Sky & Telescope August 2001 [antikvár]

Cosmologk lllogicMy grandfather was born 100 years ago and grew up in a static universe with no beginning or end. A century later, my sons are growing up in a universe that exploded from nothing billions of years ago and is thinning out as the eons go by. This overhaul of our world picture is surely the most dramatic since the Copernican revolution.It's also the most confusing. Just try explaining modern cosmology to a nonastronomer:"The universe began with the Big Bang.""Where'd it happen?";"It didn't happen rt//ywhere; it happened ever/where. Now the universe is expanding.""Into what?""Not into anything; space itself space-time, actually is expanding and carrying the galaxies with it. Astronomers used to think the expansioi^ was slowing down as galaxies tugged on each other with gravity. Now they think the expansion is speeding up.""Really? What's pushing it?"j"Something scientists call the 'cosmological constant' or Vacuum mergy.' Most people just call it 'dark energy.'"/"Oh, so it comes from dark matter?""No, that's different. Dark matter, like ordinary matter, pulls on'stuff with its gravity. Dark energy pushes on stuff."/"So the universe has been expanding faster and faster since the Big Bang, pushed by dark energy?""Not exactly. In the first fraction of a second after the Big Bang, the universe inflated like a balloon, but over the next few billion years the expansion slowed.""But you just said it's speeding up."y"It is now, but it wasn't in the distant past, except during the early burst of inflation. It took a while for the outward push of dark energy to overcome the inward pull of dark matter and begin to accelerate the expansion.""Oh. Well, what exactly is the dark energy?""Nobody knows. Some astronomers think it has something to do with quantum physics or higher dimensions.""Hmm. How about the dark matter what's that made of?""Nobody knows that either. Some of it may be made up of black holes, small planets, or dead stars too faint to see in telescopes. But most of it is probably made up of subatomic particles that haven't been discovered yet.""The whole thing sounds made up to me."Of course, it's not all made up it's backed up by abundant data, much of it very recent and very compelling. Nevertheless, modern cosmology is so counterintuitive that it sounds like nonsense. I guess I shouldn't be surprised that more people say they believe in a religious story of creation than in the story told by cosmologists. I hope that when the next century dawns today's cosmology either will be taken for granted or will have been superseded by something a lot easier for ordinary folks to comprehend.