May 27, 2010

Sometimes science fiction becomes fact. We have sent men to the moon and brought them back, placed many man-made satellites into orbit, and even sent a probe past Pluto and on beyond the furthest reaches of the solar system
Scientists, and especially astronomers, have always dreamed of other planets like ours, with intelligent life. They are actively searching for possible communication from such extraterrestrial life.
Knowing that in a few billion years, our planet will be destroyed, and possibly much sooner by various possible catastrophes, people have even dreamed of sending pioneers to colonize a suitable planet somewhere, orbiting around some faraway star.
I think I can lay these dreams to rest. Perhaps in millions or billions of years we might develop technologies undreamed of as yet. I will limit my speculation to something we are very certain of: Nothing travels faster than the speed of light, an impressive 186,000 miles per second.
When we apply this to the known astronomical distances to other stars, we’ll see that it would take ridiculously long to communicate with a likely planet, and much longer to get there. My numbers are very approximate, but adequate, I think, to make my point. Conveniently, astronomers measure distances in light years. A light year is about 6 trillion (6,000,000,000,000) miles
The moon, our closest neighbor is about 260,000 miles away. In terms of the speed of light, that’s about 1.4 light-seconds. The sun, is 93 million miles away, That’s 8.3 light-minutes away. Pluto has been demoted from the rank of our outermost planet in recent years (too small). It is, I believe several light-days away. It took years to send a probe there to send back pictures of Pluto
Our nearest star, Alpha Centauri is 4.3 light years away. We could send a signal there and get a reply back in 8.6 years. That is, if there were someone there with sufficient technology to detect our signal and reply. At that distance, it would probably take all the electrical power on this planet, and more, to send a brief message which would be detectable at that distance.
Now we move into the realm of probabilities. Just what is the probability that our neighbor Alpha Centauri has an earth-like planet, with intelligent life, with advanced technology? It turns out that most stars are unsuitable (Size & Temperature), and of the suitable stars the chances are slim that they would have a planet at a suitable distance, of a suitable size and chemical composition to support life of any conceivable kind. My guess is that the chance is something between one in a million and one in a billion.
For many years astronomers have studied all of the 8 planets in the solar system. Plainly none of them could support life with the just possible exception of Mars, our nearest planet. After years of surveillance by probes orbiting Mars, and Robot rovers sampling and examining the surface, it is pretty certain that there has never been any life on Mars.
Examining the solar planets shows that Earth is indeed unique.
In recent years astronomers have developed ways of detecting planets orbiting stars. The easiest planets to detect are the biggest ones, like Jupiter. Our methods of detecting smaller planets limit the chance of finding a suitable one; we can only detect smaller planets if their orbit happens to come in direct line between their parent star and earth. So there may be many possible life supporting planets that we could never detect. We have recently detected a few of a more earthlike size but none at a likely distance from the star, such as Alpha Centauri.
Probably our best chance of finding a planet with advanced technology would be by detecting signals like our radio, television, and microwave signals, which we have been radiating now for a century. We have been listening now for such signals for years without result. Of course, such a signal, even from Alpha Centauri, would probably be too weak to detect by our best present technology.
Supposing, against all odds, that we somehow detect an advanced civilization 50 light years away. Suppose too that we both have the necessary technology to communicate over such a distance. It might take a few hundred years just to get their attention and get their first reply.
Bouncing messages back and forth, with 100 year gaps, we would manage to bridge the language gap and start exchanging useful information. It would be fascinating, but the people who sent a message off would be dead by the time an answer arrived. However, we might advance both civilizations by the centennial exchanges of technology. Fascinating! But I’m indulging in science fiction.
Now let’s speculate about a trip to this, our nearest intelligent neighbor. With fantastic amounts of power, we might make the trip at an average speed of 5% of the speed of light (The first half accelerating, the second half decelerating). The trip would take 2,000 years- that’s 60 to 100 generations- to get there. Even a jaunt to our neighbor Alpha Centauri would take 80 years.
On our spaceship, we would have to produce food without sunlight, and totally recycle everything from air to sewage. Lots of technology we don’t yet have, and no rescues if anything fails. Science fiction has solved all of these problems, of course. Science fact, though, brings in the little question of economics. That has to do with achieving our goals within our limited means. It also raises the question of who’s to pay the bill.
If we carry on scanning the skies for signals from extraterrestrials, the cost is maybe a few million dollars a year. Taken out of the government bucket of taxes, it’s hardly missed. However, I doubt that, if such a project were financed out of donations, it would manage to scrape up enough to continue.
I wouldn’t contribute. Would you?
As for interstellar travel, that would take a hundred years at least to solve the technical problems (Fusion Power, for instance) and cost gazillions of dollars. Would you care to contribute a few hundred thousand?
I think I’ll pass on that one, too.


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