Our Definition For “Moon” Is Broken (Collab. w/ MinutePhysics)

It’s becoming harder and harder to categorize moons as moons.
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To learn more, start your googling with these keywords:
Moon: a natural satellite of a satellite of a star.
Satellite: A celestial body orbiting a larger celestial body.
Orbit: The path followed by one object revolving around another object under the influence of gravity.
Barycenter: The center of mass that two or more bodies orbit around.
Binary System: A system in which two similarly sized object orbit the same barycenter.
Hydrostatic equilibrium: Roundness that occurs when gravity is balanced by a pressure gradient force.
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If you liked this week’s video, you might also like:
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Credits (and Twitter handles):
With Contributions From: Alex Reich, Emily Elert, Peter Reich

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References:

[DanelAndrade]

Congratulations, you collab'd yourself.

[Gidaio]

How about this: As long as the barycenter for two bodies is inside one of them AND the smaller one can pull itself in to a (roughly - some percent height deviation or whatnot) spherical shape, we can the smaller one a moon.

[mytube]

Here's a set of definitions that I find reasonable:

1. A moon must be in a stable orbit around a planet, dwarf planet or minor planet.
2. A moon must be of such a size that the common barycenter lies entirely within the parent planet.
3. A moon must be dense enough to allow another object to orbit it, i.e. its Hill radius at the closest point in its orbit, must exceed the radius of the moon along the longest axis. Any object smaller than that could be called "a space rock" or something... :)

[Tarmac_Tales]

Humans : " what's your real name "

Moon : " my name is Jeff " 😂😂😂😂😂😂

[katlin]

I am stuck in a loop of 2 videos! Help

[d_wang]

Why do astronauts always have a good party?





They always planet in advance

[minergmaingx]

"Collaboration with Minute Physics."

Wait... what...? So... you guys... collaborated with... yourselves?

[MAMAJUGO]

Great, so not only Pluto is not a planet anymore, but now Charon is also not a moon anymore?
#leaveplutoandcharonalone

[TunaTheMiner]

the universe is under no obligation to conform to our bureaucracies

[that.one.thingofsociety]

Mom: Time for bed!
Me: but mom I'm watching MINUTE
Mom: are learning from it anyways. 5 more minutes
Me: wait.. this is basically school, but more fun? KEEP UPLOADING

[oida]

I would say we should borrow from the planet definition:

a moon is round, it orbits a planet (a planet orbits a star (system) or brown dwarf and A orbits B if the barycenter is within the roche limit of B) and has cleared its orbit.

[RoccosVideos]

I love this channel. It has great information and is perfect for my attention span.

[NadaMajdy]

Fun fact: in Arabic, we use the word "moon" (Qamar in Arabic) to describe a beautiful person.. Everone is moon ♥

[Pingwn]

The best definition:
If you become a werewolf when its full it is a moon.

[huh]

Honestly I think a moon should be an object that's big enough to substantially change the plants barycenter but still be within the planet

[bobbobson]

Here's an idea:
- Has to be spherical.
- Has to have cleared its orbit.
- Has to have a stable orbit; cannot be temporary.
- The system's barycenter has to be within the larger object or its atmosphere.

[ErnestJay]

if it's too big just call it "binary planet" just like binary star system.

[GuyllianVanRixtel]

I think anything that is 1km or bigger should be counted as a moon. But anything smaller than 1km, but bigger than 1 meter, should be a moonlet (small moon). And ofcourse, anything that isn't natural is not a moon/moonlet.

[yushatak]

I'd say that a moon has to have an upper limit of mass such that the barycenter of the pair's orbit is still within the host object. As for the lower bound, perhaps require it to contribute to the barycenter by at least its radius (taking into account opposing forces, of course, to be fair). If the barycenter moves to a point between multiple objects, it is a binary object (in this case a binary planet). If it doesn't move any appreciable amount, it's a satellite but not a moon. All in favor? :p

[a.d.t.mapping]

Here's my take:

Classical Definition - Can be seen from host planet and has an eliptical or circular orbit

Astronomic Definition - A celestial object that orbits a planet

Restrictive Definition - Is less than one-sixth of it's size than host planet, is eliptical or circular in orbit, has to be seen with the naked eye from the host planet, and size is no less than 1000 km.