SKY_July2014.pdf

SkyandTelescope.com July 2014 23

called ns , should be just a few percent less than 1.0. In the
simplest version of infl ation, it should be between 0.92
and 0.98. Last year, the Planck team succeeded in accu-
rately measuring the spectral index from the microwave
temperature patches. It is 0.96.
That convinced most wavering physicists that infl ation
really created the universe. Then came the B-mode discov-
ery. It put an abrupt end to a competing proposal off ered by
Paul Steinhardt of Princeton. Called the ekpyrotic theory,
this had the Big Bang arising from the collision of two 3-D
spaces inside a larger superspace. No gravitational waves
would have resulted. Steinhardt admits that the ekpyrotic
theory is now dead, at least in its original form.
Andrei Linde notes that the high temperature that the
BICEP2 team measured for infl ation also rules out 90% of
the theory’s variants that have been proposed in the last
34 years, while leaving his own simpler version standing.
But already there are signs of new complications with
this. Theorists are furiously at work to fi nd alternatives,
and new papers appear almost daily.

... to the Multiverse and the Peril of Infi nities
The B-mode patterns on the sky represent a look out of
our normal space-time into a profoundly alien pre-exis-
tence. If infl ation’s further predictions prove correct, this
is a glimpse not into a moment just after a “time zero,”
but into an opening on vastly older, wider realms.

Most theorists assert that once infl ation starts, it must

keep expanding overall. It should continue spawning

unimaginable numbers of other Big Bangs, creating end-

less bubble universes as if it were an eternally growing

ocean of foaming champaign. This is the multiverse.

Says Andrei Linde, “If infl ation is there, the multiverse

is there. Each observation that brings better credence to

infl ation brings us closer to establishing that the multi-

verse is real.”

An infl ationary multiverse would neatly solve yet

another mysterious problem. If you posit that a vast

number of big-bang universes exist, perhaps embodying

all the possible laws and constants of physics allowed by

string theory, you solve the “fi ne-tuning paradox” that

we see in physics itself. This is the mystery of why many

physical relations and fundamental constants are adjusted

amazingly well to allow any complex organized mat-

ter to exist at all, and therefore living observers such as

ourselves. If many diff erent universes exist, this mystery

goes away. We will necessarily fi nd ourselves living in one

of the rare ones that happens to be fi ne-tuned to allow for

life, no matter how infrequent such universes may be.

Some scientists see this anthropic, or self-selection,

argument as a cop-out that will sap our motivation to

hunt for more direct explanations of various phenomena.

Some call the whole multiverse a betrayal of the scientifi c

principle that good ideas should be testable. But there’s no

DARK SECTOR The South Pole Telescope (white dish), BICEP2

(in the shield on roof in the center), and the Keck Array (in shield

at right) are near the South Pole Station in its “Dark Sector,” so

called because no radio interference is supposed to go in this

direction. An LC-130 plane is taking off.

STEFFEN RICHTER / HARVARD UNIVERSITY