What is Head: Definition and 411 Discussions

A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste, respectively. Some very simple animals may not have a head, but many bilaterally symmetric forms do, regardless of size.
Heads develop in animals by an evolutionary trend known as cephalization. In bilaterally symmetrical animals, nervous tissues concentrate at the anterior region, forming structures responsible for information processing. Through biological evolution, sense organs and feeding structures also concentrate into the anterior region; these collectively form the head.

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  1. M

    Finding Turbine Angular Velocity given Net Head, GPM, and power from Alternator.

    An alternator attached to a water turbine generates 35 Watts given 50 feet of head and 10 gallons per minute. Assuming that the efficiency of the alternator is 50%, is it possible for me to find the angular velocity from this information? If so, how would I do it?
  2. Another God

    How to tell if your head is about to explode ?

    How to tell if your head is about to explode...? http://www.mit.edu/~mkgray/head-explode.html Interesting. Can someone just validate this for me from a second news source. Just so I know this isn't a big joke.
  3. Ivan Seeking

    Northern lights may head south

    Please see the thread: https://www.physicsforums.com/showthread.php?s=&threadid=7946
  4. P

    How can I use psychology to gain power over my bully?

    Okay guys get this. So there are these two or three kids at school that seem to think they're so intimidating (they might be for some people) that like to pick on me and sometimes a friend of mine also. They're your typical bullies, ugly hair, earings, and one that always wheres a leather...
  5. zoobyshoe

    Do our eyes have the ability to sense when someone is looking at us?

    I saw a program about two serious studies done to test the notion that people can tell when someone is behind them looking at them. One study was conducted by a woman who explained to the volunteers that the point of the study was to show there was something to it. The other study was conducted...
  6. Ivan Seeking

    How did ET get in your head? [Continued from the Skepticism thread]

    I think you may be the first person to accuse the UFO crowd of lacking creativity. http://www.abduct.com/question/q186.htm http://www.syndicate23.com/index.cfm/resource_id/107.htm http://library.thinkquest.org/C004978F/ufo_aliens.htm?tqskip1=1&tqtime=1019 This is me: Now don't...
  7. P

    Find Head of Vector [a,b,c] with Length 3 in Same Direction as [−3,−4,12]

    The question asked me to find the head of a vector [a,b,c] whose length is 3 and is in the same direction as vector a=[-3,-4,12] So I found the follwing: Let vector x be the unknown vector |a|=13 |x|=3 Since they are both in the same direction, they both must have the same...
  8. Ivan Seeking

    A little lightning to the head and we have magnification

    Here is a true story for your consideration. I once worked with a guy who some years previously had taken a direct hit by lightning - right in the head. As you might imagine, I asked him what it was like. First, he spent about six months in the hospital. It put him in a coma among other things...
  9. marcus

    The finite bang fallacy rears its head again

    "In short - the Big Bang could not have occurred if the universe is infinite - and the Big Bang has mounds of evidence." this is a common fallacy the particular instance was recently posted in mathforum's "infinity" thread people who actually study the big bang, the CMB, inflation...
  10. Saint

    Having your head screwed backwards

    what does it mean ?
  11. E

    Excuse Me While I Drill A Hole My Head

    Maybe I'm a little slow, but the true meaning of pi just occurred to me. tan(pi/4) = 1 arctan(x) = [sum]n=0[oo] (-1)n * [ x2n+1 / (2n + 1) ] pi = 4 * arctan(1) = 4 * [sum]n=0[oo] (-1)n * [ 1 / (2n + 1) ] = 4 * ( 1 - 1/3 + 1/5 - 1/7 + 1/9 - 1/11 + ... ) = 4 * ( 2/3 + 2/35 + 2/99 + ...
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