How
old is the universe? While scientists have pondered this fundamental
question for millennia, even a reasonable estimate has been
elusive. In just the past five years, however, experts--with
help from tools like the Hubble Space Telescope--have made
remarkable headway in refining an increasingly precise value.
A
big part of this progress rests on our understanding of a
related question: How did the universe begin? Today, most
astrophysicists agree that the universe began with the
Big
Bang
(read
an article on the Big Bang)
, an inconceivably
large explosion that created billions of galaxies and sent
them flying apart. In fact, cosmologists’ knowledge of
the dynamics of this galactic expansion is helping them figure
out when the Big Bang itself happened.
