From Earth, light takes four years to reach Proxima Centauri, the nearest star to our sun, and millions of years to cross the void to other galaxies like ours.
Compared with light, our most powerful rockets are sluggish, and journeys between the stars seem doomed to involve thousands of years of sliding through the blackness. The growth of any Galactic Empire appears destined to be a slow and sedate affair.
So, are dreams of such an empire only that, just dreams? Not if you listen to the media, as reports of the advent of warp drives and strange electromagnetic (EM) propulsion . These would unshackle us from the need for immense fuel loads and offer rapid journeys to the stars. And all we need to do is relax the laws of physics.
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But to most scientists, these laws are not for bending, let alone breaking. As a result, suspicious eyes must be cast over the most recent claims, including from within NASA, of metallic cavities in which microwaves rattle around and produce directional thrust: the . This could provide years of non-stop propulsion. All we need to do is disregard Newton鈥檚 rules about action and reaction. It isn鈥檛 the first time such talk has caused a stir.
Why can鈥檛 the proven physics of our rockets get us there? The problem is that you have to lug the fuel with you. Look at the impressive Saturn V, which was one of the most powerful rockets ever built. It鈥檚 really just a device for hauling fuel into space and eventually landing a couple of astronauts and a few tonnes of metal on the moon, a paltry 1.25 light seconds away.
Rocketry is a dead end
Journeys to the stars could be speeded up by using a rocket that fires continually, but prohibitively vast quantities of fuel would be needed. The practical reality is a vehicle that gets a short rocket boost and then drifts at constant speed, like Voyager, the space probe that has got furthest of any from Earth. But that would take 70,000 years to reach our nearest interstellar neighbour. Rocketry, as we know it, is a dead end for this.
It鈥檚 no wonder, then, that speculation continues about other ways of making such journeys. The press is abuzz with stories about wafersats weighing a few grams sailing towards Proxima Centauri on laser beams. But no wafersat will ever carry a human. True starships are required.
And here we are stuck. Science offers some interesting ideas, such as the theoretical Alcubierre drive, which suggests that if we can just bend space and time the right way, we will be able to outpace light across the universe, while keeping Einstein鈥檚 relativity happy. But to build a working drive, we will have to master engineering forms of matter and energy we don鈥檛 know even exist.
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While the popular scientific and mainstream media continue to feed on EM drive-like stories about apparent technical advancement leading to the upheaval of physics and the dawn of a new age of space flight, the science is out in the cold.
Continual hype masks the lack of experimental results and theoretical justification in academic journals, the lifeblood of scientific debate. This leaves most physicists thinking there is little behind the smoke and mirrors. In truth, until there is real scientific evidence on the table for others to pore over, critique, test and reproduce, the vast majority care little about the claims of interstellar revolutions.
And for those who are not scientists, but who dream of interstellar flight and galactic colonisation, and wonder what to make of all of this, remember the old adage: 鈥淚f it sounds too good to be true, it probably is.鈥�
