Why FTL travel is unlikely, at least in the foreseeable future

I’m a big fan of Star Wars, Star Trek, and the space opera genre.  The future I would most hope for the human race would be for us to spread out among the stars and become an interstellar species.  Now, assuming we don’t drive ourselves extinct, I do think we will eventually become an interstellar civilization, but I seriously doubt that it will look anything like the common space opera.

The first thing to understand is that science fiction concepts like hyperspace, warp drives, star gates, and similar mechanisms are plot devices.  They are built on, at best, the flimsiest of science, and more often they’re little more than hand waving.  If you talk to most physicists, they’ll tell you that the prospect of ever finding a way to travel faster than the speed of light is grim, at least with the laws of physics as we currently understand them.  Of course, that could change tomorrow with a new discovery (see the related articles below), but if we’re contemplating what’s likely to be, rather than what we’d like to be, we should probably think in terms of Einstein’s universe.

There are physicists who speculate about things like wormholes, the Alcubierre drive (a kind of retro-theory for warp drives), and many other mechanisms.  But these are extremely speculative concepts, requiring that aspects of nature exist that we currently have no empirical support for; notions like exotic matter with negative mass.  And they would probably require cosmic amounts of power.  Some people have pinned their hopes on things like quantum entanglement, but just about every physicist throws a wet blanket on any possibility of using entanglement to communicate faster than light, much less travel at that speed.

Am I being overly pessimistic?  After all, didn’t people once say that flying would be impossible, or breaking the sound barrier, or many other accomplishments?  It’s always worth contemplating the large list of things that people have historically said would not be possible, who were subsequently proven wrong.  It’s why I’m not using the I word (impossible), but the U word (unlikely).  However, an important thing to contemplate about these past accomplishments was that there had always been something in nature that had done it before us.  (For the examples above, birds and meteorites.)  The naysayers weren’t saying that it was impossible, but that humans would never be able to do it.  For what I’m saying here to be equally short sighted, we would have to see things in nature that were exceeding the speed of light.

So, is there anything in nature that does go faster than light?  Well, cosmic inflation, if it happened, would have happened faster than light.  Galaxies beyond our cosmological event horizon are moving away, relative to us, faster than the speed of light due to the ongoing expansion of the universe.  And a couple of years ago, scientists thought they maybe had detected neutrinos going faster than light.  But while space itself can move faster than light, there’s no indication that anything in space, matter or energy, can do so.  The relative movement of galaxies that are so far away that they’re causally disconnected from us doesn’t seem of much use.  And the neutrino thing turned out to be an equipment issue.

So, exploring the galaxy will likely have to be done a sub-light speeds, at least with known science.  If you read science fiction, you’re probably fairly familiar with things like generation ships, suspended animation, and relativistic trips.  These may be possible, but I think they’re also unlikely.  A relativistic ship, which needs to be traveling near the speed of light to experience the effect, would have staggering energy requirements.  Generation and sleeper ships are more plausible, but they would be expensive and risky affairs.

A great deal of the cost and risk in interstellar travel exists from a desire to send biological humans.  But it’s far more economical and less risky to send small robot probes, particularly if those probes are intelligent enough to build everything they need for exploration using materials in the destination solar system.  Such probes might also build additional probes to send on to other stars.  These self-replicating probes, even if the maximum speed we can ever manage is 1% of the speed of light, could explore the entire galaxy, building an increasingly wider interstellar communications network.  It’s a lot cheaper for these probes to transmit their findings back to their parent probes, up the chain, eventually back to Earth, than to try to physically go there ourselves.

You’re probably feeling a strong reaction against giving up the idea of humans physically making the trip, thinking of people like Columbus and Magellan.  Two important things to remember about the age of exploration.  The first is that is was humans exploring further into their existing biosphere, going places where other humans already existed.  The second is that, given the technologies of the time, they really had no choice but to physically go themselves.  If Portugal and Spain could have sent out robotic ships to explore, without the cost and risk of sending humans, that’s probably what they would have done, at least for the initial explorations.  Despite romanticism, most people don’t risk their lives if they don’t need to, or incur costs they can avoid.

If we’re lucky, we  might be able to upload copies of our minds into these probes, or transmit them later, and experience these remote locations ourselves.  This may seem outlandishly speculative, but unlike breaking the light barrier, there’s nothing in the laws of physics outright preventing it, at least none that we know of yet.

Barring a new physics, that might have to be enough.

Related articles

• Warp Speed, Scotty? Star Trek’s FTL Drive May Actually Work (madsciencetech.wordpress.com)
• Physicists spooked by faster-than-light information transfer (nature.com)
• Einstein’s nightmares… part two (hunt4truth.wordpress.com)
• Questions from the public – Why can’t things go faster than the speed of light ( and what is a Tachyon) (fortheloveofscience2013.wordpress.com)
• Our Star-Trek Future? NASA Scientists Engineering a Warp-Drive Solution for Faster-Than-Light Space Travel (dailygalaxy.com)