Is there really nothing faster than light?

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SUMMARY

The discussion centers on the implications of Einstein's theory of relativity, specifically the assertion that nothing can travel faster than light. Participants clarify that while massive objects cannot exceed the speed of light (299,792.458 kilometers per second), the expansion of spacetime itself, as described in the Big Bang theory, is not constrained by this limit. The conversation highlights the distinction between the speed of light and the apparent motion of objects due to spacetime expansion, emphasizing that while stars can move at significant speeds (e.g., 15,000,000 kilometers per hour), they do not surpass the speed of light in a vacuum.

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  • Understanding of Einstein's theory of relativity
  • Familiarity with the concept of spacetime expansion
  • Knowledge of the speed of light (c) and its implications
  • Basic grasp of the Big Bang theory and cosmic inflation
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This discussion is beneficial for theoretical physicists, students of physics, and anyone interested in the fundamental principles of cosmology and the nature of light and spacetime.

  • #31
bob012345 said:
It seems fast to our everyday experience but I have always been struck by how slow the speed of light is in comparison to the scale of the universe. Or on the scale of the laboratory when accurate time bases might be required across a room when lightspeed is only ~30 cm/ns.
Or in relation to modern computing: the PC I am typing this on has 6 cores each of which can multiply a 64 bit float in the time it takes light to reach my eyes from the screen.
 
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  • #32
hmmm27 said:
So why is it "space is expanding", not "everything is shrinking" ?
I know this isn't a serious question but still:
Occam's Razor is pretty useful here.

In the 'space is expanding' scenario, only one thing need change: spacetime.
In the 'everything is shrinking' scenario, multiple things must change - not just matter but also the speed of light.
 
  • #33
Dale said:
What is the experimental distinction between the two?
Is there one ? (doable with current knowledge)
 
  • #34
pbuk said:
I am typing this on has 6 cores each of which can multiply a 64 bit float in the time it takes light to reach my eyes from the screen.

Don't sit so close to the screen. It's bad for your eyes.
 
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  • #35
Vanadium 50 said:
Don't sit so close to the screen. It's bad for your eyes.
Yes you are right, I had in my head that FMUL was 5 cycles but it's only 4, and again I was thinking 2.5GHz for about 2' from the screen but my new beast is much faster than that.
 
  • #36
hmmm27 said:
Is there one ? (doable with current knowledge)
There isn’t, which is why the question is pointless. It is a distinction without a difference.
 
  • #37
hmmm27 said:
Our what ?

Might want to check your reference for the speed of light : it's considerably faster than a measly 15M km per hour.
The speed of light is 300,000 Km/sec
 
  • #38
Dale said:
There isn’t, which is why the question is pointless. It is a distinction without a difference.
WEl, it's not that there isn;t
Keldude said:
The speed of light is 300,000 Km/sec
Perhaps you missed @hmmm27's post here?
 
  • #39
hmmm27 said:
1,080,000,000 > 15,000,000

Still, 13% of the speed of light is scary fast.
15,000,000 is 1.4 percent of 1,080,000,000
 
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  • #40
jbriggs444 said:
15,000,000 is 1.4 percent of 1,080,000,000
:eek:Still scary fast. Thanks.
 
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  • #41
PeroK said:
Your English is fine. It's your arithmetic that's bad!
“Your calculations are correct, but your physics is atrocious.” Einstein to Lemaître.
 
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