Well, actually not the World but the whole Universe!  As summarized by the
BBC:

http://news.bbc.co.uk/hi/english/sci/tech/newsid_727000/727073.stm

And all the gory details form the Nature article (watch the wrap):

http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v404/n6781/f
ull/404955a0_fs.html

This is perhaps the best evidence yet that the total energy density of the
Universe may be exactly 1.

Even if you don't find this mind-numbingly exciting, I have a book to
recommend:

"Just Six Numbers : The Deep Forces that Shape the Universe" by [Sir] Martin
J. Rees.
Hardcover, 173 pages (December 1999), Basic Books; ISBN: 0465036724, $22
list, $15.40 from Amazon.

This is the best popularization of Cosmology that I've read.  It's not too
long, extremely readable, and doesn't tell you anything you don't need to
know.  The author describes much of what we know about the origin,
structure, and possible fate of the Universe that we live in, using as a
basis for discussion six fundamental numbers that describe things like the
relative strengths of forces that define the behavior of matter and how even
small changes in any of them would result in a Universe in which life as we
know it would be impossible.  The first number discussed is the total energy
density of the Universe referred to in the URLs above.

Whether you believe in the existence of a divine Creator, or think that
everything "just happened", this book will provide you with a vast number of
interesting things to think about, and will leave you with a substantial
understanding of the
Universe that we live in.

If I were asked to pick just one science book that *everyone* should read,
I'd have a hard time thinking of a better one than this.

G.