# Confirmed! James Webb Space Telescope has bagged the oldest known galaxies

#### Unclear Engineer

This article says "The observations match what astronomers expected based on existing galaxy formation models."

So, how old does a galaxy have to be for it to be "unexpected"?

And, how long would an exposure need to be for Webb to detect such a galaxy?

rod

#### rod

My notes. Using cosmology calculators can check figures here in the report. z=13.2, look back time distance = 13.396 Gyr, age of universe at z=13.2, 0.326 Gyr, comoving radial distance = 33.386 Gly distance. Using H0=69 km/s/Mpc, 4D space expanding ~ 2.36 x c velocity. The universe radius for z=13.2 when the galaxy first appeared, about 2.35 Gly so the diameter of the early universe then about 4.7 Gly compared to present, about 93 billion light years (CMBR z=1100). Indeed, 4D space is expanding very fast in the BB cosmology.

LAMBDA - Links to Calculators (nasa.gov)

#### Turtle

So as the light travels long distances it red shifts, from a high frequency to
a lower one, even until it turns into cosmic microwave background. This is because it is being stretched?

But red light or microwaves are of lower wattage than x-rays or blue light.

Where does the lost energy go from the light as it is lowered in frequency? As space is stretching as the light goes through it the light is losing energy.

What if for some billions of years the light just was reflected back and forth
between two perfect mirrors some minor distance apart? Would it still shift?

Thanks

#### billslugg

The shifting of the wavelength is only seen in your stationary reference frame. To the observer on the distant star, the star gives off nothing but yellow light in all directions.
From your perspective, the star is moving away from you at a high velocity. Light coming towards you is red shifted, light going away from you is blue shifted. The loss of energy in the red photons is exactly balanced by the energy gain by the blue photons.
What if the only light emitted was in a beam straight backwards? In that case the loss of energy of the red photons would be accompanied by a gain in kinetic energy of the star.
Kinetic energy is not conserved when going from one reference frame to another. In your rest frame, nothing has any kinetic energy except a flying bullet. From the reference frame of the bullet, it is at rest with zero kinetic energy and you and the entire Earth is going at bullet speed.

#### Unclear Engineer

Bill, I think you mis-posted regarding "light going away from you is blue shifted", in that you would not see "light going away from you". It is light coming toward you from the direction you are traveling towards that is blue shifted. In expanding space, light coming toward you from a distant object looks red shifted, and light from that object that has passed you will continue to be red shifted such that a distant mirror that reflects some of it back toward you will show that additional red shift. (The reflected light would be redshifted going to the mirror and redshifted even more while traveling from the mirror back to you.)

The OP seemed to be thinking more about the density of energy in space as light traveling in that space is stretched by the expansion of space. Yes, the light received when red shifted is at lower energy, but presumably that light would be shining onto something for longer period of time, so the total energy transferred would be the question to answer. (I don't have the time to do the math, right now.)

The part of the OP that asks about how light shining back and forth between mirrors that are not far apart being affected by the expansion of space is a much more complex to address. Do we assume that the mirrors and the distance between them are somehow unaffected by the expansion of the space around them, or do we assume that the mirrors themselves and the distance between them is expanding like everything else?

rod

#### rod

Are there direct observation tests for 4D space expanding in our solar system?

Consider H0 = 67 km/s/Mpc. That value can be converted to c.g.s. units. ~ 2.17 x 10^-18 cm/s/cm. If I use H0=73 km/s/Mpc, ~ 2.37 x 10^-18 cm/s/cm for 4D space expansion rate. On Earth, do we see this tiny 4D space expansion taking place?

My post #3 calls attention to different distances and universe sizes as well as ages used in GR math to explain the redshift of 13.2. Many of those distances and ages are not directly verifiable like the Galilean moons moving around Jupiter, for example. I know I cannot see today a universe somewhat smaller than 5 billion light years diameter or the present universe size of some 93 billion light years in diameter.

#### billslugg

Unclear Engineer - My reference to light going away from you as being blue shifted was in the case of light being emitted on the far side of a star moving away from you. In the case of a high velocity star moving away from an observer, the light aimed back at the observer is red shifted, the light aimed in the direction of the star's travel is blue shifted. When accounting for the energy balance the two cancel out.

Yes, the energy density is lower due to the red shift but the space is expanded thus the total energy remains the same.

Light passing between two mirrors whould appear red shifted when coming towards the observer and blue shifted when going away from the observer.

#### Helio

Doppler motion explains light shifts as a light source and viewer move through space relative to one another. GR (General Relativity) addresses the shift of light as it travels through expanding space, so expansion “stretches” the light, and always toward red.

Where this energy goes likely requires a great understanding of GR, but I’m inclined to think there is more mystery to this. [It was deSitter who produced, initially, a model for redshift in light in a static universe, but simplified by leaving all matter out of his equations.]

Although a photon packet of light does take longer to impact something (so dimmer), I’m confident the total energy is less by the loss in energy due to the cosmological redshift for each photon.

#### Helio

I finally got an answer to a gedaken experiment where a mirror is placed on an inelastic pole, and at an extreme distance (a billion lyrs.) A green laser reflects off of it and it shows redshift upon its return, according to physicists.

iPhone

billslugg

#### Turtle

Thank you Hellio,

So light traveling through space is red shifted (according to physicists) and its total energy is lowered. Where does this energy go?

Of course ( I heard this) the high vacuum of space is never considered to be empty, not really. There are the quantum fluctuations. Other than light there are other energies that radiate out there. Magnetic fields and gravity which have no particular frequency to them. Do they lose energy and get absorbed?

Helio

#### billslugg

I have read a number of "explanations" and as best I can tell, the loss of energy in a red shifted photon is compensated for by an increase in kinetic energy by the object that emitted it.

Helio

#### Helio

Thank you Hellio,

So light traveling through space is red shifted (according to physicists) and its total energy is lowered. Where does this energy go?

Of course ( I heard this) the high vacuum of space is never considered to be empty, not really. There are the quantum fluctuations. Other than light there are other energies that radiate out there. Magnetic fields and gravity which have no particular frequency to them. Do they lose energy and get absorbed?
Perhaps, but there isn’t a definitive answer, IMO, given that to test these hypotheses in a lab is beyond reach, apparently.

Often the explanation is that as a wave/photon moves through space, it will stretch with the expansion of space. This results in a longer wavelength, hence a redshift. I suspect, however, that great strength in the electromagnetic field will easily overpower the stretching action. But I just don’t know.

#### Helio

I have read a number of "explanations" and as best I can tell, the loss of energy in a red shifted photon is compensated for by an increase in kinetic energy by the object that emitted it.
This is certainly the case for Doppler. Light has no mass but it does have momentum.

Where the energy goes during expansion, if it does go, is still a mystery to me. Since the expansion is constantly increasing the relative speed between emitter and receiver, then I once assumed Doppler would explain it, but I’m told this isn’t the case. One problem with Doppler is how to handle light coming from a distant emitter traveling faster than light.

#### billslugg

Here is another explanation based on what I read:
There are two different frames of reference here. In our frame the photon is seen as being red when it gets here. In the frame of reference of the star the photon is seen as yellow as it leaves the star. To us it is always red. To them it is always yellow. Within each frame of reference energy is conserved. There is no requirement that energy be invariant between frames. It is conserved within each frame but can be different as viewed from each different frame.
An observer sees a bullet flying by with a lot of kinetic energy. An observer on the bullet sees it as having no kinetic energy.

#### Turtle

Here is another explanation based on what I read:
There are two different frames of reference here. In our frame the photon is seen as being red when it gets here. In the frame of reference of the star the photon is seen as yellow as it leaves the star. To us it is always red. To them it is always yellow. Within each frame of reference energy is conserved. There is no requirement that energy be invariant between frames. It is conserved within each frame but can be different as viewed from each different frame.
An observer sees a bullet flying by with a lot of kinetic energy. An observer on the bullet sees it as having no kinetic energy.

As I understood it then, in our frame the photon is seen as being red when it gets here but if the photon was reflected back to the frame of reference of the star it would be seen as even redder. The energy has to be lost out there somehow.

rod

#### rod

As I understood it then, in our frame the photon is seen as being red when it gets here but if the photon was reflected back to the frame of reference of the star it would be seen as even redder. The energy has to be lost out there somehow.
Turtle, keep after this The loss of energy in a photon as 4D space expands, applies to the CMBR light too with a postulated redshift of 1100 today. I would think the 1st law would apply and the energy is not lost but goes somewhere else When it comes to JWST reported and confirmed galaxy or object redshifts at 13.2, I keep in mind that to accept such distances used in BB cosmology, the universe was less than 5 billion light years in diameter when that object appeared, the universe is some 93 billion light years in diameter today, thus expanding much faster than c velocity. In science, do we see a universe less than 5 billion light years in diameter? My answer is no. Do we see a universe today some 93 billion light years in diameter? My answer is no. Do we know where that energy went to explain the light time distance and comoving radial distance for objects with redshifts 13.2 in BB cosmology? My answer is no, and you seem to open up a potential hole here in the explanation for cosmological redshifts, distances used, and long age timescale for the universe.

#### Unclear Engineer

For red shifted photons, the energy is inversely proportional to their wavelength. So, a "stream of light" (presumably many photons) emitted over a shot period of time, when traveling through space that stretches by some factor "X" will have stretched the photons to have 1/x their initial energy but will have also stretched the length of the beam (between "on" and "off") by a factor of X. So, the time it takes for the whole beam to arrive at an observer is increased by a factor of X. So, a beam of photons with energy decreased as 1/X lasting for a time period increased by a factor of X should result in X times 1/X = 1 times the total amount of energy transmitted.

So, the energy seems to not have increased or decreased due to the expansion of space.

How one envisions this at an individual photon level might be an issue - how "long" is an individual photon? But it works fine using the continuous wave approach.

That is different from the issue about the different frames of reference for the photons, (which always appear to be traveling at the speed of light in all frames of reference). As bill has explained, using kinetic energy of particles of matter (instead of photons), the energy levels of particles traveling at different velocities do not seem to be have the same total kinetic energy in all frames of reference and will not give the same calculated result for total energy of a "system" of particles. E.g,. the kinetic energy of his speeding bullet hitting a heavy, zero-velocity target looks like 1/2 the mass of the bullet times the square of its velocity from the target's frame of reference, while, in the bullet's frame of reference, it looks like that heavy target is speeding towards it, with a kinetic energy that is 1/2 the mass of the target times the square of the same relative velocity. So, the total kinetic energy of the pair changes drastically by changing the frame of reference.

Similarly, the photons in expanding space will seem to have different energies to observers traveling at different speeds with respect to each other in the different parts of the expanding space, even though they all measure the speed of the photons as the same speed of light.

rod

#### rod

Unclear Engineer in post #18 stated. "For red shifted photons, the energy is inversely proportional to their wavelength. So, a "stream of light" (presumably many photons) emitted over a shot period of time, when traveling through space that stretches by some factor "X" will have stretched the photons to have 1/x their initial energy but will have also stretched the length of the beam (between "on" and "off") by a factor of X. So, the time it takes for the whole beam to arrive at an observer is increased by a factor of X. So, a beam of photons with energy decreased as 1/X lasting for a time period increased by a factor of X should result in X times 1/X = 1 times the total amount of energy transmitted.

So, the energy seems to not have increased or decreased due to the expansion of space."

So, what Turtle asked about as 4D space expands in BB cosmology, redshift light does not lose energy but remains the same as when first emitted. Do you have a reference source where lab experiments on Earth show this? It seems then the explanation for the CMBR redshift of about 1100 has no issues with energy loss but could if lab experiments cannot verify this.

#### Unclear Engineer

All I am saying is that light that is redshifted by expansion of space ends up occupying a larger volume of space, so the question about where the energy goes when expansion decreases the "energy" of "photons" is answered by it simply gets expanded to a lower density, but does not change total energy in the universe.

With regard to whether experiments on Earth can verify that space is actually expending here, I don't think it is measurable in dimensions so small. And, if the meter sticks on Earth are expanding at the same rate as space, then it would not be evident with simple measurements, anyway. So, hard to prove or disprove.

rod and Helio

#### Helio

All I am saying is that light that is redshifted by expansion of space ends up occupying a larger volume of space, so the question about where the energy goes when expansion decreases the "energy" of "photons" is answered by it simply gets expanded to a lower density, but does not change total energy in the universe.
That's certainly a logical way to look at it, but I have some doubts that cosmologists see it that way.

How would this approach explain a monochromatic beam that reflects light from a very distant object that is in the observers frame of reference? This is the gedanken experiment I mentioned earlier. Your view would, I think, have the emitting green light return as green, not more red, as is the answer I think may be the consensus color.

#### billslugg

I too have thought that stretching of a light wave lowers its peak intensity and increases wavelength but the area under the curve stays the same thus nothing is lost. Note this change is only apparent to those in other frames of reference, in the frame of the photon, its energy never changes. Nothing changes. Its clock is stopped.

#### Turtle

OK, in a laboratory we can gate a single photon and measure its energy with a photo detector, can't we? And a yellow one has more energy than a red one. And it doesn't make any difference if those photons came from a light bulb or a far off star.

So four little photons, one yellow one red from a far off star one yellow and one red from a very near light bulb and SMACKO onto a photo detector and there they die a horrible death.

And then two of them remember as their life passes in front of them, "I used to have more energy than this, I thought I was yellow." "Yeah, and I thought I was blue." "What happened!"

And the other two little photons answer, " We don't know, we think somebody stopped your clock."

The trouble with observers is some are bigger than others. Some confined to a small laboratory space and some perhaps unbounded by a cosmic distance. So to an observer a billion light years tall, what would this look like?

#### Helio

I too have thought that stretching of a light wave lowers its peak intensity and increases wavelength but the area under the curve stays the same thus nothing is lost.
I don’t understand this. If you look at the CMBR spectral distribution, it will be much, much less than it’s original 3000K distribution.

Note this change is only apparent to those in other frames of reference, in the frame of the photon, its energy never changes. Nothing changes. Its clock is stopped.
Indeed, there is no time lapse in their frame, so their wavelength only makes since in other frames.

iPhone

#### Helio

OK, in a laboratory we can gate a single photon and measure its energy with a photo detector, can't we? And a yellow one has more energy than a red one. And it doesn't make any difference if those photons came from a light bulb or a far off star.

So four little photons, one yellow one red from a far off star one yellow and one red from a very near light bulb and SMACKO onto a photo detector and there they die a horrible death.

And then two of them remember as their life passes in front of them, "I used to have more energy than this, I thought I was yellow." "Yeah, and I thought I was blue." "What happened!"

And the other two little photons answer, " We don't know, we think somebody stopped your clock."
Talking photons are doubly funny since they aren’t allowed to talk given their time to destination is zero sec.

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