"Imperfection clings to a person, and if they wait till they are brushed off entirely, they would spin for ever on their axis, advancing nowhere." -Thomas Carlyle
When you take a look up at the sky, the two most prominent objects are the Sun and the Moon.
And every day, like clockwork, they rise in the East and set in the West.
Why's that?
Because the Earth rotates on its North-South axis! Not only does it rotate, but it rotates from West to East, and that's why we see everything rise in the East and set in the West over the course of a day or night.
Image Credit: Phil Hart.
It gets better, though. If you rose up, above the Earth's North Pole, and looked down at the Earth as it revolved around the Sun, not only would the Earth spin counterclockwise, it would also orbit the Sun counterclockwise!
So you might ask what other objects in the Solar System do? We can start with the Moon, of course.
Just like you might expect, the Moon both orbits counterclockwise around Earth and rotates counterclockwise on its axis, so that the same side of it always faces us!
Fine, fine, you say. But what about the other planets? Isn't there some variety there?
Not a chance. Not in the least, in fact!
Not only do all of the rocky planets revolve counterclockwise around the Sun, and not only do all of the gas giant planets revolve counterclockwise around the Sun, but something like 99% of the known asteroids, kuiper belt objects, and comets also revolve counterclockwise around the Sun!
WHY?!
Stars -- all of them, as far as we know -- form when clouds of gas collapse. Since one direction will be shorter, that will collapse first, and so we'll get a disc. (Or, in our "complicated scientific jargon," a pancake. Yes, seriously, you say pancake to an astrophysicist and they'll know you're talking about this process.)
But this pancake isn't just going to sit there. In general, there will be an overall, bulk, rotational motion, due to the law of conservation of angular momentum.
So not only should the planets all revolve in the same direction, but if this idea is correct, the Sun should rotate counterclockwise, too!
And not only does it rotate counterclockwise, we can measure that rotation by following sunspots!
But you might decide to look at the individual planets, and see if they not only revolve counterclockwise about the Sun, but if they also rotate counterclockwise about their own axes, tilted or not. The results may surprise you.
Image credit: Calvin Hamilton, and click for a huge version!
While Mercury, Earth, Mars, Jupiter, Saturn, and Neptune all rotate counterclockwise, at tilts varying from less than a degree up to substantial, significant tilts, two planets stand out as weirdos.
Venus, rotating almost perfectly backwards, and Uranus, rotating on its side, are the unexplained bizarre children of our Solar System.
Unlike some Moons (like Neptune's Triton) that go backwards, we can't blame Venus and Uranus on gravitational capture. There are ideas out there, such as big collisions in the young Solar System, but there is currently no compelling evidence that favors any one theory over the other.
So almost everything in the Solar System revolves and rotates counterclockwise (from the North), but Venus? Uranus? We just don't get it, at least, not yet. Even in something as well-studied as our Solar System, we still have plenty of unexplained mysteries.
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Obviously it's because their names both end in "nus", an acronym for "Non-Usual Spin."
PLUTO! <3
.. sorry.
Good hypothesis, Squiddhy! Let's find a way to test it...
What about Pluto? You might want to mention that it has become tidally locked with Charon giving it it's unusual axis.
Before we knew much about Uranus, astrologers were singling that planet out as unusual. They were right but not for the right reasons.
Venus does not spin backward. It is placed upside down. :D
Check it out. If you roll it through 180 degrees and keep looking from above (north of the ecliptic) then the same ccw spin becomes a cw spin. So the real question may be what caused Venus to flip upside down. A really good impact might do it.
Ethan,
You are a born teacher! I look forward to reading you blog like none other - new ones just don't come fast enough.
So, is the whole universe spin neutral or not?
Well, in general, an agreement made between a minor and an adult is void. However, if the agreement was for necessities (such as food or an apartment) and the minor benefited from the contract for the necessities, that portion of the contract is enforceable on the minor. Also, if a minor signs an agreement, becomes an adult, and does not revoke the contract within a State-defined period of time after becoming an adult, the contract is considered assumed by the now-adult.
Actually, several asteroids have retrograde orbits:
http://en.wikipedia.org/wiki/List_of_notable_asteroids#Retrograde_and_h…
Also (IIRC) some long-period comets also orbit retrograde.
p.s. I think "Geneva escorts" posted on the wrong site.
Uranus and Neptune aren't really Gas Giants, though. They are Ice Giants; they are of markedly different chemical makeups than the two Gas Giants. Probes have also shown that Neptune and Uranus formed between the orbits of Jupiter and Saturn. It was the gravitational action of these two massive bodies that kicked them out to their current orbits.
We know the Earth was hit by a dense, Mars-sized planet early in it's history, working it's way in from L5, that ended up with the formation of the moon. If Venus had gotten hit by a slightly smaller, less dense planet, working its was in from L4 instead, that would be enough to reverse the spin without leaving enough left over material for a large moon.
Most races (be it humans, machines or animals) on a circular or oval track run in a counterclockwise direction. The exceptions being the Australian version of NASCAR (AUSCAR) and some European horse tracks.
The reason for the counter clockwise direction for some sport like NASCAR is fairly obvious. Since the driver is on the left side of the car (in this country at least) driving
Well the results of the two interpretations, backwards spin vs upside down axis, are the same. The usual system in astronomy is to define the north pole as being the one that lies above the invariable plane of the solar system, rather than defining north by the sense of rotation, which is in some ways a more sensible way to do things. In that interpretation Venus is the right way up (by definition) and spinning backwards.
This is northern hemisphere chauvinism. All these heavenly bodies rotate and cycle in the same direction but that direction is anticlockwise only when considering the north as up. If the Aztecs had conquered Spain and not the other way around we all would have said that they rotate clockwise.
Isn't there a huge problem with conversation of angular momentum in all of this? Assuming that the angular momentum of universe was originally zero (I'm not a cosmologist, but seems like a reasonable thing to suppose) then where is all the missing clockwise angular momentum? And don't say dark matter. ;)
d'oh. CONSERVATION above, obviously.
@Nir
Something tells me that Ethan has probably heard of relativity before. We all know that the spin is the other way if you look at it from the south. The point is, either way you look at it, the spin is the same all the time except for a few exceptions.
@Nir
If the Aztecs had conquered Spain, we'd all look at everything from the southern hemisphere POV.
Everything - including the clocks.
So we would still say that the solar system rotates counterclockwise, but we would mean the opposite direction.
People let's remember about different people in countries like this. Let's stop the war!
It would be interesting to know the solar system's orientation with respect to the galactic orbital rotation (or maybe the local neighborhood's motion). Is this sort of rotation more random or do solar systems tend to reflect the galactic rotational direction?
It seems that the majority of the matter in the solar system follows the sun's rotation (and probably the proto-solar pancake's rotation). I would guess that solar systems with respect to the galactic rotation are more random but the tendency would be that on average, more systems would rotate in the same relative direction as the galaxy.
Joe
@Geneva escorts and opony:
the condor flies at noon. bring your watermelon hamster.
Nir; DTH Greg: um... the Aztecs lived in the northern hemisphere. To equator runs through Equador. Perhaps if the Incas had invaded Spain... Or if Australians were in charge of manufacturing globes...
@5/christopher,
If I understand you correctly you're suggesting that Venus may have originally rotated ccw, but a collision or other event effectively flipped it upside down so its north pole now points south and vice versa.
I think this is exceedingly unlikely. Think about flipping a spinning globe upside down. Due to conservation of angular momentum it would require two perfectly matching forces (collisions) in opposite directions. The first would start the migration of the geographic north pole southward, and the second would strike at just the right place and time to cancel the angular momentum of the first once the poles are flipped 180 degrees. In the interim Venus would have a different axis of rotation.
I could be completely wrong about this (it's been ~20 years since classical mechanics) but I don't see any other way. If I'm wrong I'm sure I'll be corrected :)
Another interesting thing about Venus - its day is longer than its year (243 Earth days to 225). It may be rotating backward, but it is barely rotating at all.
OK, so far.
As well your recent Me At The Bar post shows that the stars of our Milky Way Galaxy rotate; but does not clarify if clockwise, counterclockwise or not aligned to galactic plane.
Furthermore, some suggest the alignment of spiral galaxies within superclusters. e.g., http://universe-review.ca/F03-supercluster.htm, 2nd figure figure 3-01b shows this. And also wiki, "the orientation of the spin axis of spiral galaxies is not a chance result, but instead they are preferentially aligned along the surface of cosmic voids"....???...But, I can not determine quality of the observation; and strength of this hypothesis. Clarification or comment, anyone please.
IIUC @DTK Greg, "clockwise" is actually DEFINED as a result of looking at the ground for celestial actions (the shadow of a stick planted in the ground (northern hemisphere here, for historic/cultural reasons), later transformed into mechanical watches with moving hands) which will automatically reverse the sense of rotation. Look the other way, you add one minus sign.
Venus' "inverted" sense of rotation is still an interesting enigma, I think. But maybe I'm just starstruck.
I've already presented counterexamples of retrograde asteroids.
At the risk of seeming to be (being?) a Prick, I present counterexamples to refute some other assertions.
Numerous comets orbit retrograde, the most famous being comet Halley:
http://en.wikipedia.org/wiki/Comet_Halley
Search for "retrograde" in the text.
These are considered to be anomalies resulting from interactions with Jupiter (or perhaps other planets).
One KBO is known to orbit retrograde:
http://www.cfeps.net/CFEPS/KV42_Press.html
(On the basis of the orbit given in the image, I hypothesize an interaction with Neptune.)
If 'we' ever detect a minor Trans-neptunian planet that orbits retrograde, I will (as is my right as a Prick) declare it to be an interstellar interloper.
@Trevindor 21:
Venus is an angular momentum problem no matter what: retrograde or not, a huge amount of angular momentum got lost somewhere. The only other planet with a really long day is Mercury's, and that's the result of a 3/2 orbital resonance with the sun.
Interesting but not directly relevant to this: Venus's sidereal day (period of rotation) is as described, but the solar day is about 116 Earth days. (That is, if an entity on the surface of Venus could see through the clouds, that's how long it would take from sunrise to sunrise.) A solar day on Mercury is 176 Earth days, and the sun's apparent motion is weird.
Uranus has an even more ridiculously long solar day, because of the axial tilt.
Well the rotational angular momentum of the planet is several orders of magnitude less than the orbital angular momentum, so at least it is plausible that collisions could be responsible for altering the planet's spin. This seems to be borne out by simulations of terrestrial planet formation: the rotation axes are essentially randomised during the final stages of accretion by giant collisions (rather like the one that is postulated to have formed the Moon).
Perhaps itâs safe to say that due to the sundial->clock face evolution, if the map-makers and clock-inventers come from the same hemisphere, then the solar system will run âccwâ, if they come from different hemispheres, it runs âcwâ.
I suspect those speculating on the Aztecs conquering Spain were thinking of the Inca. The Aztecs also lived in the Northern Hemisphere and would have the same view of "clockwise" as Europeans.
@Christopher beat me to it- who whacked those planets (Venus & Uranus) so far over?- and since I'm a Southern Hemisphere person, I like to think of everything going clockwise- they use less typing energy and waste less carbon in print!
re: Venus retrograde rotation, Wikipedia (for what it's worth) reports:
and
Venus is being contrary (just like a woman) while Uranus is being stubborn (just like an ass).
very strange and not perhaps a coincidence.... in all major religions also counter clock wise motion is performed as in hindu religion in marriage ceremony the bride and the bride groom go around the fire in anti clock wise direction, in mecca muslims go around the the stone anti clock wise ....
and the dancing dervishes also move that way
earth orbit and gravitational pull since the earths orbit is not completly round is it possable that the gravitational pressure is partly causing some earthquakes
the pull is strong enough to swing the earth around and if is not a constant that could explane changes is the magnetasphere to ?????
Hi
I want to know that " is Pluto planet or not because according discovery channel from 2006 Pluto is not a planet due to its some spacial character ,and it is known as DOT Planet
It seems that the majority of the matter in the solar system follows the sun's rotation (and probably the proto-solar pancake's rotation).
Ha-Ha, he said "Proto"
If political economies were discussed with the same liberation from ideological rigidity and humorous fascination with sharing curious facts as is demonstrated in this string of comments by astrophysicists and cosmophyles, there would be a lot more prosperity and less violence among humans on the planet. Thanks.
Or not.
You humans are weird.
:-)
"@Christopher beat me to it- who whacked those planets (Venus & Uranus) so far over?"
Its only the presence of the ovesized and nearby moon that's stopped our earth from flipping over.
Rotational instability is pretty much inevitable over periods of millions of years without something nearby that would soak up that disturbance.
So maybe the only weird thing about the two is that we see both being weird at the same time, but a period without one planet playing silly buggers might be fairly unusual.
NOTE: we're due to lose a planet in a hundred million years or so. Either Venus or Earth seems most likely, but that darned chaos is playing merry hell with the simulation.
@Joe Blow
I agree that :
"It would be interesting to know the solar system’s orientation with respect to the galactic orbital rotation (or maybe the local neighborhood’s motion). Is this sort of rotation more random or do solar systems tend to reflect the galactic rotational direction?"
The rotation of the solar system, and of Earth are quite different from the rotation of the galactic plane. It's always a pleasure to prove this: the milky way does not run along the equator.
Perhaps someone will fill us both in as to the behavior of the rest of our galactic neighbors...
can you solve this question ??
What will happen to these two periods if Earth were to revolve clockwise around the Sun and the Moon clockwise around Earth? Which period will be shorter or longer than the other one
Venus has a thick atomospher solid cloud that is 72-79km the surface is not visible.In that case it slow rotate and backwards.the surface of the temperature does not change day to night.Venus has no magnetic field detection that lack of Iron-core wich develop magnetic field.so it retrograde.
Uranus the only planet lies on side.in the angle of inclination 98 degree verticals.it is nearly parallel to the other planets
Loard Budhdha has said whole world is in our body. Actually we can say all thinkings are in our mind.There are lot of thinks to do.
We're told that we always see the same side of the moon. I'd like to know if that is true over a long period of time. Are its rotation and revolution so perfectly synchronized? If so, what's up with that?
@ Michael Rowan
That crystal ball you got at Spencers costs $19.95. Who are you, MIss Cleo?
Humanity got so good at hunting that it became boring. Being that we are, by nature, violent predators we started raiding other tribes. Those tribes turned into City-States and then Nations. In the midst of all that there was the creation of warfare.
Your doe-eyed naivity is adorable but the fact is the human races [plural, we are a species collectively and not a ''race''] don't want to get along. You can blame poverty, religion or whatever but it all boils down to the fact that we are a warrior people and, here's the kicker, especially the more money we have. Open a history book and read about Rome, Spain, Britain and now...the USA. We've been in a constant state of warfare since the end of ww2.
While we all love to have money, whether it's just enough to survive on or whether we hop continent to continent in a private jet...we're still the same vicious animals we've always been.
And talking about these things is usually a first step to war. Fingers get pointed and before you know it you're picking your family member's body parts out of the ashes of what was once your home.
And this discussion isn't a waste of time. The clock is ticking for the entire solar system. The only way survive the system's demise is to find new worlds that can support our biology. These studies, while ancient, didn't really progress until recently. Understanding our own solar system is the first step to understanding the rest of the universe. And that can lead to the survival of our species. But hey, thanks for the pretentious preaching, anyway. Always love to have someone wagging their finger in the face of one of our most important groups in the long run...scientists, astronomers specifically.
Informed people are a treat.
On the other hand there are the uninformed.
There is recent "info" that 1 in 4 do not know about the earth's rotation.
So I conducted my own survey - frightening!
What were these people doing in class?
It could be because the two planets are bigger
Nir commenter (#12) said: "This is northern hemisphere chauvinism. All these heavenly bodies rotate and cycle in the same direction but that direction is anticlockwise only when considering the north as up. If the Aztecs had conquered Spain and not the other way around we all would have said that they rotate clockwise."
Hate to break it to you, but the Aztecs as well as Mayans were also in the Northern Hemisphere.
This article left Pluto out as another body in the solar system that rotates clockwise as well as 8 moons that rotate the opposite direction of the other six planets. This is no mystery at all; just proof that the big bang theory is total bunk, unless you think it's likely that asteroids or comets from outside of the solar system just so happened to have hit 12 bodies in the solar system... and instead of destroying them or knocking them out of the solar system just made them spin backwards.
@Clay Rains #50: What an amusing non sequitur. And an equally amusing ignorance of astrophysics. "Hitting" is most definitely unnecessary to change angular momentum. The various moons (many more than eight!) which either rotate or orbit retrograde are late captures, rather than having formed contemporaneously with their planets.
Your theory makes perfect sense.
Never read any thing wiser than your
Perfect Sense Theory.
Which direction does saturn spin
I find this blog really helpful. fanx
you talk of things you've never seen and have no real proof of, you could at least have some decency and state that you just spit out what you have been told.
questions:
If moons rotate AND orbit, why is there only one side of our moon that is ever visible from the earth - no matter which hemisphere we view it from?
Also, Isn't it possible the sun does not rotate as everything orbits around it?
If the view of the sun's face changes, isn't that because we are in constant motion circling it?
m.j.c.,
You can answer your first question yourself. Place an object in the center of a room. Walk all the way around the object without rotating. To ensure that you don't rotate pick out an object hanging on the wall opposite where you started and make sure you keep facing that object. You will find that you cannot see the object at the center of the room during most of your "orbit". IOW, you have presented DIFFERENT sides of yourself to the central object. In order to present the SAME side of yourself (the front side where your eyes are), you must rotate yourself so that you can no longer see the object on the far wall at all times. In fact, you must complete one rotation per "orbit", as evidenced by the fact that after the far-wall object disappears from view, you will only see it again when you have returned to the point from which you started.
As for your second question, if the changing features of the solar surface were due only to the revolution of the earth around the sun, we would see the changes occurring at a frequency of once per year. In actuality, the frequency of the periodic changes is much higher, so they cannot be due to revolution of the earth and must be due to the rotation of the sun.
I need help with a question. Which direction does Saturn spin.
The vast universe, and there may be more than one, but probably not, and all it contains, all the solar systems, stars, galaxies, all came from some "bang" i.e. "nothing" --- then where did the (so-called) "bang" come from --- talk about arrogance, scientific deception & denial. Go read about Galileo & Scientific Method (I'm not advocating approval of ANY earthly building, church [small 'c'], or group of people) --- I'm just thinking of a really great circa 1996 book: 48 Biographies of Historic Scientists and Their Christian Faith.
It didn't "come from" the big bang. Where did the big bang itself come from? Where does the darkness come from when you switch the light out, John?
We KNOW about the scientific method AND Gallileo, we've read all about it. What do you mean to have changed when we read it? The arrogance of the church wanting what they already know to remain only within the elite?
And what about scientists and their christian faith? If we can presume anything from it,we would have to presume that knowing what the hell is going on, looking into what makes things work in real life, causes you to abandon the need of a god to "explain" it all.
Also, think on how many religions and churches there are, only one of which, at most, can be right, yet all making the same claim of divine revelation. What does that tell you about arrogance, when so many claim, and must be wrong, that the One Big Brother of the Universe came ESPECIALLY TO THEM to tell them what is "Really Going On"?
Venus was flipped over and Uranus was knocked on his side