Hank Green: The eternal catch-22 of deep space exploration, by which I mean, sending probes beyond our solar system toward other stars, is that whatever we invent now to send out there is pretty much guaranteed to be obsolete in 50 years. And when you're talking about voyages that, in a best case scenario, will probably take a century or two, that means that any spacecraft that we send out today is probably going to be passed on the way by whatever solar/nuclear/cold fusion/antimatter/warp drive propelled spacecraft we invent in the future. Which brings us to Alpha Centauri, our closest galactic neighbor. Is it time to give interstellar travel a shot? How would we do it? And given this catch-22, does it even matter?

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Alpha Centauri is a triple star system. The binary stars Alpha Centauri A & B are orbited by a tiny red dwarf named Proxima Centauri, that's much farther away than the other two. Seen together, Alpha Centauri A & B are the third brightest star in the nighttime sky. That's because relatively speaking, they are very close, just 4.3 light years away, and because of that, there's always been talk of someday sending a probe in that direction.

But things got even more interesting in 2012, when a team of European astronomers announced that they had discovered an Earth-like exoplanet orbiting Alpha Centauri B, Earth-like means that the planet, dubbed Alpha Centauri BB, has a mass of just 1.13 times that of earth. That alone is a rare find, but for it to be discovered orbiting our closest neighbor, that's exciting stuff! The bad news is that because the planet orbits its star in a brisk 3.2 days, it's way too hot to support life as we know it. The good news is that before it broke in 2013, NASA's planet hunting Kepler Space Telescope found that small, rocky planets like Alpha Centauri BB are often found in multi-planet systems, so there may be more.

Back to the bad news, though, it's still 4.3 light years away. That's 41.2 trillion kilometers, or roughly 280,000 times the distance from the earth to the sun. Trying to put that in some perspective here, Voyager 1 is speeding at over 62,000 kilometers per hour, if traveling in the direction of Alpha Centauri, which it is not, the trip there would take more than 70,000 years. And conventional vehicles are even slower. The space shuttle, which maxed out at a speed of 28,300 kilometers per hour would take about 165,000 years to reach Alpha Centauri, at which point there probably won't be any humans left to hear about it.

So, can we get there faster? Those who dream of exploring our nearest star system like to talk about developing spacecraft that can travel at 1/10th the speed of light, which would get us there within a human lifetime. We've talked here about very hypothetical propulsion systems like the good ol' warp drive as well as the not-hypothetical, like the solar electric systems that may one day speed up the time it takes for humans to travel to Mars, but even though we're still decades away from getting to the next planet over with a manned mission, that doesn't mean that we should just ignore the opportunity to send a probe to Alpha Centauri. Should we wait until we develop a technology, whether it be solar sails or antimatter engines or nuclear-electric vehicles, should we wait until we can travel at 10% the speed of light? That might be a long time to wait, like several dozen millennia, and I just can't wait that long.

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