I was sitting outside enjoying the sun. When i noticed «heat waves», close to the ground. What exactly are heat waves, and why can i see them?
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The Sun heats up the surface of the Earth, the surface in turn heats up the layer of air right next to it. Hot air is less dense than colder air, and for this reason it rises up. Hot air also has a different refractive index than colder air, meaning that light bends somewhat when passing from cold air to hot air, and therefore you see this as distortions that you call “heat waves”. It’s the same reason why you see things differently through a mass of water, especially if there are ripples on it, like looking at the bottom of a stream.
Great response from u/nmxt
I’ll just add that a related effect combined with light reflecting off the ground can make those rippling blue (because of the sky) heat waves appear to be on the surface of the ground as well. This is the cause of the mirage appearance of water in the distance of a desert or on a flat, hot black asphalt road.
The Sun heats up the surface of the Earth, the surface in turn heats up the layer of air right next to it. Hot air is less dense than colder air, and for this reason it rises up. Hot air also has a different refractive index than colder air, meaning that light bends somewhat when passing from cold air to hot air, and therefore you see this as distortions that you call “heat waves”. It’s the same reason why you see things differently through a mass of water, especially if there are ripples on it, like looking at the bottom of a stream.
Great response from u/nmxt
I’ll just add that a related effect combined with light reflecting off the ground can make those rippling blue (because of the sky) heat waves appear to be on the surface of the ground as well. This is the cause of the mirage appearance of water in the distance of a desert or on a flat, hot black asphalt road.
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