The announcement this week of a plan to send a fleet of small, light-powered spacecraft to our nearest neighbouring star, Alpha Centauri, shows that starships of the future won't carry hundreds of crew, as they do in science fiction. If you want to go far and fast, you have to go small.

The plan, called Breakthrough Starshot, is being funded by billionaires Yuri Milner and Mark Zuckerberg. Support is coming from astrophysicists Stephen Hawking and Freeman Dyson, who worked on a starship project in the 1970s called Daedalus.

But unlike Daedalus, or fictional starships such as the Enterprise of Star Trek fame, which are huge vessels carrying hundreds of crew, the Breakthrough project involves a fleet of tiny spacecraft. Each one is only a few centimetres across and would be blown across space on a powerful laser beam, like leaves scattered by a leaf blower.

The extremely lightweight craft could potentially reach 20 per cent of the speed of light and arrive at the nearest star to our sun in just two decades.

While this concept has its challenges, such as building the world's most powerful laser, pointing it skyward while telling everyone it's not a space weapon or making sure the high velocity craft are not destroyed by a passing piece of space dust, the idea of sending something very small, very far away, has a lot of merit.

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Russian tech entrepreneur Yuri Milner wants to deploy thousands of tiny spacecraft to travel to our nearest neighbouring star system. (Matt Dunham/Associated Press)

Space is so vast that if you want to go anywhere beyond our solar system, you need to travel extremely quickly.

Otherwise, it will take longer than your lifetime to get there. And when it comes to speed, small, light objects take much less energy to move than massive vessels that have to act as space colonies to keep the crew alive during the voyage.

You can also send a lot of small ones, so if some are lost, the mission can still succeed. A giant starship has all the eggs in one basket, so to speak.

Hard on the human body

The other reason to go small is for the health of the crew.

Astronauts such as Scott Kelly, who just spent a year aboard the International Space Station, have shown that spaceflight is hard on the human body.

Bones lose calcium, the immune system is depressed and vision problems can appear, in addition to the psychological stress of living in a tin can, separated from family, friends and the great outdoors for long periods of time.

Setting out on a journey that would take decades makes little sense from a health point of view. Instead, we can explore remotely, with tiny machines that carry artificial versions of our senses, to find out what's out there.

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Future long distance space travel is unlikely to look like the Starship Enterprise. (Luke MacGregor/Reuters)

So, until faster-than-light travel is invented — which, so far, defies the laws of physics — interstellar ships will be small.

That raises an interesting question: Have other civilizations on other planets come to the same conclusion? Are there fleets of tiny alien spacecraft, wandering among the stars, that are too small for our telescopes to detect?

Maybe tiny alien spaceships do exist

In science fiction, alien spaceships are usually portrayed as large vessels, usually saucer-shaped, that carry strange-looking occupants of some kind.

But from an efficiency standpoint, that is not the best way to explore the galaxy. Perhaps tiny, robot, alien spaceships are passing by all the time, but they are too small to show up in our telescopes or we mistake them for interstellar space dust, micro-meteoroids or small asteroids.

I was thinking about this one warm summer evening, when a small insect began buzzing around my head. At one point, it hovered motionless right in front of my face, then made a series of very precise motions involving 90-degree angles.

I wondered, "Is this an alien spaceship checking me out?"

It gives new meaning to the definition of UFO.