EVERYTHING YOU NEED TO KNOW ABOUT THE UNIVERSE THIS MONTH...
How large is
We really don’t know the answer,
but we know that it’s at least as
large as the Big Bang and cosmic
expansion tell us.
The concept of the size of the universe
has taken huge strides forward in just
the last few years. There was a time
not long ago when astrophysicists
didn’t know how big the cosmos is.
The Big Bang theory reminds us that
once the universe was small. We know
the fastest any radiation can travel is
the speed of light. We also know the
universe is 13.8 billion years old.
At first blush, you might expect
radiation across the universe to
expand by something like 30 billion
light-years after that time. But that’s
too simplistic. The Big Bang wasn’t
like a bomb going off; space itself
expands over time so that 1 centimeter
in the early cosmos becomes 2 centi-
meters and so on. Because of space-
time’s expansion, we know the
universe is at least 93 billion light-
But there’s a major proviso to that
number, which refers to the visible
universe. Our visible universe may not
be the entire universe, and on top of
that, some cosmologists even believe
the cosmos could be infinite.
So at best, we can say the universe
is at least 93 billion light-years across,
which is a pretty good hike.
— David J. Eicher
HOT BYTES >>
TO THE TOP
Rosetta passed within 4
miles (6 kilometers) of
scientists their best
NASA released New
Horizon’s latest long-
distance look at Pluto to
celebrate the birthday
of the world’s finder,
THE PERFECT RING
Hubble shots of Beta
Pictoris, the only stel-
lar debris disk with an
imaged giant planet, saw
little change in 15 years,
implying near uniformity.
The universe holds at least 125 billion galaxies, and may contain far more than that, a number that seems staggering compared
with a single galaxy like NGC 6946.
TONY HALLAS (NGC 6946); ESA/ROSETTA/NAVCAM – CC BY-SA IGO
3.0 (COMET WATCH);
WRI (#YEAROFPLUTO); NASA/ ESA/D. APAI AND G. SCHNEIDER (UNIV. OF ARIZONA) (THE PERFECT RING)