SO, we've hit a rock with something the size of a washing machine.

When Nobel prizes are handed out, I want it noted that I've often come very close to hitting our washer with half a brick. What's more, I didn't have to travel four billion miles to attempt the feat. No-one at all called it a great achievement.

It is possible I've misunderstood the science. My best guess is the Philae robot probe thing bears no useful resemblance to a washing machine. Equally, its actual functions are as mysterious as a spin cycle. I appreciate - or pretend to appreciate - that hitting a target after a 10-year journey through inky darkness is tricky. You probably have more chance of finding intelligent life on Ukip. But what has truly been done, and why, means as much to me as moveable type did to a medieval serf.

It wasn't supposed to be this way. I am a child of what they once called the Space Age. I was the one who stayed up all night in a house at Kildonan Strath, above Helmsdale, fiddling with a wireless on a July night in 1969 to hear Neil Armstrong tell the universe we had arrived. I would have trampled Major Tom underfoot for the chance to escape the planet.

The next (and only) house on the hill belonged to an old lady who still depended on gas mantles and lanterns for light. As symbols went, the contrast was obvious enough. But what I remember best was her flat, blithe refusal to countenance the daft fantasy that any man could ever walk on thon Moon.

This wasn't early conspiracy theory. There was no ignorance of what people got up to with missiles. For the old woman in the little house in Sutherland all those years ago, the old Moon, the changing Moon, the Moon that scudded through clouds and moved the sea, was a different kind of presence. The idea that some American could stand upon it was not contained within her universe.

The Apollo landings were supposed to change all that. The species was supposed to step, dazzled, into a new age of possibilities without limit. Science fiction - still fiction, you'll recall - depends even yet on the entirely ignorant hope that when a few minor technical wrinkles are ironed out, we'll be off, voyaging. Space Age propaganda still maintains that this is, for some reason, "our destiny".

So the director Christopher Nolan produces a blockbuster film, Interstellar, with a fine disregard for mundane physics and ­humanity's moral flaws ("Nice universe; we'll take it"). So people sign up for Mars colonisation projects designed, explicitly, around the idea that if you dare to go there you can never come back.

Meanwhile, we throw tin boxes at rocks. Wallace and Gromit at least managed a cooker that could ski. Where's the progress?

I'm not being churlish, necessarily. I'd still go if Nasa would risk another Homer Simpson episode. But I wouldn't pay Richard Branson upwards of $200,000 just to join the club of appalling people who think nothing of handing $200,000 to ­Branson for the chance to almost - and this is an important detail - get into space. Set aside the recent tragedy and even the ­preposterous misnomer "Virgin Galactic" illustrates what became of those brave 1960s hopes.

Ideas of meaning and purpose have been lost. Jokes, meanwhile, grow easier. So they can send something the size of a washing machine four billion miles, but can't deliver a tumble dryer on a Tuesday? They can find a lump of rock moving at 40,000 miles an hour, but can't find the lump who forgot to tell Bob Geldof that another Band Aid effort isn't the reason why rich pop stars were put on this Earth? And so forth.

Space exploration is fantastically expensive. The European Space Agency's Rosetta effort to pin a tail on comet 67P will not leave much change from £1.1 billion. You could render any number of ­charity pop songs superfluous with that. You could aid victims by the tens of thousands and show an ignoramus that there is more to science than catching space debris.

On the other hand, the United States alone was party to $220bn in arms sales between 2004 and 2011. Poor Britain, with just 5% of the market, managed to offload only $27bn of the best scientifically designed armaments to other countries, most of them "developing", in the same period. Meanwhile, the last English Premier League football deal was worth £3bn, and some of the players pocketing that cash couldn't hit a fridge with a fridge magnet. It becomes a matter of why and if we care, and what we care about.

The idea that we should abandon space because there are better uses for the money is fatuous. There are always better uses and never enough money. On the other hand, the idea that there is forever a scientific imperative to contest the costly physics of space travel "because it is there" makes no sense. You can bewail the usual ignorance of the public or the media, but the fact remains that people began to carp about exploration because the point ceased to be arguable, far less obvious.

We could do fantastic things with those arms bazaar budgets, that's the cliché. How would your list go? Hunger, cancer, clean water, ebola, an end to incessant charity appeals? Any and all. But in one odd way, spending 25 years working out how to harpoon a comet throws all the arguments into relief. How should this tiny virus of a species conduct itself on its own little spinning rock? Curiosity is worth something. The eroding of humanity's inquisitiveness worries me more than its persistence.

So, how do you hit a comet with a washing machine-sized thing? I have no idea. Mark Twain fancied that in 1835 he "came in with a comet" (Halley's one). He left with it, too, almost to the day, in 1910. Even a sceptic like Twain found curiosity bewitching. Space travel might these days be a dull business of commercial satellites and billionaires, but an introverted, miserly species sounds worse.

The Moon was approaching full when she emerged over Sutherland in the last week of July 1969, with lots of stars at her back.

I remember looking up and wondering: two people were perched on her. Only fools would have turned down the chance to catch a comet then.