Expert: Paul Wagner - 11/11/2009

Question
Dear Dr. Wagner,

I have devoted quite some time attempting to locate a knowledgeable astrophysicist to answer what I believe is a relatively straight-forward question.  
That is, as I understand cosmology, we know that light travels at a constant velocity in a vacuum (~186,000 miles/sec).  Further, we cannot overlook a significant observation: The universe itself is expanding FASTER THAN LIGHT SPEED. I am at a loss to completely comprehend the ramifications of such a discovery.  

Nonetheless, if that observation is correct, this would seem to lead to many other considerations, not the least of what I've sought over some time.  For example, how can anyone state that "our universe" is really ONLY ~ 13.8 billion years old (based on the distance that light can travel as the universe expands AWAY from us even FASTER)?
Moreover, since ALL we can ostensibly ever observe without travelling beyond light-speed is the distance light travels over the course of ~13.8 billion years to finally reach us from the outer edges of ‘our universe’, how can we presume to interpret a "Big Bang" theory " theory as the origin of what we consider to be "the beginning" of such a universe from what must be a rather limited perspective?

Respectfully,

Steven James
Computer Engineer


Answer
Hi Steven

This is a great question--and even though I am not an astrophysicist, I do more or less know where to find the answer:

http://www.wonderquest.com/ExpandingUniverse.htm


ON the other hand, do not expect the laws of relativity to be intuitive.  What seems to make sense to you may NOT fit into the laws of relativity, something frustrating for the layman.  

In simple terms, we can measure two things right now--the speed of objects in the universe relative to us ( and pretty much relative to each other ) and the location of those objects.  When you take their speeds, and their locations, and reverse the directions, they all seem to meet at one point--the singularity event of the big bang.

As for the technical aspects of those measurements, etc. I will leave that for you  to read in the link above.

Hope that helps

Paul Wagner