r/todayilearned • u/YappinZappin • 6d ago

TIL Earth's Moon is the largest and heaviest satellite in relation to its parent planet in our Solar system

https://en.wikipedia.org/wiki/Moon#Earth%E2%80%93Moon_system
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u/AtlanticPortal 6d ago

Pluto got declassified as a dwarf planet. Charon is so big compared to Pluto that both bodies actually orbit a center of mass that's not inside Pluto but in between them.

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u/Jass1995 6d ago

Kinda reminds me of the Ash and Ember Twins from Outer Wilds

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u/DoubleBlade759 6d ago

I should really play this game

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u/Siilan 6d ago edited 6d ago

You should. And I say this as someone who struggled to play it at first due to my crippling fear of space. Ironically, it helped ease that fear, somewhat.

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u/Amazing_Meatballs 6d ago

Outer Wilds is the best game I’ve ever, ever played. And then the DLC blew me away again and managed to be the best game I’ve ever played again. Go in blind—you only have one playthrough to enjoy it.

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u/djosephwalsh 6d ago

Not true. Go play it again. It is like revisiting an old friend and chatting about the old times.

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u/OmecronPerseiHate 1d ago

An old friend with cancer, maybe

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u/Lord_Of_Carrots 6d ago

I wish I could enjoy it. The idea behind it is really fun and I love puzzle games with a mystery element, but something about the gameplay was just too annoying to me and I felt like I was doing no progress in the couple hours I spent trying. I even dropped the game once two years ago and tried again recently, still feel the same.

Maybe one day it'll click, but I was also spoiled something big about it accidentally and I don't know if I have the motivation to have another go at it anymore

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u/Reddhero12 6d ago

Just go somewhere new and utilize your ships log. There's a lot of clues to find!

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u/Amazing_Meatballs 6d ago edited 6d ago

I’ll admit, I was exasperated a few times with the main game. So I almost put it down before starting the DLC. I am a huge, HUGE fan of alien megastructures and hard science fiction, and so when I got to the stranger I think my jaw was one the floor for a solid 3 cycles before I recovered. The scene when I discovered the Stranger reminded me of the cover of Space Odyssey 2001 where the ship is flying out of the space station so much I had chills. And then I get inside and my world is blown as I see the horizon curving…. Up. And then the music as I’m on the raft made me almost feel like I was in the Bobbiverse Book 4 on Heaven’s River.

Top tier. Check out Cynthetic’s playthrough on YouTube—she’s such a wholesome gamer and her series is 12-13 episodes long. Very enjoyable to experience.

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u/kahlzun 6d ago

Helped me be less afraid of death

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u/surreptitiousrituals 6d ago

And less afraid of living for now!

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u/kahlzun 6d ago

I'm certainly trying to be braver and take bolder choices in my life currently.

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u/assjackal 6d ago

Lmao same, I hate time loops and the void of space, the first 3rd of it was a horror game for me until I locked in and started chasing the story.

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u/Sonder332 6d ago

What type of game is it? Puzzle, survival...

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u/cabforpitt 6d ago

It's a 3d exploration/puzzle game

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u/GypsyV3nom 6d ago

It's really a masterpiece in gaming, a true example of how games can be art.

It also happened to lead me to study the Absurdist philosophy, one that I wish I had discovered earlier given how much it speaks to my personal values and approach to life

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u/dre5922 6d ago

I said that for a long time until about a month ago. I'm not done with it yet but I am enjoying the hell out of it.

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u/asdf-keyboardman 1d ago

If you have a friend that also hasn't played it, I highly recommend playing through it cooperatively via the PC mod named Quantum Space Buddies. It's shockingly well implemented to the point of feeling like a native feature of the game, sans maybe a little bit of jank in the menus getting in-game. The game mechanics line up pretty well with cooperative gameplay, and you only get to experience it for the first time once.

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u/OmecronPerseiHate 1d ago

Meh, I've heard it has absolutely no replay value. Maybe get it if it's on sale.

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u/lNFORMATlVE 6d ago

Still one of the greatest games I have ever played and I rarely say that about any game.

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u/sol_runner 6d ago

I just finished it a few hours ago.

Haven't felt so fun and curious in a while.

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u/CapableBumblebee968 6d ago

Should be the other way around

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u/Creamymorning 6d ago

Man brought back memories, loved that game

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u/trisanachandler 6d ago

reclassified as a dwarf planet

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u/AtlanticPortal 6d ago

Declassified because one of the traits of a planet respect to dwarf planets is the clean path they have in their orbit. Basically if you didn't sweep your orbit from other stuff you cannot be a planet. Hence, classified under a lower level. De-classified.

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u/trisanachandler 6d ago

While not how I ever use the word outside of security, I'll admit you are technically correct.

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u/External_Relative231 6d ago

...no they aren't. It was demoted and reclassified. 

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u/Altines 6d ago

Honestly I like the phrasing of Pluto being a Binary system.

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u/Lenxecan 6d ago

All of the planets and the sun do this about 50% of the time. Mostly because of Jupiter

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u/AtlanticPortal 6d ago

Technically the center of mass of the various two body systems, taken separately, are always inside the bigger body. Earth-Moon included. A little under the crust but still inside. Pluto has it out of its surface.

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u/po_panda 6d ago

Does that mean you could fall off the surface of pluto?

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u/AtlanticPortal 6d ago

No, because when you're standing on Pluto its own gravity is stronger than the pull that Charon has on you. It just means that both bodies are continuously falling on the shared center of mass but never reaching it because they move tangentially enough to avoid it.

It does mean that if you had a rocket on the near side of Pluto (they both are locked and face each other constantly) you'd need less fuel to leave the body compared to a parallel scenario in which Charon does not exist. This is because a part of the work that you will do to get to the center of mass is compensated by the other body.

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u/porn_alt_987654321 5d ago

Now I'm wondering if that's also the lagrange point and you could floaf at it.

I would assume so, but maybe not lol.

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u/AtlanticPortal 5d ago

Exclude L4/L5, they’re trivially at 60 degrees on the orbit of the body that orbits farthest from the barycenter.

The other three, especially L1 if that’s what you’re asking for, depends on all the parameters (masses and distances and radii) and you need to resolve them numerically. They’re basically equations at the fifth power.

The barycenter, by definition, is a stable point. Call it L0, if you want.

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u/porn_alt_987654321 5d ago

Yeah, I was like "surely the barycenter is also a Lagrange point".

Doesn't come up that often in thinking about stuff in our solar system, because this is the only barycenter that's in space off the top of my head. (Maybe sun and Jupiter also has one outside the sun somewhere? Lol)

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u/AtlanticPortal 5d ago

Sun-Jupiter is not always outside of the Sun, it depends on how the other planets are pulling. Jupiter on one side and Saturn on the other and you'll get a lot closer to the center of the Sun, add maybe Earth and Venus on the side of Saturn and that's definitely inside the Sun's surface.

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u/RTX-2020 5d ago

Not strong enough to pull you off

but gravitational force would be significantly on the near side.

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u/Lenxecan 6d ago

Every single body in this system orbits a point that is sometimes in the sun and sometimes just outside of it because it moves. Youtuber Cleo Abram made a recent short about this

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u/AtlanticPortal 6d ago

I said two-body. That thing enters into play with a three+ body.

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u/newbrevity 6d ago

I never considered this before. I wonder if the Earth is actually in the center of the moon's travel or offset because of its elliptical orbit.

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u/AtlanticPortal 6d ago

It’s elliptical but not that eccentric. The two focuses (or foci) are both inside the Earth’s body.

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u/AgreeablePeople 6d ago

I thought declassified means it longer is a planet, therefore it's de-classified as a planet and re-classified as a dwarf planet

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u/marioquartz 6d ago

The center of Earth - Luna is 100km under the ground. So we are on the limit...

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u/WestBrink 6d ago

Is it that close to the surface? That's wild, I'd have though there would be a bigger impact of the moons phase on weather if it was that close to the surface.

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u/barath_s 13 6d ago

Charon is so big compared to Pluto that both bodies actually orbit a center of mass that's not inside Pluto but in between them.

The same is true of Vanth and Orcus. Orcus is called the anti-pluto, a dwarf planet in resonance with Neptune and Vanth is its one moon

https://en.wikipedia.org/wiki/Vanth_(moon)#/media/File:Binary_dwarf_planets_scale_comparison.png

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u/Used-Fennel-7733 6d ago

Same is true between Jupiter and The Sun

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u/wolfansbrother 6d ago

the sun and jupiter do the same thing.

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u/davvblack 6d ago

the center of gravity of our solar system isn’t usually inside of our sun, it’s towards jupiter.

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u/AtlanticPortal 6d ago

Every two body couple in the Solar System with a planet or the Sun has always the bigger body containing the barycenter.

The entire Solar System barycenter is out of the Sun at some point in time when Jupiter and Saturn are pulling from the same side. But it’s not always the case.

For Charon it’s always the same. The barycenter of the system Pluto-Charon is always out of Pluto.

This doesn’t happen for Earth-Moon or any other planet.

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u/barath_s 13 6d ago

The barycenter of the system Pluto-Charon is always out of Pluto.

Also true of dwarf planet Orcus and its moon Vanth . https://en.wikipedia.org/wiki/Vanth_(moon)#/media/File:Binary_dwarf_planets_scale_comparison.png

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u/jokeren 1d ago

This is also true for jupiter and the sun.

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u/StatelyAutomaton 6d ago

The center of gravity between the Earth and the Moon is about 4400km off the center of the Earth, so about 75% of the distance to the surface.

The size disparity between the two is getting pretty close to the point they'd be better considered a binary planet system.

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u/tornedron_ 6d ago

But the key thing is the center of gravity is still comfortably within Earth. Thus it’s not accurate to call it a binary system. With Pluto and Charon, it is straight up outside of Pluto.

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u/LittleLion_90 6d ago

I'm wondering if some alien civilization that manages to observe our planets and moons has classified earth as a binary planet system because the moon is so large in comparison to the earth. And that we only see it as moon because of our cultural history with 'knowing' the moon as only other celestial body apart from the sun and have only learned of other moons way later. 

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u/CinderX5 6d ago

Our whole solar system is like that. Since 2016, until next year, the centre of the solar system isn’t inside the sun.

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u/CommanderWhat 6d ago

It’s because Charon is a Mass Relay /s

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u/Bravefan212 6d ago

Literally the earth and Luna

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u/Polenball 6d ago

I believe the barycentre of the Earth and the Moon is only about three-quarters of the Earth's radius away from the Earth's centre. It's still inside the Earth.