1. A few days ago I just read here that our galaxies (one of which we are part of) move or expand faster than light,
  2. And read here that light we see from stars is extremely old, maybe more than several years.

If galaxies' expansion is faster than the light of stars, then is it possible that we see our own Sun as a star somewhere because light may reach us later than expansion?

  • $\begingroup$ perhaps you should read some more (and more reliable) sources. Did you look at wikipedia? No galaxy expands. The space between distant galaxies expands, though. Also, "expanding faster than light" makes no sense: light doesn't expand. $\endgroup$ – Walter Jan 18 '14 at 10:16
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    $\begingroup$ @Walter: The phrase "expanding faster than light" does make sense; it means that the speed of expansion is greater than the speed of light. It's just happens not to be true for any one galaxy. $\endgroup$ – Keith Thompson Jan 20 '14 at 16:57

I think the original answer has confused you somewhat - it is spacetime that is expanding faster than light - when viewed from sufficiently far away - we certainly are not moving away from the Sun at anything even remotely close to the speed of light (in fact the expansion of spacetime is not a motion at all in the true sense, but a change in the underlying metric).

  • $\begingroup$ Space is expanding locally, too. But otherwise I agree that's the probable confusion on the part of the OP--the galaxies themselves don't expand (at least not for those reasons); the distance between them increases. $\endgroup$ – Stan Liou Jan 17 '14 at 10:35
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    $\begingroup$ well they do expand because the metric is expanding $\endgroup$ – adrianmcmenamin Jan 17 '14 at 10:43
  • $\begingroup$ No. The cosmological constant provides a repulsion, but it just finds itself in equilibrium with the non-Λ portions of gravity and other forces relevant to the object. So one can say that they're slightly bigger than they would be if they there was no Λ. Now, for the 'phantom energy' version of dark energy, they do expand, and so much as to eventually tear everything apart. $\endgroup$ – Stan Liou Jan 17 '14 at 10:52
  • $\begingroup$ In my question I did not mean that earth is moving away from sun.. I meant our whole solar system is moving away from other stars in our glaxy If we are part of a glaxy. In this case we can say that sun is a star of our galaxy which is expanding. If it does expand faster than light then is it possible ?? $\endgroup$ – Asadullah Ali Jan 18 '14 at 1:41
  • $\begingroup$ It is the fabric of "spacetime" itself that is expanding - this is what astronomer's call the metric. The further away you are from an object the greater the rate of that cumulative expansion. There is no possibility that the Earth will survive for long enough for the speed of the expansion of the distance between the Earth and the Sun to become anything like the speed of light. NB This expansion of the metric means every object in the universe is "moving away" from every other object. $\endgroup$ – adrianmcmenamin Jan 18 '14 at 12:10

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