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StayYou61 t1_iy6hbtt wrote

Pink Floyd would have had to specify the dark side of which moon.

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Just_Michael1138 t1_iy6j5xx wrote

The Dark Side of Moon Two, by Pink Floyd. Available in all your finer Mandela's near you.

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foo-fighting-badger t1_iy7awk8 wrote

unless the other moon isn't tidally locked

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ronnyhugo t1_iy9gere wrote

When the moon is half-full, half the far side of the moon is in fact a part of the light side of the moon.

How did people ever start mistaking "dark side" for being "far side"?

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Connect_Eye_5470 t1_iy9stld wrote

Because it never receives any reflected light from Earth, thus from our perpsective it is the 'dark side'.

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ronnyhugo t1_iych9dl wrote

All that shiny moon stuff is 99.9999% from the sun. Otherwise we'd never have any dark bits of the moon towards us, would we? :P Its not like the moon actually gets carved in half when half of it is dark, its still there, it just doesn't get sunlight! :P

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ronnyhugo t1_iy9fz1h wrote

I wish people used "far side of the moon" when they mean the far side that is never seen. Because there is light there.

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ZylonBane t1_iy6gi1a wrote

We would have been forced to come up with actual names for them.

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p-d-ball t1_iy6hkqf wrote

"Moon 2 is full tonight! But Moon 1 is waxing."

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Macktologist t1_iy8j1xv wrote

Our moon was named by the same type of people that have a boy and girl and refer to them as brother and sister to the other one.

“Go see what Brother is doing.” “Timmy, please make sure to look after Sister.”

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Deadmeat5 t1_iy8hrt3 wrote

One will be called "Moon" while the other will be called "Moon Moon", of course.

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FINALCOUNTDOWN99 t1_iy77wo9 wrote

"We choose to go to Moon 2 in this decade, and not the other moon, not because it is easy, but because its easier than Moon 1."

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mfb- t1_iy7qhdm wrote

"We choose to go to Moon 1 in the next decade, and not the other moon, not because it is easy, but because the Americans already went to Moon 2."

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Cosmo_the_Thylacine_ t1_iy6euyy wrote

i think surfing would be a lot more interesting... and dangerous

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Any_Palpitation_3110 OP t1_iy6fcy1 wrote

Yes I think the tides would way different. But that was the obvious one and only one I could think of. But I wonder what else would be changed?

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PoppersOfCorn t1_iy6fu6s wrote

The length of our day, depending on mass and its orbit

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Any_Palpitation_3110 OP t1_iy6nln8 wrote

So would more mass from our moon and/or moons inherently make earth spin slower or faster? Or is it way more complicated than that

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PoppersOfCorn t1_iy6ql60 wrote

The moon caused a lot of drag on our rotation and massively slowed us. It is reckoned the Earth used to have a ln 8/10 hour that gradually slowed.

So if we had another moon and depending on what type of resonance it had as well as its mass, yes, it could have changed our day either nearly nullifying the drag from the other moon, or even causing more "drag" and slowing our day even futher.

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Radiant_Nothing_9940 t1_iy77zjj wrote

How does a moon produce “drag” I’m curious as I haven’t heard this before. I thought our earth slowed for other reasons…

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PoppersOfCorn t1_iy79h20 wrote

So basically, from the gravitational interaction between earth and the moon. The moon creates a bulge on the earth surface(tides) but this bulge isn't directly underneath the moon, so it causes torque, and the difference slows the earths rotation and also results in the moon continually moving away from earth

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Ripper209 t1_iy7dm16 wrote

How does general relativity explain this?

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JapariParkRanger t1_iy7e26z wrote

There are no major relativistic effects needed to explain tidal forces.

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Ripper209 t1_iy7ekfy wrote

Can you please elaborate?

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JapariParkRanger t1_iy7f6e1 wrote

General Relativity has little to do with tidal forces.

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Ripper209 t1_iy7g210 wrote

Ngl im kinda stupid, how does the moon affect the tides then

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TwoUglyFeet t1_iy7lii5 wrote

Gravity. The moon pulls on the earth like two people holding a rope. This force is called tidal force and causes to water (and the earth) to move to side closest to the moon. These are what tides are.

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Ripper209 t1_iy7m41w wrote

In terms of general relativity, is this "rope" nonexistent? Are they just moving along curved paths caused by the mass of the moon and earth?

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TwoUglyFeet t1_iy7nlu4 wrote

The moon is in earth's gravity well. This bending is the reason we see the forces of the Earth and moon acting on each other.

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Ripper209 t1_iy7srji wrote

Thank you very much this was really helpful

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strange--alien t1_iy88lp4 wrote

If you imagine this scenario, having a tennis ball on a string and holding it above your head spinning it like a helicopter rotor. Generally speaking, the tennis hall represents a moon, rope is the gravitational tether between the two, and (with a bit of imagination) your hand are represents the earth. So, when spinning the tennis ball around, the mass of the tennis ball sets a limit on the speed of spinning. One rotation is an earth day. If you had a heavier ball like a basket ball (larger moon) the speed of rotation would be slower because the earth has to sling a heavier moon. Spinning a lighter ball like a ping pong ball (tiny moon) would be so easy that the tiny moon wouldn't have any affect on spinning speed basically. Smaller you get and the moon wouldn't be able to hold itself in the earth's gravity and would fling off in to space. To summarise, larger moon puts a brake on our earth's rotation, Smaller moon would ease pull back on our earth. Two moon's would be wack! Double the werewolves, double the astrology readings. Spooky

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Ripper209 t1_iy9mz4n wrote

This is exactly what I'm looking for thanks!

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strange--alien t1_iya1txe wrote

I could hear your unspoken question very clearly. Btw I messed up one piece. One tennis ball rotation is one moon orbit (27 days), not one day. Still same physical concept though.

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robit_lover t1_iy7rayi wrote

To add, the earth and moon produced drag on each other, and since earth is so much larger it slowed the moon down enough that it doesn't rotate relative to earth anymore.

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XNormal t1_iy7ksti wrote

A related question is what would be different if Venus had a moon the size of ours. It would have been visible to the naked eye and everyone could see that not everything revolves around the Earth. Could have had an interesting effect on the history of science and religion.

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AzarthIV t1_iy6o6z3 wrote

Mythology.

Oh, theres a goddess/god of the moon? Well, theres two moons now, so either a deity of two moons or one for each. Anyways, some mythological stories would probably change a lot.

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Aekiel t1_iy7i5gs wrote

They'd be twins, probably. Or rivals constantly at each other's throats. Or both.

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blazingknight144 t1_iy6grgo wrote

Youtube channel "What if.." had a scenario like this I think? I recall that there could be stronger tides, and also the possibility that the gravitational pull of the bigger moon will destroy the lesser moon and absorb it.

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noseboy1 t1_iy6q9se wrote

On the topic of moon collision, I don't imagine that being necessarily true... or, at least, not on a timeline even remotely significant to human existence. But, like, several planets have multiple moons that seem to be fine. I do think it might screw with tidal locking though, but again idk

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Any_Palpitation_3110 OP t1_iy6vqq3 wrote

So it's possible somewhere in time and space there is a civilization that has two moons side by side almost touching by not quite yet?

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Ok_Neighborhood_1203 t1_iy6xp4y wrote

That could actually be a stable configuration... the two moons would orbit their barycenter, and that barycenter would orbit the planet. It wouldnt last forever but easily hundreds of thousands of years, like the rings of Saturn.

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PandaEven3982 t1_iy90oye wrote

Depends on relative masses. Terra and Luna are following a barycentric orbit of Sol :-)

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Ok_Neighborhood_1203 t1_iy968gk wrote

True... though in the case of the moon-earth system, the barycenter is about 1000 miles inside the Earth. And all the other planets, meteors, comets, and dust in the rest of the solar system are perturbing our orbit too. Even the surrounding stars and galaxies have tiny effects on orbits if you can measure them precisely enoigh.

Neat fact, the Sun-Jupiter barycenter is outside the surface of the sun. So, the solar system actually orbits empty space :)

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PandaEven3982 t1_iy97cd6 wrote

Grinz, nod, yup. Wake me up when we have an O'Neill colony at L4. Or when we can explain the math of null gravity versus microgravity :-)

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mfb- t1_iy7qme4 wrote

Two moons in a close orbit around each other are possible and such a configuration could last for a very long time. Tides would be like for a single moon in that case.

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noseboy1 t1_iy6w5bv wrote

My astrophysics is not nearly as well informed as I'm sure many are here, but the nice thing about space is that it's infinite. With infinite space and stars and planets and moons I'm sure it exists.

... but generally speaking, because of how fast everything moves and the fact that gravity would dictate the two also pull on each other, so they should collide, that possibility is probably stupid low.

But hey, it was once thought binary stars were impossible, turns out they're actually pretty common, the rule book gets thrown out on stuff like this every time we make a better telescope.

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Glad-Style-1375 t1_iy77v7a wrote

We don't know if space is infinite....

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noseboy1 t1_iyd9yi5 wrote

Fair. I think it's still vast enough for a pair of moons to be bumping uglies sonewhere

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Radiant_Nothing_9940 t1_iy77u64 wrote

Space sadly isn’t infinite. It’s just very big. Also they wouldn’t be pulled together if they were binary, same way our moon isn’t pulled towards earth. If you want an example of a planetary binary, we actually have one in our solar system; Pluto and Charon are 2 bodies orbiting a barycenter which I believe (I might be wrong) is outside of Pluto’s surface. Charon and Pluto are pretty damn close together, and could likely be much closer. If 2 objects are too close, they will begin to pull each other apart. The issue then is not whether or not 2 objects could sustain distance from each other without colliding, as they just orbit each other, but more an issue of the 2 objects not ripping each other apart through tidal forces.

Sorry if this is illegible or sounds like thinking out loud, I’m pretty fucking tired so forgive me at least a little bit.

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The_elk00 t1_iy7d37j wrote

Space is such a crazy concept to think about. If it's not infinite, what's the end or edge like? Does time move at an insurmountably slow speed at the edge? Is space infinite but there's just nothing there? Is it a wall? Does all matter become more tightly packed that it acts like a wall but can expand?

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Aekiel t1_iy7hyfh wrote

There's a lot of debate about this.

The prevailing theories at the moment are that the universe is either infinite or finite. If it is infinite then there is no question of whether it is bounded or not (it is unbounded as you can't name two points within the universe and have the distance between them encompass everything within it).

If it is finite then the question is whether it has an edge or not. If it has an edge it is referred to as a bounded universe and we have little idea what could be at or beyond the edge of such a universe.

If it is a finite but unbounded universe then there's a definable volume to the universe (that is growing all the time due to expansion), but it doesn't have an edge. This is where the common balloon analogy comes in (a balloon doesn't have an edge, but as it expands the surface area of the balloon and distance between two points expansions).

Current thought rules out a finite bounded universe as it violates homogeneity, but there's no settled consensus on whether we live in an unbounded infinite universe or an unbounded finite one.

EDIT: If we do live in a bounded finite universe there's also debate as to the geometry of it (is it like a sphere? a torus? something weirder?).

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Radiant_Nothing_9940 t1_iy8c0ym wrote

There’s also the theory that it’s a 4d hypersphere, meaning reaching one “edge” will just be the same as making it to the opposite side and nothing else. I love this theory as it adds both an explanation for the expansion of space (the sphere itself is expanding, so all the 3d things are getting further apart) as well as possibly leaving a scientific space for a god. I am an atheist, but if we live in a 4 dimensional (or more) universe, a god could easily exist outside the 3d bounds of it, and would therefore be able to see and interact with any part of it.

Too bad this universal theory is likely untrue and these days not considered a prevailing theory. It just explains so much for me, and could even let string theory exist, but I think the math just doesn’t work out.

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O5-20 t1_iy6jvyd wrote

I’m guessing the effects would depend upon the size, mass, and orbital distance of the new moon.

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LegitimateGift1792 t1_iy8x5if wrote

And did they assume current moon would be the same? Or would we have like Mars' moons.

I remember seeing a show long ago about the Moon and why it is so unique (singular and large compared to planet size) for this system and how that might be why Earth has life.

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NewPlanetarium t1_iy6l0ij wrote

This is a pretty interesting scenario! Here's an interesting article that explains what would happen if Earth captured a second moon today.

This scenario though is obviously unrealistic today, and if a second moon was captured it would have occurred billions of years ago more realistically if it would ever happen. In this case, if the second moon was the same size as our moon, then the three body system would cause the two moons to collide and form a larger moon than our Moon. This would wreak havoc on the tides, seasons, and length of days. Life as we know it wouldn't exist, though life would adapt to the different conditions if they are suitable for complex organisms.

In another scenario where the second moon is rather small, more like the captured asteroid moons of Mars, not much would change, though it would be neat to have a second moon.

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_verixsans t1_iy6lvf5 wrote

Which moon would we build a civilization on?

And which moon would we visit first for the Apollo missions?

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noseboy1 t1_iy6qd64 wrote

The closer one for the visit, the larger for settlement (slightly better gravity conditions)

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egregiouscodswallop t1_iy6pqwv wrote

I think we'd go to Moon 1 first and Moon 2 second, if only because those are the only names we could think of

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Jogaila2 t1_iy6p7ys wrote

Tides would be quite different. So weather too.

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Bipogram t1_iy6njgk wrote

It depends on what type of moon it is.

Phobos-esque? A little scrap of rock that offers little more than the IAU to argue over names of features on it.

Vesta-like? More hydrated minerals! Woohoo!

As moon's go, Luna's rather nice. Small enough to not have a ludicrous escape speed and large enough to have had some interesting times with volatile-delivering comets.

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m4nu3lf t1_iy6o19w wrote

There would be one more moon than we have today.

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StanleyChoude t1_iy86v7r wrote

I thought we’d have twice as many moons as we currently do

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Grifcannon26 t1_iy7b505 wrote

That depends - would this second moon also be hallow Giorgio tsoukalos approves 👍

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codikane t1_iy87qsz wrote

We would have more Lagrange points in the earth-moons system. This would mean more spots for potential telescopes and/or space stations. We would have less stable tides. Greater third-body perturbations on high-Earth satellite orbits could cause them to be less stable. Something about women's cycles may be different...not sure what. We'd have a scientific theory about how the two moons formed. Undoubtedly a story in all ancient texts about how the two moons got there. And we'd have a pretty sweet night sky, though it would have more light pollution and the stars and our galaxy would be more difficult to see with the naked eye.

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Pure_black_void t1_iy6xih1 wrote

Fucked up tides?????? Idk man I think it’d be mad cool but who knows the gravitational madness that might ensue😂

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JustMotorcycles t1_iy77yuw wrote

Necklace Nebula. A binary star system where the hot smaller star orbits ... INSIDE the bigger, cooler partner. fucks with my head.

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imapassenger1 t1_iy7gmhh wrote

If they orbited each other while orbiting Earth it would be interesting, if that's possible.

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piero_deckard t1_iy7m7ra wrote

Astrophotographers interested in deep space objects would have an even harder time finding suitable conditions...

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Fosferus t1_iy7piuw wrote

Love songs would be very different. Older cultures would have applied different traits to each moon. I imagine the larger one would be seen as 'male' and the smaller 'female.' These assigned traits would have leaked into our figures of speech and cultural touchstones.

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FeatherLightDK t1_iy7sra6 wrote

So we already have a moon called moon... would a second moon then be called moon moon?

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PandaEven3982 t1_iy8ricl wrote

Hmm. No circadian rhythm, but something more complex. Tides very high when both moons in conjunction. Increased vulcanism in tectonics from gravitic stresses. Lots of effects on biology.

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SpartanJack17 t1_iya7evq wrote

Hello u/Any_Palpitation_3110, your submission "what would be different if we had two moons" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

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zer05tar t1_iy70t1p wrote

We could definitely see that one was fraudulent and one was real.

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