Re: The Astronomy Thread
Posted: Tue Jul 21, 2015 4:51 am
hi hi
Pluto was discovered in 1930. Pluto was conclusively determined to be too small to have perturbed the gas giants in 1978. All of this happened before I was born. Why should I, the new generation, care about the cultural baggage of decades long past? All this stuff about people's mistaken search for Planet X has nothing to do with what Pluto is anymore. I don't have any emotional investment in the search for Planet X, it was not for my generation.
Earth is more massive than Mars, why does that not exclude Mars? The Earth's core is nowhere near the same composition as Jupiter's core, so why are they considered comparable? Mars and Pluto both have solid, stratified cores, unlike Earth which has a molten, moving core.
If any planet can be said to be in a ballistic orbit, it is Jupiter, because it has the fewest number of outside influences on its trajectory, on account of being the single most massive object. Pluto, on the other hand, is in a very orderly resonance orbit with Neptune.
If anyone is curious as to how gas giants fling themselves into positions around stars, they may be interested to know that the gas giants in our own solar system have moved into different positions over time. This is a process known as Planetary Migration, and using Nice Model (which brute forced the n body problem) we can see that the gas giants originally started in significantly different positions then they are currently in. Forming in nearly circular orbits between 5.5 and 17 AUs. Saturn, Neptune, and Uranus move into higher orbits because of their small size, which disturbs the orbits of planetesimals and sends them into Jupiter's orbit. Meanwhile Jupiter moves into a lower orbit because it has enough mass to eject objects from the solar system entirely. Then, once Jupiter and Saturn crossed their mean 1:2 resonance, Saturn was ejected further out and disturbed the orbits of everything in the entire solar system, including Uranus and Neptune (which switch places in almost half of the models), and may have caused the Late Heavy Bombardment.
((Models also predict a lengthening of Mercury's orbit which could lead to it being ejected from the solar system, and in a small percentage of the models, causing collisions between any of the inner solar system planets, including Earth and Venus, or Earth and Mars, in about 3.3 billion years. Gregory Laughlin, University of California, 2009))
The universe is a big place. As we discover more about exoplanetary systems, we're learning that our own solar system may not be the gold standard for which to base all of our understanding on.
Pluto was discovered in 1930. Pluto was conclusively determined to be too small to have perturbed the gas giants in 1978. All of this happened before I was born. Why should I, the new generation, care about the cultural baggage of decades long past? All this stuff about people's mistaken search for Planet X has nothing to do with what Pluto is anymore. I don't have any emotional investment in the search for Planet X, it was not for my generation.
Do you have any evidence that shows that we are not better off defining it as such? Otherwise, that sounds an awful lot like an argument from silence. I mean, if someone doesn't want to call Pluto a planet, that's fine, but it is a stretch to say that someone else is scientifically wrong for calling it a planet....but I see no reason to believe that we're better off defining it as such.
Earth is more massive than Mars, why does that not exclude Mars? The Earth's core is nowhere near the same composition as Jupiter's core, so why are they considered comparable? Mars and Pluto both have solid, stratified cores, unlike Earth which has a molten, moving core.
If any planet can be said to be in a ballistic orbit, it is Jupiter, because it has the fewest number of outside influences on its trajectory, on account of being the single most massive object. Pluto, on the other hand, is in a very orderly resonance orbit with Neptune.
If anyone is curious as to how gas giants fling themselves into positions around stars, they may be interested to know that the gas giants in our own solar system have moved into different positions over time. This is a process known as Planetary Migration, and using Nice Model (which brute forced the n body problem) we can see that the gas giants originally started in significantly different positions then they are currently in. Forming in nearly circular orbits between 5.5 and 17 AUs. Saturn, Neptune, and Uranus move into higher orbits because of their small size, which disturbs the orbits of planetesimals and sends them into Jupiter's orbit. Meanwhile Jupiter moves into a lower orbit because it has enough mass to eject objects from the solar system entirely. Then, once Jupiter and Saturn crossed their mean 1:2 resonance, Saturn was ejected further out and disturbed the orbits of everything in the entire solar system, including Uranus and Neptune (which switch places in almost half of the models), and may have caused the Late Heavy Bombardment.
((Models also predict a lengthening of Mercury's orbit which could lead to it being ejected from the solar system, and in a small percentage of the models, causing collisions between any of the inner solar system planets, including Earth and Venus, or Earth and Mars, in about 3.3 billion years. Gregory Laughlin, University of California, 2009))
The universe is a big place. As we discover more about exoplanetary systems, we're learning that our own solar system may not be the gold standard for which to base all of our understanding on.