THINKING ABOUT SCIENCE MASSIMO PIGLIUCCI

Planet X and the Issue of Definitions in Science

lanet X, the long-hypothesized tenth member of the solar sys- P tem, has finally been discovered by a group of astronomers at the Gemini Observatory in Hawaii and Yale Uni- versity. Or has it? Controversy is rag- ing over the question of whether X (at the time of printing unofficially called “Xena,” after the warrior princess of recent television memory) is in fact a , a “planetoid,” or just a large . At roughly 3,000 kilometers in diameter, Xena is smaller than Mercury (4,900 km), but larger than Pluto (2,300 km). Well, that ought to settle it, right? After all, isn’t Pluto a planet? Maybe. First of all, size is not all that matters: The moon measures 3,500 kilometers, Europa—one of Jupiter’s moons—3,100, and Triton (Neptune’s moon) 2,700. So Xena easily falls between and moons (as does Pluto). Then there is the issue of the sharp skewness of Xena’s orbit: most planets This artist’s concept shows the planet catalogued as 2003UB313 at the lonely outer fringes of our solar sys- tem. The planet was discovered by the Samuel Oschin Telescope at the near San Diego, have an orbit that lies more or less on the , on January 8, 2005. Image credit: NASA/JPL-Caltech same plane as Earth’s orbit (I’m taking our own rock for comparison out of any cosmic significance), while the new planetoids (whatever they are!) beyond pure anthropocentrism, not because of planet is by far the most skewed, with the orbit of Neptune. The proposal Massimo Pigliucci is a professor of evo- a deviation of 44 degrees off the aver- was quickly withdrawn because of loud lutionary biology at SUNY-Stony Brook, age! But Mercury also sticks out of the protests by the astronomical commu- a fellow of the American Association for pack, and Pluto even more so (though nity, concerned with the perception of the Advancement of Science, and author neither approaches Xena’s inclination in downgrading Pluto. However, Gareth of Denying Evolution: Creationism, this respect). V. Williams, who directs the MPC, Scien tism and the Nature of Science. In 1999 the Minor Planet Center still supports a “dual status” for Pluto, His essays can be found at www.rationally (MPC) proposed to consider Pluto PLANET X AND THE ISSUE OF speaking.org. itself, while still a planet, a member of DEFINITIONS IN SCIENCE the so-called , an area of Continued on page 50

20 Volume 30, Issue 1 SKEPTICAL INQUIRER to suggest to the girl that a different colored sheet of paper using the principles above, must be guided by compassion, be used. She refused the offer. Her trick was thus exposed: recognizing that the subjects of his or her investigations are She had been palming the note she allegedly “read” while a ultimately people and that lives may be at stake on either side blank sheet remained in her ear. An article in the SKEPTICAL of the equation. Compassion, as a guiding principle, is a good INQUIRER followed, and people were no longer deceived measure in science. (Alcock et al. 1988). But eighteen years later, Alcock wonders what happened to this girl. The governmental authorities Conclusion who had been involved in promoting the girl’s abilities were In sum, there is plenty of ripe territory for discussion of ethics apparently not pleased by being deceived, and the girl’s where- in investigations and the above principles are only a sketch. abouts could not be confirmed. She may even have been sent Moreover, there are many case studies that could be considered to jail. In this case, informed consent was given, but it raises and the brief ones above are only a start. I would like to see a the possibility of another ethical principle for investigations: a continuing series of case studies and continued efforts by inves- duty of compassion. tigators to formalize a system of ethical principles for investiga- tion. As with scientific studies in other fields, a formalized pro- Compassion fessional ethic leads to greater confidence in the science and its Finally, it may well be that the result of an investigation is conclusions and provides greater incentive for self-reflections that a life is ruined, a person is jailed, or worse. Considering by its practitioners. Hopefully, the SKEPTICAL INQUIRER will this, the investigator should be careful in choosing how he solicit and publish occasional case studies in ethical issues from exposes the fraud, if fraud is discovered. And he must balance its fine stock of qualified investigators in the future. the weight of the potential consequences to the perpetrator against the likely benefit to the public at large. As with all pur- References suits, compassion is generally a good guiding principle for just Alcock, James, Kendrick Frazier, Barry Karr, Philip Klass, Paul Kurtz, and James Randi. 1988. “Testing psi claims in China: Visit by a CSICOP behavior. If one need not harm someone else, one shouldn’t. If dele gation.” THE SKEPTICAL INQUIRER 12(2): 364–375. harm is necessarily a consequence of doing a higher good, then Macrina, Francis L. 2000. Scientific Integrity. Second ed. Washington, D.C.: the option involving the least harm should be chosen. Any ASM Press. (See p. 80.) Nickell, Joe, with John F. Fischer. 1988. Secrets of the Supernatural. Amherst, other approach may be vindictive or cruel. An investigator, New York: Prometheus Books, 47–60. !

PLANET X AND THE ISSUE planet? For that matter, not even the dis- “planetlike” questions in some instances OF DEFINITIONS IN SCIENCE tinction between stars and planets is quite but not others. On the other hand, Continued from page 20 as neat as most people think: often, one Sykes himself goes on in the same inter- test is whether the body produces more view to suggest a very interesting ques- according to a recent New York Times energy on its own than it receives from tion: why does Pluto, and even more article. outside. But by that criterion, Jupiter so Xena, have such a skewed orbit? But Why does all of this matter, and what qualifies as a quasi-star (though it doesn’t one can pose the question regardless of does it tell us about science? According have nuclear fusion reactions going on whether one thinks of Pluto and Xena as to some people, for example Mark V. at its core—then again, neither do black planets or planetoids! Sykes (quoted in the Times) “the kinds dwarfs or neutron stars). Science is littered by equally use- of questions we would ask about the Wittgenstein’s point was that often it less, and sometimes downright harmful, object would be planetlike questions [if doesn’t serve much purpose to get hung debates. In my own field of evolutionary we thought of it as a planet].” Really? It up on precise definitions, something biology, emotions have run high for seems clear that this is a case of getting that a lot of scientifically minded people decades on the “crucial” question of stuck on the alleged importance of sharp have an ingrained tendency to do. How what a biological species is, while at the definitions, something that philosophers many times have you heard a scientist same time plenty of researchers have such as Ludwig Wittgenstein have long claiming that “if we can’t agree on a conducted brilliant studies on individ- warned people to stay away from. definition, then we don’t know what ual species and on the process of specia- According to Wittgenstein, many we are talking about”? Turns out that tion, apparently entirely unencumbered interesting concepts (such as the decep- we do know what we are talking about, by the lack of a universally-agreed-upon tively simple one of “game”) do not admit and that definitions often (though not definition of what species are (for of clear-cut definitions based on a small always, of course) hamper rather than more on this, see my recent article in set of necessary and sufficient conditions. help progress. Philosophy Now, issue 50, 2005). Is there a size for a non-stellar body below For example, it is hard to fathom Let us all take a hint from a philos- which it ought to be thought of as a what Sykes had in mind when he said opher, once in a while, and beware of planetoid and above which it becomes a to the Times reporter that one would ask Wittgenstein’s warning: “Philosophy is a

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