Download Our Incredible Universe

MODERN TIMES
by Art Hobson
[email protected]
Our Incredible Universe
Stonehenge and other prehistoric sites testify to the age-old human thirst to
understand the universe. Today science is in the midst of a revolutionary burst of
cosmological discovery. We live in fact in the golden age of cosmology—the study
of the structure, origin and evolution of the large-scale universe.
The Cosmic Background Explorer (COBE), an observing satellite able to map
the details of the faded afterglow of the big bang creation of the universe, ushered in
this golden age in 1992. This year, another satellite known as the Microwave
Anisotropy Probe (MAP) reported further details that confirmed the picture that has
been developing since COBE.
We now know fairly precisely when the big bang occurred: 13.4 billion years
ago. More importantly, we have a fairly well-confirmed theory, called “inflation,” as
to what caused the big bang. It has to do with quantum physics, the theory that
describes how nature behaves at the microscopic level. A major principle of quantum
physics is that most microscopic events are inherently unpredictable, or
uncertain. One consequence of these uncertainties is that the amount of energy in
every microscopic region of space fluctuates unpredictably from very small amounts
up to occasional large amounts. Our universe began from a huge--and therefore
highly improbable—quantum fluctuation in the energy of a tiny part of the emptiness
that existed before there was a universe.
This unusually large energy fluctuation within an unbelievably small region of
space—far smaller than an atom or an atomic nucleus--unleashed new microscopic
forces that created the universe. These forces actually created space and time along
with all that we see around us today. During a tiny fraction of the first second, the
universe went through a short period of rapidly accelerating faster-than-light
expansion called “inflation.” This initial expansion stretched the universe enormously
(although its overall size was still smaller than 1 millimeter) and permanently
imprinted the patterns of the microscopic quantum fluctuations that occurred just after
the original energy fluctuation. COBE and MAP recorded these stretched-out patterns
as they appeared 300,000 years later, when the universe had cooled sufficiently to
allow the light from the big bang’s flash to be released and travel through space.
The universe has been expanding at the speed of light ever since, simply
because there is nothing to stop it. By today, the quantum fluctuations that were
imprinted on the early universe have been shaped by the force of gravity into the giant
clusters of galaxies (a galaxy, such as our own Milky Way galaxy, is a collection of
billions of stars) that characterize the large-scale universe. In other words, the weird
and wonderful microscopic principles of quantum physics are magnified and writ
large in the heavens probed by our largest telescopes.
If you are wondering how all this can possibly be, you aren’t alone. I warned
you that it’s incredible--but backed by substantial evidence.
We now know that the universe is not made of the stuff we had always thought
it was made of. The “ordinary” matter and radiation that make up everything you can
see (stars etc.) or feel (tables etc.) form only about 4 percent of the universe’s total
mass (or “weight”). Another 23 percent is made of “dark matter”--but “invisible” or
“transparent” matter would be better terms. There have been hints of dark matter for
decades, but MAP provided conclusive details.
Dark matter seems to show itself only through the gravitational forces that it
exerts on ordinary matter. It might also exert a subtle sub-atomic force known as the
“weak force.” It is truly ghostlike: It does not shine, it can pass right through
ordinary objects without a trace (many particles of “ordinary” matter do this too), and
nobody knows quite what it is. It is probably made of microscopic particles, it is
widespread throughout the universe and probably all around us on Earth, and it was
probably created in the big bang and has remained nearly unchanged since that
time. It’s played an important role in the scheme of things. Our universe could not
have “condensed” from the hot gases of the big bang into anything like the galaxies,
stars, planets and people that we see around us were it not for the gravitational
influence of dark matter.
There’s more. The remaining 73 percent of the universe was only discovered
during the past decade. It is called “dark (or invisible, or transparent) energy.” It is
strange stuff indeed. Dark energy is a so-called “field,” a little like the gravitational
field that pulls things down to Earth and holds the solar system together. It seems to
be spread smoothly throughout the universe, and to be related to gravity. But it is an
odd kind of gravity, because gravity pulls while dark energy pushes. In fact, it pushes
on every bit of space within the universe, and causes it to actually accelerate (speed
up) in its expansion. Nobody knows what it is or how it originated.
The big bang, inflation, dark matter, dark energy, and the expanding
accelerating universe have all fallen into place during the past decade to form a
striking and probably enduring picture of our cosmic home. There is both scientific
and poetic truth here. The new cosmology presents an awe-inspiring epic that in
beauty and inspirational power surely does justice to the poets of old who were
likewise moved by the glories of the heavens and Earth. It is a joy and a privilege to
live in such an incredible universe.