This one's been puzzling me for a long time, and I haven't yet found a satisfactory answer.

How can the Hubble Telescope send us back pictures of the universe in its early galaxy formation some 12 billion years ago and 12 billion light years away, when the light from that early universe should have long since past us? I mean, it seems like the universe expanded along with the light rays, so that when we look back 12 billion years, we shouldn't see anything!Hmmm?

Well I think the reason is because of how long the light that we do see takes to get to us, and so much time has passed that we could be actually looking at the universe 12 million years ago. No matter where you look, you'll be looking into the past, keep in mind that it does take light some time to travel across the universe... so the beginnings of the universe light would have already passed, but the light from 12 million years ago is still on it's way over!!

Gerry, I don't know whether this is a good explanation, but I interpret that as meaning that the stars 12 billion light years distant are the earliest ones formed from the big bang.
since it takes 12 billion years for that light to reach us, the Hubble is seeing that now. If it takes pictures of stars 6 billion light years away, we are seeing those as they were 6 billion years ago since it took that long for them to reach that distance. I think the light from the big bang that has "already passed us" would at that moment in time be lightless just prior to the big bang and so there wouldn't be anything to see - no universe, no light, no galaxies - what do you think? I think we couldn't see anything only in the event that the expansion was at the speed of light, which is - according to Einstein - impossible.

Here's the dilemma. The Hubble looks back 12 billion light years and sees the Cosmic Background Radiation remnants of the Big Bang, and the galaxies in their early formation some 12 billion years ago, 12 billion light years away, a billion or so years after the Bang. Now at that point in space where the Hubble is looking, there likely right now are very mature galaxies and stars and planets that we can not see because the light from those mature galaxies has not yet reached us. But someone who is living right now on one of those planets in those distant galaxies likely have an equivalent Hubble telescope of their own, and their focusing on us, our galaxy, and all they see is the CBR and galaxies in their early formation, just as we see it when we look toward them!! So its like the Universe expanded to its present size almost instantaneously, that allows its early light to reach us after a long 12 billion years. ???????

Gerry

Here is a very good site that answers questions on cosmology. Take a look at the two questions (listed at the top of the page),

"If the Universe is only 10 billion years old, how can we see objects that are now 30 billion light years away?"

and

"Where was the center of the Big Bang?"

Perhaps these will help.

http://www.astro.ucla.edu/~wright/cosmology_faq.html#MX

Thanks for the link. I will study it closely.

gerry

I was pressed for time when I posted the above, and I wanted to say that I think your question is one of the more perplexing I've ever come across here. The link I provided did not answer your question to my satisfaction, and I'm still wrestling with the idea. If you get to the point where you truly understand the explanation please let me know what it is. I plan on looking into this further.


Minn.

In the Beginning, say 13 billion years ago, all of space and energy were bundled in a tiny ball of infinetesimal size. There was no Time, just energy occupying zero-space.
For clarity, I will assume the size of the Universe at this point to be the size of a party balloon, since it is difficult to talk about 'zero' anything.
All of space and energy as we know it occupies the surface of the balloon, again, for clarity, using a curved 2-dimensional analogy for the universe. (Forget what lies inside the balloon, that's another topic). Then, suddenly, in a fraction of a fraction of a micro-second.....BANG.....Time begins, and the Universe starts its expansion outward into the Nothingness.
The rate of this expansion is unclear: is at lightspeed, 3 times lightspeed, 1000000 times lightspeed, or less than lightspeed? The rate of expansion of space-time need not necessarily follow Relativity principles. But the speed of light MUST. If the expansion rate is less than c, the light from the "Bang" cannot escape into the nothingness, that is, it cannot penetrate the space-time 'wall' because it is confined by gravity (space-time curvature) to forever stay within the space-time limits of the universe (somewhat similar to light not being able to escape a black hole).
And so rhe light must encircle the universe, whose size at this point is that of a balloon, and the Big Bang, and light from same, is everywhere in the universe, no central point, just thinned out energy and light occupying space thinned by the expansion. As the 'balloon' size universe expands more and more, the light goes with it for the ride, also the energy, and ultimately, say a billion years later, small infant galaxies begin to form EVERYWHER in this 'infant' universe. In the meantime as these galaxies are forming, the original light from the 'Bang' is still moving out to the reaches of the expanded universe. Ultimately, 13 billion later, we find ourselves on the Third Planet from the Sun in the Milky way Galaxy, and as we look out 12 billion light years into space, we see the distant galaxies in their early formation, just as they, now, see galaxies in our region in their infant stages.

What do you think??

Very interesting, but after going over the diagrams in the following site--I even got out a ruler to measure the change in distance (the diagrams are quite accurate)--I think the answer lies in the idea of time and distance used in the Hubble law, which is explained elsewhere in the tutorial listed in the link I gave above. My only question is how valid is it to postulate a universe (as given for the diagrams) that is 78 billion light years across. Maybe it it isn't an issue at all. Anyway, I suggest going through the tutorial and taking a look at:

http://www.astro.ucla.edu/~wright/photons_outrun.html