Astronomy is a passive science. Its practitioners normally earn their livings finding out what they’re given: gentle and different types of radiation emitted by stars and nebulae, generally after it has bounced off different objects, reminiscent of planets. However there’s an exception. A small however devoted band of astronomers is just not content material with the views which nature affords. They select, as an alternative, to light up their targets artificially, by beaming microwaves at them and searching on the reflections. They’re, in different phrases, observing by radar.
