LS: Speaking of Science Column January 12, 2009

Looking for an Earth exit plan? Warp drive is not likely to help

In last week’s column, it was stated that in the past few years, more than 300 planets have been discovered that orbit stars other than our sun. These planets are called exoplanets.

Most exoplanets discovered to date are giant planets, similar to Jupiter or Saturn in our solar system. Most of these are very near the star they are orbiting. The size and nearness to the star make them easier to detect, but also lead to conditions on these planets that would not be conducive to life as we find it on Earth.

But this doesn’t mean there are no planets similar to Earth out there — they are just more difficult to detect.

So if exoplanets are common companions to the stars we see (and it seems they are), how close is the nearest one? How long would it take for us to travel there in case we need to emigrate from Earth? Or, perhaps the more eerie question, how long would it take for a non-human life form to drop by for a visit?

To determine this, we first need to understand the distances involved. A useful unit for measuring the distances between stars is the light-year. Light travels at a speed of 186,000 miles per second, so in a year, it would travel almost 6,000,000,000,000 miles (or 6 trillion miles).

At this speed, the light of the sun takes about 8 minutes to reach Earth, traveling a distance of about 93 million miles. The same light takes 5 1/2 hours to reach Pluto, which is just under 4 billion miles from the sun.

Now for the bad news: using our best technology, it takes us about 10 years to send an Earth-made object, like a probe, to Pluto. That means that light travels about 16,000 times faster than we can.

Traveling outside our solar system, the next-nearest star we encounter is Alpha Centauri, which is a little over 4 light years away. Unfortunately, no exoplanet has been detected orbiting Alpha Centauri, so it is not a likely candidate as a safe harbor for the evacuation of Earth.

The nearest star where an exoplanet has been detected is called Epsilon Eridani, 10.5 light years from earth. The exoplanet is a giant planet, half again as large as Jupiter (so if you weigh 100 pounds on earth, you’d weigh about 350 pounds on this planet). Although this is also not a good candidate for supporting Earth-type life, there are seven stars within 10 light years of Earth, so there may be other candidates.

Again, the picture is not so bright if we need to relocate our population. Using the speeds and distances we’ve talked about, if we took off today and traveled as quickly as we can manage at present, it would take us 168,000 years to get to Epsilon Eridani.

Obviously, we need to do better than that to make interstellar travel feasible.

Now for the sci-fi fans out there, we can improve this by inventing something like warp drives, which allow faster than light travel, but in the real world of physics, the possibility of warp drive is very, very unlikely. (But I don’t want to discourage anyone from trying to find out how to do it!)

For those familiar with relativity theory, we can also try improving our travel speeds to those approaching the speed of light (don’t ask me what propulsion system is needed — we need some inventors to come up with that). This is because the closer you get to the speed of light, the more slowly time passes for the traveller.

So a traveller to Epsilon Eridani might make it there within their own lifetime, even though thousands of years would still elapse on Earth. Consequently, it would still be, essentially, a one-way trip with a low likelihood of finding a friendly environment at the other end.

Hmm … in the meantime, we’d better take care of our own planet to the best of our ability.

The evacuation plan is not too promising at the present.

Vincent King is a certified health physicist who has been involved in radiological sciences for more than 30 years. He is a volunteer at the Western Colorado Math & Science Center.

Is there a science or math topic you’d like to write about? E-mail, at warp speed, .(JavaScript must be enabled to view this email address).


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