Answers to even more questions

Episode Summary

Executive Summary: This episode of CrowdScience addresses follow-up questions from previous shows, covering: (1) deep-sea anglerfish colour vision despite darkness, (2) why human eyes appear to change colour, (3) whether Jupiter's moons drift like Earth's moon and might collide, and (4) how cats always land on their feet. Experts explain adaptations, physics, and evolutionary reasons behind these phenomena.

Main Topics: Colour Vision in Deep-Sea Fish (Priority: 5/5): How anglerfish and other deep-sea fish can perceive colour despite total darkness, using modifications in rod photoreceptors to detect bioluminescence. Chameleon Eyes: Why Eyes Change Colour (Priority: 4/5): Why some people's eyes appear to change colour (e.g., from brown to olive green) based on lighting, due to melanin and light scattering. Jupiter's Moons: Drift and Collisions (Priority: 4/5): Whether Jupiter's moons drift away from the planet like Earth's moon, and the possibility of collisions among them, focusing on chaotic orbits and resonance. Cat Landing Physics and High-Fall Survival (Priority: 5/5): The physics behind cats always landing on their feet, including conservation of angular momentum, and the surprising survival advantage at terminal velocity. Evolution of Colour Vision: Mammals vs. Fish (Priority: 3/5): Comparison of colour vision evolution in mammals vs. fish, highlighting how nocturnal ancestors lost colour vision in mammals but some regained it. Moon's Drift and Fate (Priority: 3/5): Context for the follow-up questions: the moon's slow drift (4 cm/year) will not lead to escape before the Sun's death engulfs the system. Bioluminescence and Its Role in Vision (Priority: 4/5): The role of bioluminescence in deep-sea ecosystems and how it provides colour signals for organisms like anglerfish.

Key Arguments: Anglerfish can have good colour vision in the deep sea using rod photoreceptors, not cones, to detect bioluminescent signals—an adaptation for survival where sunlight is absent. Mammals lost excellent colour vision during a nocturnal ancestral phase but some primates, including humans, regained a third opsin for improved fruit detection. Eye colour changes in some people (e.g., from brown to green) occur due to a balance between melanin (brown) and light scattering (blue/green), with brighter conditions enhancing the scattering effect. Jupiter has 97 confirmed moons, but only four Galilean moons are massive; many small outer moons have chaotic orbits, and some may eventually collide over billions of years. Cats land on their feet by bending and twisting different body parts to conserve angular momentum, and they may survive higher falls better because reaching terminal velocity allows them to relax and absorb impact. The moon drifts away from Earth at 4 cm/year, but it will not escape before the Sun engulfs both Earth and Moon billions of years from now.

Data Points: Moon recession rate: 4 cm per year - The rate at which the moon is moving away from Earth. Number of Jupiter's moons: 97 confirmed - The number of known moons orbiting Jupiter as of the last count. Percentage of Jupiter's moon system mass by Galilean moons: 99.99% - The three most massive moons of Jupiter account for almost all of the moon system's mass. Smallest moon size (Jupiter): A few kilometers wide - The approximate size of the smallest known moons of Jupiter. Depth with no sunlight: Deeper than 1,000 meters - The depth at which sunlight is absent in the ocean. Number of cone pigments in reef fish: About four - The number of different visual pigments (opsins) in cone photoreceptors of coral reef fish, indicating good color vision. Number of cone opsins in most mammals: Two - Typical number of cone opsins in mammals (most have two, except some primates with three). Laplace resonance ratio (Io:Europa:Ganymede): 1:2:4 - Timeline when Io (moon of Jupiter) completes one orbit, Europa two, and Ganymede four, in a stable resonance. Timeframe for Callisto resonance shift: 1.5 billion years - Predicted time for Callisto to potentially move away from Jupiter and get locked into resonance with the other Galilean moons. Height where cat injuries decrease: Around the 8th floor and above - Height at which cats often sustain fewer injuries when falling from buildings (based on research). Maximum survival height for cats: 20 stories or higher - A known example of a cat surviving a fall from a 20-story building, suggesting terminal velocity reduces injury.

Pivotal Quotes: "It wasn't until like about five years ago that we realized that, look, actually, these deep sea fish, or at least some of them, have different types of visual pigments. And it's not the cones. Surprisingly, it's in the rod photoreceptors that are normally used for dim light vision." — Lars Schmitz: Describing how deep-sea fish can have colour vision in darkness using rod photoreceptors, a surprising adaptation. "The injuries increase as the cats fall from higher heights up to about the eighth floor. And after that, the injuries seem to start going down dramatically. That cats falling from even higher heights will get fewer injuries." — Greg Gabor: Explaining the counterintuitive finding that cats falling from higher heights may sustain fewer injuries. "Eventually, it will maybe escape, but to be honest, we don't need to worry about that because this is going to happen billions of years in the future, and by that time, the sun would have reached the end stage of its lifetime, which means it will blow up, expand, and probably reach the earth and the moon and will just engulf us and we'll be vaporised." — Sarah Russell: Summarizing the fate of Earth's moon: it will not escape before the Sun destroys the system.

Implications: Listeners gain insight into the surprising sensory adaptations of deep-sea life, the complex dynamics of planetary moon systems, and the physics of cat falls. The knowledge reinforces that evolution and physics often produce counterintuitive outcomes (e.g., cats surviving higher falls).