The BBC has produced a wonderful series called Richard Hammond’s Invisible Worlds. It’s visually stunning and it’ll wow you with a lot of cool science. The first episode is called Speed Limits. Because I study speed limits on perception, I was very excited.
To introduce the topic, Richard Hammond explains that vision is too slow to see many interesting things, things which can be revealed by high-speed imaging techniques. Indeed, watching the show I learned some fascinating facts about the motion of the wings of bumblebees and hawkmoths, and about shock waves, lightning, flowing water, rain drops, dolphin locomotion, bubble cavitation by pistol shrimps, Himalayan balsam seed shooting, fungal spores, and water striders.
Given that the whole show is based on the fact that the poor temporal resolution of human vision makes many aspects of the world invisible, I was expecting some halfway-decent explanation of the central concept of temporal resolution. Unfortunately, most of the statements in the show that bear on the topic of human perception are misleading or wrong. What made watching this especially painful for me was that the show’s staff actually consulted me for advice on the topic, to the extent that they sent me draft scripts. I dutifully used Track Changes to mark misleading statements and wrote fairly lengthy explanations of why more was needed, and spoke on the phone for several hours to a producer about doing more to explain human perceptual limits. All to no avail. Or at least, extremely little avail. Maybe it would have been worse without me..?
The confusion that lies behind the statements made in the show is not uncommon, and thus the show provides some teachable moments. It’s spurred me to take head on the common conflation of latency and temporal resolution. Maybe in the future, I’ll be able to prevent my students and maybe even future BBC producers from making the same mistakes. In a few following posts, I’ll get deep into ths. But for now, I’ll encourage you to watch one of the “Invisible Worlds” shows. Just don’t listen too carefully to the parts referring to human perception. Here’s some teaser text from the website:
. I mustn’t put my finger in a tank containing a pistol shrimp
Pistol shrimps are less than an inch long, but with an oversized claw, shaped like a boxing glove, they’re not to be messed with. In real time it looks like they see off opponents such as crabs by simply jabbing at them. But use high-speed cameras and you can tell something far stranger is going on. They win their fights without ever landing a punch. All their damage is done at a distance, as their closing claws force a jet of water to spurt out at close to 70 miles per hour, creating a low pressure ‘bubble’ in its wake. When this collapses, massive light, heat and energy are briefly created. Inside the bubble it momentarily reaches temperatures as hot as the surface of the sun, soaring to more than 4,000C. It’s this invisible force that causes much of the damage.
So the knockout punch comes from the bubble, not the claw.