Quote:
Originally Posted by peacegirl
I am not talking about infrared light. Haven't we been talking about the visible spectrum this whole time, so why move the goalposts now? I never thought of sunlight as being visible (unless it's extremely hot out and we can see heat waves).
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When you observe 'heat waves' you are not seeing the heat itself, you are not seeing the air that is 'warm', you are seeing the light that is passing through that warm air that is rising through cooler air. As light passes through air it is slightly refracted, and air of different densities will refract light at slightly different angles, warm air is less dense than cool air. So when warm air rises through cool air the light passing through that air will 'shimmer' and the image we see will seem to wiggle about. If we were seeing the object directly with no distance or travel of light to account for we would not see this shimmer of the image of the object, because we would not be seeing it through the air in between. The fact that we see the shimmer of the image of the object, proves that we are seeing the object by detecting the light that has passed through this warm and cool air that is causing image of the object to seem to wiggle about. We 'see' by detecting the light that has traveled the distance from the object to our eyes, and since light takes a finite time to travel the image we see is of the object as it was in the past.