Hands-on MirageFloor 1 | Mirrors in Mind
The laser beam brushing the surface of the hot plate is visible until you blow down through the hole. Your relatively cool breath above the hot plate makes a denser, cooler patch of air sufficient to deflect the beam upwards… and it disappears. Now try the reverse: turn on the hair drier to heat the cool plate. The laser beam travels faster through the less dense hot air, so it’s bent down onto the plate, and becomes visible.