A 'smart ruler' could help swarms of space telescopes image exoplanets

We've talked plenty of times here about the infeasibility of launching a mirror big enough to directly image exoplanets using current rocket fairings—at least as long as we're not sending them 500-plus AU away to a gravitational lensing point.

We've also talked at length about the potential solution to that problem—interferometry, where multiple smaller satellites link up precisely but are spaced far enough apart to act as one gigantic mirror.

The problem is, from a technical standpoint, it's really hard to build these kinds of systems. ...