A few weeks back I wrote a slightly misguided article on the dimensions of the Universe. I sent my questions on this topic to one of the world’s preeminent astrophysicists, Dr. Neil Tyson deGrasse, and he actually got back to me. He then referred me to a colleague named Prof. Tim Paglione, Ph.D who was also kind enough to respond. Prof. Paglione is the Coordinator of Astronomy at York College, CUNY.
After talking with him I haven’t gotten any closer to an answer but I have determined there seems to be some conflicting information coming from the scientific community regarding the distances involved in observable space.This could be a direct result of my relative ignorance…but I can cite a bunch of sources that seem pretty simple and straightforward.
Prof. Paglione pointed out the most distant object known to be observed is actually the gamma-ray burst GRB 090423, discovered in April of 2009, which occurred roughly 630 Million years after the big bang…or 13.1 Billion light years ago. I confirmed this assertion in a couple of places, most notably NASA and the linked article at Sky and Telescope’s web site. However, This whole question began to take shape in my mind when I recently listened to an interview with Brian Greene on the WNYC public station program entitled “Radio Lab”. On an episode called The (Multi) Universe(s), (which is available as a free podcast) at roughly -31:20 the interviewer, Jay Abrumran asks Greene, “How much space can we see…What’s the observable…?”
Brian Greene replies, “Roughly 42 billion light years in any given direction.”
If you don’t know, Brian Greene is the author of The Elegant Universe, a professor at Columbia University and he is one of the smartest men on the planet. Nevertheless, skeptic that I am…I didn’t just take his word for it. After some research I discovered this Wikipedia page. I later read a web page put up by someone at UCLA that reports the number is even higher…47 billion light years. This page has all sorts of math I will probably never be able to understand but it seems to support the author’s claim. It would be great if someone I know is a mathemagician and can explain this to me.
So what gives? Who has the correct information on this topic? I have tried to clarify my question and point out the sources of conflicting information. Hopefully Prof. Paglione will have time to further enlighten me.