Mars, Mercury May Have Formed From Earth and Venus 73
goran72 sends along a report on a radical new theory of planet formation that suggests that Mars and Mercury were formed from the scraps of Earth and Venus. The theory has testable predictions — for example that the compositions of the rocky inner planets should be more similar than the current theory of planet formation would have them.
And Hot Jupiters? (Score:3, Interesting)
Re:And Hot Jupiters? (Score:4, Interesting)
Very true but the 4 inner planets have almost circular orbits.
Any planet that get flung around will have a very eliptical orbit.
The Hot Jupiters are a different thing. They are caused by the system having enough material to cause drag and slow them down enough to collapse the orbit.
Re:And Hot Jupiters? (Score:5, Interesting)
Very true but the 4 inner planets have almost circular orbits.
Any planet that get flung around will have a very eliptical orbit.
Orbits get circularized by a number of effects over time, both orbital and viscoelastic coupling. Hot-Jupiter orbits somehow get circularized, after all, and they're much harder to circularize than smaller planet orbits.
The Hot Jupiters are a different thing. They are caused by the system having enough material to cause drag and slow them down enough to collapse the orbit.
Any process that can move Jupiter and super-Jupiter size planets will easily reposition smaller planets.
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How do we know that our system didn't have a Super Jupiter that was gobbled up by the sun sometime in the solar system's past.
A super Jupiter being gobbled up by our sun could have caused a mass extinction in earth's past.
It would probvably cause a lot of radiation to be released by the sun and some quite large coronal mass ejections.
Just because we don't have one now doesn't mean we didn't used to have one.
Re:And Hot Jupiters? (Score:5, Informative)
Jupiter sized planets can only form out past the "Snow line" where water can form ice. Otherwise you get terrestrial planets that max out a few times bigger than earth.
When a jupiter sized planet moves into a terrestrial orbit it EATS the planet already there.
Since the earth is still here, no hot jupiter ever existed in sol system.
LOLplanets (Score:2)
When a jupiter sized planet moves into a terrestrial orbit it EATS the planet already there.
Om Nom Nom Nom
http://boingboing.net/images/cookienebula.jpg [boingboing.net]
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Anything that moves a super-sized planet will eject smaller planets from the system.
The hot-jupiter orbits start circular and are slowly spiralled in.
Actually, most eccentric orbits will be maintained. Only specific conditions will circularize an orbit and most eccentric orbits that get curcularized become unstable in the process.
It is very unlikely that the inner planets moved much with the possible exception of mercury.
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Anything that moves a super-sized planet will eject smaller planets from the system.
Experimental evidence strongly suggests that there are no hot Jupiters in the solar system. Therefore, motion of hot Jupiters did not in fact scatter inner planets out of the solar system because our solar system does not have any hot Jupiters.
However, the process by which hot Jupiters are repositioned also can reposition smaller planets. There's nothing special about Jovians that allows them to move but forbids smaller planets to move. The observation of hot Jupiters is a evidence of a mechanism that m
Re:And Hot Jupiters? (Score:5, Interesting)
Eccentric orbit's are destabalized during the process of circularization which then either ejects them OR crashes the orbit. But it is also true the eccentric orbits tend to be a bit more stable than true circular ones...but only a little.
I never said the sol system had a hot jupiter. But it had been cited in the grandparent therefore I was adressing the issue. Hot Jupiters happen in specific conditions where the gas that formed the original system was thick enough to not get blown away quickly. Therefore the jupiter sized planet, with it greater porportional size and gravitational field effect due to lower density, are disporportinaly slowed through friction. As they slow they eat or eject all inner planets until they get close enough so that the solar wind HAS cleared everything out.
The sol system did not have these conditions therefore no hot Jupiter.
With the higher density but smaller size of rocky planets they are not as likley to experience the slowing effect before they clear the neighboring space therefore any moving will probably be due to colision or near collision with other large bodies and will be entierly random.
The reason Venus, Earth and Mars probably haven't moved is because the planets chemistries match theory fairly closely. Planetary genesis theories suggest that there will be subtly chemical differences at varius altitudes from the star. Mercury has unexpected chemistry which could come from collision (there is evidence for such an event) or being moved
Re:And Hot Jupiters? (Score:4, Insightful)
Eccentric orbit's are destabalized during the process of circularization which then either ejects them OR crashes the orbit.
I can't make any sense out of this statement. "Circularization" is by definition decreasing the eccentricity of an orbit. Decreasing the eccentricity of an orbit will not "eject" or "crash" the orbit; you have to increase the orbital eccentricity to do that. You can't "destabilize" an orbit by "circularizing" it; the two things are opposites.
But it is also true the eccentric orbits tend to be a bit more stable than true circular ones...but only a little.
I have not the slightest notion what you mean here. Circular orbits are not unstable! About the most you can stay is that circular orbits are "destabilized" into elliptical ones, but I can't see how that makes them "less stable" that orbits that start out elliptical in the first place.
I never said the sol system had a hot jupiter. But it had been cited in the grandparent therefore I was adressing the issue. Hot Jupiters happen in specific conditions where the gas that formed the original system was thick enough to not get blown away quickly. Therefore the jupiter sized planet, with it greater porportional size and gravitational field effect due to lower density, are disporportinaly slowed through friction.
I don't know what model you're assuming, and I don't know what you mean by "disproportionately" or what sort of scaling law you're assuming. About the best I can say here is that it is extremely model dependent.
As they slow they eat or eject all inner planets until they get close enough so that the solar wind HAS cleared everything out.
The sol system did not have these conditions therefore no hot Jupiter.
With the higher density but smaller size of rocky planets they are not as likley to experience the slowing effect before they clear the neighboring space
about all I can say is that this is extremely model dependent. If the small rocky planets are clearing their region, as you note, the amount by which they move in reaction is going to be inversely proportional to the planet's mass, and hence smaller planets will move more, not less. Have you actually calculated a scaling law? It will depend on what you assume to be the dominant effect, but it's not at all clear that the mechanism vanishes with small planets.
therefore any moving will probably be due to colision or near collision with other large bodies and will be entierly random.
Random, yes.
The reason Venus, Earth and Mars probably haven't moved is because the planets chemistries match theory fairly closely. Planetary genesis theories suggest that there will be subtly chemical differences at varius altitudes from the star. Mercury has unexpected chemistry which could come from collision (there is evidence for such an event) or being moved
There is not enough chemical knowledge of the composition of the inner planets to definitively base this statement on experimental data. (Venus in particular is very poorly characterized). The chemistry seen on the surface is highly affected by the planetary differentiation (that is, what got segregated to the core), and we currently know little about the cores of Mars, Venus, or Mercury.
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the moon formed extremly close to it's primary and that regularized it's orbit. In addition it formed out of an accretion disk created by the impact. These discs spontaeously circularize due to internal collisions.
A better example are the moons of mars. They were both captured and both have a moderatly elliptical orbit.
Your argument is exactly the same argument I am making. Planets that form out of an accretion disc will have regular orbits. Planets that are moved to there current position will tend to
Oh great! A planetary scandal! (Score:4, Funny)
Venus and Earth are not even married! And now they are trying to say that Mars and Mercury are illegitimate children of a lesbian union of planets?!
NO! I will not accept it! GOD DID IT! Things are the way they are because God did it that way and need no further explanation!
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It's even worse than *that*!
Earth and Venus are known as "sister planets".
And as hot as that is, I'm still going to have to disapprove.
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DOG demands that you believe without question.
DOGMA requires you to follow without sight.
DOGMATIC insists that you do it by ritual.
When followed none of these allow you to question the nature of things, you should accept them blindly, with faith and tolerance for those who do not.
Anyway, when whatever you believe proves wrong, just rephrase it.... We didn't mean that the earth was flat and the center; we meant that the earth is so great that it seems flat and its the theological center......
Where do planets come from? (Score:4, Funny)
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No. Not really.
You missed it by 3 minutes.
Not sure about their "problems" (Score:3, Interesting)
If the rocky planets formed from a homogenous debris disk, they should all be roughly the same size and orbit the sun in similar circular orbits, Youdin explained.
Uh, why? The disk varies with distance in the standard model. (Orbital speeds, density, composition, etc.) So you wouldn't even really expected the planets to have the same size.
Armitage agreed. "In the standard model the composition varies with distance from the sun," he said.
Huh, that's odd. There was work done about a decade or so ago that said the opposite: there was enough mixing between planetismals in the inner solar system to largely homogenize the compositions. But, then, Phil is an expert in this, so maybe more recent simulations have quashed that.
Re:Not sure about their "problems" (Score:5, Insightful)
Also, I wonder how they get the protoplanetary disk to break up into bands. Saturn's rings aren't really banded as much as you might think. The degree to which they are is largely due to moons (or their on-going generation). Left to themselves, the rings should spread and homogenize.
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The comparison to the rings of Saturn is useful, but not completely germane. The banding of Saturn's rings is more akin to
Re:Not sure about their "problems" (Score:4, Interesting)
Actually, it's the reverse. If you put a planet in the disk, it tries to open a gap. (See the Keeler and Encke gaps in Saturn's A ring for examples.)
So that's not it. (And besides, it sounds like these guys are positing the bands form FIRST.)
Makes sense (Score:1)
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Gas. Lots and lots of gas.
It's very windy there too.
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Well John Gray [amazon.com] is more of a computer scientist then an astronomer. (He is a really good professor too)
inner composition of mars (Score:2)
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You know what? (Score:1, Flamebait)
All of the planets formed in the general vicinity of the sun from the same materials. OF COURSE, their cores should have a similar makeup, THEY ALL SHOULD! This does not prove anything.
These stupid astronomers need to get a real job.
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Why would they be the same material? Why is the disk homogenous? The temperature gradient and dynamical gradients could, in fact, cause the disk to differentiate.
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Sort of. The real effect is in what is solid enough to accrete. Gases don't participate, which is why you find so little hydrogen compounds (water, methane, ammonia) in the inner solar system relative to what you would normally expect and why the giant planets are, well, giants.
I don't believe as it's currently thought that the proto-Sun had a wind during the planet formation stages. If there were, it'd surely hamper the process. (Eventually, it would have done so when it cleared out the system.)
Oh, my... (Score:2)
Re:Falsifiability (Score:4, Informative)
Last I checked, the solar wind isn't a stream of electrons.
It's roughly equal numbers of electrons and protons [utk.edu], as I recall, with a very small amount of helium nuclei in the mix.
Some good graphs here [solen.info]
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I wish I had mod points today, thanks for posting that. It was an excellent and constructive criticism.
Haha, that didn't stop the mods from deciding that a post about problems with astronomy during a discussion about astronomy is somehow -1 Offtopic. Ah well, it wouldn't be the first time someone was just a little too eager to find an excuse to dismiss or silence me or any other critical thinker. I hope others react to that the same way that I do, which is to realize that these are small-minded men who are easily threatened when you challenge their pet beliefs and that therefore, the worst thing you could
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You're probably right. I know a few plasma physicists who would agree with you that field lines aren't frozen in. However, it's a good simplifying assumption that may help you explain other phenomena. You just have to keep that in mind when you apply it.
Electric Universe Crack Head. (Score:1, Informative)
Re:Falsifiability (Score:5, Insightful)
The Structure of Scientific Revolutions [barnesandnoble.com], Thomas Kuhn's magnum opus, should be required reading before engaging in a debate on science. There's an aphorism that goes "all theories are wrong, but some are useful." We can and do use theories we know have flaws because in the vast majority of cases, they predict and explain what happens in nature. When a better theory comes along to explain the observations, we begin to use that one instead.
It's absolutely useless to say "this theory is wrong!" as long as the theory, however flawed in some cases, works well in the general case. What do you propose to replace it? Does your replacement make specific, verifiable assertions about nature that are more correct or accurate than those of the prevailing theory? I thought not.
(On the off chance that it does, and you can provide evidence, please, submit an article to Science or Nature; you'll be famous for generations.)
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"All theories are wrong, but some are useful."
That one's a keeper. I like it; it may just go up on my wall of quotes.
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I drank what?
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This is an ideal that quickly falls apart when the effective message from government and private funding is "you support the mainstream theory or
Re:Falsifiability (Score:4, Insightful)
The more petty among you will read what I said and decide (entirely without consulting me) what alternative theory I believe in and will probably proceed to make a contest of it because you cannot grasp the simple essence of "this is an open question" and therefore cannot conceive of anything except one ideology versus another. It's alright not to know; sometimes there is great freedom in it.
The problem with just "not knowing" is what do you do then? I agree we shouldn't treat these theories as absolute truth, but that doesn't mean they're not useful. The scientific method works by making a hypothesis, making predictions from that hypothesis, testing them, and modifying the hypothesis if necessary. But you have to start somewhere. Make some guesses, even if they're bad guesses. If you just shrug your shoulders and say "I dunno", you'll never get anywhere.
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It means you try as many different alternatives as possible and as each one fails (that is, as you find the limitations of each), you get rid of it instead of making ad-hoc modifications to save the theory. This is childishly simple. There is no need to create this big mystique around it which amounts to pretending like the broken system we have now is the only possible way to deal with these questions. In fact you could say that the real "trium
Re:Falsifiability (Score:5, Insightful)
Your comment on frozen lines in plasma not withstanding. Its an approximation, that works well for a lot of cases. And anyone in the field will tell you that. Newer models allow this to be relaxed more and more. But really it doesn't change things that much with typical astronomical plasmas.
And the different redshift thing? Could you be more specific? There are really no theories that predict the comsmic microwave background and isotope ratios other than the big bang. Which also leads to the standard red shift interpretation. There really nothing else we have come up with that works. We have just have so much red shift data now. There really are no alternative that explain this without some serious arm waving.
and are humble enough to admit that maybe you don't know
I'm sure you are humble enough for both of us.
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The rest doesn't merit a response because you are either interested in finding your own answers or you are not, but they are the type of issues that are fairly easy research topics. This one line was something I wanted to comment on, however, and that was just to ask a rhetorical question.
Do you not see how manipulative that is? You don't like what I say, that's fine, I never asked you to nor did I ever expect you to. But to call my character into questio
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So why do you imply that I'm not humble? Because I know how to think critically? Because I question instead of taking knowledge on authority (establishment science, if nothing else, is an authority)? Because I am unashamed of both of these things?
Why do you imply that others especially those who disagree are not also humble, think critically and don't go blindly with authority?
I'm guessing you don't have a reason at all, you just don't like that something I said had an unsettling effect on you and you thought you'd take a poke at me because of it. You will never find joy that way.
That is called trolling. Not the t
Re:Falsifiability (Score:4, Insightful)
Then, perhaps you should elaborate in what alternative you believe in instead of making pronouncements about how wrong a theory is without offering a more valid alternative.
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Then, perhaps you should elaborate in what alternative you believe in instead of making pronouncements about how wrong a theory is without offering a more valid alternative.
That's just it. I don't have all the answers either, nor did I claim to. See, you sound like you just can't stand admitting that this is the case, which is why if I poke holes in your favored theory, you immediately demand that I give you something with which to replace it. That's what religions people do; I expect more strength than that from science. That line of mine that you quoted, it was put there for the sole purpose of avoiding the request that you have made anyway. There are many theories. Pe
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That's just it. I don't have all the answers either, nor did I claim to
In other words, you don't know and so you think other don't know either. Your failure to recognize or accept evidence or a theory does not invalidate the evidence or theory. You argue from ignorance.
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I'm consulting you. Which alternate theory do you actually believe is closest? I'm curious as to which theory doesn't make any assumptions, since you've basically said that assumptions make theories worthless. A theory that doesn't require any assumptions must have all of the possible questions already answered, and so everything is must be figured out. I don't think I'm the only one who'd find learning about that very interesting.
Trying to modify existing theories to match new data isn't inherently any mor
Re:Falsifiability (Score:5, Informative)
When astronomy has a crisis in the next 5-10 years or so, perhaps most of you will be surprised. For a good starting point to see what I am talking about, do some research on black holes and what Schwartzchild really said vs. what is commonly attributed to him in colleges and textbooks everywhere (ask yourself if the most amateur of journalists would report so inaccurately). Or research Edwin Hubble and the fact that there are two equally valid interpretations of the redshift equation and we have settled the question of which to use by making an assumption. Or explain to me how a star that is powered by an internal thermonuclear reaction could have an atmosphere that is many times hotter than its surface (if you think that's a simple matter, you do not appreciate the question). Or why it is that a steady, flowing stream of charged particles is called an electric current everywhere it is found, unless those charged particles come from the sun and compose what is called the solar wind? Or why Hannes Alfven, the originator of what is now called magnetohydrodynamics, has thoroughly discredited his own theory, including during his Nobel Prize speech (especially the part about magnetic field lines being "frozen" in plasma), yet scientists continue to use this discredited theory to come up with fanciful ideas like "magnetic reconnection"? It's time to come up with new ideas instead of unscientifically shoring up old, failed ones in the name of preserving your funding.
The first two statements are insinuations and don't actually say anything (I'm not going to spend many hours reading Schwartzchild, Hubble, etc based on a vague insinuation). As for the high energy of the Sun's corona, the entire Sun is a rotating ball of plasma with strong magnetic fields and a power source in the center. That makes numerous opportunities to create highly energetic particles and throw them out. A steady flowing stream of charged particles is not an electric current because we haven't assertained the most important characterist of a current, namely that there is a net flow of charge. For example, water is a flowing stream of charged particles. However, the charges are tightly bound to each other so there's no EM effect until you almost touch the water. The Solar Wind contains a lot of charged particles, but it is electrically neutral, there is no net flow of charge. It is a plasma without an electric current.
Hannes Alfven hasn't "thoroughly discredited" magnetohydrodynamics. And "appreciating" a question like "How did the universe get here?" doesn't mean the question is well-defined. It implies that there's some process that makes universes. There may well be no such thing.
Having said that, you have mentioned a large variety of subjects: the Sun and its plasma environment, black holes, origin and current dynamics of the universe, and plasma dynamics. A lot of that we really don't have a good grasp on and it is likely that we'll see serious challenges to our understanding of these phenomena.
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> And if it's like any other mainstream astronomical theory, the testable predictions really won't matter. At all. If those predictions are found to be false, they'll just make a long series of ad-hoc modifications to the theory in order to "save" it instead of seriously questioning their worldview/paradigm/framework (whatever you care to call it) because of the pseudoscientific disaster that astronomy has become.
That's true of any institution -- it eventually becomes self-serving to maintain the status-
Book to be written (Score:2)
New book title coming soon: Mars is from Earth, Mercury is from Venus.
Re:Book to be written (Score:5, Funny)
Mars is from Earth, Mercury is from Venus.
...and methane is from Uranus.
Sorry..
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"Mars is from Earth, Mercury is from Venus. ...and methane is from Uranus.
Sorry.."
No. No, you're not sorry.
Not at all, you cheeky little monkey!
Mr. Darwin the planets are breeding (Score:2)
The earth and venus were fucking and made the stupid war and speedy communications and shit what do we DO!
"No worries I have my SUPERNOVA OF NATURAL SELECTION"!!!!
Wait, earth wasn't (Score:2)