Indeed, when we learn in physics class that an object falls in a parabolic arc — thus we are able to calculate where to place a cup so that it catches our marble as it rolls off the table — we could also say that we believe in a flat Earth. This is because the true path of the marble around the center of a spherical Earth is elliptical, not parabolic. But clearly, the parabolic arc calculation — valid only for a flat Earth — worked, so doesn’t that prove the Earth is flat?

Of course not. The parabolic assumption is a close enough approximation for that scale of experiment. It is not, however, close enough for long range artillery.

No matter what shape we believe the Earth to be, the 2006 definition of “planet” is a terrible definition. It came from astronomers who feared that planet-sized Kuiper Belt objects would be so large in number that future students would not be able to name all of the solar system’s planets. Memorizing the names of the solar system’s planets seems to be one of Jim Jakoubek’s concerns, too. The astronomers panicked and created a rushed, poorly-thought-out, lousy definition. They also waited until most of the planetary scientists left the conference before presenting and voting on their horrible definition.

The “clear the neighborhood around its orbit” requirement makes it lucky for the Earth that the Moon does not count as not being cleared. Dodged a major meteorite on that one!

Obviously, planetary scientists have rejected the definition, otherwise they would not be finding planets orbiting other stars, as they explicitly violate the IAU definition. The rest of us have rejected it, too, as we accept that there are planets orbiting other stars. Oops, I should not have implied that I speak for Jim Jakoubek.

By the way, I like the idea of a saddle-shaped planet, but it does not work with any of my models of the universe. Even the parabolic arc model for falling marbles fails, because gravity is just too weird for a saddle planet.

Lest anyone lose any sleep over my teaching skills, I can assure you my son knows all the NINE planets of the Sol System in order of distance from the sun as well as the names of the belts, most of the major moons, the names of the different Mars rovers and all 5 space probes that have or will leave the system.

In fact it was while discussing the New Horizon fly-by of Pluto that the topic of its status came up. I presented both sides of the argument and why I side with keeping it as our ninth Planet. And anyone who has an eight yr old boy won’t be surprised when I tell you that he now intentionally leaves Pluto out when he recites the planets because he knows it will get me to scowl and then laugh…. LOL

Thanks to Mr Z for stating exactly what I would have. He is one of the reasons, along with most of the commenters here, that I feel confident in what I pass on to our son about space, AGW, and the fact that Trump kept a criminal out of the Whitehouse and for that alone we owe him our eternal gratitude…… ;-)

BTW, I am pleased to report it is not hard to find school material that lists nine planets instead of eight. I guess this is yet another topic where the “consensus” is more fable than fact. :-)

Jim Jakoubek: I don’t have the final word on anything, and neither do you. The point here is that there is clear disagreement about this subject, not just among the general public, but among planetary scientists themselves. I recognize that disagreement, and report on it. I also recognize the valid reasons that exist for disagreeing with the IAU decision.

Just because a governing body passes a decree means nothing, especially if that governing body did not have the support of the community which it is supposed to represent. Its decree might be correct, but if people disagree they have that right, and in this case there is plenty of vagueness to the issue to allow for debate.

My main point in my comment to you, however, is that people have the right to disagree, and that this subject has plenty of room for rational, reasonable, and heartfelt disagreement. You however came at Steve Earle with insults and contempt. It is the common technique used today for anyone does not like someone else expressing a dissenting view. I simply called you on it.

You want to try to convince us that the IAU was right, you are going to have to give us reasons and a rational argument. Calling those who disagree with you believers in a flat earth won’t cut it.

For example, the IAU definition says a planet must “clear the neighborhood around its orbit.” Every planetary scientist I know finds this a laughable requirement, especially since no planet in our own solar system has really successfully succeeded in doing this. Furthermore, this requirement is vague and unclear. How much clearance is required? Why should a planet require this?

Moreover, the definition ignores the reality of thousands of exoplanets, all of which are called planets by astronomers. According to the IAU definition, they can’t be called that, because the definition also requires that a planet must “be in orbit around the Sun.”

Usage is not following this IAU definition, in any way, so why should any good scientist accept it? In truth, most planetary scientists do not.

If you support the IAU definition, it behooves you to help make sense of that definition, and thus possibly convince others that the IAU definition should stand. Insults and contempt however will not convince anyone, and will likely contribute to the definition’s eventual rejection.

I see that a decision about this subject was made 12 years ago by the governing body to define what
a planet is and you do not like it so it has to be a bad one.

Good to know that you have the final word on the subject.

Talk about the Coming Dark Age. Heh.

Jim Jakoubek: Heh. In a post of mine, linking specifically to a story by planetary scientists objecting to the bad IAU definition of planets and insisting that Pluto still is one, you arrive to tell us that the IAU definition is it, and that anyone that disagrees with you, even these planetary scientists, are the equivalent of a member of the Flat Earth Society.

Do you not see the irony here?

It “reeks” of unjustified contempt? How did we jump from a definition that was agreed to 12 years ago of what a planet
is to a Trump thing?

Yes, I am certain that Pluto is no longer a planet. It is a dwarf planet as defined in 2006. Maybe you should have read
the criteria of what defines it. I’m sorry that you can not accept the fact and you show some contempt yourself do you
not?

Tell me then, how many planets are there in the solar system in your judgement?

Denying Pluto planetary status as you think was silly, petty and very illogical. Up until 2006, there was no definition
what so ever. Well, it is a planet sir. It is a dwarf planet and it exists in a region of space that is filled with garbage
from the formation of the solar system.

When the IAU determines that it should be a planet, then great but this is the governing body is it not? And Pluto is not
by current definition.

Thanks for showing your true colors BTW. I don’t fall in line with you and well, its a Trump thing…….

You should be able to locate a physical copy of this relatively easily
“The Search for Planet X”
Tony Simon- Scholastic books
ca. 1961
http://d.gr-assets.com/books/1350409828l/3517949.jpg

Jim Jakoubek: Your comment could easily be thrown into a bin labeled “You want more Trump? This is how you get more Trump!” It reeks of unjustified contempt for someone who simply disagrees with you about the definition of what makes a planet.

You are certain that Pluto is no longer considered a planet. Too bad you haven’t convinced a large majority of the planetary science community. The very post these comments are linked to indicates clearly that planetary scientists don’t agree with you, that many still consider Pluto a planet. Furthermore, the scientists running New Horizons feel the same.

As I mentioned in another comment,

There is no consensus on the meaning of these words because the planetary science community has never accepted the very bad ruling by the IAU that tried to take planetary status away from Pluto. In general however, they consider any object with sufficient mass to have a spherical shape to be a planet, with dwarf planet assigned to smaller minor members of this group. The giant moons of Jupiter and Saturn, for instance, are considered by planetary scientists as planets. Some are bigger than Mercury.

Denying Pluto planetary status was a silly, petty, and very illogical decision by the IAU. Disagreeing with it is perfectly reasonable. Implying that those who disagree with you are ignorant fools is no way to change their minds.

How about this?

In 1930, Clyde Tombaugh discovered an object that was declared to be the “Ninth Planet” in the solar system. In the almost 100 years that have followed, it has been determined that beyond the orbit of Neptune debris from the formation of the solar system exists and in some cases, some of the debris did manage to attain enough mass to become a sphere and because of this, did manage to collect other objects of lesser mass and they now orbit the main body. We call them
moons.

There is also a lot more debris out there which was not known in 1930 that suggests that there is an undiscovered planet
out there.

Since 1930, several objects have been discovered in the region that Pluto orbits and they are of the same size, if not bigger, and indeed have their own moons.

Pluto was an important discovery and for about 70 years was considered a planet. Now it is not as it has been realized
that there are many objects out there that rival and surpass it.

I for one do not wish to discount Tombaugh’s work or discovery. But it was the first step into a part of the solar system
that we knew nothing about and now know a little more.

After reading your comment, it does not surprise me that kids today can not name the planets of the solar system
including the one they are standing on…….