The Genius of the Barn Owl's Feathers

> Over the next few days, the owl makes 16 more strikes at mice, missing only four times, each time by less than two inches.

How did the experimenter measure miss distance in pitch darkness? IR illumination is presumably out in case the owl was able to see it, and I didn't think thermal imaging was a thing yet in the late '50s.

	▲	gucci-on-fleek an hour ago \| parent [-]
		Completely random guess, but perhaps ultrasonically? Ultrasonic rangefinders are relatively cheap and accurate these days, so maybe they were too in the '50s?

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smusamashah 2 hours ago | parent | prev [-]

Reminded if this video immediately https://youtu.be/-WigEGNnuTE they got almost nothing on the mics.