Reading an interesting but in some ways rather silly interview with Elon Musk, about Space X and his plan to colonise Mars, I was stopped in my tracks by his reported assertion that “you could cycle to the nearest star in a few hundred thousand years”. That didn’t sound right and a few moments’ mental arithmetic brought me to the conclusion – since checked more carefully – that he was off by a couple of orders of magnitude. The road to Proxima Centauri, 4.24 light years distant, is mostly flat and offering little in the way of wind resistance. Even pedalling 24*365, it should be easy enough to maintain an average 20mph (32kph). At that rate, the journey would take about 142 million years. That’s assuming of course that our star and its neighbour were to co-operate by remaining a constant distance apart (which of course they won’t). Proxima Centauri is actually heading this way at about 7.4 miles per second so it would be a good idea not to be in the way. It will actually close the range to about 3 light years in 25-30,000 years, which allows nowhere near enough time to intercept by bike, and after that playing catch-up at 20mph is just never going to cut it.
Joking apart, it’s interesting to contemplate interstellar distances in this way. As Douglas Adams put it in The Hitchhiker’s Guide to the Galaxy, “Space is big. You just won’t believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”
It’s often said that cosmic distances are so vast we can’t really get our heads around them. I’m not sure what people mean when they say that, but the way the cosmos is portrayed on screen, even in such worthy efforts as Cosmos (both the Sagan and Tyson versions) tends to grate on me. Even more than when something explodes and we hear it on the sound track. (In space, no-one can hear me complaining.)
The problem is, if the portrayal were more realistic, the screen would pretty much be empty. So be it I say. Rather that than leave newcomers to the subject with the impression that the stars are whizzing past one another like so many snooker balls after the break off. After all, two galaxies each containing billions of stars can ‘collide’ without any stars banging into one another. They just play out an extremely long gravitational dance.
Even less rigorous is the portrayal of faster-than-light travel in Star Trek. When the Enterprise gets up to warp 5, it’s really motoring. We’re talking 200 times the speed of light! Surely that is quick enough to justify having the stars whip past the windows like tracer bullets in an air battle? I don’t think so. At 200 times light speed, you’ll get to Proxima Centauri from here in a little under eight days. In other words, even when the stars are relatively close together, you may be passing one a week even if you are somehow able to travel hundreds of times faster than a speed which – in all honesty – we have to regard as unattainable.
If you enjoy boggling your mind with cosmic-scale distances, then you can always get another, similar fix by contemplating the Timeline of the Far Future. After hoisting that in as well, perhaps you’ll join me in wondering what the Fermi Paradox is all about. I don’t find it at all surprising that we look out and see no other signs of life. What are we expecting? I do believe the Universe is probably teeming with life, but it seems to me fairly obvious why it’s not zooming from place to place so that we would see aliens in the solar system like flies at a picnic.
Anyway, whatever you think of Mr Musk’s travel plans, you’d be wise to check his sums if he’s the one planning fuel and food for your journey.