Re: Relativistic aberration

Am Mittwoch000017, 17.07.2024 um 14:05 schrieb gharnagel:

On Wed, 17 Jul 2024 7:05:15 +0000, Thomas Heger wrote:

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Am Dienstag000016, 16.07.2024 um 16:47 schrieb gharnagel:

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"Why is the speed of light so slow when the universe is such a really,
really big place?" -- G. L. Harnagel

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This is a tautology:
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What we see in the night sky is actually our own past light-cone.

 Ah, but if we can develop tachyon astronomy, that will not be true!

Well, if light would speed up somehow in remote corners of the universe, we would still see what we see in the night sky, if this phenomenon would not change in observable timespans.
Possibly there are tachyons, but those are invisible anyhow, because we can see only light and light moves with light speed and tachyons don't.

 

This means: light is relatively slow for the wastness of the universe,
hence we can see everything only with a certain delay and the further
away, the longer the delay, according to x = c* t
(with x= distance in meters, t = delay in seconds).
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This 'longer away' is usually measured in light years and the delay in
years.
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Since the night sky shows only a delayed image of past events, the speed
of light cancels out of the equations and we can put any value into it
and always get a valid picture of the universe.
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So we only assume, that light moves always with ~300 million meters per
second through the entire universe.
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But if light would speed up or slow down, we would not be able to
measure this, because we always see the own light cone in the night sky
and c is already embedded into it (for whatever a value c actually has
in outer space).
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TH

 Ah, but the fine structure constant, which is pertinent to how stars
shine,
includes the speed of light.  That implies that c is the same throughout
space and time, n'est-ce pas?

Well possibly.
What I wanted to say is this:
what we see in the night sky is light, that stems from remote places in the universe.
Since light is very fast, but space is also very large, we have a significant delay for the travel from such remote place to us observers.
This makes the image we see a little unreal, because it is not only old, but also 'layered in time'.
To untangle this picture and create kind of realistic picture of the universe, we would need the distance to those remote places.
Since we only have light to see, we can assume c=~ 300 million meters/s as light speed.
But what if that is not always the case???
Could we somehow find out??
No, since c is already used to determine the distance to these events.
If now c alters mysteriously along the path, we had to determine the distance by other means (which we do not have), hence cannot measure, whether or not c stays always the same.
TH