Throughout human history, great missions of
exploration have been inspired by curiosity,
the desire to ;nd out about unknown realms.
Such missions have taken explorers across
wide oceans and far below their surfaces,
deep into jungles, high onto mountain peaks
and over vast stretches of ice to the Earth’s
Today’s greatest exploratory mission is no
longer Earthbound. It’s the scienti;c quest to
explain the cosmos, to answer the grandest
questions about the universe as a whole.
What is the identity, for example, of the
“dark” ingredients in the cosmic recipe, composing 95 percent of the universe’s content?
And just what, if anything, occurred more than
13. 7 billion years ago, when the universe accessible to astronomical observation was born?
Will physicists ever succeed in devising a theory
to encompass all the forces and particles of
nature in one neat mathematical package
(and in so doing, perhaps, help answer some
of these other questions)? Will that package
include the supposedly basic notions of space
and time, or will such presumed preexisting elements of reality turn out to be mere illusions
emerging from ur-material of impenetrable
obscurity? And ;nally (;ttingly), what about cosmic ;nality? Will the universe end in a bang, a
whimper or the cosmic equivalent of a Bruce
Willis movie (everything getting blown apart)?
In the pages that follow, Science News writers assess the state of the evidence on these
momentous issues. In none of these arenas
are the results yet ;rm. But as string theorist
Brian Greene wrote in his book The Elegant
Universe, “sometimes attaining the deepest
familiarity with a question is our best substitute for actually having the answer.”
6 x 1020 km
Understanding the universe requires recognizing
its immense scale. Zooming out from Manhattan
reveals the Earth, solar system, galaxies and then
walls of galaxies separated by voids. At the most
distant scales, the universe looks uniform.