Is the Universe Expanding Faster Than the Speed of Light?

[Peter (IMC)]

Thanks Hellfire, Your explanations are very much appreciated!


Suppose you´re a particle traveling at light speed... What does space-time look like to you? Is it simply not observable?

Then suppose you´re slowing down. How do you observe space-time during the slowing down process? Does it seem to suddenly come into existence and start expanding?

If you're just you and you´re slowing down, does the universe seem to be expanding?

Suppose you´re still just you and stop slowing down, does the universe seem to stop expanding?

Suppose you´re speeding up, does the universe seem to be contracting?

If I understood it correctly, slowing down is only possible if you can do so relative to something else. so perhaps the above makes absolutely no sense at all. But I haven't figured out yet why it doesn't make sense. If anybody can help?

 

[hellfire]

Cosmological expansion is a general relativistic effect. If I understand correctly you are thinking about Lorentz contraction or something similar. Note that unlike cosmological expansion this effect is not isotropic and is only in the direction of motion. But, in general, to explain features of the universe at large scales one must use of general relativity instead of special relativity.

 

[Peter (IMC)]

Cosmological expansion is a general relativistic effect. If I understand correctly you are thinking about Lorentz contraction or something similar. Note that unlike cosmological expansion this effect is not isotropic and is only in the direction of motion. But, in general, to explain features of the universe at large scales one must use of general relativity instead of special relativity.

What if your direction is constantly changing?

 

[Physics-Learner]

there is no way to change direction without accelleration.

 

[hellfire]

What if your direction is constantly changing?

Special relativity is not appropriate to explain expansion. What has to be explained is cosmological redshift, as well as cosmological time dilation, Tolman's surface brightness variation, etc. which are phenomena that require of general relativity to be explained.

 

[Peter (IMC)]

Thanks hellfire, I know where to do some reading now,. :)

I´m just confused I guess by that an electron is going around the core of an atom at light speed. Which seems to be an impossibility because being in orbit means changing direction all the time.

I know there´s that probability cloud of where the electron could be, but that too seems to make sense to me. If it is going at light speed and time stands still for it (compared to us) then time around it is happing all at once from the electron point of view... so from our point of view he´s in all places it's ever been at the same time. In fact, it feels to me like he could be anywhere in the universe as it's all the same place to him, a dot.

But I guess here too I need to do some more reading on when to use general relativity and when to use special relativity.

general and special relativity, that already sounds like a paradox as well... ( :) Just kidding )

 

[Chronos]

Lets not mix GR with QT, they don't play well together. Most physicists would object to the characterization of an electron as 'orbiting' an atomic nucleus. This is a pretty basic discussion, but captures the issues:
http://www.colorado.edu/physics/2000/quantumzone/frequency2.html