A surfer
Voila! A viola.
A cross-sectional diagram showing the basic structure of the human eye with realistic curvatures on the cornea and lens. Note the difference between the front and back of the lens. Based on a review of several practical models of the human eye.
The human brain determines the direction to a source of sound by the interaural time difference. A source of sound to the right of the listener (b) arrives at the right ear before the left ear. A source of sound directly in front of the listener (d) arrives at both ears simultaneously.
Galileo had two assistants with lanterns stationed in church steeples about a mile apart. After the first assistant revealed his lantern, the second was instructed to do the same. Galileo attempted to time the delay but found that it was faster than human reaction time. Galileo concluded that the propagation of light was, if not instantaneous, extraordinarily rapid.
Ole Rømer determined the speed of light by observing the moons of Jupiter. He found that after 6 months of observations, the moons fell out of sync from their predicted position by 22 minutes. He reasoned that this delay was caused by the extra distance the light from the moons took to cover the diameter of Earth's orbit. If the speed of light were infinite, there would be no delay.
