A story in a recent issue of Scientific American (online edition)
stated that latest evidence suggests the universe is not just very
large (e.g. 14.5 billion light years in radius) but infinite.

I conclude from that that the universe must have been infinite at the
time of the Big Bang.

But I have always understood the BB as a singularity, a space-time
point of very infinitesimal smallness.

HERES THE QUESTION: Has there been a recent revolution in thinking
about the event and circumstances of 14.5 billion years ago? Can the
universe be infinite? Or am I just making an error in logic?

rogatien...

You're making a fairly common error in logic, as noted on
this page from the BBC:

"Because of its name many people think of the Big Bang as a
 kind of explosion that happened at some specific point in
 space, but this isn't correct, as the Universe didn't spring
 from one central ignition point. Instead, during the Big Bang
 space was first created and then stretched."

More on the page:
http://www.bbc.co.uk/science/space/origins/bigbang/index.shtml


From Professor Ned Wright's site at the UCLA Division of
Astronomy and Astrophysics is a page with the question:
'How can the Universe be infinite if it was all concentrated
into a point at the Big Bang?'

"The Universe was not concentrated into a point at the time of
 the Big Bang. But the observable Universe was concentrated into
 a point."

More on the page:
http://www.astro.ucla.edu/~wright/infpoint.html

Professor Wright's Cosmology FAQs page:
http://www.astro.ucla.edu/~wright/cosmology_faq.html


Last, but far from least, is the extensive and thorough article
titled, 'The Big BAng was NOT a Fireworks Display!', Written by
Dr. Sten Odenwald, on the Astronomy Cafe, which explains the
Big Bang in its proper context, as an outgrowth of understanding
the Theory of General Relativity. He points out that the Big
Bang was not a point in space, but a point in space-time, which
cannot be separated from one another, prior to which neither
space or time existed as we now know them. Please read this
entire enlightening article:
http://www.astronomycafe.net/anthol/bang.html

Read more articles by Dr. Odenwald on the same site:
http://www.astronomycafe.net/anthol/anthol.html

sublime1-ga


Additional information may be found from an exploration of
the links resulting from the Google searches outlined below.

Searches done, via Google:

allintext:think "big bang" means point 
://www.google.com/search?q=allintext%3Athink+%22big+bang%22+means+point+

Lots to chew on here. I'm not sure I quite get it yet, but this will
help a lot. Thanks very much.

I'm basically saying what Sublime1 is saying but in a simpler (at
least to me) way. The Big Bang is NOT a explosion IN spacetime but an
explosion OF spacetime. [Right now it helps to visualize the Big Bang
happening in the 5th dimension, the 4th beingt ime, even though that
the 5th dimension might not exist.] At the Big Bang, 1 light year
(5,865,696,000,000 miles ) to something inside the universe might
apper to be 1 planck length to an oberver in the 5th dimenssion (I'm
not saying hat he exists, but it helps to visulise). If you don't
think that this is helpful, then read the following books:

1) A briefer history of time by Stephen Hawking (easy)

2) The Universe in a Nutshell by Stephen Hawking (easier)

3) Black Holes, Wormholes & Time Machines by Jim Al-Khalili (easiest)