When you’re driving and it’s sunny outside, why does it look like there is water on the road ahead of you but once you get closer it’s gone?

Question

When you’re driving and it’s sunny outside, why does it look like there is water on the road ahead of you but once you get closer it’s gone?

In: Physics

Answer 1

You’re seeing heat distortion. Hot air directly above the roadbed is refracting light from the sky in your direction. You’re seeing the sky, but since your experience tells you the only thing that looks like it reflects the sky like that is water, your brain tells you it’s water. As you close with the patch of hot air, the angles change and the phenomenon goes away.