Re: Norway hit with Hiroshima scale metorite

On Tue, 13 Jun 2006 05:33:46 -1000, Alvin Toda <aet@xxxxxxxx> wrote:

On Mon, 12 Jun 2006 20:08:50 GMT, Rumpelstiltskin
<PleaseDoNotReplyByEmail@xxxxxxxxxxx> wrote:

On Mon, 12 Jun 2006 08:16:29 -1000, Alvin Toda <aet@xxxxxxxx> wrote:

Thanx for the links. These are very interesting. The impact of these
large objects are at the poles. Am just wondering if the weak magnetic
field is enough to divert the objects to earth. You would think that
the gravity was the weak force that diverted the object. But maybe it
just has to be on a collision path to strike the earth?


Cosmic particles are drawn to the poles because of the
electromagnetic interaction between them and the earth, but
I don't think things like asteroids and comets are particularly
drawn to the poles. In their case the momentum would be
just about everything. In the case of Jupiter and Saturn,
gravity would be a bigger factor since theirs is strong
enough to change the orbits of comets and asteroids a lot
farther away from the planets as is the case with Earth. It's
often suggested that we don't get many large-body
collisions on Earth any more because Jupiter and Saturn
have, over past ages, done a pretty good job of "sweeping"
away things that don't stay in fairly circular orbits, either by
pulling them toward collision with those planets or by
slingshotting them out of the solar system.

It's great to know that Jupiter and Saturn have done a good job to
insure us of an extremely low probability of collisions with large
objects. But I wonder about the magnetic force vs the gravitational
force. Magnetic force in general is much larger than the gravitational
inherently (ie looking at the ratio of the permiability of free space
and the gravitational constant?) but it also depends on the ammount of
inducing current.

Yes, but everything is subject to gravity whereas only
polarized things are subject to magnetic force. Exactly
because the magnetic force is so powerful, large objects are
almost perfectly balanced electrically. If there's ever a
significant imbalance in the net polarity of an object , the
object will pull in anything of compensating polarity very
efficiently. For examples of the attraction/repulsion of
unlike/like polarities, there's the tingling feeling in your nose
if you put it near a conventional TV screen, or the sparks if
you run a comb through your hair in a dark room, or the
way if you brush your cat and but the brushings in the
wastebasket, the previous brushings will repel the
similarly-charge new brushings and make it hard or nearly
impossible to get the new brushings into the wastebasket,
and even if you do succeed, they'll stand away from each
other trying to escape each other's vicinity rather than
settling down.

Thus the net force of magnetic attraction in large objects
ends up being very small despite the fact that magnetism is
overwhelmingly more powerful than gravity.

I've heard that if an atom were held together by gravity
rather than by electromagnetism, then if the nucleus were at
the sun, the electrons would be out at about the orbit of
Pluto.


Anyway even weak forces acting over long times can produce effects.
IIRC recall reading a science fiction story where a guy in a space
suit lost contact with his large ship but over a long time-- like
hours-- the gravitational attraction with the ship worked to bring him
close enough to the ship to save himself. He was below the "escape"
velocity from the ship.


Yep, if you're below escape velocity and there's nothing else
around, you'll eventually get back, though it might take several
lifetimes, since gravity is so weak. Here's the relative strength
of the "four forces" (there used to be five before electricity and
magnetism were shown to be two aspects of the same thing):

http://en.wikipedia.org/wiki/Fundamental_forces

Note how fantastically weak gravity is compared to the
other forces, yet gravity dominates in holding the universe
together.







 
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"Necessity is the plea for every infringement of human freedom: it is the
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