Their metamorphosis seems more like a human’s than a butterfly’s – so much is visible, and awkward, whereas the butterfly forms in secretSome species of frog have eyes so sensitive to light that they can detect a single photon. To confirm this, scientists dissected a frog’s eye and removed the lens. If you dissected eyes in biology class, you may remember that a lens is extraordinarily simple and unlike other organs. It is a hard, clearish, object that comes out clean: no blood supply, no blood. It looks like a glass bead, and functions – inanimate – much like glass, and not like most things we find in our body (except maybe teeth, which function like knives). Look through the lens at the classroom around you, you will see it clearly, but upside down.A frog in space, moving further and further from the sun, would eventually start to see not a shrinking star but tiny flashes of light: individual photons. This is because as the photons travel further from their source, they are spread...