I think it’s fair to say that, given your ‘druthers, you’d want an instrument that could map exoplanets in the kind of detail you get with Google Earth, with enough resolution to actually see the Great Wall of the Klingons, in case they’ve built one.

Could we construct such a telescope … ever?

Here’s what it takes: Let’s assume that all the alien worlds you wish to view up close and personal are no more than 100 light-years away. That might sound pretty cramped to astronomy nerds, but there are probably several hundred thousand planets within that distance – enough to gratify even the most spirited voyeur.

At 100 light-years, something the size of a Honda Accord – which I propose as a standard imaging test object – subtends an angle of a half-trillionth of a second of arc. In case that number doesn’t speak to you, it’s roughly the apparent size of a cell nucleus on Pluto, as viewed from Earth.

You will not be stunned to hear that resolving something that minuscule requires a telescope with a honking size. At ordinary optical wavelengths, “honking” works out to a mirror 100 million miles across. You could nicely fit a reflector that large between the orbits of Mercury and Mars. Big, yes, but it would permit you to examine exoplanets in incredible detail.

The down side is obvious: Who could ever construct such a thing? Well, fortunately, no one has to. Instead, you could field a phalanx of small mirrors in space, spread out over 100 million miles. They wouldn’t even have to maintain a fixed pattern, as long as you could accurately keep track of their relative positions.

No huge mirror: just a manageable number of small ones. The ability to see detail would be the same. And, of course, it’s a heck of a lot easier to turn an array of small instruments to different places on the sky than to pivot a 100 million-mile monstrosity.

Of course, there are a few small problems of principle here. You need to collect enough light to make the imaging possible, and correct for the fact that the target exoplanet is both rotating and sliding across the sky. Both problems can be dealt with, at least in theory – which suggests that they can also be dealt with in practice, given sufficient effort.

But think of the implications. There’s a lot of talk about interstellar travel, and whether we will ever be capable of rocketing to other stars. It’s a tough thing to do.

However, if the type of telescope described here can be built, then the tyranny of distance is vanquished. You can forget deep space probes and their long travel times. We could explore alien worlds in the comfort of our own homes, as our laptops scroll and zoom through data sets collected by a mammoth, space-based telescope array.

It would also, quite obviously, be a whole new way to search for extraterrestrial life … just look for it, or its artifacts (like cities).

This is, to my mind, the ultimate telescope. It’s not for our generation to build, or even the next two. But after that …