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Is Jupiter Earth's Cosmic Protector?
Hugh Pickens writes "Last Sunday, an object, probably a comet that nobody saw coming, plowed into Jupiter's colorful cloud tops, splashing up debris and leaving a black eye the size of the Pacific Ocean — the second time in 15 years that this had happened, after Comet Shoemaker-Levy 9 fell apart and its pieces crashed into Jupiter in 1994, leaving Earth-size marks that persisted up to a year. 'Better Jupiter than Earth,' say astronomers who think that part of what makes Earth such a nice place to live is that Jupiter acts as a gravitational shield, deflecting incoming space junk away from the inner solar system where it could do to humans what an asteroid apparently did for the dinosaurs 65 million years ago. 'If anything like that had hit the Earth it would have been curtains for us, so we can feel very happy that Jupiter is doing its vacuum-cleaner job and hoovering up all these large pieces before they come for us,' says Australian amateur astronomer Anthony Wesley, who first noticed the mark on Jupiter. But others say the warm and fuzzy image of the King of Planets as father-protector may not be entirely accurate. In 1770, Comet Lexell whizzed by the earth, missing us by a cosmic whisker after passing close to Jupiter. The comet made two passes around the Sun and in 1779 again passed very close to Jupiter, which then threw it back out of the solar system."
It's a bit like saying one speck of dust is protecting another speck of dust from other, smaller dust, as they swirl around an eddy of warm air in a coliseum.
Is Jupiter Earth's Cosmic Protector?
If this is true, it gives us another criteria to look for in distant solar systems that we suspect may harbor life or that we would like to colonize: a large shield planet in the same system capable of leaving the smaller world to develop uninterrupted.
It is interesting to wonder if our odds increase or decrease on being hit when there is a large massive body in our solar system. Like the article and summary say, some objects that would not have come close could be put on course for earth via Jupiter's gravitational forces. Who knows, maybe massive bodies like Jupiter pull more space debris into our system and make it more hostile than if it were just the earth orbiting the Sun?
My work here is dung.
... is the fact that eventually we have to get off earth and learn how to survive in the hostile universe anyway.
That Jupiter really sucks?
In astrology, Jupiter is considered the "greater benefic," the planet that bestows fortune, luck, and positive benefits.
Just sayin'.
The Earth will eventually be wiped out, obviously. We can't get lucky forever.
We'd better spread outselves out.
Jupiter is the only planet in our system close enough to the sun and with a deep enough gravity well for them to have a barycenter (common orbital center) outside the sun's surface. That sort of wobbly orbital mechanics has far more effect on trajectories of small bodies than a nice, neat set of concentric circular orbits. The sun-Jupiter system will be more likely to cause fluctuations that result in small interlopers to get thrown out of the system or sucked into one of their gravity wells. Seeing the result on Jupiter is rare. Seeing it at the sun is more common. Between the two they're going to suck up far more than hit elsewhere.
But their influence is only the majority of a chaotic multi-body system. Just because they account for the most hits doesn't mean they take them all and nothing gets through elsewhere. Of course some will miss the big guys and hit (or nearly so) some of the others. That's the nature of a chaotic system of orbital mechanics. They are not exerting influence in an intentional manner, rather a deterministic but fairly unpredictable manner.
To assume a certain thing always happens because it has happened, and also to say it not accurate because there is an exception, is the sort of low caliber absolutist thinking that's common in "modern" science reporting. I have no doubt the parties credited with these viewpoints understand quite well the situation, and the apparent controversy is a function of the author of TFA.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
the far side is much more cratered than the front side which shows how the Earth
...which is much larger than the moon, protects the moon from impacts more than the other way around.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
He just had a bad day.
After realizing what he did, he flicked that comet as far away from Earth as possible. And he said he was sorry.
The comet was never seen again. Lexell, after conducting further work in cooperation with Pierre-Simon Laplace, argued that a subsequent interaction with Jupiter had further perturbed its orbit, either placing it too far from the Earth to be seen or perhaps ejecting it from the Solar System altogether.
Mit der Dummheit kämpfen Götter selbst vergebens
I find it amazing and worrisome that an object that size can get so close to Earth and hit Jupiter without astronomers learning about it until after the fact. To me, it is an indication that current near-earth object surveillance systems are not worth much.
Well, kind of, but look at it this way. If the Moon was a lone planet, it'd get craters everywhere equally. But it's not a lone planet, instead it has a bigger body always on the same side of it. Therefore, that there should be more impacts on the opposite side tells you that asteroids are quite attracted to Earth and that the Moon catches a lot of the when its on their way.
You just got troll'd!
Jonti Horner and BW Jones have written a series of papers on this, summarized in this Astronomy and Geophysics article The first paper deals with the Asteroids. The second, in press, considers the Centaurs The third, of perhaps most relevance to this discussion, considers the Oort Cloud objects.
(To simplify the simulations, Earth was inflated to one million times its actual size. A juicy target indeed)
There's actually no "Present Participle" for making/molding/pressing dies. The action itself is usually "pressing", "blanking", or "broaching". More information here.
On a side note, the Bengal tiger is quite intelligent and resourceful. I wouldn't be surprised if they did decide to go into the manufacturing business.
Entomologically speaking, the spider is not a bug, it's a feature.
> The Earth has not yet faced a galaxy coming straight at it.
The Earth is facing a galaxy coming straight at it. The Andromeda Galaxy is on a collision course with the Milky Way, and there is a very real possibility that the Sun will be ejected from our Galaxy when this happens. Fortunately, this is not going to happen for about three billion years
Just because you are paranoid does not mean that no-one is out to get you.
Whew! That's a relief... I thought you said three million years.
"Slow down, Cowboy! It has been 3 years, 7 months and 26 days since you last successfully posted a comment."
Actually from what I understand, getting ejected from the galaxy would probably be the best outcome.
There is also a chance of the Sun being put into an orbit that takes it through uninhabitable parts of the galaxy such as the core. Also when the collision happens it will trigger a very large spurt of star formation leading to more supernova and just large amounts of radiation from large new stars. Not to mention the chance of a close encounter with another star disrupting the orbits of the planets in the solar system.
https://en.wikipedia.org/wiki/Inverted_totalitarianism
The point is that not only does Jupiter protect the terrestrial planets now, but that Jupiter has protected Earth from the birth of the solar system. This is one reason that Earth isn't yet another gas giant.
The recent controversial redefinition of the word "planet" (http://en.wikipedia.org/wiki/IAU_definition_of_planet) discusses this "vacuum cleaner" effect as the third of three criteria:
Jupiter is by far the largest planet and has by far the largest such effect. A lot of the reasoning in the comments has caused one to question how well Astro 100 courses are being taught, but perhaps it is ok to venture one simple statement for why Jupiter preferentially protects the inner solar system. The comets that threaten us originate in the distant Oort Cloud (http://en.wikipedia.org/wiki/Oort_cloud). They visit the inner solar system, but their orbits all begin far outside. It is thought that external perturbations play a role in causing them to plunge inwards. Jupiter (to oversimplify outrageously) stands between us and the bombardment.
Fundamentally this is the famous "three body problem". The equations describing Newtonian gravity are straightforward to solve for two bodies, and impossible to solve precisely for three or more. Relativistic corrections add a bit of spice. As a result planetary mechanics requires numerical integration.
The solar system is full of neat resonances and points of stability such as the Lagrangian points. Jupiter's Trojan asteroids (http://en.wikipedia.org/wiki/Trojan_(astronomy)) cluster at L4 and L5 and are thought to be as numerous as those in the main belt. Our Moon's tidal locking is a) imperfect (since the orbit is rapidly growing (http://en.wikipedia.org/wiki/Moon#Orbit_and_relationship_to_Earth), and b) simple compared to resonances (http://en.wikipedia.org/wiki/Orbital_resonance) between other bodies.
That's right. You can't.
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