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Why is it not possible to see around corners?
Question Date: 2017-01-03
Answer 1:

When we see an object, it means that light left that object and traveled to our eye. And, light travels in an ALMOST perfectly straight line. This means that, in order for you to see something, you need to be able to draw a straight line from the object to your eye (or have a mirror to reflect the light). However, light doesn’t travel in a truly straight line.

Einstein’s general theory of relativity, which describes gravity, predicts that light is affected by gravity, and that the path light follows can be measurably bent by massive objects, like black holes. This has been observed by astronomers, who have seen the light from the same supernova (an exploding star) multiple times, since the light traveling in different directions was bent toward earth. So, over really, really big distances, it is possible to see around corners!


Answer 2:

The matter of the wall blocks the light. Try drawing map on paper and include there a corner of a wall. Now, draw a line through that corner. Anybody along that line on one side of the corner cannot see someone on the other side of the corner because the light would have to go through the wall.

Answer 3:

Interesting question. You can hear around corners because sound waves have a wavelength of typically a few feet. The wavelength of visible light is 450-700 nanometers, which is a million times smaller. Around a corner, waves will diffract. The amount by which a wave can diffract is roughly the same as its wavelength. Therefore, sound waves can diffract around corners (on the order of a few feet) whereas light will not diffract enough (nanometers). read more here

The military is actually very interested in this problem. Certain solutions have been realized. There exists technology where the presence of objects in a room can be determined using radio frquency signals, not light. For "seeing" around corners, one has to be very clever about how to overcome this problem. Preliminary research shows that by using very very fast lasers and ultra-fast imaging, one can reconstruct an image of what's around a corner by using light diffracting off of known surfaces. However, it takes a while and is not perfect.

This video explains it best: video

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