🎶 One of these things is not like the others
One of these things just doesn't belong🎶
Possibly the best thing about our solar system is that you could pick ANY PLANET as your oddball & be right.
Mercury: dead-on straight up, 0° tilt
Venus: sloooowwwwww
Earth & Mars: why the fuck are they so matchy-matchy?!
Jupiter: hefty enough it doesn’t orbit the sun; it co-orbits
Saturn: that tidy rotation speed? Not true for the whole planet
Uranus: sideways
Neptune: overly wobbly
Even measuring daily rotation of gas giants is a nightmare (because clouds), but Saturn is a bonus jackass of secrecy in aligned rotation & magnetic axes thwarting usual tricks.
*Venus: sloooowwww & backwards?!
Q: What about Pluto?!
A: Pluto orbits the Sun. Aside from that, EVERYTHING is weird:
1. Highly elliptical orbit (0.25)
2. Highly inclined orbit (17°)
3. Co-orbits Charon as a binary system (SO COOL! gizmodo.com/pluto-is-somet…)
4. Sideways
When I was a kid, I thought scientists had a handle on Why Planets. Exoplanets broke our formation theories, but we’d fix it.
Now I spend time marvelling that we say all this shit like we’re confident on what’s happening when really, who the fuck knows what’s inside Neptune??
Even more weirdness:
Mercury: day longer than year; warped spacetime of sun means you need to account for general relativity in its orbit
Venus: day & year are virtually the same length
Earth: big-ass moon is yanking on us so hard we’re slowing down to match it (eventually)
Q: Wait, what defines “up” & “flat” &&& ...?
A: This is delightfully complicated.
Sun defines center, its N pole points up.
Earth’s orbits defines an ecliptic plane that’s 7° from Sun’s equator.
Axial tilt is PER PLANET mismatch between orbit & rotation vs idealized 90°
Bonus confusion:
We sometimes use a different Earth-centric coordinate system to say where things are in the sky when we’re hanging out on our home planet.
The celestial equator is our equator projected into the sky, 23° mismatched from the ecliptic because that’s our axial tilt
And if we go looking at our whole Milky Way Galaxy? Our whole solar system is tipped 63° off-kilter.
Up is wherever the fuck we feel like pointing for this coordinate system & don’t stress too much because we’ll transform to a new one in a moment.
Most of planets are pointing & spinning in vaguely the same direction because of conservation of angular momentum*.
Mercury is the well-behaved child; all the other planets got in fights.
* probably. Look, we REALLY broke planet formation with exoplanets. Everything’s in flux.
But wait!
The terrestrial planets & gas giants have magnetic fields that mostly align with their rotational axis: compasses point roughly to geographic north.
But the ice giants Neptune & Uranus? Hahaha nope, they’re like 40-60° off.
Why?
Eh... it’d be cool to figure out?
It pleases me that if Pluto is joining the planetary crowd, so is Ceres. Can't pick & chose your dwarf planets, yo!
(Also: I so want Eris to join the crew, but although we think a day is just under 26 hours long we don't actually know its tilt...)
Q: Hey, why is Venus rotating backwards in the first animation, but upside-down in the second?
A: Venus is rotating exactly the same in both, it's just a matter of how you're thinking about "Which way is up?" when trying to describe our wacky lil solar system.
Planets are weird
Q: Surely we at least know our own planet really, really well, right?!
A: About that... we're still figuring out what's going on below the surface. Geophysics! It's an adventure.
nationalgeographic.com/science/2019/0…
Share this Scrolly Tale with your friends.
A Scrolly Tale is a new way to read Twitter threads with a more visually immersive experience.
Discover more beautiful Scrolly Tales like this.