10/30   Yahoo! News - Robots to Gain Eyes in the Back of Their Heads
        htt://csua.org/u/4um
        It reads " But as computer scientists at the University of Maryland
        proved mathematically in 1998, if robots could see in all directions
        they would not need any other sensors."  What kind of mathematical
        proof would that be?  How do you go about proving something like this
        mathematically?
        \_ why doesn't evolution favor eyes at the back of animals heads?
           \_ Prey animals usually have very widely-spaced eyes and can see
              in almost 360-degrees.  Predators (and humans) have forward
              facing eyes which give good depth perception.  Why do no
              vertebrates have more than 2 eyes?
              \_ The fundamental answer guiding all evolutionary processes:
                 efficiency.
                 \_ only able to last 15 seconds in the sack, eh?
                 \_ How is turning the head to look behind more efficient than
                    procesing more signals from more eyes in the brain?
                    \_ You save the energy needed to grow more eyes and the
                       brain structures needed to process the extra input.
                       \_ But you need to grow the muscles to turn the head,
                          and for some mammals, even part of the body.
                          \_ good point.
                 \_ Eyes have a lot of muscles and things, at least our full
                    functioned ones do. Also, head movement is needed anyway
                    for eating (maybe not for humans, but for prey animals).
                    Since prey animal eyes and hearing suffices, more eyes
                    probably cause more problems than they help. They might
                    also be vulnerable to injuries. Head movement is also used
                    for smelling.
                    \_ You might also want to take into account that more
                       eyes also translates to more brain mass/complexity
                       to process the information.
              \_ Flies have many eyes in two groups.
                 \_ I said VERTEBRATES.
                 \_ and mammals (and many verterbrates) have many rods/cones
                    in two groups.
                    \_ But flies have many separate lenses whereas mammals have
                       only two.
        \_ The article explains it pretty well:
           "The ability to navigate was the lowest level of capability
            needed by a robot to work in an unknown environment, she said."
           "Providing a robot with "omni-directional" vision could vastly
            improve its navigational skills, ..."
            Thus, you make the assumption that navigation is needed, then
            you prove that 360-degree eyes are sufficient for navigation,
            thus it doesn't "need any other sensors."