The speed of light
Discussion
Quick question.
I was reading an article about the nature of time (which I probably need to read again at least 5 times) where the writer said that the natural speed limit in the universe is C. Fair enough, I thought that was the case.
Later on though we got to talking about the outer edges of the universe which are accelerating away from us at greater than c. How can this be? Is this because of joint movement - us one way, them another? Or when we look out into the night sky is it all accelerating away, the further out the faster.
If this is the case how can it be faster than c?
Be gentle, A level physics, quite some time ago.
I was reading an article about the nature of time (which I probably need to read again at least 5 times) where the writer said that the natural speed limit in the universe is C. Fair enough, I thought that was the case.
Later on though we got to talking about the outer edges of the universe which are accelerating away from us at greater than c. How can this be? Is this because of joint movement - us one way, them another? Or when we look out into the night sky is it all accelerating away, the further out the faster.
If this is the case how can it be faster than c?
Be gentle, A level physics, quite some time ago.
DP1 said:
Super Sonic said:
C is the speed at which light travels through the vacuum of spacetime.
The distant edges of the visible universe moving away are spacetime itself expanding.
Does this mean that outside the visible universe time doesn’t exist as we know it?The distant edges of the visible universe moving away are spacetime itself expanding.
DP1 said:
Super Sonic said:
C is the speed at which light travels through the vacuum of spacetime.
The distant edges of the visible universe moving away are spacetime itself expanding.
Does this mean that outside the visible universe time doesn’t exist as we know it?The distant edges of the visible universe moving away are spacetime itself expanding.
We actually aren’t that sure what time is within our universe. Einstein treated as wrapped up with space as part of the substance of the universe, but quantum mechanics finds little need for it at all, and indeed acts as if it can go both ways or neither sometimes. Some theorists see it as more to do with how us humans perceive things that anything real.
At best it’s a much more variable and flexible thing than we tend to treat it in everyday life, going at different speeds in different places and for different viewpoints. There’s no certainly no sense of the time “now” being applicable to everywhere, which is weird because of course it’s one of the main things we use it for.
DP1 said:
Super Sonic said:
C is the speed at which light travels through the vacuum of spacetime.
The distant edges of the visible universe moving away are spacetime itself expanding.
Does this mean that outside the visible universe time doesn’t exist as we know it?The distant edges of the visible universe moving away are spacetime itself expanding.
You're talking billions of light years of travel or billions of years of time travel in a very short space of time, which may be the same thing.
Fundamentally, beyond the edge of the observable universe is currently un-knowable, as we are only able to observe up to this point.
This is a function of, the speed of light, the size of the universe, the expansion rate of the universe, which is thought to be accelerating and at the edge of the observable universe is accelerating faster than the speed of light relative to us.
Skeptisk said:
As far as we know we are not in a special part of the universe. If you could magically transport yourself to edge of what we perceive as the visible universe then it would be like here.
Except you wouldn't know what time to set your watch to when you got there and whether or not they were on daylight savings in that part of the universe.one thing is clear, the universe expanding means life can exist.
https://www.science.org/content/article/conditions...
''As it turns out, our universe seems to get it just about right. The existing cosmological constant means the rate of expansion is large enough that it minimizes planets' exposure to gamma ray bursts, but small enough to form lots of hydrogen-burning stars around which life can exist. (A faster expansion rate would make it hard for gas clouds to collapse into stars.)''
It then leads back to the ultimate question of some many factors that have allowed us to exist. Or does the universe exist becuase we exist?
Maybe the whole point of the universe is to generate and sustaining observers of the universe?
https://www.science.org/content/article/conditions...
''As it turns out, our universe seems to get it just about right. The existing cosmological constant means the rate of expansion is large enough that it minimizes planets' exposure to gamma ray bursts, but small enough to form lots of hydrogen-burning stars around which life can exist. (A faster expansion rate would make it hard for gas clouds to collapse into stars.)''
It then leads back to the ultimate question of some many factors that have allowed us to exist. Or does the universe exist becuase we exist?
Maybe the whole point of the universe is to generate and sustaining observers of the universe?
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