The speed of light, etc

[Sephiroth]

Chris wrote:

Because the galaxy’s absolute velocity is not greater than the speed of light. The distance between that galaxy and us may be increasing at greater than the speed of light because we are moving away from the galaxy at speed, just as it it’s moving away from us. But neither object is moving at greater than light-speed if observed from a fixed point.

OK - I can buy that. If we could be still while our galaxy was moving in space (not "space-time - what is that?) then the receding galaxy would not be moving away from us faster than light. That is a thought experiment because we don't know (someone might) how to become still/motionless in space.

Originally Posted by Sephiroth

Chris wrote:



OK - I can buy that. If we could be still while our galaxy was moving in space (not "space-time - what is that?) then the receding galaxy would not be moving away from us faster than light. That is a thought experiment because we don't know (someone might) how to become still/motionless in space.

If you’ve not come across the term ‘spacetime’ then you haven’t a cat in hell’s chance of understanding any of the issues you’re raising here (not that I’m presenting myself as an expert either, you understand).

In Einsteinian physics, space and time are not separate concepts. Time is measured as a fourth dimension of space. A four-dimensional spacetime model is essential for understanding relativistic effects, which are not mere mathematical oddities but have real-world applications (in the operation of GPS for example).

Originally Posted by joglynne

OK. <, sigh>> Skip to my final comment and don't feel you have to read/reply to this as it's probably a silly question and, as before, being totally irrelevant.

If there was a straight line from A through B & C to
point D. (Have I lost you yet)

1) I am on point A with a speedometer oh and a mahoosive telescope.

2) If I were able to see points B & D, point C being invisible (big bang or whatever) and .......

..... I can see B & D are moving apart from each other at the speed of light what would my speedometer register as the relative speed that they were travelling apart...... I am assuming super dooper planets could move that fast

Give up reading now unless you want the same headache as I have.

3) My head is seeing 2 cars, driving in opposite directions, passing at 30 mph surely they would be moving apart at 60 mph

Off to go and lie down in a dark room.

Add// Just realised I'm probably confusing the speed of light with the speed of sound but I have spent so much time pondering about all this that I blowed if I'm going to delete the sodding post!!!!!!!!!!

I’m getting a headache but only because I don’t know why I’d be able to see B and D but not C, if A, B, C and D are all in a line together

As for point 3, yes, two cars traveling through town at 30mph in opposite directions are increasing the distance between them at a rate of 60mph, but neither car is traveling at 60mph and so neither car is breaking the speed limit.

Likewise, two galaxies traveling in opposite directions at 75% of lightspeed are increasing the distance between them at 1.5x lightspeed, but neither galaxy is actually traveling faster than light and therefore neither of them is breaking the universal speed limit.

If you were an observer located in either one of these galaxies, you would never be able to see the other galaxy because the light emanating from each could never reach the other (the light would have to travel at 1.5x lightspeed in order to do so, and it can’t).

[joglynne]

Originally Posted by Chris

I’m getting a headache but only because I don’t know why I’d be able to see B and D but not C, if A, B, C and D are all in a line together

As for point 3, yes, two cars traveling through town at 30mph in opposite directions are increasing the distance between them at a rate of 60mph, but neither car is traveling at 60mph and so neither car is breaking the speed limit.

Likewise, two galaxies traveling in opposite directions at 75% of lightspeed are increasing the distance between them at 1.5x lightspeed, but neither galaxy is actually traveling faster than light and therefore neither of them is breaking the universal speed limit.

If you were an observer located in either one of these galaxies, you would never be able to see the other galaxy because the light emanating from each could never reach the other (the light would have to travel at 1.5x lightspeed in order to do so, and it can’t).

Thanks for your patience Chris and sorry about the headache. I can't see point C as it's apparently everywhere and was using point C as the starting point for the 2 things that are travelling away from each other.

I saw the following video by Brian Cox, explaining cosmic inflation, when it was first aired and since this thread started I have watched it again and keep hoping that one day there will be an explanation that I can comprehend.

https://www.youtube.com/watch?v=BD0r2Xfgh_E

[Sephiroth]

Fascinating article that challenges the Big Bang:

https://www.lppfusion.com/science/co...-the-big-bang/

The contradictions between Big Bang theory predictions and observations are not at all limited to those that have been widely dubbed a “Crisis in Cosmology”. Despite the continuing popularity of the theory, essentially every prediction of the Big Bang theory has been increasingly contradicted by better and better data, as shown by many teams of researchers. The observations are, on the other hand, consistent with a non-expanding universe with no Big Bang. The real crisis in cosmology is that the Big Bang never happened.

Well worth a read.

[Dude111]

Wow yes I guess it is!!

Its all fascinating..... Thank you for the page!!