Resolving an Apparent Paradox

I think this is my first non-newsletter post to this blog.  Someone forwarded a question that I couldn't resist answering.


"A simple astrophysics question:

"What am I missing?  Something here is inconsistent:  In a "hail Mary" attempt to get an answer, I faxed this  question to the Hayden Planetarium & Department of Astrophysics at the American Museum of Natural History in New York.  Any chance they will respond?  I won't care if they don't answer if you have the answer.

The best estimate for the age of the universe is about 13.7 to 13.8 billion years.  According to the Big Bang Theory, 13.7 to 13.8 billion years ago the universe would have been a singularity from which everything expanded. Everything in what is now the entire universe had been in one place at the time of the Big Bang and then expanded from that point. 

The furthest observed galaxy is 13.0 billion light years away from earth.  In other words, the observed light left that galaxy 13.0 billion years ago.

Matter in the furthest observed galaxy has been moving away from earth (or at least what was the origins of earth at the time of the Big Bang) for 13.7 to 13.8 billion years.  Assuming light was emitted from that galaxy 13.0 billion years ago and we are now just seeing it, the light we observe now had to have been emitted by matter or energy that was 13.0 billion light years away when the light was emitted.

The galaxy that emitted the observed light must have moved away from the matter and energy formed in the Big Bang, including the matter now constituting earth, at a speed enabling it get to a distance of 13.0 billion light years away from earth during the 0.7 to 0.8 billion years immediately following the Big Bang.

Since nothing moves at a speed exceeding the speed of light, how is it possible for the furthest observed galaxy to have moved 13.0 billion light years in 0.7 to 0.8 billion years?

My Answer:

 "Not quite so "simple."  One of the premises is wrong -- that nothing exceeds the speed of light.  In the first instants of the Big Bang, there was a superluminal (faster than light) expansion of the universe, called "inflation," that quickly separated things by such huge distances.  It fairly quickly decelerated, and the expansion continued at more or less the Hubble constant rate.  

Although, due to dark energy (constant density) increasing with the increase in space, and its anti-gravity property, that expansion is now again slowly accelerating.  At some point (billions of yrs from now or so), the more distant objects will be traveling nearly as fast (or faster?) as light, and due to their distance, the light will not reach us for eons, if ever, so will begin to disappear.  And that will continue with nearer and nearer objects. 

Here's a graphic that helps to illustrate all of this:

We live in a unique period in the history of the universe, when we can see all that we can.  And a stable period for star and planet and human life.  A mid-life period.  But of course an effective end of our physical (at least normal matter & energy) universe is not the end of existence or reality -- there are other universes that also come and go, other Big Bangs, etc.

Mark Clayson