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 2019-07-16, 03:25 #23 jwaltos     Apr 2012 Gracie on lookout. 419 Posts https://en.wikipedia.org/wiki/Cherenkov_radiation https://en.wikipedia.org/wiki/Talk:Cherenkov_radiation ...as a starting point. "Cherenkov radiation results when a charged particle, most commonly an electron, travels through a dielectric (electrically polarizable) medium with a speed greater than that at which light propagates in the same medium." This is the only technically correct assertion where faster than light propagation exists within a relative context. Some questions of my own...where is the center of the universe relative to earth (using appropriate space-time coordinates)? Prior to decoupling, when light did not exist, what other "things" would travel at that velocity? Is there a theoretical limitation on acceleration and other time derivatives (ie. jerk, snap, crackle and pop [no joking!])? What is creating space-time..something inside or outside of this known universe? Regarding the mathematics describing these concepts, what are the fundamental concepts (those which cannot be broken down) without which none of the above could be expressed? An understanding of enumeration, an appreciation of position and experiencing transformation [interactively] as a passage of time in my opinion still needs work. For example, factorization is an aspect of entanglement yet integer factorization is not yet completely tamed. Last fiddled with by jwaltos on 2019-07-16 at 04:13 Reason: additional point
 2019-07-16, 05:00 #24 jwaltos     Apr 2012 Gracie on lookout. 419 Posts https://www.sciencenews.org/article/...nce-connection This is a relevant link to the initial post and again is a jumping-off point. Last fiddled with by jwaltos on 2019-07-16 at 05:01
2019-07-16, 05:01   #25
retina
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Quote:
 Originally Posted by jwaltos Some questions of my own...where is the center of the universe relative to earth (using appropriate space-time coordinates)?
Exactly wherever you are. Since what you can observe is a sphere of radius r extending in all directions. Another observer in a another part of the universe can see a different (possibly overlapping) sphere where they are the centre of their observational extents.

Last fiddled with by retina on 2019-07-16 at 05:06

 2019-07-16, 07:07 #26 LaurV Romulan Interpreter     "name field" Jun 2011 Thailand 22·5·17·29 Posts Well, the questions make sense. My understanding of these things is extremely limited, there are a lot of "universe-related" and "space-time" related things which I can not imagine and I can not conceive in my head. But from classical geometry point of view, if I observe 3 objects running away from each-other, I can see how fast A runs away from B, how fast B runs away from C, and how fast A runs away from C, and I can calculate exactly where in space and time they where when they were a single object. This is independent of where I am and if I see objects D, E, and F. Now the real question is, if I take objects A, B and D, do I get the same point as before? I know that "space dilation" is tricky... and I never studied much in this direction, that is why I can not really grasp these things, but there are few people here with a better understanding, who could shed some "faster then light".. Last fiddled with by LaurV on 2019-07-16 at 07:08
2019-07-16, 07:53   #27
xilman
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Quote:
 Originally Posted by jwaltos Some questions of my own...where is the center of the universe relative to earth (using appropriate space-time coordinates)?
You hit the nail on the head with the word "appropriate".

Many people find visualization in two dimensions easier than in three so I'll restrict my arguments to the simpler case.

If the universe is open, and observation suggests it is, there is no center. Where is the center of an infinite plane? As retina notes, any point is as good as any other.

If the universe is closed, like a sphere, for instance, which point on the surface of a sphere, is the center of that sphere? There is no such point and retina's prescription is once more as good as any. The key word is indeed "appropriate".

I'll address some of your other questions when the round tuit supply improves.

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