FEATURES
10 THE BEGINNINGS
It began with a bang
Our universe’s earliest moments are the hardest to explore. But they hold the key to understanding the cosmos.
DAN HOOPER
14
Inflating the universe
In a trillionth of a trillionth of a trillionth of a second, our universe underwent a growth-spurt that shaped the structure we see today.
BRIAN KEATING
18
The emergence of matter
The universe forged the first elements within minutes of its birth through the process of Big Bang nucleosynthesis.
CHRISTOPHER CONSELICE
21
The cosmic dark ages
For millennia, a hydrogen fog permeated the universe,trapping light.
DANA NAJJAR
24
The first stars are born
They lived fast, died young, and seeded the cosmos with material for future generations.
MICHAEL E. BAKICH
28 LIVING IN
THE UNIVERSE
How to build a galaxy
About 13 billion years ago, our galaxy formed in the wake of the Big Bang.
MICHAEL E. BAKICH
32
Sky This Month
Twilight observing time.
MARTIN RATCLIFFE
AND ALISTER LING
34
Star Dome and
Paths of the Planets
RICHARD TALCOTT;
ILLUSTRATIONS BY ROEN KELLY
40
Our solar system’s origin
Researchers know how the Sun shines — but how did it form?
MICHAEL E. BAKICH
43
The origins of life on Earth
An asteroid impact may have killed the dinosaurs, but earlier cosmic strikes could have helped spawn life in the first place.
DAVID A. KRING
46
Looking for life in the universe
Possibilities for extraterrestrial life seem limitless, but a few scientific rules can help us find
it.
MORGAN L. CABLE
50 THIS IS THE END
The Big Crunch vs. the Big Freeze
Astronomers once thought the universe could collapse into a
Big Crunch. Now most agree it will end with a Big Freeze.
ERIC BETZ
53
The mystery of dark energy
The universe isn’t just expanding, it’s accelerating.
BRUCE DORMINEY