Jupiter Question
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09-07-2016, 06:55 PM
Jupiter Question
I have seen documentaries that say Jupiter protects the earth. But I don't understand why. The reason that has always been given is that because of its gravity. That it swings deadly things, comets, asteroids, incoming debris...that would otherwise impact earth away from the earth.

I don't understand the explanation. Specifically I don't know why Jupiter might not be just as dangerous because the same gravity might also send a rock hurtling towards earth that would otherwise have missed.

I want to hear from the science buffs. Opinions, corrections, reprimands etc.

We have to remember that what we observe is not nature herself, but nature exposed to our method of questioning ~ Werner Heisenberg
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09-07-2016, 08:35 PM
RE: Jupiter Question
You ideas have merit. My knowledge of solar system formation comes from a class I took for my major, in the early '80s. We have learned a bit more about the solar system since then. Here is some current thinking about solar system formation that addresses your questions, I think.

http://news.ucsc.edu/2015/03/wandering-jupiter.html

It would have been nice to have sat above the plane of the ecliptic billions of years ago with a time lapse camera to watch the action over those billions of years.
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09-07-2016, 08:59 PM
RE: Jupiter Question
Sure it can sling things at us, but consider shoemaker-levy 9. It ATE that comet whole Big Grin
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09-07-2016, 09:05 PM
RE: Jupiter Question
(09-07-2016 08:59 PM)skyking Wrote:  Sure it can sling things at us, but consider shoemaker-levy 9. It ATE that comet whole Big Grin

Didn't it eat it in little bite size pieces? Consider

Skepticism is not a position; it is an approach to claims.
Science is not a subject, but a method.
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09-07-2016, 09:05 PM
RE: Jupiter Question
yeah, so it chewed before it swallowed. good manners.
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10-07-2016, 03:25 AM
RE: Jupiter Question
(09-07-2016 06:55 PM)tomilay Wrote:  I have seen documentaries that say Jupiter protects the earth. But I don't understand why. The reason that has always been given is that because of its gravity. That it swings deadly things, comets, asteroids, incoming debris...that would otherwise impact earth away from the earth.

I don't understand the explanation. Specifically I don't know why Jupiter might not be just as dangerous because the same gravity might also send a rock hurtling towards earth that would otherwise have missed.

I want to hear from the science buffs. Opinions, corrections, reprimands etc.

The claim that Jupiter protects us from asteroid impacts is disputed. Really there are 3 possibilities:

1. Jupiter prevents more asteroids/comets from hitting earth than causing them to hit earth.
2. Jupiter causes more asteroids/comets to hit earth than it prevents.
3. Jupiter has no effect on the number of asteroids/comets that hit earth.

I don't think 3 is true. Why would it be exactly equal when there are so many more ways it could be unequal. I do think Jupiter often stops long period comets from entering the inner solar system(think shoemaker-levy), but it might cause asteroids from the belt to enter the inner solar system.

Another question to ponder is would you rather get hit from an average Kiper belt object or an average asteroid belt object? Comets come in a lot faster that near earth asteroids. I'd rather not get his by anything....but if I have to choose...I'd rather get hit by an asteroid than a comet.

So I don't really know if Jupiter protects us....but I think it probably does.
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10-07-2016, 03:44 AM
RE: Jupiter Question
It's about orbital velocity around the sun, and gravity-assist acceleration from Jupiter.

Jupiter absorbs a lot of the things that fly near it, pulled in by the gravity (some become part of its extensive moon system), and accelerates things that come near it but which miss, the same way our Voyager probe (and others) used the planet to gain additional speed.

Higher velocity will project the rocks to more-distant orbit, or even project them out of the Solar system. The few which are sent in our direction stand a remote chance of striking earth, but on the whole the added energy causes them to be less dangerous to us and/or head on their way past earth (picking up additional speed from the sun, if they're slung past our direction) and on out into deep space.

Thus, Jupiter acts like a broom, sweeping up debris, or else a rocket booster to sling dangerous stuff away.

"Theology made no provision for evolution. The biblical authors had missed the most important revelation of all! Could it be that they were not really privy to the thoughts of God?" - E. O. Wilson
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10-07-2016, 06:13 AM
RE: Jupiter Question
Picture each planet at the bottom of a funnel representing its gravity. The funnel for Earth is, let's say, 6 units wide and 6 units deep. Jupiter's gravity funnel is 2,000 units wide and 2,000 units deep. Jupiter's gravity funnel is equal to all the other planets combined. Now figure that the mouth of the funnel is the zone of attraction (or capture) for anything that passes by.

(Numbers remembered from Astronomy 101 at Purdue some few decades ago.)
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10-07-2016, 06:24 AM
RE: Jupiter Question
(10-07-2016 03:25 AM)Heywood Jahblome Wrote:  
(09-07-2016 06:55 PM)tomilay Wrote:  I have seen documentaries that say Jupiter protects the earth. But I don't understand why. The reason that has always been given is that because of its gravity. That it swings deadly things, comets, asteroids, incoming debris...that would otherwise impact earth away from the earth.

I don't understand the explanation. Specifically I don't know why Jupiter might not be just as dangerous because the same gravity might also send a rock hurtling towards earth that would otherwise have missed.

I want to hear from the science buffs. Opinions, corrections, reprimands etc.

The claim that Jupiter protects us from asteroid impacts is disputed. Really there are 3 possibilities:

1. Jupiter prevents more asteroids/comets from hitting earth than causing them to hit earth.
2. Jupiter causes more asteroids/comets to hit earth than it prevents.
3. Jupiter has no effect on the number of asteroids/comets that hit earth.

I don't think 3 is true. Why would it be exactly equal when there are so many more ways it could be unequal. I do think Jupiter often stops long period comets from entering the inner solar system(think shoemaker-levy), but it might cause asteroids from the belt to enter the inner solar system.

Another question to ponder is would you rather get hit from an average Kiper belt object or an average asteroid belt object? Comets come in a lot faster that near earth asteroids. I'd rather not get his by anything....but if I have to choose...I'd rather get hit by an asteroid than a comet.

So I don't really know if Jupiter protects us....but I think it probably does.

It seems to me that there are at least 4 different scenarios to consider for long period comets.

1. Object -> Jupiter -> Earth -> Sun
2. Object -> Jupiter -> Sun -> Earth
3 Object -> Earth -> Sun -> Jupiter
4 Object -> Sun -> Earth -> Jupiter

Really a continuum of scenarios between 1 and 4.

It seems to me that Jupiter's influence might count in 1. Maybe 2, but subject to veto by Sol. To put it crudely a little over 1/4 the time. It's not clear how it's been determined to be protective. I am thinking there would be some clear cut calculus that one can point to that supports that view.

We have to remember that what we observe is not nature herself, but nature exposed to our method of questioning ~ Werner Heisenberg
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10-07-2016, 06:45 AM
RE: Jupiter Question
Jupiter gets most of it, but not all. That's why we see impact craters all around the world. However, if you'll think for a little bit about the almost infinite number of ways the billions of bits of debris in our system can approach Jupiter, the Sun, and Earth, you'll realize that the (relatively) small number of strikes is pretty incredible. Be very glad Jupiter is there, doing its job, or we probably wouldn't be here. On the other hand, Jupiter does occasionally disturb one of the "stable" asteroids in our system, and takes a "pot shot" at Earth... I suppose it's properly called after the fickle god that is its namesake.

If you really want to blow your mind, consider the fact that the plane of the planetary orbits is perpendicular to the direction the sun is traveling (very quickly) through the galaxy as it spins, making the planetary orbits (and all of the debris) look like this in three dimensional projection:

[Image: tumblr_mj0vvcqnZx1qdlh1io1_400.gif]

"Theology made no provision for evolution. The biblical authors had missed the most important revelation of all! Could it be that they were not really privy to the thoughts of God?" - E. O. Wilson
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