Here is some fun dreaming for the middle of your day: How close are we to being able to travel to Alpha Centauri, the star nearest to our own?
The answer, as you’d suspect, is not close, but as George Musser explains in the latest issue of the new science magazine Nautilus, some approaches are tantalizingly more feasible than others.
Alpha Centauri is 300,000 Astronomical Units from Earth (an AU is defined as the average distance from Earth to the sun), an expanse that would take a starship moving close to the speed of light something on the order of a decade to traverse. The hard part (or, one hard part) is finding an energy source capable of powering a ship that far.
Musser, who was a longtime editor at Scientific American, considers five potential energy sources, each with its own pros and cons.
Ion drives, which Musser describes as, “like a gun that fires atoms rather than bullets; the ship moves forward on the recoil.”
Pros: Small, compact, and already proven to work in NASA’s Dawn probe.
Cons: Not powerful enough to propel a ship big enough to carry a human being.
Gigantic solar sails, which gather the miniscule momentum from wavelengths of light.
Pros: Lightweight, already proven to work on the Japanese IKAROS probe to Venus, and based on an endlessly renewable energy source.
Cons: Sailing is slow.
Nuclear rockets, which Musser explains, would work like this: “Load your starship with 300,000 nuclear bombs, detonate one every three seconds, and ride the blast waves.”
Pros: We already know how to make nuclear rockets.
Cons: 300,000 nuclear bombs don’t fit easily in the trunk.
Scavenging space for Dark Matter, whose particles—dubbed neutralinos—are theorized to “annihilate each other in a blaze of gamma rays” when they collide, and could provide a starship with infinite propulsive force.
Pros: Dark matter is EVERYWHERE.
Cons: We can’t actually find it.
Bending Space and Time. Per Einstein, the space-time continuum could theoretically be reshaped to bring distant points in the universe closer together.
Pros: Why schlep through the galaxy to visit Alpha Centauri when we can just move it over here?
Cons: As Musser writes, “It seems almost mean-spirited to point out how far beyond our current technology this idea is.”
All of these technologies are light-years from being feasible, and even if we were to master one of them, there'd still be tons of other issues to deal with (like, as Musser notes, the fact that what would feel like just a couple decades to a crew traveling close to the speed of light on a starship, would be hundreds of thousands of years back on Earth).
Still, there is something encouraging about breaking down the problem into discrete technological concepts, no matter how far-fetched the ideas may seem now. The ancients surely had their own ideas about seemingly impossible achievements, like, say, air travel, and slowly but surely, according to a path that might have been hard to anticipate ahead of time, we got there. There doesn't seem to be any reason why we shouldn't adopt the same a priori optimism towards interstellar flight.
For more on the ins-and-outs of interstellar space travel, read Musser’s excellent article here.
Image of a solar sail, courtesy of NASA.
The author is solely responsible for the content.
Leon Neyfakh is the staff writer for Ideas. Amanda Katz is the deputy Ideas editor. Stephen Heuser is the Ideas editor.
Guest blogger Simon Waxman is Managing Editor of Boston Review and has written for WBUR, Alternet, McSweeney's, Jacobin, and others.
Guest blogger Elizabeth Manus is a writer living in New York City. She has been a book review editor at the Boston Phoenix, and a columnist for The New York Observer and Metro.
Guest blogger Sarah Laskow is a freelance writer and editor in New York City. She edits Smithsonian's SmartNews blog and has contributed to Salon, Good, The American Prospect, Bloomberg News, and other publications.
Guest blogger Joshua Glenn is a Boston-based writer, publisher, and freelance semiotician. He was the original Brainiac blogger, and is currently editor of the blog HiLobrow, publisher of a series of Radium Age science fiction novels, and co-author/co-editor of several books, including the story collection "Significant Objects" and the kids' field guide to life "Unbored."
Guest blogger Ruth Graham is a freelance journalist in New Hampshire, and a frequent Ideas contributor. She is a former features editor for the New York Sun, and has written for publications including Slate and the Wall Street Journal.
Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.