Re: Postulates of Relativity and The Cosmic Background - Question


> What happens if I fire the thrusters?
>
> If I understand the Doppler effect properly, the receiver in the front
> end of the ship will detect blueshifted frequencies and will measure a
> higher temperature, the aft receiver will measure a redshifted
> background radiation and a correspondingly lower temperature, and the
> other four receivers will be unaffected.

Lets assume that there is light radiating from the center point of the
universe outward in all directions equally. Lets also assume that the
recievers can receive perfectly from any direction.

Now you are travelling at some unknown speed. You point the ship towards the
center of the universe, both the front and back recievers are travelling at
the same speed, so they both give the same wavelength.

Now you move the ship. If you move towards the center of the universe, both
recievers blue shift equally, since they are both moving at the same speed.
If you move away from the center then both red shift equally.

If you spun the ship around and around in a circle by its tail, the tail
wavelength would remain the same while the head wavelength would
redshift-blueshift (relative to the tail wavelength).

You could use the information from the recievers to determine your speed
compared to when you started. But you can't ever compare it to the original
radiation unless you know its original wavelength.

Even if you did, yes you could calculate your speed relative to the center
of the universe.
But remember two things
1. The radiation can't be constant everywhere in the universe, else nothing
would exist except it.
2. The bing bang is not part of relativity theory, so neither is a
background radiation level.

What you are said is correct in that radiation levels measured have been
used to come up with abolsute speeds for stuff, this is how the big bang was
predicted because everything seems to be moving away from a center point.
But this has nothing to do with the theory describing the motion of
everything including the background radiation itself.



.

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