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NASA Discovers Most Distant Galaxy In Known Universe
An anonymous reader writes with this snippet from cbc.ca: "'NASA's Hubble and Spitzer space telescopes (not to be outdone by the Kepler Space Telescope) have discovered the most distant galaxy identified so far in the universe... the galaxy is 13.3 billion light years away and only a tiny fraction of the size of the Milky Way. Due to the time it takes light to travel through space, the images seen from Earth now show what the galaxy looked like when the universe was just 420 million years old, according to a press statement released from NASA. The newly discovered galaxy (is) named MACS0647-JD."
This is explained thoroughly on http://en.wikipedia.org/wiki/Observable_universe
It's also worth pointing out that in the context of the universe, there is no edge. By default we tend to think of the universe as being like an explosion in space where the first particles ejected are at the edge of the explosion radius.
However, when we're discussing the universe, this explosion is actually creating space, so the expansion is not from the core to the edges, it's happening through all of space - everything is moving away from everything else. Think of it like the surface of a balloon that is being blown up. In 2d terms, all points on the surface of the balloon are moving away from each other, but none of them are at the 'edge' of the balloon.
Someone standing on the surface of a sufficiently large balloon would look around and see everything receding from them - it would be reasonable for them to feel they were at the centre of the surface of the balloon and that therefore somewhere there was an 'edge' - but they'd be wrong.
It's a perfectly good question, and a tricky one to fully explain. The first thing to look at is how you measure distances - because we're talking about light here we're firmly in the realm of relativity, so there's no such thing as "space" and "time", you have to bundle them together in spacetime. And talking of x-light-years or y-million-years doesn't actually make much sense, you have to measure both at once, so instead of distances or times things are measured in "spacetime intervals" which account for all four dimensions.
Now this is the tricky bit - for any "light-like" path (more technically called a "null geodesic") the spacetime interval is zero. So the light that we're receiving from the galaxy here and now has a spactime interval of zero. The light that this galaxy emits all travels the same spacetime interval of zero - some of those photons would have been aimed at (as you suggest) "our galaxy" when it was "closer" - although in fact "our galaxy" was just a wisp of hydrogen at the time. Other photons (the ones we see today) were essentially aimed at a point that was also 13Bn years IN THE FUTURE, and those are the ones we see hitting us today.
Long story short, you don't just aim light at a point in space, you also aim it at some point in the future, and the further away in space it's aimed then the further into the future it's aimed. In a million years we'll still be able to see this galaxy (assuming it doesn't slip over the cosmic horizon), and the photons we'll detect then are currently still in transit, aimed at when/wherever we will be then, just as the photons we detect today were still in transit last week, last year and 13Bn years ago.
Please consider this account deleted, I just can't be bothered with the spam anymore.