Merged: Why the James Webb Telescope rewrites/doesn't the laws of Physics/Redshifts

[Mike Helland]

Originally Posted by Ziggurat

Yes it is. It's a linear approximation of t(b).

t = - b/H₀ is linear. Sure.

What makes you say it's an approximation?

What dataset of b's are you comparing it to?

[Ziggurat]

Originally Posted by Mike Helland

t = - b/H₀ is linear. Sure.

What makes you say it's an approximation?

Because that's the only justification for it. Otherwise, it comes from nowhere.

[Mike Helland]

Originally Posted by Ziggurat

Because that's the only justification for it. Otherwise, it comes from nowhere.

It comes from two places.

(1)

Quantify redshift as negative blueshift:

1+b = Eobs / Eemit

With that available, using the traditional redshift distance relationship as inspiration, we may conjecture distance and time relationships, such as:

t = -b / H0

This doesn't come from nowhere. It's just using negative blueshift where redshift has already been tried.

(2)

The lookback time in FLRW is:



Which reduces to:



When gravity doesn't affect redshifts.

That z/(1+z) is equal to -b.

t = -b / H₀

[Ziggurat]

Originally Posted by Mike Helland

With that available, using the traditional redshift distance relationship as inspiration, we may conjecture distance and time relationships, such as:

t = -b / H0

This doesn't come from nowhere. It's just using negative blueshift where redshift has already been tried.

Instead of being absolutely certain that this is a valid low-b first-order approximation, you instead only "conjecture" that it might work, which is worse and even less justified.

You really don't understand math at all.

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(2)

The lookback time in FLRW is:

The universe isn't empty. There is no justification for using a result for an empty universe to describe a universe that is observably not empty.

You think you've done more than I said, but you actually did less, and you don't even understand that you did less because, again, you don't know any math.

[Mike Helland]

Originally Posted by Ziggurat

Instead of being absolutely certain that this is a valid low-b first-order approximation, you instead only "conjecture" that it might work, which is worse and even less justified.

You're confusing what I think and what the hypothesis says.

Quote:

The universe isn't empty. There is no justification for using a result for an empty universe to describe a universe that is observably not empty.

True.

Let's say a galaxy has z=1 in a universe 14 billion years old.

Using the broken z-distance relationship we could say:

d = zc / H₀
d = (1)c / H₀

And the broken z-velocity relationship we could say:

v = H₀d
v = H₀ (c / H₀)
v = c

Let's see how negative blueshift goes. First convert z=1 to b.

1 + b = 1 / (1 + z)
1 + b = 1 / (1 + 1)
b = 1 / 2 - 1
b = -0.5

Let's try the distance relationship with that.

d = -bc / H₀
d = -(-0.5)c / H₀
d = c / 2H₀

Let's try the velocity relationship with that:

v = H₀d
v = H₀ (c / 2H₀)
v = c / 2

Hey, that seems a bit more reasonable.

Due to the distance of a z=1 galaxy in an expanding universe, its recessional velocity is half the speed of light, or about 150,000 km/s, according to my negative blueshift relationships.

This applies to every galaxy at that distance from us.

Now, I realize the universe isn't empty.

But am I correct in that you are suggesting that gravity is causing every galaxy in the universe (edit: where z ≥ 1) to be pulled toward us at speeds that take a noticeable chunk out of c/2?

If you applied Newtonian gravity, it would not be noticed, and have no affect on redshifts.

FLRW gets the results it does by imagining the universe as a single swimming pool with pure water and nothing else.

[Ziggurat]

Originally Posted by Mike Helland

You're confusing what I think and what the hypothesis says.

No. That statement is a purely mathematical statement, it is independent of the physics.

[Mike Helland]

Originally Posted by Ziggurat

No. That statement is a purely mathematical statement, it is independent of the physics.

Hmmm. Are all these independent of physics too?

1 + z = E_emit / E_obs

1 + b = E_obs / E_emit

t = z / H₀

t = -b / H₀

t = z / (1 + z) * 1 / H₀

[Ziggurat]

Originally Posted by Mike Helland

Hmmm. Are all these independent of physics too?

1 + z = E_emit / E_obs

1 + b = E_obs / E_emit

These are just definitions, so yes.
.

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t = z / H₀

t = -b / H₀

I already told you: these are just first order Taylor series approximations. They are model independent for low z and b. All they require is that t(0) = 0, and that t be differentiable. That's a bit physics related, but trivially so since these conditions are always met for any model of interest. Otherwise it's just pure math.

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t = z / (1 + z) * 1 / H₀

Likewise.

I've said all this before. That you still don't grasp it is just the latest example of your incomprehension of the math involved.

[Mike Helland]

Originally Posted by Ziggurat

These are just definitions, so yes.

1 + z = E_emit / E_obs is independent of physics.

Ok...

How about E=mc²?

Is that just a definition that's independent of physics?

If no, what's different about it?

[Ziggurat]

Originally Posted by Mike Helland

1 + z = E_emit / E_obs is independent of physics.

Ok...

Yes. It's just the purely mathematical definition of what z means. You don't need any physics to establish that relationship.

Quote:

How about E=mc²?

Is that just a definition that's independent of physics?

No. All quantities in that equation are independently defined. Einstein didn't come up with the concept of any of them. The truth of that statement depends directly on the physics involved. And in fact, it's false if the mass in question isn't at rest.

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If no, what's different about it?

I just told you, but it should have been obvious.

The relativistic definition for gamma is just math, but E=mc² is not. This should have been obvious stuff. The fact that it isn't is just the latest example of how out of your depth you are. You do not have any of the intellectual tools you need to understand these subjects, let alone propose any coherent models of such.

[Mike Helland]

Originally Posted by Ziggurat

No. All quantities in that equation are independently defined. Einstein didn't come up with the concept of any of them.

E = mc²

E is energy
m is mass
c is the speed of light

to the power of 2 (just math?)

That's not independent of physics.

1 + z = E_obs / E_emit

z is redshift
E_obs is energy observed
E_emit is energy emitted

plus 1 (just math?)

That is independent of physics?

I didn't come up with any of those things. Neither did Hubble, as far as I know.

Oh well. You skipped this:

But am I correct in that you are suggesting that gravity is causing every galaxy in the universe (edit: where z ≥ 1) to be pulled toward us at speeds that take a noticeable chunk out of c/2?

I also notice that z=1 according to this calculator:

https://cosmocalc.icrar.org/

corresponds to a recessional velocity of 0.771427c. Even in an "empty" universe its 0.693147c. Quite a bit off from my 0.5c.

Without dark energy, the effects of gravity seems to take about 10% out of expansion's sails, which means, at 7 billion light years away, gravity is causing z=1 galaxies from all directions to move toward us at 23,000 km/s.

We then use as much dark energy as needed to push them away at the same amount.

That's all fun and interesting to think about. But if you used Newtonian gravity, you'd find galaxies won't be rushing toward us at 7% the speed of light from 7 billion light years away. It won't have any affect on them, which means dark energy isn't required to counteract it.

[Ziggurat]

Originally Posted by Mike Helland

E = mc²

E is energy
m is mass
c is the speed of light

to the power of 2 (just math?)

That's not independent of physics.

Yes. Because all those quantities are independently defined. The statement is only true under certain rules of physics.

Quote:

1 + z = E_obs / E_emit

z is redshift
E_obs is energy observed
E_emit is energy emitted

plus 1 (just math?)

That is independent of physics?

Yes, because that defines what z means. It has no independent definition. It is automatically true, under any rules of physics, because it's a definition.

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I didn't come up with any of those things. Neither did Hubble, as far as I know.

It doesn't matter who came up with it.

Quote:

Oh well. You skipped this:

I have no interest in trying to figure that out. You failed at such a basic and definitional level, that there's really no point in trying to look at anything more complicated.

Quote:

That's all fun and interesting to think about. But if you used Newtonian gravity, you'd find galaxies won't be rushing toward us at 7% the speed of light from 7 billion light years away. It won't have any affect on them, which means dark energy isn't required to counteract it.

We know Newtonian gravity is wrong. So why does it matter what would happen in a hypothetical which is demonstrably false?

This is why spending any serious effort analyzing your thoughts is a complete waste of time. You can't get even the basics right. You don't know any physics, and you don't know any math.

[Mike Helland]

Originally Posted by Ziggurat

Yes, because that defines what z means. It has no independent definition. It is automatically true, under any rules of physics, because it's a definition.

Then it would be z≡... but that's not actually the case:



https://en.wikipedia.org/wiki/Redshi...shift_formulae

Quote:

We know Newtonian gravity is wrong. So why does it matter what would happen in a hypothetical which is demonstrably false?

In high gravity situations like the orbit of Mercury.

We don't use GR for the (edit: other) planets or the stars.

It's a bit of fun and curiosity to apply to galaxies and the universe as a whole. But I wouldn't believe in it wholesale.

[Ziggurat]

Originally Posted by Mike Helland

Then it would be z≡... but that's not actually the case:

Wow. That's stupid.

Not everyone always uses that notation.

Quote:

In high gravity situations like the orbit of Mercury.

We don't use GR for the (edit: other) planets or the stars.

Yes, we do. Not always, but you clearly don't understand where and how GR is applicable.

Quote:

It's a bit of fun and curiosity to apply to galaxies and the universe as a whole. But I wouldn't believe in it wholesale.

You don't need to. That's not even the point. The point is that we know Newtonian gravity is wrong, and that GR is more accurate. There are lots of cases where it makes sense to use Newtonian gravity because it will give the same results as GR and it's easier to calculate. There are no cases where it makes sense to use Newtonian gravity because GR is wrong. That's not how any of this works.

You are out of your depth.

[Mike Helland]

Originally Posted by Ziggurat

There are no cases where it makes sense to use Newtonian gravity because GR is wrong. That's not how any of this works.

Does Newtonian gravity predict an infinite field of galaxies will collapse on itself?

It seems the forces from all directions start to cancel out at some distance.

Does GR predict an infinite field of galaxies will collapse on itself?

Yes it does.

What's to say that Newton isn't right in that domain of extreme distances between objects, and that FLRW's treatment of space as a perfect fluid that doesn't have bodies separated distances is not right?

[Ziggurat]

Originally Posted by Mike Helland

Does Newtonian gravity predict an infinite field of galaxies will collapse on itself?

Basically, yes. An infinite field of galaxies is not stable. Galaxies will clump up over time.

Quote:

It seems the forces from all directions start to cancel out at some distance.

Only if it was perfectly uniform, which it obviously isn't. See the irony below.

Quote:

Does GR predict an infinite field of galaxies will collapse on itself?

Yes it does.

No, actually, it doesn't. The universe could collapse on itself, or it could expand forever. In fact, you need a finite universe (closed), not an infinite one (open), in order to collapse on itself.

We should expect local collapse, and guess what, that's what we observe.

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What's to say that Newton isn't right in that domain of extreme distances between objects,

Gravitational waves, for one. They are GR, not Newtonian, and we detect them from up to 17 billion light years away. Again, we know Newtonian gravity is wrong. If you don't trust GR at very long distances, fine (though you are in no position to propose any alternative, or even a sensible objection). But it makes no sense to appeal to a theory we know is wrong to replace a theory we have no evidence is wrong.

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and that FLRW's treatment of space as a perfect fluid that doesn't have bodies separated distances is not right?

This is ironic. You criticize the approximation of uniformity, but you use it yourself when claiming that Newtonian gravity would cancel on cosmological scales. It won't, because it isn't. And unlike GR, since your Newtonian universe would be eternal, you can't even appeal to finite time to prevent local collapse from having already merged the Milky Way with Andromeda, for example.

[Mike Helland]

Originally Posted by Ziggurat

No, actually, it doesn't. The universe could collapse on itself, or it could expand forever.

Einstein showed that GR could predict the orbit of Mercury in 1916.

The Friedmann equations were published in 1922.

LCDM is based on FLRW which is based on GR.

If there's a problem with LCDM, that doesn't mean FLRW is at fault.

And if there's a problem with FLRW, that doesn't mean GR is at fault.

GR has been experimentally verified using metrics that existed before FLRW was devised. That doesn't give FLRW a free pass as an accurate description of the universe however.

In those pre-Friedmann metrics there was no scale factor and no expansion of space.

The orbit of Mercury, or the creation of a black hole are predicted by models that don't have the expansion of space.

[W.D.Clinger]

So long as we're listing predictions that don't have anything to do with the subject of this thread, I'll play along...but only to emphasize the irrelevance of Mike Helland's attempts to distract us from the subject of this thread.

Originally Posted by Mike Helland

The orbit of Mercury, or the creation of a black hole are predicted by models that don't have the expansion of space.

Similarly, James Clerk Maxwell predicted the existence of radios waves based upon a model that doesn't have anything to do with red shifts or expansion of the universe.

Dmitri Mendeleev predicted the existence of scandium, gallium, technetium, and germanium based upon a model that doesn't have anything to do with red shifts or expansion of the universe.

Edmond Halley predicted the return of (what is now known as) Halley's comet based upon a model that doesn't have anything to do with red shifts or expansion of the universe.

In the context of this thread, all of those predictions are every bit as irrelevant as the predictions cited by Mike Helland. The fact that unrelated predictions have been made should not distract us from predictions that are relevant to this thread. Of greatest relevance to this thread are certain predictions based upon general relativity, notably:

• the big bang
• an expanding universe
• the cosmic microwave background

General relativity has of course predicted many other interesting phenomena, such as black holes, gravitational lensing, gravitational waves, gravitational time dilation (which GPS takes into account), and so on, but those predictions are relevant to this thread mainly because their success makes it much harder to reject general relativity and its predictions (such as those listed above) that are directly relevant to this thread.

Mike Helland wants to distract us by talking about predictions that don't have anything to do with this thread, apparently because he hasn't been able to sustain a coherent argument against the relevant predictions made by GR.

[Mike Helland]

Originally Posted by W.D.Clinger

So long as we're listing predictions that don't have anything to do with the subject of this thread, I'll play along...but only to emphasize the irrelevance of Mike Helland's attempts to distract us from the subject of this thread.

....

Mike Helland wants to distract us by talking about predictions that don't have anything to do with this thread, apparently because he hasn't been able to sustain a coherent argument against the relevant predictions made by GR.

Lol. Ok, buddy.

I don't have a problem with GR or Einstein or whatever it is you think I'm saying.

[Ziggurat]

Originally Posted by Mike Helland

Einstein showed that GR could predict the orbit of Mercury in 1916.

The Friedmann equations were published in 1922.

LCDM is based on FLRW which is based on GR.

If there's a problem with LCDM, that doesn't mean FLRW is at fault.

And if there's a problem with FLRW, that doesn't mean GR is at fault.

GR has been experimentally verified using metrics that existed before FLRW was devised. That doesn't give FLRW a free pass as an accurate description of the universe however.

In those pre-Friedmann metrics there was no scale factor and no expansion of space.

The orbit of Mercury, or the creation of a black hole are predicted by models that don't have the expansion of space.

None of this has anything to do with justifying using Newtonian gravity for cosmology.

[Mike Helland]

Originally Posted by Ziggurat

None of this has anything to do with justifying using Newtonian gravity for cosmology.

GR is more accurate than Newtonian gravity.

That doesn't mean FLRW is a more accurate description of the universe than Newtonian gravity.

That's all I was saying. Questioning LCDM and even FLRW isn't the same thing as trying to overthrow GR.

[Mike Helland]

Regarding the expansion rate of the universe, and how it changes:

"Yes, dark energy is real. Yes, distant galaxies recede faster and faster as time goes on. But the expansion rate isn't accelerating at all. "

https://bigthink.com/starts-with-a-b...-accelerating/

Quote:

Over time, the Universe expands: a region of space that takes up a certain volume today will, tomorrow, expand to take up a larger amount of volume. The matter and radiation within it has a constant number of particles, but as the volume increases, the density drops. Dark energy is different though; it has a constant energy density, so even as the volume increases and the Universe expands, its density doesn’t drop.

Because the expansion rate is always proportional to the square root of the total energy density (from all the different components, combined), a Universe made solely of radiation, normal matter, and dark matter will eventually see its expansion rate drop to zero, and that corresponds to a distant galaxy, over time, receding from us slower and slower, and we’d also see its redshift decreasing with time.

But in a Universe that also has dark energy — our Universe — even as the radiation, normal matter, and dark matter densities drop to zero, the dark energy density will always maintain that same constant value. Because the square root of a constant is still a constant, that means the expansion rate won’t drop to zero, but rather will only drop to some finite, positive, greater-than-zero value.

In a universe where gravity doesn't affect redshifts (eg. an "empty" FLRW universe), the density of the universe's various ingredients never changes, meaning Hubble's constant is static.

That's why t = H₀^-1 z/(1+z) doesn't actually need the subscript 0.

[Ziggurat]

Originally Posted by Mike Helland

In a universe where gravity doesn't affect redshifts (eg. an "empty" FLRW universe), the density of the universe's various ingredients never changes, meaning Hubble's constant is static.

That's why t = H₀^-1 z/(1+z) doesn't actually need the subscript 0.

Again, so what? I asked this before, and you never answered.

We don't live in any empty universe. Counter-factual hypotheticals aren't relevant.

[Mike Helland]

Originally Posted by Ziggurat

Again, so what? I asked this before, and you never answered.

We don't live in any empty universe. Counter-factual hypotheticals aren't relevant.

We also don't live in a perfect fluid.

The empty universe is an example of a universe where gravity doesn't affect redshift.

My answer to your question was, do you really suggest that gravity is accelerating z-1 galaxies from all directions toward us at 7% the speed of light, enough to significantly affect redsdhifts?

[Ziggurat]

Originally Posted by Mike Helland

We also don't live in a perfect fluid.

And cows aren't spheres. So what? You made a perfect fluid assumption yourself when you said an infinite Newtonian universe shouldn't collapse because forces should all cancel.

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The empty universe is an example of a universe where gravity doesn't affect redshift.

But it's not our universe. So why does it matter?

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My answer to your question was, do you really suggest that gravity is accelerating z-1 galaxies from all directions toward us at 7% the speed of light, enough to significantly affect redsdhifts?

Your question makes no sense. You are giving me a value of speed as if it was an acceleration, but speed and acceleration are not the same. They aren't even dimensionally equivalent (like torque and energy). It's like asking if a rock weights 300 Kelvin. And it's just the latest example of you not knowing what the hell you're talking about.

[Mike Helland]

Originally Posted by Ziggurat

But it's not our universe. So why does it matter?

It's just one example of a universe where gravity doesn't affect redshift.

It's not the universe I'm suggesting we live in.

Quote:

Your question makes no sense. You are giving me a value of speed as if it was an acceleration, but speed and acceleration are not the same. They aren't even dimensionally equivalent (like torque and energy). It's like asking if a rock weights 300 Kelvin.

Lol.

If an object's velocity toward us increases, that's acceleration.

[Ziggurat]

Originally Posted by Mike Helland

It's just one example of a universe where gravity doesn't affect redshift.

Again, so what?

Quote:

If an object's velocity toward us increases, that's acceleration.

I don’t think you really understand your mistake.

[W.D.Clinger]

Originally Posted by Mike Helland

In a universe where gravity doesn't affect redshifts (eg. an "empty" FLRW universe), the density of the universe's various ingredients never changes, meaning Hubble's constant is static.

That's why t = H₀^-1 z/(1+z) doesn't actually need the subscript 0.

That's a truly remarkable claim.

As those who have been reading this thread should recall, Mike Helland has repeatedly called our attention to the fact that the Helland equation

t = H₀^-1 z/(1+z)

coincides with the mainstream equation for an FLRW model in which the universe is entirely empty of matter, radiation, and dark energy but possesses a negative curvature that is at least hundreds of times greater than would be consistent with observations of the cosmic microwave background (as interpreted by mainstream physics, of course). In that FLRW model, the value of the Hubble parameter changes over time according to the equation

H(t₁) = H₀ (1 + z)

where t₁ is the time at which photons with redshift z were emitted.

As quoted above and previously, however, Mike Helland tells us that, according to Helland physics, the value of the Hubble parameter does not change over time. That is how we were finally able to confirm that Helland physics is not consistent with mainstream physics.

And so:

• Hubble physics postulates an equation for time that is precisely the same as the equation for time in an FLRW model for a completely empty universe that has exactly the right amount of negative curvature to add up to the critical density.
• Hubble physics postulates that the Hubble parameter is constant, contrary to the time-varying equation for the Hubble parameter in that very same FLRW model.

That's quite a coincidence, don't you think? It's almost as though Mike Helland is trying to force a choice between mainstream physics based on general relativity (which predicted red shifts and the cosmological microwave background radiation) and Helland physics (which did not predict and has no explanation for red shifts or the CMB).

[Mike Helland]

Originally Posted by W.D.Clinger

As quoted above and previously, however, Mike Helland tells us that, according to Helland physics, the value of the Hubble parameter does not change over time.

That's right.

The Hubble parameter is proportional to the density of the universe. As it expands, it becomes less dense, and the expansion rate goes down.

If the universe were empty, the expansion rate would stay the same.

If the universe were not empty, but the stuff in it didn't affect redshifts, the expansion rate would also stay the same.

Quote:

[*]Hubble physics postulates an equation for time that is precisely the same as the equation for time in an FLRW model for a completely empty universe that has exactly the right amount of negative curvature to add up to the critical density.

I don't think that's right. The empty FLRW would be open, far below critical density.

[Ziggurat]

Originally Posted by Mike Helland

If the universe were not empty, but the stuff in it didn't affect redshifts, the expansion rate would also stay the same.

If frogs had wings, they wouldn’t bump their ass when they hopped.

Counter-factuals are of little interest.

[Mike Helland]

Originally Posted by Ziggurat

Counter-factuals are of little interest.

What facts are you referring to?

[arthwollipot]

Originally Posted by Mike Helland

What facts are you referring to?

counterfactual
/ˌkaʊntəˈfaktʃʊəl/
adjective
relating to or expressing what has not happened or is not the case

[Guybrush Threepwood]

Originally Posted by W.D.Clinger

That's a truly remarkable claim.

As those who have been reading this thread should recall, Mike Helland has repeatedly called our attention to the fact that the Helland equation

t = H₀^-1 z/(1+z)

coincides with the mainstream equation for an FLRW model in which the universe is entirely empty of matter, radiation, and dark energy but possesses a negative curvature that is at least hundreds of times greater than would be consistent with observations of the cosmic microwave background (as interpreted by mainstream physics, of course). In that FLRW model, the value of the Hubble parameter changes over time according to the equation

H(t₁) = H₀ (1 + z)

where t₁ is the time at which photons with redshift z were emitted.

As quoted above and previously, however, Mike Helland tells us that, according to Helland physics, the value of the Hubble parameter does not change over time. That is how we were finally able to confirm that Helland physics is not consistent with mainstream physics.

And so:

• Hubble physics postulates an equation for time that is precisely the same as the equation for time in an FLRW model for a completely empty universe that has exactly the right amount of negative curvature to add up to the critical density.
• Hubble physics postulates that the Hubble parameter is constant, contrary to the time-varying equation for the Hubble parameter in that very same FLRW model.

That's quite a coincidence, don't you think? It's almost as though Mike Helland is trying to force a choice between mainstream physics based on general relativity (which predicted red shifts and the cosmological microwave background radiation) and Helland physics (which did not predict and has no explanation for red shifts or the CMB).

Too late to fix I know, but shouldn't those two bullet point references to Hubble physics be to Helland physics?

[W.D.Clinger]

Originally Posted by Guybrush Threepwood

Too late to fix I know, but shouldn't those two bullet point references to Hubble physics be to Helland physics?

Oh, yes. Thank you for correcting me.

[W.D.Clinger]

Originally Posted by Mike Helland

Originally Posted by W.D.Clinger

As quoted above and previously, however, Mike Helland tells us that, according to Helland physics, the value of the Hubble parameter does not change over time.

That's right.

The Hubble parameter is proportional to the density of the universe.

Actually, the Hubble parameter is proportional^* to the cube root of the density of the universe, and directly proportional to the rate of change of the scale factor. Here is the actual definition of the Hubble parameter:

H(t) = ȧ(t) / a(t)

^*The density of the universe is inversely proportional to the cube of the scale factor if we assume the total amount of matter, radiation, dark energy (et cetera) remain constant over time, which is a questionable but reasonable assumption unless we're talking about periods of time that are not just astronomical but cosmological.

Originally Posted by Mike Helland

As it expands, it becomes less dense, and the expansion rate goes down.

In most models, yes. Not in all.

Originally Posted by Mike Helland

If the universe were empty, the expansion rate would stay the same.

In the specific FLRW model for which the Helland equation holds, ȧ(t) is indeed a constant. The universe described by that model is expanding, however, so the Hubble parameter is not a constant; it changes over time as described by the equation

H(t₁) = H₀ (1 + z)

where t₁ is the time at which photons with redshift z were emitted, and H₀ is the value of the Hubble parameter at the present day.

Originally Posted by Mike Helland

If the universe were not empty, but the stuff in it didn't affect redshifts, the expansion rate would also stay the same.

That may be an axiom of Helland physics, but a universe that contains stuff that doesn't affect red shifts would contradict general relativity at a very basic level. (With his sentence above, Mike Helland is implicitly (and probably inadvertently) admitting that Helland physics is incompatible with general relativity.)

Originally Posted by Mike Helland

Quote:

[*]Hubble physics postulates an equation for time that is precisely the same as the equation for time in an FLRW model for a completely empty universe that has exactly the right amount of negative curvature to add up to the critical density.

I don't think that's right. The empty FLRW would be open, far below critical density.

In the only FLRW model for which the Helland equation holds in an empty universe, the curvature parameter is Ω_k=1, implying a degree of negative curvature that is hundreds of times greater than would be consistent with observations.

Mike Helland apparently didn't realize that Ω_k=1 in that model, because he didn't understand Cappi's paper and also didn't notice that Cappi's computer code automatically calculated its value for the curvature parameter by subtracting the sum of the other density parameters from 1 (the critical density). In other words, Cappi's calculator assumed the sum of the density parameters would equal the critical density, because observations imply that sum must be very close to the critical density.

It looks as though Mike Helland is determined never to notice that important fact, probably because it undermines whatever credibility he believed would accrue from the existence of an FLRW model in which his Helland equation holds.

In reading what Mike Helland says above about the "expansion rate", I wonder whether Mike Helland even realizes that a constant but nonzero expansion rate implies the universe is expanding (or shrinking).

[Mike Helland]

Originally Posted by W.D.Clinger

That may be an axiom of Helland physics, but a universe that contains stuff that doesn't affect red shifts would contradict general relativity at a very basic level.

Using:

https://cosmocalc.icrar.org/

At z=1, in an empty universe, recessional velocity is:

v = 0.693147 c.

Now, let's fill the universe with matter, Ω_M=1. How does that affect recessional velocity:

v = 0.585786 c

So at z=1, a galaxy is receding away from us at 69% the speed of light.

But with gravity, it only moves at 58% the speed of light.

Which means that gravity is causing galaxies at z=1 (with a lookback time of 7.5 billion years, and a comoving distance of 10 Gly) to move toward us at 11% the speed of light.

Agreed?

Quote:

In the only FLRW model for which the Helland equation holds in an empty universe, the curvature parameter is Ω_k=1, implying a degree of negative curvature that is hundreds of times greater than would be consistent with observations.

It's only hundreds of times greater if the measurements are at the end of their error bars.

The measured value is actually thousands of times off, and the expected value (zero curvature) is of course infinitely far off.

You also keep saying "observations", but really it's just the value determined by CMB measurements. Unless there are other ways to observe the curvature of the universe.

[W.D.Clinger]

Originally Posted by Mike Helland

Originally Posted by W.D.Clinger

That may be an axiom of Helland physics, but a universe that contains stuff that doesn't affect red shifts would contradict general relativity at a very basic level.

Using:

https://cosmocalc.icrar.org/

That's a different calculator that, like Cappi's, automatically calculates the curvature parameter by subtracting the sum of the other density parameters from 1

In Mike Helland's words quoted below, he uses that calculator to confirm my statement above. Does he even realize he is confirming what I wrote?

Originally Posted by Mike Helland

At z=1, in an empty universe, recessional velocity is:

v = 0.693147 c.

Let's not forget that the negative curvature of that empty universe is at least hundreds of times any curvature that could be consistent with observations of the CMB.

For future reference, let's also note that the lookback time (as calculated by the calculator Mike Helland is now citing) is almost 7 billion years.

Originally Posted by Mike Helland

Now, let's fill the universe with matter, Ω_M=1. How does that affect recessional velocity:

v = 0.585786 c

Let's not forget that the universe with Ω_M=1 has no curvature at all.

Let's also note that the lookback time (as calculated by the calculator Mike Helland is now citing) is just a shade over 6 billion years.

So the "stuff" Mike Helland put into the model universes by going from Ω_M=0 to Ω_M=1 did affect the red shifts.

If I tell Mike Helland's chosen calculator to keep the lookback time at 7 billion years as we go from Ω_M=0 to Ω_M=1, that calculator tells us the red shift z goes from z=1 to about z=1.52.

So the calculator agrees that adding "stuff" does indeed affect red shift, contrary to Helland physics.

This is in a spoiler because it looks like a red herring to me, but I think I'd better explain why I disagree lest Mike Helland assume I have agreed with the mistake he's making here.

Originally Posted by Mike Helland

So at z=1, a galaxy is receding away from us at 69% the speed of light.

But with gravity, it only moves at 58% the speed of light.

Which means that gravity is causing galaxies at z=1 (with a lookback time of 7.5 billion years, and a comoving distance of 10 Gly) to move toward us at 11% the speed of light.

Agreed?

No. I do not agree that galaxies that are receding from us at 58% of the speed of light are at the same time moving toward us at 11% of the speed of light.

Unless Mike Helland insists that -0.58c is equal to 0.11c, I'm going to assume he simply misspoke.

[Mike Helland]

Originally Posted by W.D.Clinger

Let's not forget that the negative curvature of that empty universe is at least hundreds of times any curvature that could be consistent with observations of the CMB.

Nobody is forgetting that.

Quote:

No. I do not agree that galaxies that are receding from us at 58% of the speed of light are at the same time moving toward us at 11% of the speed of light.

Lol. Obviously that's not what I said.

In the empty model they move 0.69 c away from us.

In the model with matter, they move 0.58 c away from us.

This tells me that their motion is 0.69 c away (due to expansion) and 0.11 c toward us (due to gravity), since 0.69 - 0.58 = 0.11.

[steenkh]

Originally Posted by Mike Helland

This tells me that their motion is 0.69 c away (due to expansion) and 0.11 c toward us (due to gravity), since 0.69 - 0.58 = 0.11.

Can you really take two different models, subtract their results from each other, and get a meaningful result?

[Mike Helland]

Originally Posted by steenkh

Can you really take two different models, subtract their results from each other, and get a meaningful result?

Let's say no.

How do you determine the affect of gravity on redshifts and what result do you get?

(edit: for what it's worth, the only difference between the models is the matter parameter.)