http://www.metacafe.com/watch/yt-H1u8d04sKf8/geometrical_illusion/

http://www.metacafe.com/watch/828182/geometrical_trick/

Are there any explanations to the missing area? Is it just an illusion?

Mathematically, this is sum of zeros. All definitions of a line are that it has no “width” but should it also be true that it should ahs no “length”?

This photo was taken on a train travelling south to Hastings. The flat windows had horizontal and vertical scratches, perhaps from cleaning. The arc that is illuminated by the sun appears to be centred on the vanishing point of the axis of the carriage. The Sun lies on the arc. Why this arc?

I have given this some thought and I want to check my reasoning or see if there is an alternative explanation.  Was the water in the pond so still that as the first ice froze it acted as a nucleus for the next layer which froze underneath and in doing so lifted the first ice up out of the water.  Obviously, there would have to be no convection present to even out the freezing process.