Tuesday, January 16, 2007

How Wide is the Universe? - revisited

Way back in November 2005 I asked How Wide is the Universe? and have been pondering it every now and again since then.

Reading Bill Bryson's tour de force "A Short History of Nearly Everything" gave me some additional insights (see the early chapters).

And a few days ago I came across this link at Yahoo! Canada and the following article at www.space.com which I found especially informative on this matter:

Universe Measured: We're 156 Billion Light-years Wide!
If you've ever wondered how big the universe is, you're not alone. Astronomers have long pondered this, too, and they've had a hard time figuring it out. Now an estimate has been made, and its a whopper. The universe is at least 156 billion light-years wide.
In particular, it neatly outlines one aspect that beforehand I simply couldn't get me head around: why, if the universe is some 13 or 14 billion years old, its diameter in light years can be numerically greater than this. And it turns out that the above figure -- converted, of course, into distance in Light Year units -- cannot simplistically be regarded as the radius which, by being doubled, would lead to a diameter of 27 or 28 billion light years. And the key to this is explained thus:
... the universe has been expanding ever since the beginning of time, when theorists believe it all sprang forth from an infinitely dense point in a Big Bang.

"All the distance covered by the light in the early universe gets increased by the expansion of the universe," explains Neil Cornish, an astrophysicist at Montana State University. "Think of it like compound interest."


  1. This info is also outdated. Acc Scientific American, March 2005, it is 92-94 light years across.

  2. Anonymous12:25 AM

    kalim above.. so you say the whole universe is 92-94 ly across?..err maybe you want to check your source again

  3. Not sure either way. I'm no astronomer or cosmologist, just interested in all this stuff!

    I see that NASA's recently refurbished Hubble platform has taken earlier this December some fascinating snaps with its Wide Field Camera 3 (WFC3 - described at http://sm4.gsfc.nasa.gov/technology/sm4_wfc3.php ).

    See, for example, the Skymania article "Hubble sees to edge of universe" at http://news.skymania.com/2009/12/hubble-sees-to-edge-of-universe.html mentioning "incredible photograph, covering a square patch of sky just a 15th the width of the full moon. Yet that tiny bit of the heavens alone is crammed with thousands of whirls and blurs - each one a collection of many millions or billions of stars."