Cont: Why James Webb Telescope rewrites/doesn't the laws of Physics/Redshifts (2)

[Mike Helland]

It helps to read what I wrote. What I wrote is

Your metric describes a static universe that is incompatible with general relativity​

In other words, your metric proclaims itself to be static, but that claim places your metric at odds with general relativity, which says a universe with the pressures implied by your metric would not be static.

I see you've managed to spin the peanut gallery in circles with your latest "it isn't static"/"it is static" flip-flopping.

Here's a better question.

If comoving coordinates are just a map to the territory, what does the FLRW proper coordinates map look like?

Whatever it is, I'm pretty sure it has to wind up as:

http://latex.codecogs.com/gif.latex?\frac{dx}{dt} = c - H(t) x(t)​

 

[W.D.Clinger]

I see you've managed to spin the peanut gallery in circles with your latest "it isn't static"/"it is static" flip-flopping.

It must be tough to be cruising giddily along, blithely thinking you're the expert, and then you discover you're the only one in the room who doesn't understand what is being said.

He read what you wrote. And the[n] he removed the rather important stuff that he didn't understand before making a rather inane comment about the irrelevant bits that he quoted.

 

[Mike Helland]

It must be tough to be cruising giddily along, blithely thinking you're the expert, and then you discover you're the only one in the room who doesn't understand what is being said.

Does the metric describe a static universe or not?

You've said it doesn't.

If not, how's it different from FLRW in proper coordinates?

Sounds like r=0, t=0 is just the big bang.

 

[Mike Helland]

If comoving coordinates are just a map to the territory, what does the FLRW proper coordinates map look like?

For an exponentially expanding universe, we know that:

http://latex.codecogs.com/gif.latex?c - Hd = \frac{c}{1+z}​

So light's moving at http://latex.codecogs.com/gif.latex?dx/dt = c/(1+z), which is http://latex.codecogs.com/gif.latex?dx/dt = a(t) c.

So:

http://latex.codecogs.com/gif.latex?ds^2 = -c^2 dt^2 + \frac{dx^2}{a(t)^2}​

Since a(t) goes from 1 to 0 when you go from the present back in time, the dx/dt of light keeps getting closer and closer to zero, but never goes negative.

So that metric (in proper distance) should work for de Sitter, but not FLRW in general.

 

[Ziggurat]

If the dx/dt of light was c, there would be no big bang, there would be no redshifts

The velocity of light is always c, in an inertial reference frame.

It is not c, in a non-inertial reference frame.

This is not dependent upon expansion. And here's a little clue for you: expansion or not, there are no global inertial coordinate systems. You cannot make one, it's not possible. Expansion makes the issue of non-inertiality of your coordinate system pretty obvious, but it isn't in any way unique or peculiar to a universe that's expanding.

In other words, as usual, you don't know what you're talking about, and you're drawing conclusions on the basis of your own ignorance.

That's a fact.

 

[Mike Helland]

The velocity of light is always c, in an inertial reference frame.

It is not c, in a non-inertial reference frame.

This is not dependent upon expansion. And here's a little clue for you: expansion or not, there are no global inertial coordinate systems. You cannot make one, it's not possible. Expansion makes the issue of non-inertiality of your coordinate system pretty obvious, but it isn't in any way unique or peculiar to a universe that's expanding.

In other words, as usual, you don't know what you're talking about, and you're drawing conclusions on the basis of your own ignorance.

That's a fact.

Doesn't seem like that has to be the case.

If you use -c + Hd for incoming light, and c + Hd for out going light. So it needs a system of equations. But otherwise, that should describe where everything is and the null paths.

 

[W.D.Clinger]

The velocity of light is always c, in an inertial reference frame.

It is not c, in a non-inertial reference frame.

This is not dependent upon expansion. And here's a little clue for you: expansion or not, there are no global inertial coordinate systems. You cannot make one, it's not possible. Expansion makes the issue of non-inertiality of your coordinate system pretty obvious, but it isn't in any way unique or peculiar to a universe that's expanding.

In other words, as usual, you don't know what you're talking about, and you're drawing conclusions on the basis of your own ignorance.

That's a fact.

Doesn't seem like that has to be the case.

It doesn't seem like the sentence I highlighted would have to be the case, but here we are.

When Ziggurat wrote "there are no global inertial coordinate systems", I'm sure he meant to say that, in general, there are no global inertial coordinate systems. There are several FLRW models that have global inertial coordinate systems. Minkowski space is one example of such.

Amusingly, there's a connection between this topic and local flatness, of which Mike Helland revealed himself to be ignorant just yesterday.

 

[Mike Helland]

It doesn't seem like the sentence I highlighted would have to be the case, but here we are.

When Ziggurat wrote "there are no global inertial coordinate systems", I'm sure he meant to say that, in general, there are no global inertial coordinate systems. There are several FLRW models that have global inertial coordinate systems. Minkowski space is one example of such.

Amusingly, there's a connection between this topic and local flatness, of which Mike Helland revealed himself to be ignorant just yesterday.

You can skew words this way and this, that's fine. That's the internet for you.

I think what seems to be missed is that I keep getting the right answers.

 

[Ziggurat]

You can skew words this way and this, that's fine. That's the internet for you.

I think what seems to be missed is that I keep getting the right answers.

You target an existing equation, and you build up bull **** rationalization for that equation based on nonsense. Getting the equation you aim at isn't getting the right answer. You consistently get the wrong answer whenever you can't cheat by looking up the right answer ahead of time.

 

[Mike Helland]

You target an existing equation, and you build up bull **** rationalization for that equation based on nonsense. Getting the equation you aim at isn't getting the right answer. You consistently get the wrong answer whenever you can't cheat by looking up the right answer ahead of time.

The equation is just Hubble's law.

My point is you can navigate an expanding universe in proper coordinates, not just comoving coordinates.

In either case, they both obscure what's actually going on.

Space isn't getting bigger.

Time is shrinking.

We all know it's true. We observe it directly in the duration of distant supernovae and the frequency of light. But we also feel it, deep down.

 

[Ziggurat]

The equation is just Hubble's law.

And?

You aren't getting the right answer. You start with the right answer, and then proceed to screw it up. Not an accomplishment.

My point is you can navigate an expanding universe in proper coordinates, not just comoving coordinates.

No ****. One of the central lessons of GR is that you can use any set of coordinates you want, as long as you do the math correctly. You haven't discovered something new.

In either case, they both obscure what's actually going on.

Space isn't getting bigger.

Time is shrinking.

For reasons already explained at length, this is nonsense. You're just wrong.

We all know it's true. We observe it directly in the duration of distant supernovae and the frequency of light. But we also feel it, deep down.

What you mean "we", white man?

 

[Mike Helland]

Not an accomplishment.

I didn't say it was.

No ****. One of the central lessons of GR is that you can use any set of coordinates you want, as long as you do the math correctly. You haven't discovered something new.

I didn't say I did.

For reasons already explained at length, this is nonsense. You're just wrong.

It doesn't make sense that space can expand but time can't. It's just unfamiliar.

What you mean "we", white man?

Whether you admit it or not, you've probably thought that time sure seems to fly by faster than it used to.

That's literally what the data is telling us. We observe supernovae to be stretched in time. It really doesn't get any more obvious than that.

 

[Mike Helland]

And?
One of the central lessons of GR is that you can use any set of coordinates you want, as long as you do the math correctly.

Also, FLRW breaks that tradition by imposing an invariant, absolute cosmic time.

As much as that's repeated, that's clearly cast aside in cosmology and cosmology alone.

 

[Ziggurat]

I didn't say it was.

You said,

I think what seems to be missed is that I keep getting the right answers.

But you don't get the right answer. You start with the right answer and then screw it up.

It doesn't make sense that space can expand but time can't. It's just unfamiliar.

What you do or don't consider unfamiliar is irrelevant.

And space doesn't expand over space (that's meaningless), it expands over time. Time doesn't expand over time (that's meaningless), but it can and does expand over space. Your unfamiliarity with how non-Euclidean geometry works in higher dimensions isn't my problem, it's yours.

Whether you admit it or not, you've probably thought that time sure seems to fly by faster than it used to.

That's a well-understood phenomena where our subjective sense of time is tied to memory formation, and memory formation changes as we age. It's got nothing to do with physics.

That's literally what the data is telling us. We observe supernovae to be stretched in time. It really doesn't get any more obvious than that.

That's literally not what the data is telling us. That's your interpretation, based on an ass pull.

Also, FLRW breaks that tradition by imposing an invariant, absolute cosmic time.

Nope. FLRW does nothing of the sort. If you think that's what it does, then you're misunderstanding something, which is par for the course. Some coordinate systems are simpler and more intuitive than others, but any coordinate system will still work, if you handle it correctly.

I have to remind myself occasionally that if I think you understand something, I'm probably misunderstanding what you think.

 

[Mike Helland]

That's literally not what the data is telling us.

When we measure time dilation in a supernova, we are literally measuring "time expanding".

As much as you hate it, that's literally what we observe.

Nope. FLRW does nothing of the sort. If you think that's what it does, then you're misunderstanding something, which is par for the course. Some coordinate systems are simpler and more intuitive than others, but any coordinate system will still work, if you handle it correctly.

Do observers near a black hole, for example, see the universe as a different age than we do?

Is that compatible with cosmic time?

http://www.bourbaphy.fr/moschella.pdf

In cosmology one usually “breaks” the general relativistic covariance and singles out a special coordinate system: there is a natural choice of “cosmic time” that makes the universe appear spatially homogeneous and isotropic at large scales. This property is mathematically encoded in the Friedmann-Robertson-Walker line element:

http://latex.codecogs.com/gif.latex?ds^2 = dt^2 - a(t)^2 dl^2
​

 

[Ziggurat]

When we measure time dilation in a supernova, we are literally measuring "time expanding".

That's like saying when a car zooms by you and you hear that Doppler shift, you're measuring time expanding.

No. You're making a specific interpretation of your measurement. And in this case, that interpretation isn't supported by any other data. All you've actually measured is an expansion of the signal duration as you observe it in your reference frame. That's not the same as time itself.

In cosmology one usually “breaks” the general relativistic covariance and singles out a special coordinate system: there is a natural choice of “cosmic time” that makes the universe appear spatially homogeneous and isotropic at large scales.

Do you know why "breaks" is in quotes?

Because it doesn't actually break covariance. And notice that it's still a choice of coordinates. You don't have to choose those coordinates. They are "natural" in the sense that they're simpler than the alternatives (for most purposes), but GR covariance never promised equal simplicity between coordinates, only equal validity. And that's maintained.

 

[Mike Helland]

No. You're making a specific interpretation of your measurement. And in this case, that interpretation isn't supported by any other data. All you've actually measured is an expansion of the signal duration as you observe it in your reference frame. That's not the same as time itself.

Doesn't that argument work the other way?

All you've actually measured is an expansion of the signal duration as you observe it in your reference frame. That's not the same as space itself.

It's easier to think about dynamic space than dynamic time, but they can be treated equally for the most part.

 

[Mike Helland]

Do observers near a black hole, for example, see the universe as a different age than we do?

Is that compatible with cosmic time?

Does anyone want to have a go at this?

One could argue, of course, that since the universe is homogeneous, and made of plain jello, there are no black holes an observer can be nearer to or farther from than any other observer.

 

[W.D.Clinger]

For this communication, I tried to use color coding similar to recommendations made by the Vulture Central Humour Comprehensibility Committee, but my browser didn't render the forum's colors as expected so I made some changes. It is possible that other browsers will not approximate the colors I'm seeing in my browser, for which I apologize.

I think what seems to be missed is that I keep getting the right answers.

Everybody missed that.

Nobody notices that Mike Helland keeps getting the right answers. I wonder why.

Do observers near a black hole, for example, see the universe as a different age than we do?

Is that compatible with cosmic time?

Does anyone want to have a go at this?

Although FLRW models are exact solutions of Einstein's field equations, and we have exact solutions for at least three different varieties of black holes, I don't believe there is an exact closed-form solution that perturbs an FLRW model by adding a black hole. For this question, however, that isn't much of a problem. An observer located at the event horizon of a stellar black hole will reach its center in a matter of seconds. An observer at the event horizon of the black hole at the center of our galaxy will reach its center in about a minute. For the black hole at the center of Messier 87 (one of the largest known black holes), it would take about 5 hours. The scale factor of an FLRW model undergoes negligible change during such a short interval of time, so we can take a(t)=1, which implies the metric tensor of an otherwise flat universe is essentially Minkowskian sufficiently far away from the black hole.

ETA: And also implies essentially no deviation from FLRW in the vicinity of an observer whose approach to the black hole takes long enough for the scale factor to undergo appreciable change.

Which means the universe looks the same as it does to us, except for perturbation in the near vicinity of the black hole. In particular, the universe's age looks essentially the same to us as to an observer falling into a black hole and yes, that is compatible with cosmic time.

The perturbed view of an observer falling into a black hole is given in closed form by Gullstrand–Painlevé or Lemaître coordinates.

The Helland metrics (plural) that Mike Helland has been proposing do not correspond to the view of any observer in any universe that remotely resembles the universe we inhabit.

 

[Ziggurat]

Doesn't that argument work the other way?

The difference is that the standard model matches a bunch of other data as well. Yours doesn't. So you are correct that the observations of supernova time dilation do not prove the expansion of space, but theymatch it, and a bunch of other stuff matches it too. You're fitting one data point and ignoring everything else. That's not the way to do science.

It's easier to think about dynamic space than dynamic time, but they can be treated equally for the most part.

Again, time varying over time doesn't make sense, just like space varying over space doesn't make sense. General relativity allows for space to vary over time and time to vary over space, and both occur. They are being treated equally, but you don't understand that treatment, because you don't understand general relativity. Which is perfectly fine, most people don't, no shame in that. But you're pretending you do, and that is embarrassing.