MODERN TIMES
by Art Hobson
ahobson@uark.edu
AND THEN THERE WAS
LIGHT
The latest news
from the edge of the universe
Amidst wars and environmental disasters, some might regard the big bang as irrelevant. But without a rational antidote to the ideological extremism that drives the wars and disasters, the human prospect will remain bleak. I believe that science, and especially science’s beautiful emerging view of the universe, offers part of that desperately-needed antidote.
We are living in the heroic age of cosmology—the study of the structure, origin and evolution of the large-scale universe. Just since 1992, science has for the first time found precise, reasoned, and observationally-based answers to the age-old questions of universal origins. Unfolding before us is a universe far more glorious, extravagant, and subtle than could have been imagined. In 1992, the Cosmic Background Explorer or “COBE” satellite reported back to Earth with many details about the expanding universe, a theory suggested eighty years ago by the first observations of other galaxies outside our own giant pinwheel of stars known as the Milky Way galaxy.
The latest news is the first report, two months ago, from an incredible project called the Microwave Anisotropy Probe. The MAP satellite rocketed into space in 2001 and perched in orbit around the sun at a balance point in the Earth-sun system that lies a million miles from Earth, putting it far outside the orbit of the moon. It observes microwaves (just like the stuff that heats your lunch) from all directions in space, and records the differences (or "anisotropy") between the waves from those different directions.
These microwaves are part of the "Cosmic Microwave Background," the radiation that was released just 400,000 years after the big bang and that is still all around us. Before 400,000 years, the universe was so hot that its atoms were electrically charged; since charged atoms interfere with light, this prevented light from traveling through space. After its release, this radiation traveled the universe for 13.7 billion years before entering MAP’s receivers.
The result is a photograph showing the faded afterglow of the creation of the universe, the universe’s first light, a 13.7-billion-year-old fossil dating from a mere 400,000 years after the big bang. If you haven’t already seen it elsewhere, you can find it at http://www.gsfc.nasa.gov/topstory/2003/0206mapresults.html (click on image 1). The patterns that you see in this photograph eventually grew into the web of galaxies that surrounds us today.
Scientists first detected this ancient radiation, now cooled to a frigid 3 degrees above absolute zero, in 1964. The COBE satellite made a first blurred map of it, referred to at the time as "the face of God," in 1992. The latest results sharpen that view.
These first MAP results confirm the big bang theory in triumphant detail. I outlined this theory, which describes the history of the universe from 0.01 seconds after the creation up to the present, in my column of 11 January 2003. You can find it at http://physics.uark.edu/hobson/ . The new results, together with previous theories and observations, paint a fairly complete and consistent picture of the origin and evolution of the universe. Here are a few of the conclusions:
We now have a fairly precise date for the creation: 13.7 billion years ago, plus or minus one percent.
You’ve probably heard that "everything is made of atoms." Well, it’s far from true. The "ordinary" matter you see around you, matter that is made of atoms, forms only 4% of the weight or “mass” of the universe. All the stars and everything else that can be seen in the universe add up to only 4% of the universe's overall mass. Another 23% is a mysterious and invisible form of matter that is hard to detect but that is all around us and is being avidly sought in high-energy physics laboratories. Astronomical observations, especially MAP, confirm this “dark matter” and even show us roughly where it is (it surrounds the visible galaxies), but we have yet to discover what it is. The best guess is that it is as-yet-undiscovered sub-atomic particles left over from the big bang, particles that do not interact readily with ordinary atomic matter.
The remaining 73% of the mass of the universe is even more exotic. Einstein once told us that anything that has energy also has mass. Well, this other 73% comes in the form of pure nonmaterial energy, a type of energy that we were entirely unaware of until just a few years ago and that has now been well confirmed by MAP and other observations. We don't know what kind of energy this is, but it is made of neither atoms nor dark matter.
This so-called “dark energy” fills the universe, and pushes outward on the entire fabric of space so that the universe is actually speeding up in its outward expansion. Most of us had thought that the pull of gravity must be slowing the universe’s expansion, just as gravity slows the rise of a baseball that has been thrown upward. But dark energy acts like a kind of anti-gravity that accelerates the universe’s expansion. This acceleration was directly detected in 1998 in observations of the light from distant exploding stars, and is now confirmed by MAP and other observations.
There’s more: The MAP results also give strong support to the uncanny tale of the universe’s first fraction of a second, a theory called “inflation.” I must save this for a later column.
And there will be still more, as new results come in from MAP and elsewhere.
Stay tuned for more about the biggest story in 13.7 billion years.