Monday, May 06, 2013

Canadian Shoreline Visible? Not So Fast

Over the weekend, Jay Reynolds, local Cleveland Astronomer sent me a photo of an optical illusion over Lake Erie. Its called REFRACTION!

While it looks as if we can actually see the Canadian side of the lake, in reality, its over 50 miles away! Why can we see it in this photo?

The light from the Canadian shoreline is refracted (or bent). The rapid change in air density and temperature between the warm air aloft (70s) and cool air over the lake (40s) acts to bend the light down. The wind needs to be calm for this to happen so that the different air layers don't mix too much.  The result is we see that light here in Ohio when under normal circumstances, that light would have been "beamed" into the atmosphere away from our field of view.

Close up of Optical Refraction (Canadian Shoreline): Courtesy: Jay Reynolds

While it looks like the Canadian shoreline is close, its actually a mirage and over 50 miles away!

Another atmospheric phenomena I witnessed late last week was a ring around the sun at noon Friday. What causes this?

The perpetual cloud cover we've seen are cirrus clouds. These are made of ice crystals and don't produce any precipitation. Many of the ice crystals are hexagonal. If the ice crystals are oriented at just the right position, the sunlight is refracted (there's that word again!).

The sunlight is deflected twice inside the ice crystal.


As the light interacts with more ice crystals, it will form a ring of light at exactly 22 degrees from the sun or moon. Some of the light is dispersed broken up into its component colors) as it is refracted inside the ice crystal.

Special thanks to the University of Illinois website for the great graphics!