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Tuesday, 05 September 2006 18:05 |
Poor, poor Pluto.
The smallest planet of all is now no longer a true planet, according to a recent resolution passed by the International Astronomical Union that demoted the former ninth planet to the status of "dwarf planet."
The designation, as any scientist will note, is arbitrary, much like historians who argue about what date the Roman Empire really fell or when the Renaissance started, a "planet" is a category that makes things more convenient.
Pluto,
however, is now too small to make the cut, as some of its moons are of
a similar size. Also, the discovery of several similar-sized objects
orbiting the sun led the IAU to consider two alternatives ¨?¨?ÇƒÓ either
promoting three more objects to planets or demoting Pluto.
They chose the latter, though designating it a "dwarf planet" as some sort of compromise.
To some extent,
the whole debate highlights the changing nature of science. After all,
in 1930, when Pluto was christened after the Roman name for the Greek
god of the underworld, scientists knew only a fraction of what they now
know about the universe.
They had no idea
that Pluto was surrounded by so many other similar-sized objects, or
that new discoveries of orbiting bodies such as "Xena," "Sedna" and
"Quaoar" could have just a good a claim as Pluto to planethood. Simply
put, as with so much else these days, the old definitions just donët
work.
Once again, we
should be reminded that science is an ever-advancing and rarely exact
process ÇƒÓ and that definitions, categories and names all change over
time as scientists try to incorporate a steady flow of new knowledge.
For the last 76
years, Pluto has been a planet, meaning that generations worth of
students have learned its name as part of the solar system, while
countless models and planetariums include it.
Apparently, that will all have to be changed now.
Or will it?
Tradition and habit can be very difficult to alter. It is entirely
likely that models will remain the same, while teachers and tour guides
will simply note: "Oh yes, thatës a dwarf planet."
Not that Pluto
will be entirely out of the news. Besides the name of a dwarf planet,
its other contribution to science is the name of an element that is and
will be gathering no small amount of attention ÇƒÓ plutonium.
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