Once again, science has given us a big part of the answer. According
to the physicists’ standard
model, pretty much everything we can see in the universe
is made from the same basic building blocks: elementary particles
with names like quark, lepton and gluon.
From raindrops to galaxies, it’s all the same stuff.
According to Einstein’s general
theory of relativity, likewise, a subtle curvature in the
fabric of space and time can explain every known effect of gravity:
the universal force that pulls apples to the ground and holds
the planets in their orbits. Indeed, it’s this curvature
that determines how the universe has expanded in the aftermath of
the big bang and what happens when matter collapses into a black
For all their successes, however, the standard model and general
relativity leave some serious gaps. In particular, neither one
can explain why most of the universe is utterly invisible.
Astronomers stumbled onto this fact only a few decades ago, when
they began to realize that the stars, galaxies and nebulae they
can see through their telescopes are just a tiny fraction of what's
actually out there. Far more prevalent is "dark
matter"--a kind of cosmic ectoplasm that makes itself
known only though its immense mass, which produces an equally immense
gravitational field. Without that field, individual galaxies like
our own Milky Way would fly apart like broken pinwheels, and clusters
of galaxies would disperse into the void. In fact, without it,
none of those galaxies and clusters would have formed in the first
place, and we would not be here to wonder what dark matter is.
Meanwhile, in 1998, two
independent teams of NSF-supported astronomers announced
an even more astonishing discovery--the expansion of the universe
isn’t slowing down, as most observers had expected. The
expansion is actually speeding up. It is as if some previously
unknown force, now known as “dark
energy,” is driving the galaxies apart at an ever-increasing
rate. Moreover, this dark energy is incredibly abundant. According
to the best current measurements, ordinary matter accounts for
no more than 5 percent of the stuff in the universe, on average,
while dark matter amounts to some 20 percent. Dark energy is 75 percent.
The discovery of dark matter and dark energy has electrified the
scientific community. Here is observational proof that there’s
something about fundamental physics we still don’t understand (Science magazine has a recent review).
In an effort to fill the gap, astronomers are planning a
new generation of telescopes; theoreticians
are exploring exotic concepts such as superstrings and extra
dimensions; and laboratory scientists are deploying a host
of new experiments. Among those experiments are searches
for new fundamental particles and laws at the soon-to-be-completed
Large Hadron Collider in Geneva, Switzerland; the LIGO gravitational
wave detectors; dark matter
searches; measurements of
ultra-rare particle interactions; cosmic
ray observatories; and more.
NSF is supporting all of these endeavors, in part or in whole. Indeed,
they were among the leading topics at a
recent NSF symposium on ground-based astronomy--as was
the dark matter/dark energy mystery itself. With luck, we could
be on the verge of a radically new picture of the universe, and
of the fundamental nature of space, time, matter and energy.
our Place in the Cosmos? [Next]