Whats Up in the Sky April 2005
Good science measures age of universe
Last month I asked readers to send in questions that I would attempt to answer today. My thanks to Albert Holthof whose question dealt with the age of the universe and how it is determined. As soon as I received his question, I knew I was in trouble. After three days of research and writing I realized I could never fit an adequate answer into this column. However, I do owe Albert (and you) some sort of explanation, so here goes.
Albert Einstein’s general theory of relativity provides the framework for our understanding of the universe’s evolution. All of our observations clearly indicate that the universe began with a “big bang” which caused space to expand, carrying all of its matter and energy with it. When we look at distant galaxies, we see that they are all moving away from us like raisins in a rising loaf of raisin bread dough. If we run the clock backwards, we find them coming together until all matter (and space) was crowded to a single point about 13.7 billion years ago.
The best alternative method for estimating the age of the universe is from calculations of the evolution of the oldest known stars, those found in globular clusters. Those calculations agree very closely to the 13 billion year age.
Another important piece of evidence was the discovery, in 1964, of cosmic microwave background radiation, energy left over from the “glow” of the big bang. Careful analysis of this radiation confirms several important features of the big bang theory and allows us to calculate the universe’s age based on the theory’s predictions.
I find it interesting that we accept without question certain scientific theories while others are greeted with doubt and skepticism. No one argues any more about whether the earth orbits the sun or vice versa. I don’t think many of us would question the validity of the theories governing or cell phones, weather satellites, or iPods. Yet these items work because of the same theory (general relativity) that governs the universe. It should be noted that Einstein’s theories have never failed a test and are now accepted as fact, even though everyone thought he was nuts when he first published them.
Scientists must be willing to accept experimental results which seem to contradict current beliefs or even common sense. Recently it has been discovered that not only is the universe expanding, but the rate of expansion is increasing due to some mysterious unknown force called “dark energy.” Astronomers have had to rethink their entire understanding of the cosmos based on these new discoveries. That’s the essence of science.
Congratulations to Lowell Winne of Fennville who correctly answered last month’s trivia question, “What human-made object is farthest from the earth”? Answer: Voyager 1, launched September 5, 1977, holds that distinction at a distance of almost 95 AU (1 astronomical unit, or AU, equals the average distance between the earth and the sun). The spacecraft is still functioning although it takes more than 13 hours for transmitted data to reach us.
Here are this month’s viewing highlights:
- April 3: Jupiter is at opposition and is visible all night
- April 8: New Moon – solar eclipse visible across Pacific ocean and South America
- April 11: thin crescent moon close to Pleiades low in west after sunset (great in binoculars)
- April 15: first quarter moon near Saturn, Castor, Pollux
- April 24: full Moon
- April 28: use binoculars to see Venus near west horizon 15 minutes after sunset
Peter Burkey is president of the Shoreline Amateur Astronomical Association and has been an amateur astronomer and astrophotographer for 25 years. He also taught astronomy at Fennville High School from 1981 to 2003.
Peter Burkey – SAAA President