With a growing number of Earth-like exoplanets discovered in recent years, it is becoming increasingly frustrating that we can’t visit them. After all, our knowledge of the planets in our own solar system would be pretty limited if it weren’t for the space probes we’d sent to explore them.
The problem is that even the nearest stars are a very long way away, and enormous engineering efforts will be required to reach them on timescales that are relevant to us. But with research in areas such as nuclear fusion and nanotechnology advancing rapidly, we may not be as far away from constructing small, fast interstellar space probes as we think.
There’s a lot at stake. If we ever found evidence suggesting that life might exist on a planet orbiting a nearby star, we would most likely need to go there to get definitive proof and learn more about its underlying biochemistry and evolutionary history. This would require transporting sophisticated scientific instruments across interstellar space.
But there are other reasons, too, such as the cultural rewards we would get from the unprecedented expansion of human experience. And should it turn out that life is rare in our galaxy, it would offer opportunities for us humans to colonise other worlds. This would allow us to spread and diversify through the cosmos, greatly increasing the long-term survival chances of Homo sapiens and our evolutionary descendants.
Five spacecraft – Pioneers 10 and 11, Voyagers 1 and 2, and New Horizons – are currently leaving the solar system for interstellar space. However, they will cease to function many millennia before they approach another star, should they ever get to one at all.
Clearly, if starships are to ever become a practical reality, they will need to be based on far more energetic propulsion technologies than the chemical rockets and gravitational sling shots past giant planets that we use currently.
To reach a nearby star on a timescale of decades rather than millennia, a spacecraft would have to travel at a significant fraction – ideally about 10% – of the speed of light (the Voyager probes are travelling at about 0.005%). Such speeds are certainly possible in principle – and we wouldn’t have to invent new physics such as “warp drives”, a hypothetical propulsion technology to travel faster than light, or “wormholes” in space, as portrayed in the movie Interstellar.
Ten percent of light speed is still far too slow for practical human interstellar travel. To read more, click here.