If the universe occupies a sheetlike
membrane, the Big Bang may have been
just one in a series of collisions, each
“Big Bounce” refreshing the cosmos.
The modern-day notion of the cosmos’s tumultuous beginning — known
as the Big Bang — has its roots in Edwin
Hubble’s 1929 discovery that the universe is expanding. At the time, scientists
envisioned the universe explosively flying outward from a single point in space
and time.
Though this simple version of the Big
Bang idea can’t fully explain what people
see in the cosmos today, Alan Guth of MIT
added a new ingredient in 1981. Early in
its history, the universe underwent a brief
period of faster-than-light expansion,
known as inflation, he proposed. In the
years since Guth’s suggestion, inflation
has been wildly successful in explaining the structure of the universe and its
arrangement of galaxies.
Pre-Bang branes
and bubbles
By Ron Cowen s Illustration by Nicolle Rager Fuller
Cosmologists Paul Steinhardt and Neil Turok liken the early his- tory of the universe to a play in
which the protagonists—matter and
radiation — move across the stage according to the laws of physics. Astronomers
are actors who arrived on the scene
13. 7 billion years too late to know what
happened.
But that hasn’t stopped Steinhardt,
Turok and other researchers from pondering whether the universe was born in
a giant fireball around that time or might
have existed before that.
Bubbling over
Some scientists think that if inflation
happened once, it could happen many
more times — hinting at a cosmos alive
and well eons before the Big Bang. Rapid
expansion, in these interpretations, isn’t
confined to just one neck of the cosmic
woods, like a single expanding balloon.
Instead, distant patches of space keep
inflating, like a child continually blowing soap bubbles, says Alex Vilenkin of
Tufts University in Medford, Mass.
Every inflated patch becomes a separate universe, with its own Big Bang
beginning (SN: 6/7/08, p. 22). In this
“eternal inflation” scenario, the fireball
that begot the universe seen with today’s
telescopes was preceded by a multitude of
others just as surely as it will be followed
by many more, each popping off at different times in different parts of the cosmos,
Vilenkin says.
Just as the sun is merely one of billions
of stars in the Milky Way galaxy, the visible universe may be one of countless in
the cosmic firmament. Cosmologists call
this ensemble of universes the multiverse.
Not only might there have been a
plethora of universes that came before
