Of octopuses and energies
Is an octopus a reptile, mammal, or amphibian? Or is it
just a fish? Christine, Chardon, Ohio, USA
How do blue-ringed octopuses breathe? Priscilla,
Tootgarook, Victoria, Australia
An octopus is not a reptile, a mammal, or an amphibian (though it can live short
periods of time out of water ó long enough to climb out of a tank at night and
eat shell fish from other tanks). It is not even a fish.
A provoked greater blue-ringed octopus. When disturbed, the
octopus switches from its normal drab brown/yellow color to bright yellow with
bold blue rings. [Courtesy of Roy L. Caldwell © Used with permission.]
The ancestors of octopuses branched off from the ancestors of
vertebrates more than 550 to 600 million years ago. Annelids (for example,
earthworms and leeches) and arthropods (insects, lobsters, and the like) may be
their closest major related groups, says biologist
Roy Caldwell, a professor at the University of California.
Octopuses are in the mollusk group ó muscular slimy creatures
such as slugs, snails, mussels, oysters, squids, and cuttlefish.
Although not fishes, all octopuses (including the blue-ringed
octopus Reader Priscilla asked about) breathe like fish with gills. They suck
water through two internal gills, just behind two of their three hearts. The
gills extract oxygen and blow the water out through a tube, called a "siphon" or
"funnel". The octopus can shoot through the sea ó in reaction to the expelled
water jet ó although he usually walks or crawls.
When attacking prey, an octopus gets close, leaps forward by
spurting a water jet backwards, and grabs his lunch ó perhaps a crab or fish.
By the way, all octopuses have poisonous bites. The golf-ball
size blue-ringed octopus of Australia, however, is the only octopus whose bite
is known to kill humans. The poison can stop a personís heart and breathing in
several minutes. Without medical care, this can kill the victim. We have no
antidote. With medical aid to maintain ventilation, though, victims usually
There is another species, called Octopus mototi, whose name on
the Rapa Island in the South Pacific, literally means "poisonous octopus," says
Caldwell. We donít know if this creature is deadly, "but I would not let one
Q: What is energy? Mc, Cebu,
Energy? Examples spring to mind. The Sunís thermonuclear
furnace blasting forth a fiery spectrum of
electromagnetic waves. White water thundering over
Niagara Falls. A swirling
cyclone of white clouds verging on the golden peninsula of Florida.
an intuitive commonplace concept. Yet the idea was unknown to Sir Isaac Newton,
the founder of classical mechanics in the 1680s.
A fire dancer displays heat, light, and kinetic energy.
[Courtesy of Wikipedia, photo taken at Wesleyan University]
"Energy is defined as the amount of work required to change
the state of a physical system," say many textbooks in a typical circular
definition. What is energy or work, though?
More helpful: "The combination of energy and matter makes up
the Universe: matter is substance, and energy is the mover of substance," writes
Paul G. Hewitt in his Conceptual Physics (sidestepping the issue of
"All forms of energy are associated with motion," says the
Encyclopedia Britannica. Anything moving has kinetic energy, from a
supernova-exploding star to a gas molecule bopping around. A pulled bow or a
coiled spring has potential for motion. As do chemical bonds in molecules and
nuclear bonds in atoms.
As alluring as this concept is ó that energy is somehow motion
ó we must relinquish it. "It is important to realize that in physics today,"
Richard P. Feynman, "we have no knowledge of what energy is."
Feynman was one of the three recipients for the Nobel Prize in
Physics in 1965 for his contributions to quantum electrodynamics and was one of
the most influential physicists of the 20th century.
We only know that energy is conserved, says Feynman.
Energy has many forms: motion, gravitational, heat, elastic,
electrical, chemical, radiant, nuclear, and mass. Energy, however, is simply a
mathematical quantity that we can calculate but, so far, do not understand.
The energy form can switch but the energy quantity is always
the same. That is the law of the conservation of energy and the only exact thing
we know about energy. There is no known exception to this law.
What is energy? You know what it is. I know what it is. But,
we donít, really.
Paul G. Hewitt, Conceptual Physics, Ninth ed. New York:
Pearson, Addison Wesley, 2002.
HyperPhysics by Rod Nave:
(Answered Sep. 30, 2005, Updated June 12, 2009)