It's in the nature of science that sometimes things that were previously believed to be true turn out to be false. The notion that there are nine planets matched what astronomers knew for many decades but with better measurements turned out be be an unsupportable idea.
For centuries there were just 6 planets. Then people discovered Uranus and there were 7. Then people discovered Ceres and there were 8. Then people discovered lots of other main belt asteroids and there were 7 again. Then Neptune and 8 again. Then Pluto and 9. And now we've found all these other big bodies in the outer system and we decided to demote Pluto rather than add a half dozen new planets, just like we did with Ceres.
I don't think anybody particularly objected to the demotion of Ceres since it hadn't been around that long when it happened. But I can only imagine the furor that must have arisen when people tried to claim that Uranus was a planet despite the number of planets being fixed since the time of Homer. Well, Ok, there was the bit when they turned Earth into a planet and we all know about the people like Giordano Bruno literally burned at the stake over that.
So this demotion of Pluto is just another event in the long, long history of scientists revising what counts as a planet. I understand that it's uncomfortable to have to unlearn things you learned as a kid but science is all about changing our view of the world.
> Jupiter doesn’t go around the sun, and therefore is not a planet by the 2006 definition.
> Don’t believe me? In Newtonian mechanics, two bodies orbit their barycenter, or center of mass. If they have equal masses, the barycenter is the midpoint between them. If one is heavier than the other, the barycenter is closer to it. If one has much greater mass than the other, their common barycenter is located within the larger body, and the smaller object goes around that point. Only then is the smaller body said to orbit the larger one. Otherwise, the two form a binary system.
> Jupiter is ludicrously heavy: it has 2.5 times the mass of everything else in the solar system combined, apart from the sun. The sun is much heavier still—but the barycenter of their mutual orbit is outside it. Jupiter and the sun are a binary system. Their barycenter is, to be fair, quite close to the sun, and informally it may be reasonable to say Jupiter goes around it. But in terms of the formal definition, it doesn’t, so by the IAU criteria, Jupiter is not a planet.
I'm not sure why you would say that A isn't orbiting B if the barycenter of the orbit isn't inside B? We normally talk about Jupiter orbiting the Sun or Charon orbiting Pluto despite this not being true. I can see why someone might want that to be the definition for aesthetic reasons but I'm not seeing any evidence that it's the accepted definition. Wikipedia certainly says "near or within" instead of "within" in the most relevant section and I couldn't find anything clearer or contradicting that.
Well that depends on how you define what is inside versus outside the sun. The sun doesn't have a clear outer edge, it just becomes gradually less dense the further out you go. Earth and Jupiter are inside the heliosphere. These definitions are just arbitrary.
Imagine a less convenient example, e.g. a binary star system where the two stars are of roughly equal or similar mass (and the two stars aren't [somehow] 'right next to each other'). We'd say or write that the two are orbiting each other and that the center of their orbits is outside both.
If Jupiter was more massive then that would also be the case, i.e. the center of its orbit would be obviously outside the sun. Unless you're next going to argue that the entire universe is arguably 'inside the sun' because " it just becomes gradually less dense the further out you go".
The hubris of revising technical definitions that they themselves created to describe their own work? What are you on about?
"Most believe Pluto is a planet" because they were told that by scientists in the first place. Without astronomers, "most" wouldn't even know Pluto existed.
You made your API, you told people outside the company about it, you got it widely used. Are you free to deprecate it? Are you free to change it incompatibly?
You made your postcodes to better sort and deliver letters. That was your only purpose. You told everyone about them and kept telling them until absolutely every database with addresses included your postcodes, and people started using them for other purposes. Are you free to change them if some tweak would improve your ability to sort and deliver letters?
And it's happened before, will happen again, and is currently happening all the time.
In the U.S., we had postal zones in certain cities. A two digit code to specify where in a large city, the letter was to be delivered. The modern zip code wasn't widely implemented until 1967. And depending on how an area grows, it's possible for a postal zone to get subdivided changing the zip code for certain areas.
A better analogy is some sort of third-party API rating system. Consultancies put out big whitepapers about what a "storage service" is, and what the relative quality of things like Amazon/Google/Microsoft's offerings are. The change in definition of e.g.
Pluto might be analogous to that company originally having classified Amazon S3 as a "backup service" before deciding that it was really a new category of service that has now spawned many competitors.
The classification is designed to help us reason and talk about like things. We can all see how Amazon S3 and e.g. Dropbox are fundamentally different categories of service, and they need different names. We shouldn't be afraid of reclassifying things because people will have to change their models. The point of recategorization is that the old models are not as useful as the new models.
“Your only purpose”. As if such standards were set in place and there was no ongoing committee to deal with new cases and scenarios that arise as they inevitably do in any complex system.
The metric system has broken with its own past, though. The breaks were true breaks, not just elaborations, but they were executed with great care for compatibility. 1m has been defined in four or five different ways, depending on how you count.
There's a lesson here: There is a middle ground between preserving legacy and causing problems by deprecation.
So what are the “problems by deprecation” you see in the current context of redefining Pluto as not a planet? Having to reprint interplanetary tourism guides?
