Here's a video of Neil deGrasse Tyson talking about the history of the definition of planets. You can jump straight to Chapter 4 on Defining a Planet. This is a very entertaining talk. Originally, a planet was anything that moved so it included the sun and didn't include earth. If you do want to blame someone for demoting Pluto, this is the guy (he says he gets lots of blame for demoting Pluto).

Listen to Chapter 12, his reading of California's bill HR 36 relative to Pluto's status as a planet.

In places, his talk is almost a comedy routine. He takes a poke at biologists and chemists for using big long words so people need to get past the words before they deal with the subject. E.g. the red spot on Jupiter is called Jupiter's red spot. Spots on the sun are called sunspots compared to biology where you have deoxyribonucleic acid.

Planet definition criteria:
Are you round?
Are you the primary object in orbit around the sun? Excludes moon
Have you cleared your orbit of orbital debris?

Pluto has not done that and has numerous other icy bodies in its orbit. Heh, a very entertaining talk and lots of good points. Jump around the chapters or listen to the whole 80 minutes. This guy is really good.

One of the topics I will be reviewing soon is the idea of operational versus essential definitions in science. The comment petro is referring to seems a case of someone believing in an essential definition (there is one TRUE meaning for the word) rather than understanding that words generally, and in science specifically, mean what we assign them to mean. Meanings will change as our understanding of nature improves.

Pluto's "demotion" is an example of refining our understanding of what it means to be a "planet."

COIF: thanks for the feedback. I wanted to make sure I wasn't overlooking some basic flaw before providing a link to students for the unit on skepticism.

Complex language: I applaud biology's use of complex technical language because I am a bit jealous. In psychology we adopt words from lay usage and attach technical meaning to them. Then we try to explain stuff to non-technical folks and it gets all confused 'cause both groups have attached different meanings to the same words used in the same basic context. Biology doesn't have that problem.

If you don't know what deoxyribonucleic acid is you know you don't know and you don't get into arguments with those who do. But "intelligence" or "depression" or a dozen other terms that have technical meaning in psychology have non-technical folks arguing with technical folks about what to do to increase "intelligence" or decrease "depression."

My main point was the guy's failure to understand the difference between science and language. We could, if we wanted, define "planet" as any object that had more than one meat patty, and at least three different kinds of cheeses. That would be ridiculous, but not the same thing as believing that the world is flat.

Shifting topics...

On Pluto itself, and the "dubious" new definition, they could fix it up (maybe it's always been fixed and the news just reported it wrong), by specifying that the orbital debris in question had to be LARGER than the object in question to prevent its being considered a planet. Pluto has orbital debris in its path. So does Earth. But Pluto has objects larger than itself in its path (i.e. Neptune). Earth doesn't.

I'd still be a little unhappy with that definition (if Jupiter's orbit shifted so that it intersected Earth's path, would Earth stop being a planet?). But even that's better than having to say that Earth isn't a planet right now.

And I'm also unhappy in general with the idea of changing something like that once it's established. If the definition were genuinely "wrong", like the AOL commenter said, that would be one thing. We'd have to change it. But it's not, the definition of the word is subjective. We could, if we wanted, change the definition of a Prime Number, to exclude the Number 1. And somebody might be able to make an argument for why it should have been done that way in the first place. But after something like that has been set up one way, it seems needlessly confusing to change it without some compelling reason (and I don't see any compelling reason in the Pluto case).

Another thing I found unnecessarily confusing was the new designation "dwarf planet", to describe an object that is not a planet, even though it's name appears to claim that it is. ("Dwarf Planet" seems to denote a planet that is smaller than usual, not a non-planet.) Even "planetoid" would have been better than that.

They discussed dwarf planet on that video. His point there was that if he's driving a compact car, he's still driving a car. Or when they look at dwarf galaxies, they're still galaxies. So if Pluto is called a dwarf planet, then it is still a planet (which seemed to go against his main thesis of defending the downsizing/demotion--but at that point I had missed the preceding couple of minutes so might have missed some of his qualifiers).

He might have been defending the demotion, while still not liking the new label.

There are many possible definitions we might use. We could specify that a planet is anything that a person could possibly exist on (if he could get there). That would probably put Pluto back into the mix, but take the gas giants out. It might bring some asteroids in, but only ones with enough gravity to hold someone down. We could add some criteria for roundness (must come within x degrees of being a perfect sphere). But again, it's all arbitrary. The word ultimately means what we want it to, which was the point about the AOL guy. He thought that the usage was "wrong" before and "right" now, just because some people took a vote. The idea that anyone might think objective truth is determined that way is scary if you think about it.

Mercury might possibly remain a planet under that definition. I've always understood that in between the extremely hot side and the extremely cold side, there's a relatively temperate zone that a person in a suit might possibly be able to survive on (but who really knows).

What I disliked about the orbital path definino in principle, (and I admit this is subjective) was the idea of defining an object by where it is instead of by what it is. Kind of like saying "This object is technically an automobile if it's sitting in a driveway, but technically a jalopy if it's sitting in a garage". But it's the same object in both cases.

Re: Earthquakes and frequency.

There is a handy app for iPod touch and iPhone called Quakewatch. You can see the latest quakes, where they are, the magnitude and you can zoom in using standard maps, or terrain maps (from Google Earth).

You list the quakes in terms of the latest, the biggest, or the ones closest to your location. You can also open a world view map and click on a magnitude bar. E.g. click on 4.5 and you it will list all the quakes of Magnitude 4 and greater in the past week (you will see pins drop into place, and the number will appear at the bottom of the display--e.g. there have been 77 quakes 4.5 or greater in the past week).

I was recently given an iPod touch by my sis, and I've been busy tracking down and installing useful or interesting applications for it. The people who developed this app also have LDS (i.e. Mormon) news apps, so I have to wonder if the quake app was developed to track quakes so they could be plotted by anyone to see if quakes were increasing in frequency for themselves.

The time now is 3:00 pm EST (20:00 hrs UT). Northern California had a 1.0 quake 12 minutes ago, 44 minutes ago, and a 2.3 56 minutes ago (all different locations). Central Turkey had a 2.3 and a 2.9 56 and 64 minutes ago. The biggest ones are 6.8 off-shore by Bio-Bio, Chile, at a depth of 18 km yesterday. A check on the tsunami link shows there is no warning, watch or advisory in effect.

A fun app. Other apps I have are some apps for birds, Kindle, Skepticalscience, Skype and of course, a free chess game app--it plays like an ADD 9 year old on the lower half of the levels.

While on interesting items, see Google Body Labs. You can remove various layers of the body, zoom in, rotate the body, view muscles or blood vessels or nerves or internal organs from different angles.

It works well with Chrome but haven't tried it with any other browsers. And it is a work in progress. They just have a female model so if guys are wondering exactly what is going to get snipped in a sterilization procedure, you'll have to look elsewhere till they finish the male model.

Anyway, it keeps improving and someday it might be useful for medical training.

Back to QuakeWatch. Arkansas has had about 28 quakes greater than 2.5 in the past week, including a few above 3.5 (largest one is 4.1). These are all clustered in the same area. When I think of quakezones, Arkansas isn't usually the spot that springs to mind. Interesting. Must be the Hellmouth. Guess the Cleveland Hellmouth was closed after Sunnydale's.

Incidentally, USGS says number of quakes has been steady for the past 100 years, and have even declined a bit. Wonder if that inconvenient fact will get swept under the rug too? Can't have Fibbers for Jesus looking like, well, fibbers.

Hmmmm...if there were a hellmouth in Cleveland, would anyone notice?