Rediscovering dark matter in space Analysis/Humor A press release last week announced: "Astrophysicists at Bell Labs have detected the long-sought large-scale distribution of an invisible form of matter that pervades the universe." Hey guys, nobody doubts there is dark matter in the universe -- the problem is, how much and what is it? Strictly speaking, the PR people at Bell should have bolded the word "large-scale." Despite its melodrama, the announcement gave me food for thought. We can probably rule out the possibility that dark matter is chocolate. (Milky Way and Mars notwithstanding. ) Dark matter made its debut 70 years ago when Fritz Zwicky and a colleague discovered that certain galaxies were rotating faster than their observed mass implied. Zwicky deduced that galaxies are in fact large balls of dark matter, with stars thrown in on afterthought. Yet he had no idea of what dark matter might be. (It is transparent and casts no shadow.) Nor do the Bell scientists. They only know now that dark matter is more pervasive than even Zwicky believed. The new experiment used a special camera mounted in the National Science Foundation's observatory in Chile to measure the distortion -- called gravitational lensing -- caused by intervening dark matter in the appearance of 145,000 distant galaxies. The findings will be combined with recent studies on cosmic microwave background radiation and computer simulations to arrive at sharper, firmer theories of the large-scale structure of the universe. The problem of dark matter affects how astrophysicists predict that the universe evolves. If dark matter, thought to make up 90 percent of the mass of the universe, is greater than predicted, it could cause the universe to fall back on itself in a "Big Crunch." If dark matter is less than predicted, the universe might expand to remote distances in a Big Chill of the non-cinematic kind. Most scientists hope their findings will suggest an equilibrium of contracting and dilating forces that will put the universe in stable motion. Of course, if dark matter is chocolate, a big crunch would definitely be preferable. May 17, 2000