Why humanity may yet reach the stars

May 15, 2015
The Soyuz TMA-14M capsule with ISS crew members Barry Wilmore of the U.S., Alexander Samokutyaev and Elena Serova of Russia is seen above clouds as it descends before landing southeast of Dzhezkazgan

A Soyuz TMA-14M capsule is seen above the clouds as it descends beneath a parachute before landing southeast of Dzhezkazgan in central Kazakhstan in this March 12, 2015 picture provided by NASA. REUTERS/Bill Ingalls/NASA/Handout via Reuters

It’s a bitter pill to swallow, but it’s starting to look as if Einstein might just have been right about that speed of light thing. From apparently superluminal radio sources in deep space, to the neutrinos that were supposed to be arriving ahead of schedule at the Grand Sasso experiment in Italy, every apparent exception to Einstein’s ultimate speed law has turned out to be a phantom. Even in the quantum realm, where entangled particles seem to communicate with each other instantaneously across any distance, no useful information is shared at anything other than the speed of light.

This is a particular blow if you happen to enjoy the galaxy-spanning fantasies of Star Trek, Star Wars and the like. Dreams of warp drives and hyperspace are just that — dreams.

But that doesn’t mean that interstellar travel is itself a fantasy. Travel below the speed of light — but as arbitrarily close to it as you wish — is perfectly feasible. Of course, that isn’t the same thing as saying it will be easy. Imagining the technologies that will carry us to the stars places us in roughly the same position as Leonard da Vinci, when he first sketched the concept behind the helicopter. Getting close to the speed of light will demand energies and materials beyond anything within our current capabilities. Chemical rockets certainly won’t cut it, nor the ion propulsion systems employed by some spacecraft. Even dauntingly difficult fusion power wouldn’t be up to the job. But perhaps harnessing antimatter, or the power of miniature black holes, may just give us the tools. At the moment we can make antimatter in tiny quantities, but not nearly enough to fuel a ship. And while we suspect that miniature black holes may exist, and may even be produced in high-energy physics experiments like the Large Hadron Collider, so far they’ve proven elusive.

That said, any civilization willing to contemplate an interstellar expedition at close to the speed of light might also settle for something half as fast, or a quarter as fast. It would just be a question of waiting a bit longer for the news. At 10 percent of the speed of light, an expedition could reach the nearest star within 50 years. Such a mission could be achieved using fusion technologies which aren’t too far beyond those now on the drawing boards, although slowing down at the other end does add to the difficulty. Still, 50 years is a long time by any measure. The astronaut Scott Kelly has just embarked on a one-year expedition to the International Space Station, and no one has yet spent longer than 14 consecutive months in space. Clearly we have some way to go before we can contemplate decades-long interstellar missions. But current space missions already have planning and execution cycles spanning many decades, so an interstellar mission lasting 50 years does not seem entirely outlandish.

But having the technology is only half the answer: we also need the collective will to embark on such a costly, time-consuming enterprise. We need an objective, a destination close enough to achievable, but also sufficiently tantalizing to galvanize our efforts. For most of our history, worlds beyond our own solar system were no more than hypothetical entities — few astronomy textbooks published more than 20 years ago even discuss the possibility of other planets.

The unmanned Falcon 9 rocket launched by SpaceX, on a cargo resupply service mission to the International Space Station, lifts off from the Cape Canaveral Air Force Station in Cape Canaveral, Florida

The unmanned Falcon 9 rocket launched by SpaceX, on a cargo resupply service mission to the International Space Station, lifts off from the Cape Canaveral Air Force Station in Cape Canaveral, Florida, Jan. 10, 2015. REUTERS/Scott Audette

Lately, though, we have gone from knowing nothing about such worlds, to being overwhelmed with the pace of discovery. It now appears that alien solar systems are commonplace, with more than 1,000 stars now known to host planets. Our understanding of these distant locales is slowly improving, and before long we should have at least hints about the conditions and chemistry on some of these worlds. Astronomers have already figured out the expected signatures of oceans, landmasses, icecaps and atmospheric chemistry — now all they need is sufficiently good data to tease out these buried signals. Finding an Earth-like planet — or at least a world with a good chance of hosting life — would surely provide a decisive spur to interstellar exploration.

Be careful what you wish for, though, because an increase in our knowledge of other solar systems could have exactly the opposite effect — dampening our enthusiasm, not stoking it. Such worlds may not be as enticing as we now imagine. While it would be nice to find life-bearing planets, gorgeous blue-green marbles with oceans and vegetation, they may be vanishingly rare. Perhaps the majority of worlds will fall into a handful of similar categories, with very few surprises — rocks, gas giants, hot Jupiters — endless reiterations of the same few themes. While this data will vastly enrich our knowledge of the surrounding cosmos, it may have a chilling effect on our aspirations. After all, why cross light years to end up at a place much the same as the one you left? It could even be one explanation of the Fermi paradox, the puzzling absence of interstellar travelers in our own vicinity. Perhaps alien civilizations learn enough about their place in the galaxy that they lose the imperative to engage in physical exploration and colonization.

On the other hand, we won’t know until we look. Perhaps our telescopes will find something that demands detailed examination from close quarters — more than can ever be achieved by remote observation. We may send machines, or people, or perhaps by then the distinction between humans and artificial intelligences simply won’t matter. My suspicion is that, for one reason or another, we will eventually launch an interstellar expedition. But like Leonardo’s helicopter, it may bear only the slightest resemblance to our present-day imaginings.


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A journey of a thousand miles begins with one step. Let’s work towards a sustainable presence on Mars this century.

Posted by Nissl | Report as abusive

“Even in the quantum realm, where entangled particles seem to communicate with each other instantaneously across any distance, no useful information is shared at anything other than the speed of light.”

“A team of Chinese physicists have clocked the speed of spooky action at a distance — the seemingly instantaneous interaction between entangled quantum particles — at more than four orders of magnitude faster than light. ”

http://www.extremetech.com/extreme/15020 7-chinese-physicists-measure-speed-of-ei nsteins-spooky-action-at-a-distance-at-l east-10000-times-faster-than-light

Posted by Ice9 | Report as abusive

depressing and unimaginative article… clearly the author is unfamiliar with Jules Verne…. pretty much anything you can imagine is ultimately possible… science fiction is just science we haven’t figured out yet… .

Posted by raywolfson | Report as abusive

Humans will not reach the stars because earth doesn’t have the exotic material to get us there. I’m talking about element 115, which is a superheavy element in the periodic chart. Bob Lazar states that gravity is the only way to manipulate time & space to shorten the distance between two points. We can see this through gravitational lensing as we see the stars behind the sun. Humans are stuck on earth using fossil fuels as our means of travel to the moon.

Posted by exhile | Report as abusive

Mr. Reynolds, I’m so very happy to wake up to an article on Reuters written by you! I’ve always loved your books! I do find myself discouraged by the difficulty of interstellar travel. I’m not aware of any sort of self contained reaction engine that can take us to near the speed of light efficiently. I do think beamed power holds promise though. Other than that, barring breakthroughs in physics (which are not improbable), I think we’re stuck here for a long time.

Looking forward to your next book!

Entangled particles are “correlated,” but cannot be used to send information faster than light. That is their behavior is identical over distance, but you can’t wiggle one electron and have the other react identically in a spooky fashion.

Posted by HypergolicSun | Report as abusive

And 100 years ago, current science told everyone that the sound barrier was unbreakable. Don’t dismiss future discoveries just because we can’t imagine them yet.

Posted by mynrkt | Report as abusive

Thank you Alastair Reynolds. Informative opinion and for those who think about such things, more to consider. I will look for more from you with appreciation.

Posted by giotto20 | Report as abusive

With all that’s out there, I hate to think that our solar system is the dead end.

Posted by notfooled2 | Report as abusive

The author curiously misses the most realistic, probable and realizable scenario: interstellar travel with no humans onboard. In relatively short time we will have intelligent robotic systems doing things better than people (think about those self-driving cars). Why then sending people out there? In fact with robotic systems one can plan for very long missions (think about thousand years). One can also think about search missions for planets to be colonized with the aim for transferring life there (think about deeply frozen life promoters).

Posted by wirk | Report as abusive

Humanity can reach the stars still in our lifetime by employing more efforts toward development of a warp drive based on phased electrodynamic waves. http://youtu.be/6zh9abFF3ZE

Posted by BKHC | Report as abusive