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There is no fiber optics in the open space.
Let's take real example about the Farthest Known Galaxy in the Universe Discovered:https://www.space.com/18502-farthest-galaxy-discovery-hubble-photos.html
"The new record holder is the galaxy MACS0647-JD, which is about 13.3 billion light-years away."
So, in one side we see a galaxy (let's call it galaxy A) at a distance of 13.3 BLY, while on the other side there is other galaxy (galaxy B) at a similar distance from us.Therefore, we can assume that the distance between galaxy A to galaxy B could be 26.6 BLY.
We all know that the size of the whole Universe after the inflation was only 10,000 LY.
We also know that it took almost 380 Million years for the atoms to be formed after the Big bang.
Let's assume that the Milky Way was there at a distance of 50,000LY away from galaxy A (420 Million years after the BB).If I understand you correctly, that distance represents the proper distance.
We clearly know that the light travels at the speed of light. (With or without the impact of the expansion)
Due to the compact size of the early Universe (at the age of 420 MY) it is clear that the impact of the expansion rate at this compact early universe is quite neglected. (74 Km//s per 3MLY). Therefore, the light from galaxy A should cross a distance of 50,000LY in about 50,000 Year.
So, why it took the light from galaxy A so long time (13.3BY) to get to the Milky Way?
Can you please explain how the proper/commoving distance velocity could force the light to travel 13.3 BLY in order to cross a proper distance of only 50,000
However, I still don't understand why if it was closer 13BY ago, but due to the expansion its emitted photons of light had to cross very long distance (13BLY) than it also should appear bigger?
So the light was emitted from a distance of 50,000LY (that was the distance between the Milky way to galaxy A when the universe was 420My old). Proper distance. This is very clear.
Quote from: Halcand the apparent size of the object can be directly computed from that without consideration of how much time it takes. Why is it? This is totally unclear to me.
and the apparent size of the object can be directly computed from that without consideration of how much time it takes.
I still don't understand why the proper distance can set any sort of impact?
From our point of view we see a galaxy at a distance of 13.3 BLY that its light had traveled for 13.3 BY to get to our earth. With or without the expansion, the total distance is fixed and the total time is fixed.
It should take the moon light about 1.5 sec to get to earth.Let's assume that somehow we can use the expansion process to move the moon away from us so fast that the next time that we get its light is after it gets to a distance of 1LY away and 1Y from now.
Here's a link concerning why light-travel distance shouldn't be used:http://www.astro.ucla.edu/~wright/Dltt_is_Dumb.html
QuoteSo, in one side we see a galaxy (let's call it galaxy A) at a distance of 13.3 BLY, while on the other side there is other galaxy (galaxy B) at a similar distance from us.Therefore, we can assume that the distance between galaxy A to galaxy B could be 26.6 BLY.Using light travel distance, yes.
QuoteWe all know that the size of the whole Universe after the inflation was only 10,000 LY.Reference please. I'm not buying that one.
Perhaps your example could be real one like MACS0647-JD which was much further away than 50,000 LY at age 420 MY. More like 3 billion LY away, according to the limited resolution of my picture. That event is on our current light cone.
You make it sound like the moon blinks off, and then on again when it's completely somewhere else.Your numbers are unreasonable. If expansion is that severe, the universe would be 1.5 seconds old, and there would be nothing to see at all.
Think about it instead of just dismissing it because you already know a different answer.
QuoteThey also addhttp://www.astro.ucla.edu/~wright/Dltt_is_Dumb.html"The Universe is homogeneous and isotropic, so it has no edge. Thus there cannot be a maximum distance."Therefore, without an edge and in order to meet the requirement to homogeneous and isotropic it actually must be infinite or at least very, very big. Much bigger than that 92BLY.I never said otherwise.
They also addhttp://www.astro.ucla.edu/~wright/Dltt_is_Dumb.html"The Universe is homogeneous and isotropic, so it has no edge. Thus there cannot be a maximum distance."Therefore, without an edge and in order to meet the requirement to homogeneous and isotropic it actually must be infinite or at least very, very big. Much bigger than that 92BLY.
and the apparent size of the object can be directly computed from that without consideration of how much time it takes.Again, simple geometry. Consider several such round objects arranged in a ring so their edges touch, and at that distance, and compute the angle that they would appear from the center of that ring. That angle cannot change over time. Expansion of space does not add new degrees to the 360 that make up a circle.Think about it instead of just dismissing it because you already know a different answer.Suppose there are 19 circular objects of size about 1 BLY diameter, each 3 BLY distant, with edges touching. How large would they appear (in degrees?). It's not hard.
QuoteI never said otherwise.QuoteQuote from: Dave Lev on Today at 16:15:32So you confirm that as our universe has no edgeI never said that either. I only said we have no evidence of one.
I never said otherwise.
Quote from: Dave Lev on Today at 16:15:32So you confirm that as our universe has no edge
Regardless of how long it takes the light to get to us, how big (in radians or degrees) is that 1BLY circular object going to appear?
I said 3BLY proper distance when the universe was around 0.4 BY old.
There is no fiber optics in space.
Quotehttp://www.astro.ucla.edu/~wright/Dltt_is_Dumb.html"The redshift z is usually the only number in the whole story that is unambiguous and likely to be correct."Yes, this is the one empirical observation. Hard to contest it.
http://www.astro.ucla.edu/~wright/Dltt_is_Dumb.html"The redshift z is usually the only number in the whole story that is unambiguous and likely to be correct."
Why if we see a galaxy with a redshift of 10 we can't just understand that this galaxy is moving away at 10 times the speed of light?
QuoteQuote from: Dave Lev on 07/06/2020 17:48:18So, based on Redshift our scientists can easily calculate the velocity of any galaxy based on the simple formula that:v = c * z = 300,000 km/sec * zThis formula is based on Newtonian physics, meaning it is a good approximation for an object that is 1) local and 2) not receding at relativistic speed.
Quote from: Dave Lev on 07/06/2020 17:48:18So, based on Redshift our scientists can easily calculate the velocity of any galaxy based on the simple formula that:v = c * z = 300,000 km/sec * z
QuoteQuote from: Dave Lev on 07/06/2020 17:48:18Why if we see a galaxy with a redshift of 10 we can't just understand that this galaxy is moving away at 10 times the speed of light?Because, no matter how often you ignore the issue, things don't travel faster than light.
Quote from: Dave Lev on 07/06/2020 17:48:18Why if we see a galaxy with a redshift of 10 we can't just understand that this galaxy is moving away at 10 times the speed of light?
The galaxy I mentioned with redshift of 11 is increasing its present proper distance from us at a rate of a bit more than twice light speed.
A redshift of 11 represents a real velocity of 11 times the speed of light.
no matter how often you ignore the issue, things don't travel faster than light.
no matter how often you ignore the issue, things don't travel faster than light
If you don't agree with that, than please explain where is the error,
Quote from: Dave Lev on 22/04/2020 11:58:12a galaxy at a distance of 13 BLY is actually moving away from us almost the speed of light. Due to the idea that the Universe is isotropic and homogenous, a galaxy at 26 BLY should move away at 2cThat's still wrong.You can't just add relativistic velocities as if they were apples.
a galaxy at a distance of 13 BLY is actually moving away from us almost the speed of light. Due to the idea that the Universe is isotropic and homogenous, a galaxy at 26 BLY should move away at 2c
Quote from: Bored chemist on 07/06/2020 19:49:31no matter how often you ignore the issue, things don't travel faster than light.
In Section 4 we provide explicit observational tests demonstrating that attempts to apply special relativistic concepts to the Universe are in conflict with observations....3.1 Misconception #1: Recession velocities cannot exceed the speed of light....When observables are calculated using special relativity, contradictions with observations quickly arise (Section 4).
B C, you're making the mistake of modeling the universe using a special relativity model, which assumes flat non-expanding spacetime.
Dave is pushing the linear view of v=cz, which is the leftmost line going off the top of the page, which also contradicts observations, but the paper doesn't so much go into debunking this one since it is not a common misconception asserted by accepted scientific literature.
he empirical observations fall withing the grey area, and the favored model is the (0, 3, 0, 7) one, which is the 2nd from the top of the 4 lines. It yields a present recession velocity of about 2c for an object with redshift of 10.
Based on the gray line, the recession velocity between B to C is (0.8-0.6)c =0.2c, while the redshift should be (2-1)=1
I get 0.8c at z=1 and ~1.25c at z=2, using 2nd line from top in grey area. Somewhere there's probably a color version of that chart that makes it more clear which line is which model.
QuoteQuoteSo, while the recession velocity of galaxy B (from earth) is 0.6c at redshift 1, the recession velocity of galaxy C (from earth) is 0.8c at redshift 2.If we could jump to B and monitor the recession velocity of C than what shall we see?Based on the gray line, the recession velocity between B to C is (0.8-0.6)c =0.2cThese are proper recession speeds, and they actually do add that way, so 1.25c-0.8c is about 0.45c between B and C.
QuoteSo, while the recession velocity of galaxy B (from earth) is 0.6c at redshift 1, the recession velocity of galaxy C (from earth) is 0.8c at redshift 2.If we could jump to B and monitor the recession velocity of C than what shall we see?Based on the gray line, the recession velocity between B to C is (0.8-0.6)c =0.2c
Redshift at 0.45c is z=0.5 or so. Kryptid points out that redshifts don't add like you're doing.
QuoteQuote from: Dave Lev on Today at 06:03:19So, how could it be that we see B at redshift 1 and C at redshift 2 while the redshift between B to C is only 0.5?I did indeed make a mistake there. The redshift at 0.45c is a bit under 0.4. The resolution of the chart is near unreadable at such slow speeds.Maybe the numbers would be more clear if you picked galaxies a little further away, like one at hypothetical z=100 (v=~2.9c) and another receding at half that speed, z=3. Of course there's nothing visible at z=100 since any galaxy there is in the middle of the dark ages, so it emits no light. Hence it being hypothetical. We can see the recombination event at z=1100, which is just off the right side of that graph, which ends close to the edge of the visible universe.
Quote from: Dave Lev on Today at 06:03:19So, how could it be that we see B at redshift 1 and C at redshift 2 while the redshift between B to C is only 0.5?
QuoteQuote from: Dave Lev on Yesterday at 15:19:19You didn't answer my question.So, let me ask again:If galaxy B is located at almost the same direct line from A (our location) to C.How could it be that we see B at redshift 1 and C at redshift 2 while the redshift between B to C is only 0.5 (or at least lower than 2-1=1?Because the mathematics puts it at about 0.5. You subtracting 1 from 2 is completely irrelevant, since we're not counting apples here.
Quote from: Dave Lev on Yesterday at 15:19:19You didn't answer my question.So, let me ask again:If galaxy B is located at almost the same direct line from A (our location) to C.How could it be that we see B at redshift 1 and C at redshift 2 while the redshift between B to C is only 0.5 (or at least lower than 2-1=1?