Jupiter's 'job' is to protect the Earth?

The other day on an email list, the moderator sent out a message that seemed to be about science education; astronomical science to be particular.  The event that prompted the message to the list's moderator was another hit on Jupiter by something big enough to leave a scar in that planet's clouds.

I like 'stars and stuff,' so I started reading the message, only to be put off by the admonition that, "If you don't believe in God" to not bother.  That was a clue that I probably would not agree with the conclusion of the person educating us readers about astronomy, but it has nothing to do with my own conclusions about whether or not God exists.

In the message, the writer concluded that Jupiter's 'purpose' (and the purpose of the other outer planets in the solar system) is to protect Earth from "hits by comets, meteors and the like."  The writer credited God with wanting to protect the people of Earth.  That may be a comforting thought to Earthlings, but the geography of the solar system (in human scale a bowling ball in a mile-wide field, circled by objects ranging in size from the head of a pin to a pecan), leads me to think that if the gas-giants are indeed the bouncers of the Solar System, then the "God" that put them in place either needed to attend Astronomy 101 at a good community college, or be fitted with a decent pair of glasses.

Yes, Jupiter, Saturn, Uranus and Neptune capture space objects that come near them and they absorb any hits, but they also attract objects already falling towards the sun and give them a boost towards us causing potentially real Jovian thunderbolts.   Also, since the area covered by the gravitational pull of Jupiter, Saturn, Uranus and Neptune is larger than the planets themselves, it seems (to me) to be more likely that they will slingshot these space objects rather than score the bulls-eye of a direct 'catch.'  O is bigger than o.

Even though Jupiter is "the huge monster planet" with "massive gravity pull" there is still the vastness of the area it covers to contend with, and its relative size in relation to that vastness.  Using the general distance of about 8 minutes from the Sun at the speed of light to the Earth as the basic measure (1 Astronomical Unit, an AU), consider:

• the sizes of the planets relative to each other
• Pluto is roughly 40 AU from the Sun, which makes the diameter of the solar system roughly 80 AU 
• Since the formula for finding the area of a circle is A = pi r², the general area of the Solar System should be in the neighborhood of 3.14 times 40 times 40.  That comes out to 5,024 square AU, which means 5,024 squares whose sides are the distance from the Earth to the Sun.  Trim off the corners of the 80 x 80 AU diameter and that comes out to about 70 x 70 AU.  Seventy times the distance from the Earth to the Sun, by seventy times the distance from the Earth to the Sun.

That is a big chunk of virtually empty real estate, and may still be too hard to visualize.  Instead, consider a Solar System built on a human scale with a bowling ball-sized Sun, a peppercorn-sized Earth, and a pecan-sized Jupiter.  I'll leave out the other planets for the sake of simplicity.  Now set the bowling ball, the peppercorn and the pecan in a well-mown field: 

• bowling ball's in the middle
• peppercorn is 26 paces from the bowling ball
• pecan is 135 paces from the bowling ball (a pace being two steps).

In this model, it will take the pecan-Jupiter 12 Earth years to roll around the bowling ball-Sun, which the peppercorn-Earth does in one.  It is easy to see that, while the peppercorn 'passes' the pecan 12 times in the time it takes the pecan to go once around the bowling ball, the peppercorn is 'in danger' for much of its transit.

"But," someone says, "I think you're leaving out part of the equation.  What about Saturn, Uranus and Neptune?  Don't they also 'protect' the earth?  Perhaps they're all 'staggered' so that their paths pick up what Jupiter misses?"

Let's go back to the field in which are laying the bowling ball, the peppercorn and the pecan.  To see what effect Saturn, Uranus and Neptune would have, we'll have to add an acorn, a peanut and another peanut.

The acorn (Saturn) will have to go 112 paces beyond the pecan.  The first peanut (Uranus) will be 249 paces beyond the acorn, and the second peanut will be 281 paces beyond the first peanut, for a total of 777 paces, roughly 3,885 feet.

The acorn needs about 30 years to go around the bowling ball.  The first peanut needs about 85 years.  The second peanut needs 165 years.

But, where are these protectors?  Are they staggered 'north,' 'south,' 'east,' and 'west' in the Solar System so that each quadrant is 'swept?' From this representation of the current positions of the planets, it does not look that way.

In this picture, the entire 'north' side of the solar system is untended.

Add to the unprotected 'side' of the Solar System the fact that Earth is surrounded (at a distance) not only by an Asteroid Belt that lies between Jupiter and Mars, but by the Kuiper Belt and the probable Oort Cloud.

With the bowling ball's gravitational pull attracting objects from 360º around the Solar System, if the objects are nudged out of their paths by gravitational forces from passing stars, and with the paths of the outer gas-giants -- the pecan, the acorn and the two peanuts -- never  guaranteeing absolute protection (and in some cases being co-conspirators in The Attack of the Killer Comets), the thinking behind "God is protecting us from "hits by comets, meteors and the like" is sloppy.

Does Jupiter attract space objects and keep them from Earth?  Yes.  But, Jupiter also attracts space objects and flings them at Earth, just like a cartoon Jove perched on a cloud throwing those thunderbolts.  Jupiter just 'is,' and thinking one way or the other is nanoscopically unlikely to have any real effect on us.

I think it is unlikely that a person who embraces the conclusion that the pecan, the acorn and the two peanuts are in place to spare the peppercorn the wrath of the pinheads will ever be in a position in which this conclusion will be critical since this conclusion will probably cause low scores on qualifying tests.  However, the habits of mind encouraged by sloppy science in the everyday world can kill:  "Wis. mom of dead girl: Sickness was test of faith."

When considering matters of science, think scientifically.

Comments

[Gloria Teasedale]

That is so awesome.

[Valerie]

Thank you, Gloria. Your comments are always welcome. Give our regards to Rufus.

[Ron]

We recently had http://www.freakonomicsbook.com/thebook/index.html from the library. In the real estate agent chapter, they talk about society's reliance on experts. The premise that you debunked is a good example of too much reliance on an expert and a lack of giving something a couple minutes thought.