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@SB_AlphaCephei @cosmos4u @JoeWBowles Exactly, so it is important to understand WHY the definition was changed in the 1600s. They switched from a dynamical definition to geophysical because it promoted what was found to be the most important aspect of our solar system: that there exist other bodies like Earth. /1
@SB_AlphaCephei @cosmos4u @JoeWBowles 2/ When we examine how & why that happened we see it was NOT redefined from geocentric to heliocentric. That aspect was important but was NOT considered most important, because they realized these bodies don’t all orbit the Sun, but they are all geophysical so it unified physics.
@SB_AlphaCephei @cosmos4u @JoeWBowles 3/ They used to believe there were two separate physics: one for the heavens and another for the earth (“geophysics”). The heavens were inviolable & perfect while Earth was imperfect & changing but controlled by the heavens (hence astrology).
@SB_AlphaCephei @cosmos4u @JoeWBowles 4/ When Galileo saw mountains on the Moon he argued this proves that planets are geologically changing bodies and don’t have a separate physics. This unified Earth with the other planets (and therefore Earth moves). The center of their orbits was no longer the unifying principle.
@SB_AlphaCephei @cosmos4u @JoeWBowles 5/ Very quickly Kepler invented the terms Primary and Secondary planets (we still often say the former in publications) because they needed to discuss dynamical relations between planets, but it was a secondary consideration, not a paradigm shift that promoted new science.
@SB_AlphaCephei @cosmos4u @JoeWBowles 6/ We still often call moons “planet” in publications to this day, and our entire lexicon is based on that identity. E.g., we say Titan has a “planetary boundary layer”. But the importance of their status as 2ndary planets has diminished from many scientists’ thinking because...
@SB_AlphaCephei @cosmos4u @JoeWBowles 7/... the unifying physics between the heavens & Earth is so commonly accepted we don’t have to press that argument against the flow of culture any longer. We are like fish not noticing the water that surrounds us. There was never a paradigm shift that made moons non-planets.
@SB_AlphaCephei @cosmos4u @JoeWBowles 8/ In the 20th century there was a paradigm shift understanding how planets form. Previously we thought gravitational instability caused protoplanets to form directly as spherical bodies, but small asteroids unsettled that view. See Kuiper, PNAS 39, no. 12 (1953): 1159-1161.
@SB_AlphaCephei @cosmos4u @JoeWBowles 9/ Coming to understand that asteroids accreted directly without ever being round protoplanets led to a shift in “planet” usage such that it no longer included the bodies that were smaller than protoplanets. This argument was unifying between primary & 2dary planets...
@SB_AlphaCephei @cosmos4u @JoeWBowles 10/...because it was discovered in part by comparing the ring system in Saturn with the asteroid belt. Kuiper wrote: “This clarification of the satellite problem suggests a re-examination of the planet problem, in particular that of the planets of small mass, the asteroids...
@SB_AlphaCephei @cosmos4u @JoeWBowles 11/ “...The hypothesis made before was based on the assumption that gravitational instability, clearly operative in the formation of the 8 major planets, was also responsible, though in modified form, for the formation of the original group of minor planets...
@SB_AlphaCephei @cosmos4u @JoeWBowles 12/ “...it appears doubtful to the writer now that the anticipated development could arise from gravitational instability alone...It has become clear that uniformity does not exist in satellite formation and it appears necessary to abandon it also between planets and asteroids.”
@SB_AlphaCephei @cosmos4u @JoeWBowles 13/ In other words, they abandoned a unifying concept in planet formation and adopted diversity instead, which the literature shows led to the splitting of the planet concept making small, sub-round bodies a separate class. (Ceres remained a protoplanet and hence a planet.)
@SB_AlphaCephei @cosmos4u @JoeWBowles 14/ The fundamental problem with the vote in 2006 is that it was not driven organically within the community to promote a new paradigm shift. Instead it was driven by the bureaucratic need to determine what process will name the new KBOs, and relative fame in discovering them.
@SB_AlphaCephei @cosmos4u @JoeWBowles 15/ Of course the General Assembly tried to put scientific reasons onto everything, but it ended up as a balance between intrinsic and dynamical concepts with the intent to represent both sub-communities. That isn’t how taxonomy works within the scientific process.
@SB_AlphaCephei @cosmos4u @JoeWBowles 16/ Orbit-clearing was not a new paradigm shift that revised our view of reality. We already knew that some planets clear orbits while others do not. We already knew planets get ejected from star systems. I.e., we already knew since Galileo that they are changing & contingent.
@SB_AlphaCephei @cosmos4u @JoeWBowles 17/ Orbit-clearing is interesting but judging by the relative lack of discussion in the literature it has little effect on promoting the cutting edge of scientific progress. The only paper I found that is close to using orbit-clearing in a taxonomically functional way...
@SB_AlphaCephei @cosmos4u @JoeWBowles 18/...discusses statistics of KBO sizes. It points out the statistical anomaly of Pluto & Eris being both largest & nearly the same size, which is explained if they had both entered oligarchic growth phase. (It failed to include Triton, which would’ve strengthened its argument.)
@SB_AlphaCephei @cosmos4u @JoeWBowles 19/ The paper then asks why these oligarchs failed to continue growing to reach isolation mass, which is defined by assuming they absorb (rather than scatter) all the smaller bodies in their band. It has no answer but suggests maybe disruption by giant planet migration.
@SB_AlphaCephei @cosmos4u @JoeWBowles 20/ (As an aside, note that this argument strengthens unification between primary & 2dary planets since Triton was captured to become a moon by giant planet migration. It didn’t form originally as a moon.)
@SB_AlphaCephei @cosmos4u @JoeWBowles 21/ So maybe one day this will be seen as strong enough to redefine our view of nature such that orbit-clearing changes our view of nature in a fundamental way, so we must redefine the taxonomy in order to promote the new, true view. But so far it’s just one paper with no answer.
@SB_AlphaCephei @cosmos4u @JoeWBowles 22/ & as I said before, we already knew about the contingencies of planet dynamics and it was already fully integrated into our view. OTOH, using orbit-clearing can be seen as a retreat from functional taxonomy because it was motivated in part by culture’s demand for few planets.
@SB_AlphaCephei @cosmos4u @JoeWBowles 23/ That desired for a simple, orderly set of planets harkens back to the pre-Galilean view. Culture has **always** had an inadequate understanding of the contingent, chaotic nature of the cosmos. So by giving in to the public’s desire we have promoted the unscientific view.
@SB_AlphaCephei @cosmos4u @JoeWBowles 24/24 So I think it was a tragic mistake to vote on a definition instead of letting scientists continue to hammer it out in the literature through the normal scientific process. I think we had an inadequate understanding of how taxonomy is supposed to function.
