Seeing double down the road

Even though temperatures have cooled a bit recently our midday sun is still high in the sky. With direct sunlight pounding the pavement, an occasional glance down the road may play tricks on your eyes and brain.

We’re trained to think that what we’re looking at is where we see it. That is not always the case when looking through different densities.

Imagine this, you’re standing on a hot asphalt road looking ahead. As your line of sight gets closer to the road the air temperature goes up, and thus, density of the air goes down.

The change in air temperature (a few inches off the road vs. a few feet off the road) causes the light traveling to your eyes to take a curved path. So what you see as straight ahead is actually coming from somewhere else.

The hot air just above the road causes light to bend. This can make the horizon look like it's below the road.

Where it looks like the road disappears or is covered in water is actually the sky! That’s right, despite looking down towards the surface of the road you’re actually seeing the sky just above the horizon (or trees along the horizon). It’s a mirage!

In the desert this can make people think they are seeing a watery oasis in the distance instead of more dry land.

The uneven change in temperatures causes the image to look distorted or wavy, which is why it looks more like a puddle of water regardless of what’s contained in the mirrored image.