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New Study Supports Controversial Theory of Rapid Planet Formation
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Posted by: Ion Silverbolt
A new and powerful computer model shortens the theoretical time it takes to build a giant planet to as little as 300 years. The result could help explain mysteries of our solar system as well as some of the hundred or so planets found around other stars.
Planets larger than gaseous Jupiter and as small as icy Neptune might form in just centuries around a newborn star, the calculations show, compared to the millions of years astronomers once thought.
Source: Space.com
Posted by: Bored
I always said 4.6 billion years was about 4,599,993,500 too long.
Silly scientists. They're getting closer though...
Posted by: redwench
um, the earth isnt in the above category. we are not a giant planet, with the very high gravitational forces that would go with it.
Posted by: Bored
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um, the earth isnt in the above category. we are not a giant planet, with the very high gravitational forces that would go with it.
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Perhaps, but that's one screwed up curve if small planets and giant planets form in mere centuries while planets about the size of Mars, Earth, and Venus form over millions and billiions of years. In fact it is concave up: a discontinuity. Since real space-time is continuous one can only conclude that something is still wrong with the measurements or the theory.
Since the theory seems to describe small planets and large planets, and since the laws of nature are the same everywhere and for all matter and energy, then there is no physical reason, classical or reletavistic, that an "average" planet should take eons to form while extremes take no time at all. That's like saying you made a "big" snowball before you ever had a medium one. It had to be "medium" before it was "big". Therefore medium planets ALWAYS form faster than big planets. Its simple logic and common sense, combined with one of the first rules of dating rocks and other formations: an object is younger than anything it contains. A big planet contains all the matter that used to be a medium planet...
And of course a "medium" planet will form in a large cloud in less time than it would in a medium cloud, but according to Newton's laws of gravitaion this has nothing to do with the more powerful "gravity field". Its simply that if you have more "stuff" then stuff is more likely to collide with other stuff and stick.
If you are observing the gravity field from afar then it is already at exactly the same state that it always has been and aways will be(neglecting motions of the solar system(s) for the moment). If you are a particle in the center of the field there is NO net force on you, ACCORDING TO NEWTON, since you are not affected by the mass, or gravity, of particles that are outside the shell level you are at, which happens to be 0m in this example! So "local" gravity has nothing to do with the speed of planet formation, and the man that proved it has been dead for hundreds of years.
Posted by: redwench
"large planets form by sudden gravitational collapse rather than by building up gradually from rocky cores."
the earth, according to theory at least, was formed via the latter process. if this new theory holds true, giant planets are formed via the first process. different processes can indeed take different amounts of time.
Posted by: Bored
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large planets form by sudden gravitational collapse rather than by building up gradually from rocky cores."
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I know this isn't your oppinion, its that of one of the scientists on the team working on this theory. I'm just going to point out that there are actually whole teams of scientists that waste millions of dollars chasing theories that are not fundamentally sound, and from what I saw this is one of them.
Newton's Shell theorem:
1, An arbitrarily uniform spherical shell of matter attracts a particle that is outside the shell as if all the shell's mass were concentrated at its center.
2, The same arbitrarily uniform spherical shell exerts no net force on a particle located inside it.
Read that very carefully, and draw some models on paper for various sized dust clouds, and it will become obvious that gravity has nothing to do with the rate of planet formation.
Posted by: redwench
except it only applies to shells, which is not relevent here. also note the uniform part, which would be unusual in itself. the only point at which there is no net force in a distributed cloud of matter, would be the gravitational center (which may or may not be the physical center). all other points would experience attraction towards the gravitational center, since more matter would be in that direction.
Posted by: Bored
Ok, what I'm trying to show you is that the graviatational process works at exactly the same rate regardless of the mass or density of the cloud. And yes, all points are attracted to the center, but the ones that are already close to the center are attracted as if the rest of the matter did not exist. Which is why I'm saying the rate of formation is constant regardless of size. Shells are always relevent in solar systems and planetary formation because most of the matter is still in the form dispersed dust even in very old systems.
Draw a set of concentric circles on paper and put a dot at the center. Now the small circle is a model of the dust that may form a small planet, and the large one is a model of the extra dust needed to form a large planet centered on the same point.
Let all the matter in the small circle have mass M, and the matter in the outer shell has mass N. Then regardless of whether or not N actually exists, M will be attracted to the center at exactly the same rate. Even if N exists it cancels its own gravitational infuence on M.
To further visualize this divide the the circles along an X and Y axis and treat each point where an axis crosses the N shell as though it were the "center of mass" of one quadrant of the shell. Draw a point on the M circle and lable it P. Draw vectors from P to each of the axis intersections on N to show how each N-quadrant's gravity effects M. If you do the vector math and trigonometry with high enough precision the total force exerted by N on any point inside M will be zero no matter how many times you divide N up and no matter what points you choose inside M.
The shell theorem also works for highly irregular objects, simply make each shell a scaled down version of the original that is irregular in the exact same way and "parrallel" to the original.
Posted by: redwench
not quite true. the shell theory is used as a convenience when calculating various and sundry things for matter outside the shell, because otherwise, you need to get into rather nasty differential equations. but once you move to the edge of the shell, you cannot use those nice simple equations anymore.
at any rate, the more matter that is inside the shell, the faster it will attract material from outside the shell, and indeed the faster the "shell" would collapse. gravity is usually considered to be constant on earth, although it is not. the gravitational force between two objects is directly related to thier mass, and inversely related to the distance. therefore, higher mass will attract more matter more quickly. which would lead to a faster formation.
Posted by: Bored
Well, the only thing I can do at this point is suggest further reading on the subject of gravity.
F= G(m1m2/r^2)
Where G is the gravitaional constant. Actually the gravitational constant is nothing of the sort, but that's another topic in itself.
Books to read:
Black Holes: A Traveller's Guide.
By Clifford A. Pickover.
Covers a wide variety of misconceptions about gravitation and black holes, if you can get past the author's corny illustrations. Also introduces simple computer modeling techniques. Everything in here is useful when modeling planet formation.
Superstrings and the Search for the Theory of Everything
By F. David Peat
Really advanced info simplified to conceptual models. Addresses the unification of the 4 basic forces as well as attempts to relativize quantum theory. Loads of info about gravity and and other force interactions.
Fundamentals of Physics: Extended Fifth Edition
Halliday, Resnick, Walker
College physics text. Covers everthing you could ever want to know about physics on at least an introductory level, and often at a very advanced level too. Practically everything in there is directly useful when considering planet formation. Has a very large unit on gravitation, and returns to the subject in the relativity section as well.
Posted by: Null Actor
So out of curiosity, how many PhDs do you have, Bored?
Cause last I checked, accepted scientific theories can be disproven given enough time. Assuming that every scientific law that exists is absolute is a good way to halt scientific development. Especially in physics.
Posted by: redwench
and of course, the authors of the new theory (which may or not be correct) are completely unfamiliar with the laws and theories that are in those texts.
by the way, the amount of time it takes to get a book published in the scientific field is so high, that in certain instances, even a newly published book can be out of date by the time you read it.
Posted by: SpaceGhost
Hmmm, just read the article. It doesn't actually mention planets smaller than the Earth . . . it says "as small as icy Neptune" which isn't exactly a small planet when compared to Earth.
I'm not even going to start into the scientific discussion about gravitational shells except to say that for objects inside a shell not to feel gravity requires the shell to be completely uniform and spherical . . .
Posted by: The_Turks(ff7)
Man you people need a life....
who bloody cares how long a planet is created. its not like we are going to migrate to another planet in our lives.
Posted by: redwench
sorry, some of us find science to be inherently interesting, regardless of a practical application or lack thereof.
Posted by: The_Turks(ff7)
just out of curiosity, has there ever been a astronomy/planet scientist that actually went into space?
Posted by: redwench
For the first time, astronomers have obtained an accurate measurement of the mass of a planet circling another star.
The planet is one of a pair that orbit Gliese 876, one of the closest stars to our Sun, and the closest star around which a planet has been found.
By accurately measuring the motion of the parent star across the sky, the astronomers have been able to pinpoint the planet's orbit and hence its mass.
The planet, called simply Gliese 876b, has been found to be about twice as heavy as Jupiter and orbits its star at a distance of about one-fifth of the Earth's distance from our Sun.
"Knowing the mass of extrasolar planets accurately is going to help theorists answer lots of questions about how planets form," Dr Benedict says.
"When we get hundreds of these mass determinations for planets around all types of stars, we're going to see what types of stars form certain types of planets. "
mmmmm, science. tasty.
http://news.bbc.co.uk/2/hi/science/nature/2542919.stm
Posted by: Ion Silverbolt
Quote:
Originally posted by The_Turks(ff7)
Man you people need a life....
who bloody cares how long a planet is created. its not like we are going to migrate to another planet in our lives.
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Well if we do, I nominate you to be the first one to go there. One way of course.
Posted by: Ion Silverbolt
Quote:
Originally posted by The_Turks(ff7)
Man you people need a life....
who bloody cares how long a planet is created. its not like we are going to migrate to another planet in our lives.
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Well if we do, I nominate you to be the first one to go there. One way of course.
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