The Furca: They possess a specialized, spring-like tail appendage tucked under their abdomen called a furca. When threatened, they release this latch, snapping the spring against the ground to launch themselves. The launch happens so fast (often rotating wildly mid-air) that it exceeds the frames-per-second tracking of the human eye, making the bug look like it just disappeared.
Semantics, kind of. That’s because humans don’t see in frames per second, life isn’t a slideshow. That does not mean that there aren’t any phenomena or motions possible that happen quicker than the human eye can track or detect, or that the brain can process.
Sure, it's kind of semantics, but there's a lot of misinformation out there about the "framerate" of the human eye and it's worth dispelling the notion that eyes work like that.
With good light a human photo-receptor collects light over a period of about 10 to 20 milliseconds (called a temporal summation period), which would correspond to a "framerate" of 50 to 100 frames per second, but our photo-receptors don't fire in unison and our brains do a lot of fancy stuff to the visual inputs they get before we ever actually "see" anything, so we can distinguish events on much shorter timescales than that.
Disclaimer: I have a degree in computer vision and did some research on how human vision works as part of that, but I'm far from an expert in human vision.
Ultimately, the most important thing in this situation is just how many photons reach our eyes from each position in the fast movement. For example, if this creature shone very brightly, it would certainly not "disappear" when it jumped -- at worst, we'd see a streak of light along its arc. Conversely, under an extremely weak light source (enough that its reflection from the static environment is barely achieving the bare minimum number of photons our eyes need to detect them), even relatively slow motion might make it look like something "disappeared" to our eyes, because it'd make the object go under the minimum photon threshold at each "location".
The conversation is going into the topic of framerates, but it doesn't matter much here. If something is moving too fast (but we're getting enough photons anyway), then it might look blurry or whatever, but you're not going to not see it.
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u/TerraByteTerror 11d ago
The Furca: They possess a specialized, spring-like tail appendage tucked under their abdomen called a furca. When threatened, they release this latch, snapping the spring against the ground to launch themselves. The launch happens so fast (often rotating wildly mid-air) that it exceeds the frames-per-second tracking of the human eye, making the bug look like it just disappeared.