Saturday, May 22, 2010
HOW LONG IS A LIGHT YEAR?
In November of last year I began to serialize Chapter 4 on Search for Extraterrestrial Intelligence from SIMPLE SOLUTIONS for Humanity. To gain an appreciation of distance, it is useful to link this dimension with time. To begin with, the title is nonsense, for a light year is not a dimension of time. This is the distance light travels in one year. Rounding it off, call it 6 trillion miles (6,000 billion miles or 6,000,000 million miles).
Thus, one light year is a very long distance. To travel 6 trillion miles, you would need to make more than 30,000 round trips from Earth to the Sun.
I was on the Big Island of Hawaii for the New Year period in 1983. On January 3 I happened to be golfing at the Volcano Golf and Country Club. I forgot exactly at what hole, but in the back nine, the ground shook. We then noticed that a couple of miles away a lava fountain appeared at Puu Oo. Kilauea Volcano has now been continuously erupting for 10,000 days. This is close to a billion seconds.
I had returned to the University of Hawaii a few months previously after a three year assignment working for the U.S. Senate. Much of my professional life thusly unfolded, plus a decade of retirement...and that was about a billion seconds ago. Light traveled 186 trillion miles during this 27+ year period.
Let me repeat, light traveled 186 trillion miles from January 1983 till today. The closest star is Proxima Centauri at 4.2 light years, so if intelligent life lived there, we could have each have sent three messages to each other during this period. But our Milky Way Galaxy is huge. Light would take 100,000 years from one end to the other. Another way of contemplating all this is that during this period from when I saw that eruption of Kilauea Volcano in 1983 till today, light would have travelled just 2.7% across just our galaxy, and ours is not a particularly large one.
How vast is space? Best estimates are that there are from 200 billion to 400 billion galaxies in our universe, and each galaxy has, oh, 100 billion stars. Interesting, though, that our neighbor galaxy, Andromeda, is closer to Planet Earth than the center of our galaxy. Thus, it would take light (or an electronic signal) only 25,000 years to reach the edge of the Andromeda Galaxy from Hawaii.
So, if you're wondering if flying saucers regularly visit us from other stars, consider that the fastest man-made object is Helios 2 at slightly more than 150,000 miles per hour. A spacecraft travelling at that speed would take almost 20,000 years to reach Proxima Centauri. If you can remember that far back, Pioneer F(also #10, the one with info about our civilization) is headed for Aldebaran, a star 65 light years away. We long lost contact with this probe, but if it succeeds in getting there, you will need to wait another 2 million years.
But why go to Aldebaran. Let's shoot for Proxima Centauri (which, unfortunately, is a Red Dwarf, and pretty useless for life, but we'd be in the neighborhood of Alpha Centuari, only a few miles further) and not be limited by current knowledge. Nuclear pulse propulsion (which once was Project Orion, cancelled by the 1963 test ban treaty), can get us there in 85 years. But, for what? The bottom line is that it would probably take 100 times the current annual energy use of the entire planet.
Today, I recommend that we refine the astroscience, but not spend anything on actual manned space travel. We landed on the Moon, and that was worth the ultimate fracturing of the Soviet economy. But international grandstanding was apparently necessarily to end the Cold War. Today, we have no equivalent enemy worthy of such grandeur. Yes, let's advance knowledge, but the $120 billion Bush the Younger budget and $500 billion Bush the Elder proposal for Man on Mars can be delayed...by about a millennium.