Let's post awesome optical illusions

[Copadope]

If you look directly at something, especially at night, it can have a tendency to disapear.  It is also an effective tactic when driving.

EDIT:  Oh and does anyone notice that once you get below a certain level of illumination you only see in black and white?
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Quick and Dirty Lesson in Sense and Perception:

This also has to do with the different light receptors in your eyes. There are two main types of receptors: rods and cones. Rods collect information only in black and white, and are much more effective in very dim environments. Cones come in three different flavors (as explained in Kylearan's post) and collect color information.

Inside your eyes, the very center of your field of view is covered almost exclusively with cones because they deliver the most detailed information about what you're seeing. But they don't work well when there is very little light. That's why at night if you're trying to see a very dim light such as a star, you're able to see it better by looking "next" to it rather than directly at it. When the light from that star hits your eye outside of the center of your field of view, it hits more rod receptors which will pick it up better.