Pluto “Fans”

July 29, 2015 2 Comments

The recent fly-by of Pluto by the New Horizons spacecraft has reignited a debate that should have stayed buried forever. I’m not saying the IAU’s 2006 definition of planet wasn’t lacking, it’s just that this specific debate should have died and stayed dead.

Plutesters, hehehe.


The problem is that it is entirely unclear why we’re defining “planet” to begin with. Categorization of phenomena is supposed to help us organize them epistemologically. This is why we have a taxonomy of species. Any definition of space objects should be designed to help us classify and study them, not contrived for cultural reasons. We shouldn’t try to exclude KBO’s or other minor bodies because we don’t want to have 15 planets, and we shouldn’t try to include Pluto because we feel bad for it. The classifications we come up with should mirror our current understanding of how similar the bodies are. On the other hand, our precise definitions should produce the same results as our imprecise cultural definitions for well-known cases. As evidenced by the outrage caused by the IAU’s “exclusion of Pluto from planethood”, people don’t like changing how they think about things.

Images of Pluto and Charon.


Which brings us to the current debate. Fans of Pluto seem to be hinging their argument on the fact that Pluto is geologically active, and that it’s diameter is actually larger than that of Eris. Previously it was thought that Eris was both more massive (by 27%) and larger in diameter than Pluto (with the flyby of New Horizons, we now believe Pluto has the larger diameter). This is what moved the IAU to action in the first place; if Pluto is a planet, then so is Eris. There is no world in which we have 9 planets. We either have 8, or 10+.

Then you have Makemake, Haumea, Sedna, and Ceres. How do those fit in? It’s possible we would end up having far more than 15 planets, based on current predictions of KBO size distributions. This illuminates a fundamental problem: what is the use of a classification that includes both Sedna and Jupiter? These two bodies are so different that any category that includes both is operationally useless for science within our solar system. But continuing that logic, the Earth is also extremely dissimilar to Jupiter. The Earth is more similar to Pluto than it is to Jupiter. So having Earth and Jupiter in the same category but excluding Pluto also seems weird.

Unless we consider our definition of similarity. There are two ways to evaluate a body: intrinsic properties (mass, diameter, geological activity, etc), and extrinsic properties (orbit, nearby bodies, etc). One would be tempted to define a planet based on its intrinsic properties. After all, at one time Jupiter was still clearing its orbit, and in the future Pluto will eventually clear its orbit. Does it make sense for the same body to drop in and out of statehood. Well… yes. The fact that a human stops being a child at some point doesn’t make the category of “child” any less useful for a huge range of societal and cultural rules.

In fact, “intrinsic properties” is sort of a gray area. Rotation rate doesn’t really count, since tidal locking is common yet caused by extrinsic forces. Geological activity is also not necessarily intrinsic. Io has extreme internal activity caused by tidal heating. One can imagine the same for a planet close to its parent star. Composition can change as atmosphere is blown away by the parent star, and even mass and diameter can change through planetary collisions.

Regardless, defining a planet only on its intrinsic properties means that moons are now technically “planets”. “Moon” becomes a subcategory of “planet”. This is actually a great definition, but too radical to get accepted currently, so thus functionally useless.

So we must define a planet at least partially based on extrinsic properties. The rocky inner planets and the gaseous outer planets are similar in that they make up the VAST portion of the mass within their orbital region. Earth is 1.7 million times more massive than the rest of the stuff in its orbit. On the other hand, Pluto is 0.07 times the mass of the rest of the Kuiper Belt. Yeah, it makes up less than 10% of the Kuiper Belt. This is a pretty clear separation.

After that revelation, everything falls into place. We have large, orbit-clearing objects, and we have smaller objects that are still in hydrostatic equilibrium but are part of a larger belt of objects.

It turns out, this definition is already in place. For all the hub-bub about the IAU’s definition, most everybody agrees with the splitting of bodies via two parameters that measure likelihood of a body ejecting other bodies in its orbit (the Stern-Levison parameter Λ), and a body’s mass relative to the total mass of bodies in its orbit (planetary discriminant µ). The split occurs at a semi-arbitrary Λ=1 and µ=100.

What everybody is really arguing about is whether or not we get to call both types of bodies planets, or just the big ones.

Stern and Levison propose the terms überplanet and unterplanet, but I think major planet and minor planet is more adoptable.

Finally, just plain old “planet” should refer by default to major planets only, but can contextually refer to both classes in some cases.

Problem solved.

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Separating Science and Religion

March 22, 2014 Leave a comment

I read this article for school:

Alan Lightman’s The Accidental Universe

When asked to write an essay about it, this is what came out. I don’t normally post essays like this, but I’ve been meaning to write a post much like this for a while anyways, so it’s convenient.

Lightman descends into the realm of religion, masking his language with a thin film of scientific consideration, but none of its hard, decisive, rational edge. Lightman never even touches the basic principles of science, but uses philosophical arguments to parade a seemingly-scientific theory around.

Falsifiability is a method for evaluating scientific theories popularized by Karl Popper. It contends that a theory cannot be proved by showing evidence in favor of it. A theory may be shown to be strong if it can make empirically confirmable and correct hypotheses, but a theory can never be proved – only disproved. So to be a scientifically valid, a theory must have a way to be disproven (thus by not being disproven, it continues as the dominant theory). This is one of the problems with the multiverse theory, the theory of intelligent design, and even string theory: it is most likely impossible to disprove them. If an intelligent creator revealed itself, such a turn of events would not inherently make the multiverse theory wrong, per se (a multiverse theory can coexist with intelligent design). It would only make it irrelevant. Of course, this reveals an even bigger fundamental problem with those theories: they don’t explain the mechanics behind physical phenomenon in the traditional sense. Instead, they provide a framework of thought into which actual scientific theories can be slotted. But the multiverse theory is only one framework among many, and there is no way to show that one framework is strictly better than another.

Is it not just as reasonable, just as falsifiable (or not, as the case may be), to conclude that the universe as we know it is the only one, albeit a very lucky one? One could posit that it is indeed accidental. How does this postulate contend with the others on the battlefield of scientific thought? In some regards it may triumph over its opponents, because it relies on any contrary observation to disprove it, while both the multiverse theory and intelligent design can be valid even in the face of one or the other being true. So really, the Random Chance theory is more falsifiable, and thus more scientific.

But of course the Random Chance theory is completely unpleasing to the philosophical human mind. A much more palatable theory is the multiverse theory, which, like a wolf in sheep’s clothing, slips in among the legitimate scientific advancements and completes a scientist’s world view satisfactorily. But is a scientist’s world view scientific? No. Science is a tool for developing a physically accurate view of the world, and we employ it because the human mind is not built to obey scientific rules. Our capacity for cognitive dissonance is astounding. Thus a scientist can in good conscience accept a non-scientific belief to assuage his existential conflicts by slathering the belief in the manner of other physics theories.

Another such unfalsifiable belief system is string theory. String theory is a self-consistent way of interpreting physical data using notions that fall out of mathematical equations but have no basis in experimental science. Indeed, string theory exists only as a way for some physicists and mathematicians to unify all of reality under some Platonic mode. But it is only that; a way to think about the universe, to help explain the Great Unexplainable, as Sax Russell calls it. String theory cannot produce hypotheses that can be tested to confirm the mode of thought. It can explain the observed, but only as well as previous existing theories. While it is nice that it can bring physical laws under a single wing, niceness is not a necessary quality of scientific theory. It is a subjective human measurement applied in the realm of philosophy.

Philosophy is not useless. It is a tool, like science, for examining the world. However, instead of measuring and describing physical phenomenon objectively, it takes human concepts or unimaginable realities (such as that beyond the realm of science) and compresses them down and creates a set of rules for the human mind to follow. It generates modes of thought that allow us to function and think about that which might otherwise turn us into quivering lumps of existential dread.

But assembling a philosophical system of thought only to pass it off as a product of science is dangerous. Besides preying on those incapable of evaluating the modes of thought on their own, it tricks the creator as well. Thus we can see the inevitable and unending conflict between the “rational” scientist and the “faithful” man of religion. Neither of them realizes that they are jousting with philosophical ideas, and as a result keeps hitting his opponent not at the weak spots, but at the bastions of his belief. The scientist calls his mode of thought “scientific truth” (a misleading term in and of itself), and the religious man calls his mode of thought “religion”.

Unfortunately for the world, nobody (certainly not the loud ones) seems to realize that science and religion are not diametrically opposed. Religion is not taken entirely on faith; while it does depend on some unfalsifiable core, it builds up a philosophical belief system around that which, beyond the basic axioms, is self-consistent and pretty damn useful. The scientist, used to tackling scientific theories, thinks that by attacking the core tenets of religion, he can bring down the entire system. But the core is unfalsifiable, so the methods of science are useless. Science and religion shouldn’t even overlap in their realms of explanation. In truth, they don’t. But unfalsifiable philosophy is given the title of science, and physical explanations are given the title of religion, so two incompatible systems are faced against each other. It would be better for everyone if both sides retreated to their realm of the human experience, but since they won’t, we get tripe like Lightman’s essay.

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