Whats an easy way to describe what "clearing the neighborhood" means in relation to Pluto not being a planet?

Answer 1

When the solar system was forming there were large numbers of small objects orbiting the sun at all distances. As each planet formed it became large enough that its gravity pulled on all the nearby smaller objects which then crashed into it. The regions around the orbits the 8 bodies now recognized as planets (Mercury through Neptune) are relatively free of small objects while the orbit of Pluto is still fairly crowded. Pluto it seems never grew big enough to pull in its smaller neighbors.

Answer 2

Frankly, the definition invented by the IAU (International Astronomical Union) is so convoluted and self-contradictory, there is no easy way to describe what it means.

For example, since Pluto crosses Neptune's orbit, and Neptune hasn't cleared away Pluto, is Neptune a planet? Apparently the IAU made an unacknowledged exception to the "clearing the neighborhood" rule for Neptune.

And Earth. Every year the mass of the Earth increases by several MILLION ton of debris that falls into our atmosphere as meteors. Since it still falls, by definition Earth has not yet "cleared the neighborhood". So you could very correctly argue Earth isn't a planet either. Whoops- comet Shoemaker-Levy smashed into Jupiter back in 1999. Guess Jupiter isn't a planet either.

And neither is a single one of the 200+ exo-solar "planets" discovered in the last few years (guess we need another name for them). Their orbits aren't circular, so they don't make the cut. That one, though, the IAU caught; so they made the exception that the current definition doesn't apply to solar systems other than our own. That loophole is about as unscientific as it gets, one that should insult the sensibilities of everyone interested in science over the age of 5.

So in short, there really is no good way to explain what "clearing the neighborhood" means, because no one really knows, certainly not the ones who came up with the definition in the first place.

And as an aside, the IAU meets again in about 4 years. Already the major scientific and astronomical publications are calling for a redefinition, something with scientific rigor, that can unambiguously applied to all bodies. So again what defines a planet will change.

Stay tuned.

Answer 3

Well: let me explain about Pluto the smallest planet in our
galaxy see here we know Mars is an red giant because it's closer
to the sun very hot but Gastirus place as much of Astronomers
discovered it http://yahoo.usastronomy.com took 8000light years
for space travel which yourself can by space shuttle later on
of course great idea
good luck!

Answer 4

Unfinished article on Wiki:
http://en.wikipedia.org/wiki/Clearing_the_neighbourhood