The 4% solution

What will historians remember about 2003 in 50 years?\nIf I gambled, I'd bet they'd recall the results from NASA's Wilkinson Microwave Anistropy Probe (WMAP), launched in June 2001. If you haven't heard about the satellite elsewhere, thank media short-sightedness.\nThe clumsily-named satellite has managed to both confirm and confuse contemporary theories about the origin, the composition and the future of the universe.\nSome background: Since 1965, scientists have known that the universe is full of cosmic background radiation (CBR), heat left over from the Big Bang. WMAP has made extremely precise measurements (to 200 millionths of a degree Kelvin) of CBR's temperature.\nWMAP is just about the closest physics has come to a perfect experiment. Astronomy professor, Stuart Mufson, said in an interview, "They knew what to look for, they built the instrument, they launched it, and they found it."\nNASA physicist Gary Hinshaw spoke to the IU Physics Department on Oct. 22 about WMAP and its findings. Hinshaw, a member of the team that designed and built the satellite, is in his 40s, but he looks 25, an impression confirmed by his enthusiasm (while explaining one graph, he called the measurements "killer pieces of data").\nFor the first few hundred thousand years after the Bang, "the universe was just a hot plasma with no structure to it," Hinshaw said. The seeds of the structure we see today (galaxies, planets, people) were fluctuations in the density of that plasma.\nWMAP's measurements allowed Hinshaw and his colleagues to understand those fluctuations. And from that data, the scientists arrived at a startling conclusion: Only 4 percent of the mass of the universe is ordinary matter and energy (that is, the stuff you're made of). Another 23 percent is dark matter, possibly particles that physicists think exist. And the other 73 percent?\n"Quite frankly, we don't have the faintest idea what it is," physics professor Tim Londergan told me. \nHinshaw was equally blunt. "We have no idea what 73 percent of the stuff in the universe is," he said. "This is a huge problem for both cosmology and basic physics."\nForget the missing weapons of mass destruction. We're missing 73 percent of the universe!\nThis missing mass, called "dark energy," acts as gravity's opposite, repelling instead of attracting matter. Astronomers began searching for dark energy when they noticed that distant supernovae were dimmer than they should be if the universe were accelerating at a constant rate.\nEinstein considered the possibility of an expanding universe when he developed the theory of general relativity, Hinshaw said. Einstein rejected that idea, later calling it "his greatest mistake." It wasn't. His only mistake was abandoning the inflationary universe model.\nWe may know whether that model is correct soon. Mufson is working with a NASA team on the Supernova/Acceleration Probe, which will measure the universe's expansion to discover whether the universe will expand forever, remain as it is or implode in a "Big Crunch."\nThe media has all but ignored WMAP. It's harder to explain cosmology than to run stories on Ahhhnold. But Hinshaw and his colleagues' findings (remember: scientists don't know what 73 percent of the universe's mass is!) are far more remarkable than some minor election in one state of one country. They're even more interesting than a war. And their results -- conclusively overturning what we think we know about the universe -- will last longer than the problems in the Middle East.\nGalileo proved we aren't the center of the universe. Darwin proved humans aren't the most important species on earth. And now WMAP has proved that we know almost nothing about the universe in which we live.\nWMAP is the most important story of the year. And isn't it a shame you first read about it in a college newspaper?