Neil deGrasse Tyson and Michael Brown - Is Pluto a planet?

In this video clip, Michael Brown and astrophysicist Neil deGrasse Tyson disagree on whether the word "planet" has any useful meaning. I also add my thoughts at the end.

Category:

Science & Technology

Tags:

• Pluto
• planet
• Neil
• Tyson
• science
• astronomy
• cosmology
• astrophysics

[SuperMagnetizer]

Let's just call midgets "minor people" from now on. After all, their size disqualifies them from being real people.

Planet Pluto has 3 of its own moons.

[theinquisitor]

So do you want to call Sedna, Ceres and Eris planets too? As well as dozens or perhaps hundreds of others? If you include Pluto and not those, then it becomes an absurdly arbitrary category.

If we had known Pluto's size when it was first discovered, it would never have been called a planet.

[SuperMagnetizer]

Here is my recommendation. All bodies orbiting the Sun that are spheroidal in shape should be called planets. These should be further subdivided into three main categories: terrestrial planets, gas giant planets, and planetoids. Asteroids would not be spheroidally shaped.

Sedna, Ceres, Eris, and Pluto should be known as planetoids, as distinct from asteroids.

[theinquisitor]

The term planetoid is already in use as a broad category to describe anything from rocks a few tens of metres across to objects like Ceres. The term dwarf planet is used to describe bodies like Ceres, Sedna, Pluto, etc.

Also, objects of that kind that are trans-Neptunian are called Plutoids.

This difficultly arises because we're trying to put discrete barriers between objects that lie on a continuum. A planetoid by any other name would be just as interesting.

[SuperMagnetizer]

It's interesting you bring up the fact that these object all lie on a continuum. In fact the spectrum would extend from micro-meteoroids up through the most massive stars and even to black holes. The delineations would therefore be quite arbitrary. The problem is we lack the vocabulary to describe the bewildering array of objects the Universe has set before us. This brings to mind the Eskimos, who have dozens of different names for snow. But I personally loathe the term Plutoid.

[theinquisitor]

Indeed, it is mostly arbitrary. Although there are a few cases where there is a distinctive line between some objects.

Such as a neutron star. There's no object that falls between a neutron star and a normal star, unless you count the brief moments of transition between the two. And there's nothing between a neutron star and a black hole.

The tipping point where gravity overcomes the nuclear forces makes this limit very definite, giving us some discrete categories.

[Kuren420]

Neil was great in this video but the video kind of sucked. Go Neil!

[rajuncajunqueen]

i love neil i love pluto an i really loved that last arrow lmao thanks

[williamcardno]

You say "let's not forget the word 'Theory'" at the end though, when "theory" has never had more than one use in any context:

A model or framework that makes sense of the evidence/ideas provided.

[ReadMyCommentBitch]

"everyone else just has to grow old and die"

[albinoman13bt]

Sorry, Tyson is right, Pluto isn't a planet. It's a big comet. It's over half ice, just like a comet. It has a highly elliptical, tilted orbit, just like a comet. It resides in the Oort Cloud, again just like a comet. There are bigger asteroids and moons in the solar system. It's so small, that because of it's "moon", Charon, the orbital axis is outside Pluto, unlike the planets. Remember, we did had 13 planets at one point.

[npdarren]

...but serves as a general term to describe something. We use "planet" to describe things in the same manner. Whether we call it a planet or a spaghetti monster, or whatever, Pluto will still be Pluto. All words are good for is allowing us to form a schema in which we can visualize something by its description.

[npdarren]

I'd say "Bah, just let people call it what they want to call it", but I know better. So long as there are some people who genuinely believe Pluto is a planet, and people who genuinely believe it is not, there will be conflict, even if we somehow segregate the definition into different categories.

My opinion; "planet"is a word, and the meanings of words are dictated by the opinions of people. The word "gay", for example, has several connotations...

[puncheex]

@SuperMagnetizer: Ah, but some of the planetoids are. Pallas, Ceres, Juno and Vesta are all spherical. The actual current definition is:

"A 'planet' is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit."

You were close, though.

[puncheex]

@SuperMagnetizer: Yeah, and it orbits in a highly inclined, highly elliptical orbit on the inner edge of the Kuiper belt.

You know, biology has this same problem with words. When I was a kid, we know what birds were, what dinosaurs and apes and monkeys and humans were. Now, birds are dinosaurs, dinosaurs are reptiles, humans are apes, apes are monkeys (and therefore we are monkeys, as well as primates, tetrapods, amniotes, chordates and bilateria). So what's in a name?

[SuperMagnetizer]

Good points, thanks! But that last arrow into Pluto hurt.