Let’s say I have a magic spaceship that can take me to any point in the universe that I’d like and I want to travel to the absolute edge, the star that is at the furthest away from everything at the leading edge of the expanding universe. So what do I see when I get there? Is it in the middle of a gas cloud? Is it like a first generation star or would there be heavier elements in it? Is there just hydrogen and helium or dust? Would be part of a galaxy or would it have formed on its own? Would it be traveling so fast that there would be a visible to the human eye red and blue shift depending on which side of the star I was looking at?
There is no “edge” to space. Think of being a bug walking around on the interior surface of a balloon; although there is a boundary (beneath your feet) there’s no perceivable edge.
So, generally speaking, it would look just like it does here in the Local Group. There are variations (superclusters and celestial voids) but they appear to be relatively quasi-random in their initial distribution. (They’re not truly random as structure as since formed and objects like the local Great Attractor are continually causing macrostructures to form, but the initial distribution was more-or-less even, AFAWK.)
Stranger
There is no “farthest star”. No matter how far you travel from Earth there is always more stuff farther out.
This may be because the universe is infinite. Or it may be because it curves around and connects with itself on the backside. That’s still an open question. But there is no edge.
And, as far as we can tell, no matter how far away from Earth you travel things look pretty much the same. Now. when astronomers look at distant objects through a telescope they do look different. They look like things looked early in the evolution of the universe. But that’s just because the light has taken so long to get here. If you could magically poof yourself out to one of those distant galaxies right now it would look pretty much like our Milky Way does.
I believe this what is called the, Cosmic Event Horrizon and Cosmic Singularity. Get a chance, read Brief History of Time by S. Hawking.
Oh yeah, just Google ‘‘Hubble Deep Field’’.
But really far objects don’t look odd because they’re really far, they look different because we’re seeing them as they were billions and billions of years ago, when the universe was a lot younger.
If there’s any astronomers waaay out there looking back at us, they’ll see our local region of space as it was billions and billions and billions of years ago, as it was when the universe was a lot younger. So if we think the universe is 15 billion years old, when we look at something 14 billion light years away it’s only going to be 1 billion years old, we’re not seeing what it looks like now but what it looked like 14 billion years ago.
But the CMH isn’t a physical location; it’s a distance from wherever the observer is to the boundary at which the velocity of expanding space exceeds c. It would be true for any observer anywhere.
As Lemur866 says, the reason things far away look funny is because we’re seeing light that was emitted billions of years ago. Current thinking has the age of the universe at about 13.7B years (plus or minus a few hundred million years, but that’s subject to revision as cosmological models are refined or modified.
Stranger
Any books that you would recomend on the subject for your typical ''backyard astronomer?------Thanks!
Not a specific book on this topic, but Voyage To The Great Attractor: Exploring Intergalactic Space is a great book on collaborative scientific discovery, specifically about the discovery of the Great Attractor by the Seven Samurai, and covers a fair amount of general cosmology (expansion of space, early conditions of the universe, et cetera) in a very accessible way.
Greene’s books (The Fabric of the Cosmos: Space, Time, and the Texture of Reality, The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory) cover some of the underlying physical theory of cosmology in what is a quite readable manner for the layman. (Greene is a string theorist, not an astrophysicist or cosmologist, but he illustrates the areas where his field overlaps those topics quite lucidly.)
A lot of people like Michio Kaku (Parallel Worlds: A Journey Through Creation, Higher Dimensions, and the Future of the Cosmos, Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the 10th Dimension) but for some reason he doesn’t really grab me. I’m sure he knows his stuff, but he just seems to kind of wander around in his prose without really getting to a point, or else beating the same information again and again.
You might check out Sagan’s venerable Cosmos, too; I don’t know that it covers this topic in any great depth, and there’s certainly information that is out of date, but his politicking and technical gaffs outside his field aside, Sagan did have a gift for making space science and physics eminently accessible.
Stranger
Where were those stars 14 billion years ago? Closer because the universe had yet to expand during that time or were they out there already and the light has been traveling 14 billion light years to get here?
(Sorry if this should have been a new thread. This is my first real post as a paying member.)
Steven
Closer to what? Our sun didn’t exist 14 billion years ago. It’s generally considered to be a third-generation star of around 5 billion years.
Closer to each other? 14 billion years ago a totally different looking universe existed with galaxies and energetic objects together in a smaller volume of space. They were already moving away from one another at a high rate of speed, though.
The gases and heavier metals that they threw off with high energies eventually collapsed to form new galaxies, and these eventually threw off more material that became us. It’s hard to picture because there is no center to this picture. It’s happening everywhere.
Wow! Great info! Thanks.
I do have Carl Sagans, Cosmos, Pale Blue Dot and Demon Haunted World, all of which are great reads. Will look into the other titles you mentioned as well.
I recently bought my first telescope, a 5’’ Meade. Took a trip outside of Barstow, CA and I just can’t get enough of what there is to look at above. The book Nightwatch has been my ‘‘bible’’ for viewing at the night sky. What a great hobby! Thanks again.
Exapno,
That makes sense. I guess I was wondering if the light that reaches us has traveled 14 billion light years (from our current point of reference) or has the expansion ‘streched out’ time?
Of course this is not my field so pardon my ignorance.
Early stars were likely to be Population II (and perhaps Population III) stas; large, metal-poor, fast burning, short-lived stars that exploded in supernovas generating the vast bulk of elements heavier than iron in stellar nucleosynthesis.
The rate of expansion is thought to have been nonconstant, with an initial burst of expansion until “ordinary” baryonic particles coalesced from quark-gluon plasma, followed by most constant expansion until atomic matter can form and free photons are emitted (roughly 10[sup]13[/sup] seconds or 300-400kyr). This burst of photons (due to transparency of the background) is the Cosmic Microwave Background radiation that was discovered by Arno Penzias and Robert Woodrow Wilson of Bell Labs (though predicted by others previously). Expansion from that point should have been roughly constant, with the farthest reaches of the visible universe moving away at just under c. The light that reaches us has actually been standing almost still (from the totally fictional viewpoint of an objective observer) against the fabric of space, barely making headway against plenum expansion to make its way to Earth, sort of like a guy running up a down elevator. (In reality, there is no objective observer and no way to directly observe the expansion of space, so the light is always moving at c with respect to any real observer, but for the purposes of illustration and in the spirit of the Chico Marx we’ll pretend that we can stand outside the madness of Special Relativity and be objective.)
So, those stars were nearby (in cosmological terms) but are being pulled away by the expansion of space. There are stars even further, beyond the visible universe, that we can’t now and, barring some kind of Star Trek-ish supersymmetry/hyperspace/quantum warp/whatever drive that allows us to massively violate causality, will never see.
No worries; it was in the same line. Welcome aboard. (Get it? Welcome “aboard!” I kill myself, I do. Oh, no, wait…I’ve just been at work way too long. Sorry about the bad pun; it won’t happen again, until the next time I do a 16 hour day.)
Stranger
The point from which the light was emitted, should it be measured by our (again, hypothetical and totally impossible objective observer) would be more than 14 billion light years away, owing to the “streching” of space. You mention time, which is a very astute observation; “time” is, in a sense, streched; that is to say, while the light we’re seeing is 14Byr old, the light coming one second later is actually more than 14Byr+ 1 second old. So, not only are we seeing into the past, but we’re also seeing it in slow motion, thanks to the expansion of space, as well as being redshifted (which is due to the relative velocity of the emitter with respect to Earth.)
Some theories (currently in vogue) hold that expansion of space will continue to accelerate until all celestial objects are accelerating away from each other in excess of lightspeed (again, from the point of view of the objective observer) and thus will simply disappear from view, leaving a lonely, dark universe, until atoms are rendered into component particles, and those shorn from each other, by the forces of expansion exceeding nuclear and subnuclear binding forces. This might be a good time to start looking for escape hatches or connecting tunnels to another universe. See ring sinularities and Kerr-Newman black holes for some entirely speculative and totally unsubstanciated theories about connecting to other universes, though there’s no guarantee that the physics of your new universe are going to be anything like this one, since as far as we know the fundamental constants appear to be arbitrary. So, you could explode like a microwaved grape or collapse into a supercompact ball of protoplasm from intense local gravity. Or maybe you’ll just get fried by infalling radiation or torn apart by tidal forces.
Happy dreams…
Stranger
Except that light can’t be old. Light itself is ageless: No time at all passes for a photon between the moment when it’s emitted and the moment it’s absorbed, even if those two points are separated by billions of lightyears of space. Yet another of the fascinating quirks of special relativity.
Pedant. 
True, light has no vector in time (since it’s moving exactly at c, its Lorentz contraction is infinitesimal) and thus is indistinguishable from when it was emitted to when it is absorbed; sort of like Dick Clark. But for our (once again, totally unrealistic objective observer) the photons have been around for 14 billion+ years, even if they’re too dim to realize it.
Now go work on your thesis, damnit! 
Stranger
-Yuk yuk, I get it. Hey thanks, Stranger, for the links. Who says Wiki can’t be enlightening?
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