[meteorite-list] Lunar/Martian controversy

From: j.divelbiss_at_att.net <j.divelbiss_at_meteoritecentral.com>
Date: Thu Apr 22 10:18:02 2004
Message-ID: <122120030159.1864.1bce_at_att.net>

Sterling,

First off I'm not about to challenge your mathematical grasp of this moon
ejecta thing.

I wondered how your facts about moon ejecta and its' avoidance of earth
relates to Eric's comment about the short CRE age for lunar meteorites?

The two comments don't jive to this simpleton.

John


> Hi,
>
> Just as it's hard to get to the Moon (from Earth, that is, I haven't made it
> yet), it's even harder to get TO the Earth FROM the Moon.
> Yeah, I know, it flies in the face of the obvious (Earth LOOKS flat)!
> There's the
> Moon just hanging around up there in the heavenly neighborhood, always right
> next
> door. Surely if you dropped a rock off of it, the rock would go plonk! straight
> down
> to my backyard, crushing the BBQ pit or splashing into the swimming pool!
> Wouldn't
> it? Did you hear a noise? Go look...
> OK, you've thrown The Rock. You had to throw it as fast or faster than 2340
> m/sec
> or it would never escape the Moon. (Quite an arm you got there, kid!)
> That means The Rock will reach the "neutral point" where the pull of the
> Moon and
> the tug of the Earth equal each other and cancel out. If you had really great
> control
> of that arm and managed to toss The Rock at exactly the right speed, it would
> reach
> the neutral point with ZERO velocity and it would STOP!
> Yes, it would just hang out there, going nowhere and enjoying a fine view of
> both
> planetary bodies for the rest of Eternity (that's where I want to build my
> retirement
> home) or until the first little perturbation came along and then it would then
> fall,
> either back towards the Moon or on towards Earth.
> Since the "neutral point" is very close to the Moon, the fall towards the
> Earth
> will convert all The Rock's potential energy of position into good old kinetic
> energy. The Rock will achieve the full escape velocity of Earth in falling that
> it
> would take to get the heck off the planet if you were going the other way:
> 11,200
> m/sec.
> Since in "real life" The Rock will probably have cruised past the "neutral
> point"
> with some residual velocity all its own, its terminal velocity will always BE
> GREATER
> THAN the Earth's escape velocity!
> Hey wait! Slow down! You missed the turn! You drove right past it! It's back
> there... That's life on the gravity freeway. So, unless The Rock is hideously
> unlucky, it's going somewhere but that somewhere ain't the Earth!
> Not only that, The Rock will have some vector given to it by the
> circumstances of
> its ejection and it WON'T be heading toward the one tiny spot of space where the
> teensy-tiny Earth is going to be five days, two hours, 11 minutes and 43 seconds
> later. (Kid, do you throw a curve ball?)
> Since the big fat Earth only takes up 1/32,400 of the Moon's sky, the odds
> of
> hitting the Home Planet are small (I won't say "astronomically" small, I won't,
> I
> won't...)
> And the "lucky" Rock, the one that heads straight and unerringly towards the
> Earth dead center on target, right for your backyard? Well, since its entry
> angle is
> 90 degrees, straight screeeeeming vertically down through the atmosphere, it's
> going
> to burn up a long, long time before it reaches your BBQ pit or your swimming
> pool.
> So, almost all the Rocks thrown from the Moon will go their own way in the
> solar
> system, distaining a visit to the Big Brother planet, so close and yet so far
> away.
> Maybe, in 100,000 years, we and our planet might acidentally bump into some
> Lunar
> Escapees that have been wandering around in generally Earth-like solar orbits
> and we
> can get re-acquainted, but the odds are against it.
> Bottom Line? The answer to "How do we get from the Moon to the Earth?" is
> same as
> the answer in the very old and not very funny joke about asking directions:
> "You cain't get there from here."
>
>
> Sterling K. Wdebb
> ---------------------------------------------------------------
>
> j.divelbiss_at_att.net wrote:
>
> > Q: Do we think that it is possible for the moon's impact ejecta into space to
> > escape Earth's gravity? I would think not, or very-very little.
> >
> > Cautious this time,
> >
> > John
> >
>
>
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Received on Sat 20 Dec 2003 08:59:00 PM PST