Whale,swimming and floating

From: Dagmar Fertl (dfertl@geo-marine.com)
Date: Mon Nov 17 2003 - 11:27:54 EST

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    What helps a whale float and swim to the surface of the water?

                                           Michela
    ***************************************
    Michela,

    First, let's talk about buoyancy or 'floatibility'. Let's think of what
    happens when we drop a cork into water -- it floats. This means it is
    positively buoyant. Something that sinks in the water is negatively buoyant.
    Does that make sense? So, without getting too technical (since I don't know
    how old you are or what grade of school you're in)...

    The large layer of body fat that whales have is called blubber. It insulates
    whales (keeps them warm), but is lighter in weight than water, and helps
    whales float. But, whales cannot have too much of it. Too much positive
    buoyancy would prevent these mammals from diving far below the surface.
    Additionally, buoyancy of whales is affected by the volume (amount) of
    gas-filled (air-filled) cavities (e.g., lungs). To counteract this buoyancy,
    whales is a delicate balance of heavy muscle and bone. Bone and lean muscle
    is heavier than water, sinks, and is therefore 'negatively buoyant'. The
    gas-filled cavities (e.g., the lungs) change in volume with water pressure.
    So, as a whale dives, the volume or space in the lungs compresses (becomes
    smaller), which helps the whale become heavier, so to speak.

    Now the really tricky part. Some whales conserve energy while diving by
    gliding (or coasting) by using their tail, while right whales (a certain
    species of whale) actually do the reverse and glide while they are ascending
    (coming up).

    There is a really cool experiment you can do to learn more about buoyancy.
    Perhaps you can suggest it in school. See:
    http://www.tmmc.org/learning/education/teacher_resources/blubvsbuoy.asp

    Hope this helps,

    Dagmar Fertl



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