Why does the road look watery on hot sunny days?

[Phy6explorer]

The other day, when I was traveling in the car, on a really, really, scorching, sunny day, in the distance I noticed that the road looked watery.Anyone knows why that happened?

PS:There is no problems in my eyes.Even my Mom,Dad and brother noticed it.

 

[DaveC426913]

It is a mirage. Very common on hot days.

In a nutshell, there is a layer of warm air right above the hot pavement. This layer refracts the light, resulting in light rays that came from the sky appear to come from the roadway.

http://en.wikipedia.org/wiki/Mirage
http://www.goalfinder.com/product.asp?productid=41
http://www.dewbow.co.uk/glows/mirage4.html

 

[Danger]

Under some conditions, it can get really weird. You might see a car 100 metres above the road, or a tree in the middle of your lane.
This effect is responsible for a very large percentage of UFO reports.

 

[Manchot]

On hot sunny days, black pavement gets significantly hotter than the atmospheric temperature. It heats up the air directly above it, which causes the index of refraction of the hot air to change. Even though the effect is slight, you can observe total internal reflection if you are viewing the effect from a position almost parallel to the plane of the pavement.