd be trillions of years old by now, and therefore we'd expect a lot more galaxies near us to be that age too.

We don't see any evidence of nearby galaxies that old; denying the conclusion means falsifying the hypothesis.

Also, they'd have to go on forever to not look clumpy, and then we would still need a source of red-shift to stop them being as bright as the surface of a star in all directions.


> Yes, you.

I know that. I'm heretic. Moreover, I'm too stupid to understand all these great theories. I need simple explanations.

> For the broader point, if there were galaxies trillion of light years away whose light had time to reach us, they'd be trillions of years old by now, and therefore we'd expect a lot more galaxies near us to be that age too.

Of course, not. Space is mostly empty. If elementary particles are generated constantly from pure energy (which doesn't violate laws of conservation) just of pure luck at cosmic scale, then light from distant neighbors slowly pushed this newborn dust into the center of a gigantic void, where it started to concentrate. In such case, we will have huge gap of void between our region of space and our neighbors.

> Also, they'd have to go on forever to not look clumpy, and then we would still need a source of red-shift to stop them being as bright as the surface of a star in all directions.

Surface area of a distant object reduces at r^2, while brightness of the distant object diminishes at r^3. Moreover, the probability of hitting something grows with d^1, so total brightness diminishes with (d^3*d)/d^2 = d^2. The number of objects in the sky increases with area = d^2. So, d^2/d^2 = const. I see no infinity. At average, the brightness of sky must be very similar in all directions. The larger the distance - the closer to average brightness must be. CMB must be almost ideal.


> If elementary particles are generated constantly from pure energy (which doesn't violate laws of conservation) just of pure luck at cosmic scale, then light from distant neighbors slowly pushed this newborn dust into the center of a gigantic void, where it started to concentrate. In such case, we will have huge gap of void between our region of space and our neighbors.

Requires simultaneous behaviour from all directions at great distances while also not having that behaviour here, and also having us being really close to the physical center of this phenomenon rather than off to one side — even a fraction of a percent would be easily noticeable given the CMB is so close to the same in all directions; we see a red/blue-shift dipole from us moving at 370-ish km/s relative to it's comoving rest frame, so that's the scale of fractional away-from-perfect-centre you'd have to explain.

> Surface area of a distant object reduces at r^2, while brightness of the distant object diminishes at r^3.

If space was flat, which is your presumption, those would both be 1/r^2.

> Moreover, the probability of hitting something grows with d^1

You should be able to tell that's wrong by it being an unbounded function, when probability stops at 1.

You should look up Olber's paradox.


> If space was flat, which is your presumption, those would both be 1/r^2.

You forgot about red shift, which also diminishes the source, so, very very roughly, it's 1/r^3.

> Requires simultaneous behaviour from all directions at great distances while also not having that behaviour here, and also having us being really close to the physical center of this phenomenon rather than off to one side — even a fraction of a percent would be easily noticeable given the CMB is so close to the same in all directions; we see a red/blue-shift dipole from us moving at 370-ish km/s relative to it's comoving rest frame, so that's the scale of fractional away-from-perfect-centre you'd have to explain.

When we are in a fog, we always in the center of the visible area. With such larger distances, the probability of hitting something for a photon is very near to 1, even when interstellar space is extremely clear (hard to calculate exact numbers for me).

> You should be able to tell that's wrong by it being an unbounded function, when probability stops at 1.

When we see direct light, then probability is below 1. When don't, then it's 1. :-/

> You should look up Olber's paradox.

You should look at the picture of the darkest spot on the sky: it's full of stars. :-/

https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field


> Nobody pointed to a source of energy for this "expansion" of "space".

Several have been made, the suggestions have issues.

> Usually, coordinate system doesn't expand with time.

Define "usually". Do you have experience of other universes?

> An extraordinary claim requires extraordinary evidence.

Indeed, but this comment box is too small to do the evidence justice.

Edit: that's unhelpful in retrospect, so I suggest the Youtube channel "PBS Space Time". The videos build on each other, so start at the beginning and work through the back catalogue.

> Yes, CMB emitters are much further away, at a distance of about 4Tly,

I have no idea where you got this belief from.


> Define "usually". Do you have experience of other universes?

I have experience with coordinate systems. I can bend or expand space-time on my computer all day long, to simulate reality, but I cannot do that in the real world at all.

> Indeed, but this comment box is too small to do the evidence justice.

Looking for the paper or a blog post! However, I suspect that you will just stretch evidence until it will match your model.

> I have no idea where you got this belief from.

Just by looking in the window, I see that some object are close, other are far away, then even further away, and so on, up to 4Tly. Nothing extraordinary. No Big Bangs, no FTL speeds, no hidden sources of energy of epic size, just ordinary physics.


> I cannot do that in the real world at all

Sure you do, just by sitting there.

Reminds me a bit of my dad; he did radar simulation for military IFF and one of his work anecdotes was about increasing the number of decimal(!) digits of pi the software used.

He stopped boasting about that when I pointed out the extra digits were less relevant than the curvature of spacetime caused by Earth itself.

> Just by looking in the window, I see that some object are close, other are far away, then even further away, and so on, up to 4Tly

I had dreams like that once. Woke up to find I was suffering from testicular torsion.

If you seriously believe you can see 4e12 light years through your window, that's probably hallucinogens of some kind (not necessarily intentional).


> Sure you do, just by sitting there.

I 100% sure that I cannot bend or stretch imaginary coordinate system outside of my imagination. Can you point to real physical process which causes stretching or bending of the mathematical abstraction?

> If you seriously believe you can see 4e12 light years through your window, that's probably hallucinogens of some kind (not necessarily intentional).

I cannot see objects smaller than a star or galaxy with naked eye. However, we can see light stretched to the microwave range.


> Can you point to real physical process which causes stretching or bending of the mathematical abstraction?

"General relativity" as we keep telling you.

> I cannot see objects smaller than a star or galaxy with naked eye.

Only a factor of about a trillion in the size of those two things.

> However, we can see light stretched to the microwave range.

With your eyes? No. And certainly not through your window, whose own thermal emissions relative to the CMB makes your previous claim roughly as unphysical as saying you can look through the sun's photosphere to see Jupiter during an occultation.


General Relativity is a mathematical model. Model needs mapping between physical world and model.


My phone's GPS only works because that mapping keeps being better than anything else we've tested on that scale.

The atomic clocks (as I mentioned in another comment) demonstrating gravitational time dilation within a building is another fun example.


Your phone works because engineers did it.

I see strong annual signal in GPS: https://link.springer.com/article/10.1007/s10291-017-0686-6 .

Why it there?


> Your phone works because engineers did it.

The engineers implemented results from GR.

> Why it there?

Not that it matters, but the answer is in the introduction.


> ~300M years is the time between the Big Bang singularity and the CMB, but not really relevant.

Nobody else has pointed out my mistake here, the time between them is ~380ky not ~300My. My bad.


> a transition somewhere

A transition from what to what?

> which is not the case.

Why not?

> Sometimes, somewhere there must be a galaxy past CMB.

If there is we'd have to wait for the light from it to get to us, by which time the CMB will have receded further and it would then be in front of the CMB.


> A transition from what to what?

A transition from plasma to the cold mater in the form of galaxies we see.

> Why not?

As you see, there are big clusters everywhere. It means that some regions were cooler from the start, to form these cluster in so short period of time. It means that regions around them were hotter, thus they should emit light longer.

> If there is we'd have to wait for the light from it to get to us, by which time the CMB will have receded further and it would then be in front of the CMB.

300My is a short period of time. Why they cannot sometimes overlap?




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