For that matter, the newly adopted definition for “planet” is pretty terrible. If it were up to me, I”d go with a definition that was based on orbital characteristics and a minimum surface gravitational acceleration threshold—maybe size and density, too. But none of this “cleared its orbital path” crap.

I think it’s actually a pretty clever definition because it’s self-limiting – at exactly the point where there are lots of objects of similar size we might be tempted to call planets, the fact that there are lots implies that none has successfully cleared its orbital path and so none has reached planet status. This way we circumvent the whole issue of hy the boundary on size, density, orbital parameters, or whatever (remember, Saturn is less dense than water), was set here rather than there. It also fits in nicely with the most widely accepted theory of planet formation by accretion onto smaller planetesimals.

Oh and the Dark Matter result probably is more interesting, if only because almost all astronomers believe observations require the existance of DM whilst almost all of the public seem to believe it’s just a conspiracy. I’m pretty sure that says something significant. It seems like an odd thing to spam(?) a blog about though…

The new definition of a planet is, however, completely stupid. The new concept of a “dwarf planet” further complicates matters. If a dwarf planet is not a planet then why does it contain “planet” in its name? Whether you go to the store and buy a baseball hat or a cowboy hat they’re both hats.

An older and more cynical voice also pipes up noting that funding changes the playing field as well. If an established scientist has secured millions in funding based on a particular theory, they”re not going to be happy if that theory is questioned or disproved – especially by a young “nobody”. I”ve no doubt that there are times when the established scientist will work to discredit the newcomer; thereby saving reputation and funding. I hope it”s rare – the exception, not the rule.

This sounds like the academic field of astronomy that I used to work in. As opposed to the idealised science described by Eric. Of course, those are both extreme examples. Real academic research is somewhere in between.

The conflict between the Steady State and Big Bang theories in cosmology is one good example. Steady State stood, on increasingly flimsy ground, as an accepted alternative to the Big Bang until very recently. It was only microwave background measurements in the early 90s that finally killed it.

I’ve heard Alan Dressler’s Voyage to the Great Attractor, about the measurement of the Hubble Constant, described as a fair book about the scientific process but a great insight into scientific egos. Dressler is not the world’s most humble bloke.

Isn’t the term planet simply arbitrary? I mean because we live on a big ball as humans we are inclined to revere other big balls–planets.

I understand this change to be simply human, and done for the sake of neatness and order. Not science.

There is no inflexible dogma. As new evidence emerges and is incorporated into the general body of knowledge, the “orthodoxy” changes. There are no absolute truths in science—only the best available information.

At uni I did a subject called “Philosophy and Science”, class was made up of half philosophy students and half science students. A lot of the science students actually got really angry about the idea that their knowledge wasn’t certain. They insisted that scientific knowledge was set truth – they couldn’t cope with the idea that all those hours of study could be potentially be rendered invalid (although I think that was a particularly pessimistic view of what was being discussed).

I’ve never quite understood how those students could ever do serious scientific research if they were so unwilling to question the established order of things.

An older and more cynical voice also pipes up noting that funding changes the playing field as well. If an established scientist has secured millions in funding based on a particular theory, they’re not going to be happy if that theory is questioned or disproved – especially by a young ‘nobody’. I’ve no doubt that there are times when the established scientist will work to discredit the newcomer; thereby saving reputation and funding. I hope it’s rare – the exception, not the rule.

I’m not sure about this. Newton had his corpuscular theory of light, but Young’s two-slit experiment clearly demonstrated that light was a wave. I think the wave theory was held strongly through the 19th Century, with Maxwell demonstrating that light is an electromagnetic wave. Then Einstein published his explanation of the photoelectric effect in 1905, the work which won him the Nobel Prize. Einstein’s theory introduced the concept of photons and I think it’s only then that the particle nature of light was seriously considered again. So Einstein showed that the particle theory had to be taken seriously, and that light behaved as both a particle and a wave.

Then De Broglie came along and we realised that electrons also exhibit wave-like properties, extending wave-particle duality to subatomic particles.

The advent of infra-red astronomy in the 80s, and the subsequent discovery of the Kuiper Belt, did change our view of the Solar System. I don’t think that’s reflected in the IAU decision, though, since the definition of the word ‘planet’ wasn’t really tied to our understanding of the physical mechanics of the Solar System. It just meant a hunk of rock or gas in orbit around the Sun.

Oh well, we astronomers like quibbling about semantics, I guess. :)

We’ll have to agree to disagree on Pluto. I certainly agree that it provides excellent fodder for discussion on how our knowledge of astronomical phenomena has increased, via the use of scientific method to guide our investigations, and how this has led us to redefine existing terms so that they can be used in future in useful ways. But I disagree that the reclassification of Pluto is a direct consequence of scientific method, as it is not a new hypothesis that is causing the change. To me it is more like the Academie Francaise deciding on the official French word for email (“courriel” — speaking of places near home, this word originated in Quebec, where I grew up).