Re: "Pluto Now Called a Plutoid"


"Bryan Derksen" <bryan.derksen@xxxxxxx> wrote in message
news:a2kfk.7311$nD.2922@xxxxxxxxxxxx
K_h wrote:
"Bryan Derksen" <bryan.derksen@xxxxxxx> wrote in message
news:IE5fk.5767$nD.3059@xxxxxxxxxxxx
K_h wrote:
"Bryan Derksen" <bryan.derksen@xxxxxxx> wrote in message
If Stern is correct then your argument on this point is invalid.
Funny thing is both sides of this particular point are based on Stern's
arguments. However, the side that says "it can clear its orbit" is from
a scientific journal article backed with detailed physics and rigorous
analysis, and the side that says "it can't clear its orbit" is just
something he said to some MSNBC reporter. I think he needs to support
the second point a bit better. :)

I cannot speak for Stern, so your disagreement with him should not
involve people like myself.

You've been pretty free with "speaking for Stern" to this point so long as
he was saying things that supported your position. For example, you're
simply parroting the following statement Stern made in that MSNBC article,
apparently without really understanding it:

A world with 70% Earth mass will not have cleared the Kuiper belt and so
will be orbiting within the Kuiper belt.

This is false. Stern's own methods show it to be false. Have you even
opened up the paper my calculation was based on yet? Show me where I made
an error and maybe you'll have something to base an argument on, otherwise
it's just meaningless repetition.

From what I have read on this subject, there could be a world 70% as massive
as the Earth orbiting within the Kuiper belt. Such a world has obviously
not cleared out the entire Kuiper belt but it may have largely cleared out a
region within the Kuiper belt. So the question arises, how much "clearing"
is needed before such a world qualifies as a planet? For example, how wide
would such a clearing need to be? More generally, what is the cut-off value
of the Stern-Levison value for planethood? Obviously, such a cut-off value
needs to be part of the definition of a "planet" under the IAU's incomplete
definition. Worlds with small Stern-Levison values might clear out their
orbits over very long time scales so what is a "mature" planetary system and
what is an "immature" planetary system?

Of course, one can say that any world within the Kuiper belt will have
"cleared" its immediate path around the sun since they seldom collide
with each other. That raises the question as to how much "clearing" is
needed before a world can be said to have "cleared" its orbit. Pluto
orbits the sun without hitting anything so, in a sense, it's orbit is
"clear". This is part of the problem with the IAU's definition, it is
not defined how wide the "clear" zone has to be. With this ambiguity an
Earth sized world, in the Kuiper belt, has not cleared out the Kuiper
belt.

This is all stuff that I've been pointing out ways of quantifying right
from the start of this subthread. And when you chart the numbers for
various solar system objects you'll find that there is no ambiguity;
there's a huge gap between planets and non-planets as defined by the IAU.

Well, fine but see my above questions. All the extra stuff that you have
been pointing out need to be added to the IAU's definition (at least as a
footnote) so that it is clear what "clearing its orbit" means.
Unfortunately, the IAU's definition does not explain any of this; hence its
ambiguity.

Are you actually interested in learning about any of that, though? You
seem to be more intent on arguing for argument's sake, refusing to yield
any objection to the IAU's definition no matter how absurd a position it
devolves into (e.g. Saturn not being "round"). Since the Stern-Levison
paper potentially addresses your concern about this aspect of the IAU's
definition I expect you're likely to just continue ignoring it.

I have not ignored any of it; the IAU's definition does not reference any of
it. None of my objections are absurd, Saturn is oblate enough that it is
unclear, from the IAU's definition, if it qualifies as "nearly round" since
round is a synonym for spherical and, as I have explained several times now,
Saturn is oblate enough that it isn't "nearly round". It seems like you are
ignoring all these issues I have been pointing out.

K


.

Relevant Pages

  • Re: "Pluto Now Called a Plutoid"
    ... However, the side that says "it can clear its orbit" is from a scientific journal article backed with detailed physics and rigorous analysis, and the side that says "it can't clear its orbit" is just something he said to some MSNBC reporter. ... I cannot speak for Stern, so your disagreement with him should not involve people like myself. ... Kuiper belt and so will be orbiting within the Kuiper belt. ... And when you chart the numbers for various solar system objects you'll find that there is no ambiguity; there's a huge gap between planets and non-planets as defined by the IAU. ...
    (rec.arts.sf.science)
  • Re: "Pluto Now Called a Plutoid"
    ... Sun, has sufficient mass for its self-gravity to overcome rigid body ... approximately as capable of clearing its orbit as Mars is. ... would likely be called a planet, ... cleared out its region in the Kuiper belt. ...
    (rec.arts.sf.science)
  • Re: "Pluto Now Called a Plutoid"
    ... The dynamics of "clearing" is still somehwat in its infancy. ... If Stern wants to jump in on this thread that would be entirely welcome. ... However, the side that says "it can clear its orbit" is from a scientific journal article backed with detailed physics and rigorous analysis, and the side that says "it can't clear its orbit" is just something he said to some MSNBC reporter. ... To say that a planet must have "cleared its orbit" presumes that there was material there to be cleared. ...
    (rec.arts.sf.science)
  • Re: "Pluto Now Called a Plutoid"
    ... "A planet is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape, and has cleared the neighbourhood around its orbit." ... So yes, it would likely be called a planet, even under the IAU's definition. ... a planet 70 percent as massive as the Earth _would_ clear its region in the Kuiper belt. ... It would be approximately as capable of clearing objects from its orbit as Mars is, and Mars is considered a planet. ...
    (rec.arts.sf.science)
  • Re: "Pluto Now Called a Plutoid"
    ... If Stern is correct then your argument on this point is invalid. ... To say that a planet must have "cleared its orbit" presumes ... world has not cleared out its orbit, far out in the Kuiper Belt, as Stern ...
    (rec.arts.sf.science)