Hubble squints at most distant galaxy The Hubble Space Telescope has squinted at what's "likely to be the most distant object ever seen in the universe" – a galaxy some 13.2 billion light-years from Earth. The dim cluster of blue stars existed just 480 million years after the Big Bang, NASA explains, and is a significant find for scientists aiming to explain how …
If we were there, looking back at us, we'd look pretty much the same.
Of course, there are certain problems concerning here, there, now and then when you're talking about the edge of the observable universe. But it's a nice prelude to getting rat-arsed in the pub tonight.
It is (almost) meaningless to speak of the 'distance' between us and such a faraway object. the NASA article carefully talks about the light having been emitted from the galaxy 13.2 billion years ago. At the time the light was emitted, the galaxy would have been much closer, but expansion of the universe over the intervening aeons will have greatly increased the distance between us.
Indeed, if we ask the question: "how long would it take a light beam emitted today from Earth to reach this galaxy?" the answer may well be that the light could never reach its destination, as the space between us expands faster than the light beam can travel.
This should explain faster than light....... Taken w/o permission, from:
http://www.nytimes.com/2011/01/16/opinion/16greene.html?_r=1&scp=3&sq=universe&st=cse
" If the dark energy doesn’t degrade over time, then the accelerated expansion of space will continue unabated, dragging away distant galaxies ever farther and ever faster. A hundred billion years from now, any galaxy that’s not resident in our neighborhood will have been swept away by swelling space for so long that it will be racing from us at faster than the speed of light. (Although nothing can move through space faster than the speed of light, there’s no limit on how fast space itself can expand.)
Light emitted by such galaxies will therefore fight a losing battle to traverse the rapidly widening gulf that separates us. The light will never reach Earth and so the galaxies will slip permanently beyond our capacity to see, regardless of how powerful our telescopes may become.
Because of this, when future astronomers look to the sky, they will no longer witness the past. The past will have drifted beyond the cliffs of space. Observations will reveal nothing but an endless stretch of inky black stillness.
If astronomers in the far future have records handed down from our era, attesting to an expanding cosmos filled with galaxies, they will face a peculiar choice: Should they believe “primitive” knowledge that speaks of a cosmos very much at odds with what anyone has seen for billions and billions of years? Or should they focus on their own observations and valiantly seek explanations for an island universe containing a small cluster of galaxies floating within an unchanging sea of darkness — a conception of the cosmos that we know definitively to be wrong?
And what if future astronomers have no such records, perhaps because on their planet scientific acumen developed long after the deep night sky faded to black? For them, the notion of an expanding universe teeming with galaxies would be a wholly theoretical construct, bereft of empirical evidence. "
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what would you rather say? that car is 1 mile/ 1.609 Km / 5280 feet /63,360 inches away???
or quote how long the light from that car takes to reach you???
would you rather say they said it was 77,596,374,671,916.02 Billion Miles away??? 13.2 billion is a lot easier..
And then you LOSE it.. inanimate objects cannot travel faster than the speed of light .... so yes, the light WILL eventually reach the observer... swot up on yer 'special relativity'... :)
Now if a super advanced civilization builds a FTL drive, they might come and see us, Buuuut... I doubt if our solar system will have formed by then...
It depends how accurate you need to be. Let's suppose the car is 1500m away and travelling away from us at 20m/s when it emits a short pulse of light. That pulse will take 1/200,000 of a second to get to us, by which time the car will be a further 0.1mm away. And if we reflect the light straight back, it will need to travel a further 0.1mm before it could be detected by someone in the car. So how far away is the car? It all depends on what you want to measure. (Note that this is all simple Newtonian mechanics, Relativity may be neglected at these speeds and distances.)
But when we're talking about something much farther away and 'travelling' much faster, these differences can become very significant indeed. Because the observed redshift is caused (mainly) by space expanding and not ordinary velocity, it is possible (indeed likely) that light now leaving the Earth can never reach this distant object.
If you wish to learn more, I recommend Liddle's "An Introduction to Modern Cosmology", which deals with these concepts while avoiding the complexities of Tensor Mechanics and Minkowski Space-Time.
Go on then, give us a pop science explanation of what happens when two objects move directly apart from each other, each traveling at 0.51 times the speed of light relative to the mid-point, with a light source on one object and an observer standing on the other. I'm intrigued as to how the light will get to the observer.
Now here is an interesting thing.
No one seems to notice that when we look at distant objects we are looking back into history. If this galaxy when seen is 450m years old then one would assume it is close to the big bang centre, certainly closer than 450m light years. If it is 13.2bn light years from us that would mean we must be between 12.75bn and 13.65bn light years distance from the big bang. I read that the estimated age of the universe is13.75b years. The question is how did our galaxy manage to travel that distance in that time without getting close to light speed?
I think there is something suspicious about these numbers.
Everything (including us) came from the centre of the big bang (according to current theories). We are travelling through space, but space is also constantly expanding. So our galaxy hasn't necessarily travelled that distance, but the space between us and the other galaxy (and everywhere else) has expanded.
Even if our galaxy and this other galaxy were not moving, the distance between them would still change due to the expansion of space.
Even more interesting ( or mind-boggling ) is the set of inflation hypotheses that suggest that in the first ~1e-32 s after the big bang our 'universe' expanded from less than the size of a proton to ~10 cm across (or much more). This was an inflation of spacetime - no FTL rules were broken.
The current expansion seems quite staid by comparison
The edge of the observable universe is about 46–47 billion light-years away.
The age of the universe is about 13.75 billion years.
Things at the edge, while being 13.75 billion years old, are not 13.75 billion light years away.
Because of inflation / expansion / dark energy, while the light was travelling, as Chris points out.
That all of these supposed measurements of the cosmos are based on our current theories and observations. Once that new James Webb space telescope comes on stream, assuming it does, I think there will be new observations that challenge these very theories. And at some point in the future, we are likely to view our current set of theories as we now regard the ideas that were dominant before the age of enlightenment. A flat earth in the middle of everything.
Big thumbs up for space telescope science
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