Last month I wrote about the history of our universe, and how we got from The Big Bang to where we are today. But what of the future? How will the evolution of our universe unfold? Theories on its fate have varied over time. We know that the universe is expanding, but will this expansion continue forever? Cosmologists used to think that gravity would eventually slow the expansion. If it turned out that the average density of matter in the universe exceeds a certain level, gravity would cause the universe to contract, ending in the eventual destruction of all matter in The Big Crunch. If the average density was below that critical level, the universe would expand forever. It was thought that if we could measure the average density, we’d know the answer. However, in the late 1990’s, while studying the brightness of distant supernovae (the explosions of massive stars) astronomers discovered that instead of being slowed down by gravity, the expansion of the universe is in fact accelerating. It seems there exists in the universe a force that counteracts the gravitational attraction exerted by matter, causing the expansion of the universe to speed up. Cosmologists call this force dark energy. As stars and galaxies move farther apart the gravitational attraction between them is weakened, and dark energy becomes stronger because there is more space between objects. As a result it seems likely that the universe will expand forever, with galaxies moving away from one another at a faster and faster pace. Eventually they will be so far apart that an observer in our Milky Way will no longer be able to view other galaxies, and the skies will be very dark indeed. There may, in fact, be no observers left because as the energy present in the universe spreads out there will be fewer and fewer stars hot enough to have planets that can sustain life. Not to worry, though, because all this will be happening trillions of years from now, long after our Sun has burned out and the Earth along with it. Though cosmologists are constantly coming up with new theories and predictions for our cosmic future, this seems for now the most likely scenario. As T. S. Eliot wrote in his poem The Hollow Men, our world will end “Not with a bang but a whimper.”
Join the Springfield STARS Club on Tuesday, April 27th at 7:30pm at the Springfield Science Museum for a talk by Dr. Richard Fienberg on Travels from Pole to Pole, astronomical observing at Earth’s North and South Poles, and plans for lunar observatories at the Moon’s poles. Dr. Fienberg is editor emeritus of Sky & Telescope magazine, and is currently Press Officer and Education & Outreach Coordinator for the American Astronomical Society. His areas of research include the aurora borealis, planetary nebulae, active galaxies, and the center of the Milky Way. An asteroid was named in his honor. Refreshments will be served, and the public is welcome free of charge.
Amanda Jermyn, of Longmeadow, has been a member of the Springfield Stars Club since 2000 and currently serves on the club's board of directors. For more information, visit the Springfield Stars Club Web site at www.reflector.org or call 1(800)336-9054.
Copyright © Amanda Jermyn