From the Blog

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.

GRB 090423...It's wicked far away

GRB 090423...It's wicked far away

Feb
19
Posted by Jake DiMare at 9:49 am

I fell asleep the other night mulling something about the universe over in my mind and I need more input. Perhaps by sharing some reader will either be an astrophysicist or know one who can explain. I already tried asking Neil deGrasse Tyson on Facebook (no kidding) but he’s yet to get back to me. Everything I am about to say is based on widely accepted, observable, measurable science…not pseudoscience.

Galaxy M94

Galaxy M94

So, the Universe is widely accepted to be 13.7 Billion light years old. Meaning, since the big bang the Universe has been expanding, at an accelerating rate, for 13.7 Billion years. However, with our current technology the diameter of the observable universe is 93 Billion light years. Because light travels 186,000 miles in a second, when we see something 40 Billion light years away we are seeing something that is 40 Billion light years in the past. The light photons leaving whatever it is we are observing traveled for 40 Billion light years before they passed through our cornea and were transmitted to our brain to wonder about.

Here’s the thing: We can’t see the big bang. We can see things 40 Billion light years in the past but not the big bang…Because it is further away than 40 Billion light years even though it only happened 13.7Billion light years ago. You might be thinking there is something wrong with the math but there isn’t. Einstein’s general theory of relativity stated that nothing can travel faster than light but space can expand faster than light.  And it does.

So here’s my question…Which sounds like a really complicated 4th grade word problem. (If two trains leave the station at…) If our galaxy left the big bang on a local piece of space which is expanding away from that event at a rate which is faster than the speed of light and accelerating, doesn’t that mean our galaxy, solar system and in fact the earth is travelling faster than the speed of light…relative to the big bang? Which means that we on the earth are travelling faster than the speed of light…away from the point of origin in the Universe?

If the answer is yes…knowing what else Relativity says about space and time…how fast is time travelling at the point of origin? (which is standing still relative to us).