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Glenn Harlan Reynolds: Stars closer than you think



Thanks to innovations in space travel, voyaging to the stars is no longer just a conceit of science fiction. "Ad astra per aspera," is an old Latin phrase meaning, roughly, "to the stars, through hard work." We're still a long way from traveling to the stars, but some people are already putting in some hard work.

The other night, instead of watching the Super Tuesday primary returns, I traveled down to Chattanooga for a session of the Tennessee Valley Interstellar Workshop, a series of meetings focusing on the how and why of traveling to other solar systems. The subject wasn't a new one to me, but I learned some things about what's going on now. And while the prospects of anyone currently alive getting to walk beneath an alien sun are poor, there are a number of current technologies that may allow us to send a probe, and perhaps even follow it up with people on a one-way trip.

As obvious as it sounds, the problem with interstellar travel is that other stars are so very far away. The distance from the Earth to the Sun, 93 million miles, is called an Astronomical Unit. Traveling from the Earth to the moon (about a quarter of a million miles, and a tiny fraction of an AU) takes days. Traveling to Neptune, about 30 AU, takes years. The nearest star, Proxima Centauri, is at a distance of 271,000 AU. The distance between stars is so great that AUs are a poor measurement unit; it's measured instead in light years, a light year being the distance light (which moves quite fast, at roughly 186,000 miles per second) covers in a year. To travel to other stars, we need to be able to achieve speeds that are some respectable fraction of lightspeed. Even at 10% of the speed of light, the nearest star is over 40 years away.

There are various ways of doing this. Nuclear fusion, which we sort of know how to control (we can make hydrogen bombs, which use fusion, but we can't make a controlled reactor yet) offers enough power. Antimatter, which we currently know how to make and store in tiny quantities, would be even better. We're currently experimenting with light sails, which use the pressure from solar radiation (yes, light exerts a tiny amount of pressure) to accelerate a spacecraft; for interstellar missions, that pressure might be augmented by solar-powered lasers focused on the sail.

There are even some (very) modest signs of progress on the holy grail of interstellar travel, a "warp drive" that would allow faster-than-light travel, though no one at the workshop was talking about that. As physicist/science fiction writer Les Johnson (he's the principal investigator on NASA's Near Earth Asteroid Scout mission, which will use a solar sail) said, the focus at these workshops is on ways of interstellar travel using known physics, not physics that we hope to discover. But nobody there would mind if science fiction came true, as it has a way of doing.

And, in fact, the event wound up with a panel of science fiction writers who talked about just that. Just a couple of decades ago, one noted, the only people who firmly believed that there were planets circling other stars were science fiction fans. Now we're discovering new planets all the time, and some estimates suggest that there may be billions of these exoplanets throughout our galaxy. So that's one reason to be talking about interstellar travel: Now there's somewhere to go.

Another reason is that while talk is no substitute for action, it can be a pretty important precursor. Much of our progress in space to date has been achieved because of people (usually science fiction fans) who wanted to explore places where no human had ever gone. As physicist and science fiction writer Greg Benford remarked, ultimately, we can do this, "but you can't do it if you stop thinking about it." Science fiction keeps people thinking about it, and that's good.

Well, it wouldn't be the first time. In 1938, the British Interplanetary Society had a workshop on missions to the moon. Thirty-one years later, one of the participants — Arthur C. Clarke, a science fiction writer who along the way conceived the idea of the geosynchronous communication satellite — was on hand for the launch of Apollo XI, which carried the first astronauts to the lunar surface.

That happened sooner than many expected, in part because the believers acted to make it so. Perhaps that will happen again. Ad astra per aspera!

Glenn Harlan Reynolds, a University of Tennessee law professor, is the author of The New School: How the Information Age Will Save American Education from Itself, and a member of USA TODAY's Board of Contributors.


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Posted: March 3, 2016 Thursday 03:35 PM