Discovering farthest known galaxy in the universe

[John Clark]

The James Webb telescope has discovered a galaxy with the red shift of 14.44. From that you can calculate that it took light 13.5 billion years to reach us, it started its journey only 280 million years after the Big Bang.  And because of the expansion of the universe the galaxy is now 34.7 billion light years from the Earth. What I find really fascinating is that although we can see the galaxy if we tried to send a laser beam to it, because of the expansion of the universe, the beam would NEVER reach it; in fact that's true for any galaxy that has a red shift larger than 1.8, and this one had a red shift of 14.44!

James Webb telescope breaks its own record again, discovering farthest known galaxy in the universe

John K Clark    See what's on my new list at  Extropolis

^aq

[Alan Grayson]

On Wednesday, May 28, 2025 at 2:42:02 PM UTC-6 John Clark wrote:

The James Webb telescope has discovered a galaxy with the red shift of 14.44. From that you can calculate that it took light 13.5 billion years to reach us, it started its journey only 280 million years after the Big Bang.  And because of the expansion of the universe the galaxy is now 34.7 billion light years from the Earth. What I find really fascinating is that although we can see the galaxy if we tried to send a laser beam to it, because of the expansion of the universe, the beam would NEVER reach it; in fact that's true for any galaxy that has a red shift larger than 1.8, and this one had a red shift of 14.44!

James Webb telescope breaks its own record again, discovering farthest known galaxy in the universe

Does a red shift of 1.8 imply recession at light speed? How is that calculated? AG 

^aq

[John Clark]

On Wed, May 28, 2025 at 5:04 PM Alan Grayson <agrays...@gmail.com> wrote:

>> The James Webb telescope has discovered a galaxy with the red shift of 14.44. From that you can calculate that it took light 13.5 billion years to reach us, it started its journey only 280 million years after the Big Bang.  And because of the expansion of the universe the galaxy is now 34.7 billion light years from the Earth. What I find really fascinating is that although we can see the galaxy if we tried to send a laser beam to it, because of the expansion of the universe, the beam would NEVER reach it; in fact that's true for any galaxy that has a red shift larger than 1.8, and this one had a red shift of 14.44!

James Webb telescope breaks its own record again, discovering farthest known galaxy in the universe

> Does a red shift of 1.8 imply recession at light speed?

If you're looking at a galaxy that has a red shift of 1.8 then you're looking at how that galaxy looked 10.2 billion years ago, back then it was not moving away from us faster than the speed of light but today it is, so although we can see it we could never reach it in a finite amount of time, not even if we could move at the speed of light. And a red shift of 1.8 is the boundary line for that sort of thing.  

 

> How is that calculated? AG 

The general integral for finding the lookback time tL(z) is complicated and involves calculus because it depends and a lot of things that are changing, it's:

tL(z)=∫(1+z′)H(z′)1dz′

where you integrate between zero and the redshift z

H(z) is the Hubble parameter at redshift z

H(z)=H0Ωm(1+z)3+ΩΛ  in a flat universe with dark energy

H0 is the Hubble constant today

Ωm is the matter density parameter

ΩΛ is the dark energy density parameter

John K Clark    See what's on my new list at  Extropolis

nxv

[Alan Grayson]

On Friday, May 30, 2025 at 5:01:10 AM UTC-6 John Clark wrote:

On Wed, May 28, 2025 at 5:04 PM Alan Grayson <agrays...@gmail.com> wrote:

>> The James Webb telescope has discovered a galaxy with the red shift of 14.44. From that you can calculate that it took light 13.5 billion years to reach us, it started its journey only 280 million years after the Big Bang.  And because of the expansion of the universe the galaxy is now 34.7 billion light years from the Earth. What I find really fascinating is that although we can see the galaxy if we tried to send a laser beam to it, because of the expansion of the universe, the beam would NEVER reach it; in fact that's true for any galaxy that has a red shift larger than 1.8, and this one had a red shift of 14.44!

James Webb telescope breaks its own record again, discovering farthest known galaxy in the universe

> Does a red shift of 1.8 imply recession at light speed?

If you're looking at a galaxy that has a red shift of 1.8 then you're looking at how that galaxy looked 10.2 billion years ago, back then it was not moving away from us faster than the speed of light but today it is, so although we can see it we could never reach it in a finite amount of time, not even if we could move at the speed of light. And a red shift of 1.8 is the boundary line for that sort of thing.  

Sorry for this question, but what puzzles me about your comment is that the further back in time we observe, the faster galaxies are receding, so how can a galaxy NOT receding faster than light speed in the past, now be receding faster than light speed? AG

[John Clark]

On Sat, May 31, 2025 at 1:01 AM Alan Grayson <agrays...@gmail.com> wrote:

> Sorry for this question, but what puzzles me about your comment is that the further back in time we observe, the faster galaxies are receding, so how can a galaxy NOT receding faster than light speed in the past, now be receding faster than light speed? AG

Space is expanding, so the further away a galaxy is the faster it will be receding from us. 10.2 billion years ago a galaxy with a red shift of 1.8 was much closer to us than it is now, and it was receding from us much slower than it is now. Today it is much further away and thus receding from us much faster than back then, in fact it has just gone over the line and is now receding faster than the speed of light.

Remember although Special Relativity says nothing can move faster than light, General Relativity is able to make a more nuanced statement, it says matter energy and information cannot move between two points in space faster than the speed of light, but it places no such limit on how fast space itself can expand.  If intelligent life develops on that galaxy then astronomers there looking at the Milky Way will see it as it looked 10.2 billion years ago, but they will never be able to see what it looks like now.  

 John K Clark    See what's on my new list at  Extropolis

bd;

nx

[Alan Grayson]

On Friday, May 30, 2025 at 5:01:10 AM UTC-6 John Clark wrote:

On Wed, May 28, 2025 at 5:04 PM Alan Grayson <agrays...@gmail.com> wrote:

>> The James Webb telescope has discovered a galaxy with the red shift of 14.44. From that you can calculate that it took light 13.5 billion years to reach us, it started its journey only 280 million years after the Big Bang.  And because of the expansion of the universe the galaxy is now 34.7 billion light years from the Earth. What I find really fascinating is that although we can see the galaxy if we tried to send a laser beam to it, because of the expansion of the universe, the beam would NEVER reach it; in fact that's true for any galaxy that has a red shift larger than 1.8, and this one had a red shift of 14.44!

James Webb telescope breaks its own record again, discovering farthest known galaxy in the universe

> Does a red shift of 1.8 imply recession at light speed?

If you're looking at a galaxy that has a red shift of 1.8 then you're looking at how that galaxy looked 10.2 billion years ago, back then it was not moving away from us faster than the speed of light but today it is,

Applying Hubble's law, the rate of expansion in the early universe was hugely greater than it is today. If that's correct, how can you claim that if 10.2 billion years ago it was not receding faster than light speed (which is possible), but today it is (which seems impossible)? AG

[John Clark]

On Sat, May 31, 2025 at 9:26 AM Alan Grayson <agrays...@gmail.com> wrote:

>  the rate of expansion in the early universe was hugely greater than it is today.

That was true during the time of Cosmic Inflation, and that's why the temperature of the Cosmic Microwave Background Radiation from opposite points in the sky is almost identical, at that time those two places were in causal contact with each other. However the Era Of Inflation only lasted about a billionth of a billionth of a second, after that the rate of expansion became much Much MUCH slower.

  John K Clark    See what's on my new list at  Extropolis

$%O

[Alan Grayson]

On Saturday, May 31, 2025 at 7:59:35 AM UTC-6 John Clark wrote:

On Sat, May 31, 2025 at 9:26 AM Alan Grayson <agrays...@gmail.com> wrote:

>  the rate of expansion in the early universe was hugely greater than it is today.

That was true during the time of Cosmic Inflation, and that's why the temperature of the Cosmic Microwave Background Radiation from opposite points in the sky is almost identical, at that time those two places were in causal contact with each other. However the Era Of Inflation only lasted about a billionth of a billionth of a second, after that the rate of expansion became much Much MUCH slower.

Correct. Then why did you claim that the farthest galaxy is NOW receding faster than light speed, when in the past it was receding much slower? AG 

[Alan Grayson]

Even without Inflation, doesn't Hubble's law imply the universe was expanding faster in the past, possibly faster than light speed, than at present? AG

[John Clark]

On Sat, May 31, 2025 at 10:17 AM Alan Grayson <agrays...@gmail.com> wrote:

> doesn't Hubble's law imply the universe was expanding faster in the past

NO. Until the late 1990s everybody, including Edwin Hubble, figured that the expansion of the universe must be slowing down due to gravity's attraction, but then we discovered the expansion is actually accelerating, and nobody knows why. So the universe is expanding faster now than it was 10 billion years ago.

  John K Clark    See what's on my new list at  Extropolis

rbb

[Alan Grayson]

On Saturday, May 31, 2025 at 8:40:02 AM UTC-6 John Clark wrote:

On Sat, May 31, 2025 at 10:17 AM Alan Grayson <agrays...@gmail.com> wrote:

> doesn't Hubble's law imply the universe was expanding faster in the past

NO. Until the late 1990s everybody, including Edwin Hubble, figured that the expansion of the universe must be slowing down due to gravity's attraction, but then we discovered the expansion is actually accelerating, and nobody knows why. So the universe is expanding faster now than it was 10 billion years ago.

I am aware of that. Does it mean Hubble's law is wrong. It says, if I understand correctly, that the further back in time we go, the greater is the rate of expansion? AG 

[John Clark]

On Sat, May 31, 2025 at 11:27 AM Alan Grayson <agrays...@gmail.com> wrote:

>> NO. Until the late 1990s everybody, including Edwin Hubble, figured that the expansion of the universe must be slowing down due to gravity's attraction, but then we discovered the expansion is actually accelerating, and nobody knows why. So the universe is expanding faster now than it was 10 billion years ago.

> I am aware of that. Does it mean Hubble's law is wrong.

Yes. As originally stated Hubble's law didn't take the acceleration of the universe into account. For nearby galaxies, those only a billion or two light years away, that discrepancy isn't significant, but for more distant objects it is.  

 

> It says, if I understand correctly, that the further back in time we go, the greater is the rate of expansion? AG 

NO. The universe is accelerating so the further back in time we go, the LESS is the rate of expansion, and in the future it will be expanding even faster.
 

[Brent Meeker]

On 5/31/2025 6:26 AM, Alan Grayson wrote:

On Friday, May 30, 2025 at 5:01:10 AM UTC-6 John Clark wrote:

On Wed, May 28, 2025 at 5:04 PM Alan Grayson <agrays...@gmail.com> wrote:

>> The James Webb telescope has discovered a galaxy with the red shift of 14.44. From that you can calculate that it took light 13.5 billion years to reach us, it started its journey only 280 million years after the Big Bang.  And because of the expansion of the universe the galaxy is now 34.7 billion light years from the Earth. What I find really fascinating is that although we can see the galaxy if we tried to send a laser beam to it, because of the expansion of the universe, the beam would NEVER reach it; in fact that's true for any galaxy that has a red shift larger than 1.8, and this one had a red shift of 14.44!

James Webb telescope breaks its own record again, discovering farthest known galaxy in the universe

> Does a red shift of 1.8 imply recession at light speed?

If you're looking at a galaxy that has a red shift of 1.8 then you're looking at how that galaxy looked 10.2 billion years ago, back then it was not moving away from us faster than the speed of light but today it is,

Applying Hubble's law, the rate of expansion in the early universe was hugely greater than it is today. If that's correct, how can you claim that if 10.2 billion years ago it was not receding faster than light speed (which is possible), but today it is (which seems impossible)? AG

Hubble expansion is not a speed, it's a speed per unit distance.  Even if the Hubble parameter were much higher the past, a galaxy that was then much closer would be moving away more slowly.

Brent

[Brent Meeker]

There were no galaxies or even atoms at the time of the Big Bang.  Since galaxies have formed the Hubble parameter has been much smaller

Brent

[Brent Meeker]

And to be clear it was thought that the Hubble parameter was decreasing asymptotically to a constant value.  But even with the Hubble parameter constant a receding galaxy is slower when it's close and recedes faster as it gets further away.  The recession speed is proportional to the distance; that's Hubble's law. 

Brent

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[Alan Grayson]

On Saturday, May 31, 2025 at 2:24:00 PM UTC-6 Brent Meeker wrote:

And to be clear it was thought that the Hubble parameter was decreasing asymptotically to a constant value.  But even with the Hubble parameter constant a receding galaxy is slower when it's close and recedes faster as it gets further away.  The recession speed is proportional to the distance; that's Hubble's law. 

Brent

This is confusing. Does Hubble's law hold in a universe where the expansion is speeding up? TY, AG 

[Brent Meeker]

On 5/31/2025 3:22 PM, Alan Grayson wrote:

On Saturday, May 31, 2025 at 2:24:00 PM UTC-6 Brent Meeker wrote:

And to be clear it was thought that the Hubble parameter was decreasing asymptotically to a constant value.  But even with the Hubble parameter constant a receding galaxy is slower when it's close and recedes faster as it gets further away.  The recession speed is proportional to the distance; that's Hubble's law. 

Brent

This is confusing. Does Hubble's law hold in a universe where the expansion is speeding up? TY, AG

Depends on what you mean by the speed of expansion.  Hubble's parameter is the expansion speed per distance, so speed is proportional to distance.  Hubble's law assumed this to be a constant.  Then since every galaxy is moving to a greater distance then every galaxy is speeding up.

Brent

[Alan Grayson]

Doesn't that imply that distant galaxies, at earlier times, were moving faster than nearby galaxies, and thus contradicts the fairly recent finding that the rate of expansion is increasing, not decreasing? AG 

[Brent Meeker]

More distant galaxies are always receding faster than less distant galaxies.   But in the past those more distant galaxies and the nearby galaxies were both closer than they are now and so were both receding more slowly than they are now.

and thus contradicts the fairly recent finding that the rate of expansion is increasing, not decreasing?

"Rate of expansion" is NOT the speed of galaxies.  It's the Hubble parameter, the constant of proportionality, H, in the equation (recession speed of galaxy at distance d) = H*d.  Note H has the dimension of 1/time, NOT length/time.  The recent discovery is that H is increasing.  Any value of H>0 implies that more distant galaxies are receding faster than less distant galaxies.

Brent

[Alan Grayson]

On Saturday, May 31, 2025 at 9:48:27 AM UTC-6 John Clark wrote:

On Sat, May 31, 2025 at 11:27 AM Alan Grayson <agrays...@gmail.com> wrote:

>> NO. Until the late 1990s everybody, including Edwin Hubble, figured that the expansion of the universe must be slowing down due to gravity's attraction, but then we discovered the expansion is actually accelerating, and nobody knows why. So the universe is expanding faster now than it was 10 billion years ago.

> I am aware of that. Does it mean Hubble's law is wrong.

Yes. As originally stated Hubble's law didn't take the acceleration of the universe into account. For nearby galaxies, those only a billion or two light years away, that discrepancy isn't significant, but for more distant objects it is.  

I think you mean that taking the acceleration of the universe into account, Hubble's law departs from linearity, while distant galaxies are still receding at ever increasing speeds, where the latter result is purely a consequence of geometry. Correct? AG 

 

> It says, if I understand correctly, that the further back in time we go, the greater is the rate of expansion? AG 

NO. The universe is accelerating so the further back in time we go, the LESS is the rate of expansion, and in the future it will be expanding even faster.

Why will the universe keep expanding into the future? I don't think that's a given based on what we know. AG 

[Alan Grayson]

On Saturday, May 31, 2025 at 2:24:00 PM UTC-6 Brent Meeker wrote:

And to be clear it was thought that the Hubble parameter was decreasing asymptotically to a constant value.  But even with the Hubble parameter constant a receding galaxy is slower when it's close and recedes faster as it gets further away.  The recession speed is proportional to the distance; that's Hubble's law. 

Brent

Isn't the increasing recessional speed of distant galaxies purely a geometric effect of the expansion of the universe? A long time ago, as I recall, that was your argument, and I recapitulate it by imagining points on an expanding sphere. AG

[John Clark]

On Sun, Jun 1, 2025 at 2:50 AM Alan Grayson <agrays...@gmail.com> wrote:

> Why will the universe keep expanding into the future? I don't think that's a given based on what we know. AG

Since we don't know what's causing the universe to accelerate we don't know if that acceleration will continue at a constant rate, and thus we can not speak with any authority about what the ultimate fate of the universe will be; for all we know the acceleration might drop to zero or even reverse itself. In fact, very recently there have been indications that the rate of acceleration, called a "jerk" in physics, is negative so the acceleration of the universe is getting smaller. The evidence for that is only at 3.2 Sigma and you need 5 Sigma to claim a discovery, but it's enough to be very interesting.

Incidentally the rate of change of a jerk is called a snap, the rate of change of a snap is called a crackle, and the rate of change of a crackle is called a pop. In his talks Nobel prize winning astronomer Adam Riess likes to show a slide of a newspaper showing a picture of him under a bold headline that says "A COSMIC JERK".

  

John K Clark    See what's on my new list at  Extropolis

rb2

[Brent Meeker]

Distant galaxies recede faster than nearby galaxies at all times. 

, and thus contradicts the fairly recent finding that the rate of expansion is increasing, not decreasing?

No.

Brent

[Brent Meeker]

On 6/1/2025 12:02 AM, Alan Grayson wrote:

On Saturday, May 31, 2025 at 2:24:00 PM UTC-6 Brent Meeker wrote:

And to be clear it was thought that the Hubble parameter was decreasing asymptotically to a constant value.  But even with the Hubble parameter constant a receding galaxy is slower when it's close and recedes faster as it gets further away.  The recession speed is proportional to the distance; that's Hubble's law. 

Brent

Isn't the increasing recessional speed of distant galaxies purely a geometric effect of the expansion of the universe? A long time ago, as I recall, that was your argument, and I recapitulate it by imagining points on an expanding sphere. AG

Yes, it's primarily a geometric effect that speed increases with distance.  The recent discovery that speed increases with time modifies this slightly since we observe nearer galaxies later in time.

Brent