The myths and reality about interstellar travel

Is reaching alien planets outside our Solar System actually possible, and if so, how would it work?

Science fiction writers and moviemakers have shown us countless visions of humanity spread out across the Universe, so you might be forgiven for thinking that we've already got this in the bag.

Unfortunately, we still have more than a few technical limitations to overcome - like the laws of physics as we understand them - before we can start colonising new worlds beyond our Solar System and galaxy.

That said, several privately funded or volunteer initiatives such as the Tau Zero Foundation, Project Icarus and Breakthrough Starshot have emerged in recent years, each hoping to bring us a little bit closer to reaching across the cosmos.

The discovery in August of an Earth-sized planet orbiting our nearest star has also raised fresh hopes about visiting an alien world.

Interstellar spacecraft will be one of the topics discussed at BBC Future's World-Changing Ideas Summit in Sydney in November.

Is travelling to other galaxies possible?

And if so, what kinds of spacecraft might we need to achieve it? Read on to get up to (warp) speed:

WHERE WOULD WE GO?

Where wouldn't we go? There are more stars in the Universe than there are grains of sand on Earth - around 70,000,000,000,000,000,000,000 - and billions of these are estimated to have one to three planets in the so-called 'Goldilocks' zone: not too hot, not too cold.

As we're just starting out, the best contender so far is our nearest stellar neighbour - the triple star system of Alpha Centauri, 4.37 light-years away.

This year, astronomers at the European Southern Observatory discovered an Earth-sized planet orbiting Alpha Centauri's red dwarf star Proxima Centauri.

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