OlivetheNerd
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Has anyone noticed that the planets on our solar system that are closest to the sun have a much slower rotation than the outlying planets?
I wonder if there’s a reason for that, or if it’s just coincidence. I had a hypothesis that the sun’s intense gravitational pull had an effect on the speed of a planet’s rotation - but wouldn’t that make the planet move faster?
These are just thoughts I’m having that I thought I would share for no reason.
NASA left Pluto off of the list because it’s a dwarf planet instead of a full planet. I managed to find a list of dwarf planets and the speed of their rotation.
Here’s the table without the red rectangle for those who want to see the data without visual interference.
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Also, here are my sources cited:
Speed of planet’s rotation: https://spaceplace.nasa.gov/days/en/#:~:text=Earth%20takes%2024%20hours%20to,and%20Neptune%20takes%2016%20hours.
Source for dwarf planet speeds: https://www.schoolsobservatory.org/learn/astro/solsys/dwarfs
NamasYAY
1 without checking my phone on the toilet: 10,000,000 years
Spoopytoad
The goblins spinning planet pedals faster when closer to fire ball cuz scared and trying to escape...
LabiusCorpus
I love space posts.
PowerPedant
For the gas giants, it depends a bit on the latitude: They (probably) don't have a surface, and don't rotate as a solid body.
BlindGardener
The suns’s gravity pulls on the closer planets in such a way that it slows down their rotation
BlindGardener
Also the ‘day’ of a gas giant is dubious as fuck
Thisisabigmistake
We're just a giant rotato.
ramblercomet5772
Imagine having to work nearly 6,000 hours a day. Makes me appreciate the 9-5.
DaisyfromDownunder
Obviously it has something to do with the relative air speed of an unladen Swallow.
TI99Kitty
A European swallow or an African swallow?
DaisyfromDownunder
Possibly a giant gulp.
Streiquer
According to the 10,000 hour rule, You can become an expert at anything in only 2 days on Venus!
MisterLemons
Jupiter is fun to watch through the telescope because the red spot is visible for 5 hours at a time. You can tell how long you've been out by watching it.
manulofdoom
Venus is an oddball, though. Not only is it way slower than Mercury, it also spins in the other direction, compared to other planets in our system.
destinychopsticks
Pluto is more of a real planet than you’ll ever be!! >:(
Aimoss
Poor Pluto ☹️
cousteau
Ackshually, a "day" in Mercury is about 176 Earth days, or about 4224 hours. Those 1408 hours are the time it takes the planet to complete one revolution (aka "sidereal day"). But that's not a "day" since by the time the revolution has finished the planet has completed like ⅔ of a "year" and it's not pointing in the right direction. Same happens on Earth - a sidereal day (rotation) is about 23:56 h, not 24h (with 366.25 rotations per year - 365.25 days plus one revolution around the Sun.)
CgnCalling
The sun rarely shines on Uranus
tasapisi58365
I heard a photon has a mass. So could the impact of light cause the rotation?
tasapisi58365
Also the orbits.
tasapisi58365
Cosmic rays from the other direction keep us in the orbit. Light causes gravity.
tasapisi58365
It's probably possible to travel in space. Just need to get far enough from the sun or other concentration points.
tasapisi58365
I realized this after micro dosing on fly agaric
RummageSaleBubbler
Fun fact: Each planet's day is exactly one day long.
fantabuloustimewaster
Mercury's spin is in a tidal resonance with its orbit, with three days per two years or suchlike. Compare to the Moon, which is in a one-to-one spin-orbit resonance, so that the same side always faces Earth. These resonances are enhanced by tidal forces. 1/3
fantabuloustimewaster
Venus is a mystery as far as I know. My understanding is that it's too far from the Sun to really be tidally locked. If it had been nearer the Sun and gotten locked in the past, its rotation would be prograde instead of retrograde. I have read "big collision" as a hypothesis. Venus also has a very young surface, which could be a result of a big enough collision. 2/3
fantabuloustimewaster
The giant planets have much more mass and formed from material from a much larger swathe of the solar system. The rotation of that material speeds up as it falls into the planet, like an ice skater pulling their arms in during a spin. Moons are material with too much angular momentum to fall all the way to the planet's surface and get incorporated. The Theia impact gave Earth a ring, part of which fell to the surface, and part of which "fell" away to form the Moon. 3/3
makeamericasmartagain9000
US Companies: we should move our production facilities to Venus and we are gonna pay the same monthly salary we do on earth.
teamsloth
In the case of Venus, a day is longer than a year. I understand its mostly due to the planet spinning the opposite direction of the other in the solar system.
RoombaTheAssaultVacuum
A day on Venus is longer than a year. It will complete a full orbit around the sun before it completes one rotation on its own axis.
ShadowTeller
Now take it one step further. ask if the earth's day has always been 24hours. Ask what the 3body problem is. @op :) there is amazing things, keep asking questions after you get answers, there is always more to learn and how things relate to each other. OO another good one I looked into, What role did/does Jupiter play in how Earth can have life on it?
iBoulderDash
Venus is a weird one because it actually rotates in the opposite direction of other planets, even if it does so very, very slowly. There's more than just tidal lock going here and astronomers aren't quite sure why.
sparkplay
There is also a theory about the reason Venus rotates the other way and it's that it had a massive collision with another planet/moon sized object. The new resulting rotation was slow.
Kotarisu
And combine that with the atmosphere having super-rotation, Venus is just a very crazy (albeit fascinating) place.
JonWallace1985
Two different reasons: Mercury is totally locked, like others said. Venus however was hit by something so hard it reversed its rotation.
giddisey
So a point on the equator of Jupiter is moving at almost 10x the speed of sound
TruckerKunIsekaiGod
Gravity from moons, general planet mass and densities, and moons mass and densities, relative distance from the sun, various other things but mostly Moons. Notice that the planets that have faster rotation tend to have moons. Mercury and Venus have no moons.
Jupiter has 95, Saturn has 126. These gas giants need more moons to help spin their mass.
Uranus has 28, Neptune has 14.
MediocreExtremist
* numbers = as we know so far
TruckerKunIsekaiGod
Yes, as we know so far.
cousteau
I am suspicious about the veracity of your statement.
manulofdoom
"to help spin their mass", what the hell, bro
TruckerKunIsekaiGod
I am sometimes not so good with words..
supercerealsteph
I wish I saw more posts like these- the question but also the investigation and then the community response. Good stuff!
rbudrick
Those day lengths are oddly rounded to the hour instead of showing hours+minutes. One example: Mars is not 25 hours. Iirc, it's something like 24 hours plus 37 or 38 minutes.
ChelVanin
Probably tidal locking. It’s the reason we always see the same side of the moon.
CrashOvary
Planets and moons get squeezed like squishy balls by gravity, and as they rotate the direction of squish changes. The friction from...
mikeatike
... that causes the rotation to slow down, eventually causing the same side to...
manulofdoom
...always face the sun or planet
OlivetheNerd
That’s a good point! I’ll have to do more reading into that.
EverNotRelevant
In brief, it's because of their relatively close proximity and enormous differences in mass. That's why Earth always sees the same face of the moon!
ChelVanin
Np
threenotch23
Tidally locked like the Moon to earth. I can’t explain how it happens though.
cousteau
Tide goes in, tide goes out (you can't explain that!), and all the water moving around the planet drags the planet and slows it down, is my guess. Also works with planets without an ocean, because the mere stretching of the planet is enough to dissipate rotation energy.
Enoan
Oversimplification: the gravity creates a bulge on the planet (on earth we see this as tides) and then that bulge gets pulled away by the planet rotating. Pulling something away against gravity takes energy, so the planet will slow down. Once the planet slows down to the point that the same side faces the other body (moon for earth, the sun for Mercury and Venus) there is no more tugging the bulge away and so it stays at that speed.
cousteau
Over-oversimplification: tide goes in, tide goes out, and as tide passes by the current drags the planet.
OlivetheNerd
Thanks for the answer! :)
CrashOvary
Planets and moons get squeezed like squishy balls by gravity, and as they rotate the direction of squish changes. The friction from...
CrashOvary
... The deformation generates heat, and that heat energy has to come from somewhere, and in this case it is from the rotational energy...
CrashOvary
Over long period of time the squishing of gravity zaps the rotational energy until it is eventually in phase with the orbit.
CrashOvary
I should add that I believe that this is kinda how it works, I could be wrong.
Ghlargh
I would call that tidal friction really.
Vega7285
You're on the right track, actually. It's due to a phenomenon called tidal locking. https://en.wikipedia.org/wiki/Tidal_locking
JimmyGTraveler
TIL!!!! Thanks
ArisCarroll
learned about this while playing the dyson sphere program to figure out where to put the dyson sphere and the receivers
TheCriticsWereConciseItOnlyTookFourLines
Yeah, same reason we basically always see the same side of the moon.
Ionico
Came to say this. Good work!
teamsloth
If it was tidal locking like the moon, there would be continuous day on one side and continuous night on the other. They would also have to show infinite on the first chart here as they wouldn't change. So I don't think this is correct.
Tenugui
+1 for critical thinking, but tidal locking isn't like two magnet faces stuck together. Even earth's moon has a bit of variation in the side facing earth, so over time we see about 59% of the moon's surface. Mercury has settled into a non-synchronous rotation, probably due to it's eccentric orbit. The mechanics of Venus are even weirder.
whatsisname
It takes time to get tidally locked, and it takes less time the closer together the bodies are. Mercury is tidally locked in a 3:2 resonance. Venus would be but isn't probably because of its energetic, thick atmosphere.
GravelordIncogNito
If it was just that, Mercury's day would be much longer than Venus'. Venusian day is so long because its global warming caused an atmosphere so dense that it slowed down the planet's rotation. So we've got that to look forward to.
Hevach
Luckily there's not enough carbon on earth to give us an atmosphere like Venus, even if we just lit all the wells and mines on fire in our dying spite. We're not entirely sure why it happened but evidence points to a cycle of catastrophic global volcanism in which Venus got a billion years worth of volcanic activity all at once somewhere around 500 million years ago, resurfacing the planet and megaloading its atmosphere.
Vonph
And I still won't get everything done that I need to, on any given day.
vindik8or
There's something more weird going on with Venus' rotation since it's actually retrograde and lasts longer than its year.
OlivetheNerd
Thank you for the response! :)
RanOutofWit
You're def thinking about things the right way. A rotating body in orbit around a more massive body is - well, part of it is "falling towards" the more massive object as it rotates towards it, and then "pulling against" as it rotates away, and then you factor in things like gravitational fields rotate with object, stressing against space, and then that the object they are orbiting is also rotating, so angular momentum kicks in as a braking affect and... yeah, I'm having another drink.
DavidBrooker
For added context, in the case of a tidally locked body, the term "day" is ambiguous. (It's actually ambiguous all the time, but more noticeably in this case). A sidereal day is the time it takes for a planet to complete a complete rotation, 360 degrees. For a tidally-locked planet, that is equal to a year. A solar day, meanwhile, is the time it takes to complete a cycle of day and night. For a tidally-locked planet, that occurs precisely *never*. A day is an infinite period of time.
AnonOmis1000
Well tidal locking is not limited to 1:1 ratio. I think one of the inner planets has a 2:3 ration of orbit to revolution
DavidBrooker
Tidal locking usually implies a 1:1 ratio. The term spin-orbit resonance is normally reserved for non-synchronous orbits.
AnonOmis1000
My bad
DavidBrooker
For reference: a solar day on Earth (one day and one night) is almost exactly 24 hours (it used to be exactly 24 hours, but since defining the second from atomic properties, the solar day now differs by about one part in a billion). Meanwhile, a sidereal day on Earth (one complete rotation of the planet) is 23 hours and 56 minutes, or thereabouts. It makes little difference day-to-day, but it's an important distinction for astronomy and other scientific fields.
Trustrup
4 minutes seems rather significant for our calendars.
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RandyKnapp
We don't use sidereal days for calendars