This Looks Like The Right Place



This from the man with all the answers! Been finding them at the bottom of a bottle again have you?
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Due my own lack of spelling skill I usually cut people a lot of slack in that department. But yikes man, learn how to use a spell-checker.
--
Grant Edwards grante Yow! Is this TERMINAL fun?
at
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wrote:

I disabled my spell checker because it kept asking for verification on hobby specific words. It seems as though every post I made had some different acronym that needed to be added to its list of words. I got tired of it.
Ed Cregger
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Fine. So you still proofread before posting, right?
m-m
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(correct the spelling)> wrote:

Of course, but things still slip through occasionally.
Ed Cregger
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This thread seems to have a life of it's own, somehow.
m-m
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Too True. This has taken so many tangents that it is UNi-real ! :-))
Eric
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| Doug McLaren wrote: |
| > | > | I would expect ANY solid object entering the atmosphere at high | > | velocity to show a hot entry
Certainly common sense would lead one to believe this. But it's not that simple ... | > Actually, when a meteor lands, it's usually not even hot. | > | > The outer parts of it often ablate off, leaving the cooler candy | > center inside, and once it gets into the thicker part of the | > atmosphere, it slows to terminal velocity and has several minutes to | > cool off. | > | More or less bollocks.
Less rather than more, obviously.
Depends on the size and speed/angle of the meteor when it enters our atmosphere. If the meteor is huge, our atmosphere will do almost nothing to it and it'll smack into the ground at almost full speed. (And if it's big enough, it'll spawn the creation of a major motion picture or just kill everybody on the planet.) But if it's smaller, it certainly does slow to terminal velocity, which is probably less than 500 mph.
| > The reason that space craft re-entering get so hot is that they're | > going around 16,000 mph when they hit the atmosphere, and they need to | > bleed off all this speed. If a metor just happened to hit our | > atmosphere without much velocity (it could happen under the right | > conditions) | | It actually couldn't. Gravitational potential makes sure of that.
Apparantly there is a minimum speed that a meteor can enter our atmosphere from space. I was thinking that if it came in just right it could hit our atmosphere with very little kinetic energy relative to our planet, but apparantly not. I could work out the math of this and verify it myself if I wanted to, but for now I'll take their word for it, that anything natural that hits our atmosphere is going very fast.
Apparantly this minimum speed is 11 (kps) kilometers per second.
You can find a reference to this minimum speed at
http://www.astro.uu.nl/~strous/AA/en/antwoorden/meteorieten.html
Other pages you might find useful include :
`Are meteorites hot or cold when they hit Earth?'
http://curious.astro.cornell.edu/question.php?number !5 http://www.badastronomy.com/bad/news/salisburymeteor.html
(answer: could be either one.)
`Do meteors slow down to terminal velocity?'
http://curious.astro.cornell.edu/question.php?number 0
(answer: yes, in most cases, unless it's a very large meteor. But most are small.)
And here's an article about a meteor that hit a car, complete with pictures --
http://antwrp.gsfc.nasa.gov/apod/ap021118.html
considering that the final meteorite weighs 27 pounds, if it hit the car doing 11 kps (and the measured speed from the videos taken is even higher), the car would have been utterly disintegrated, not just smashed up. It probably hit the car at a few hundred mph.
(An object at 11 kps has almost _7000_ times the kinetic energy of one at 300 mph.)
Also consider that this particular meteorite was so spectacular that there were many eye-witnesses, and 16 people even were able to film it. It has been very well studied.
| Thatas about tantamounyt to saying thata frictionbaless ball will roll | to a stop at the bottom of a pudding bowl. No matter ehere you strat it | from it won't.
This analogy is extremely apt outside out our atmosphere (and I'm sutiably impressed. Seriously.), and I'll concede that a meteor must have a minimum speed to reach our outer atmosphere. (Well, I already have.)
However, once it hits our atmosphere, your frictionless analogy completely falls apart.
| The only metioors tha arrive 'slowy' are teh ones that start here.
Well, it depends on how you define slowly. 200 mph isn't slow in terrestrial circles, but it's certainly slow in celestial circles,and meteorites certainly do land at that speed.
| > If the Weekly World News said they'd found Martian meteorites, I'd | > probably skip over that and look for more pictures of the batboy. But | > if NASA does, well, it's probably worth reading, and I haven't done | > more than skim over the stuff so far. | | Just because a rock has te same composition as a bit of Mars doesn't | mean it comes from there.
I haven't read all the stuff yet. As mentioned before, I'm skeptical, but given the credentials of the people who have made the claims, I'm not going to dismiss them out of hand. (If you want to, feel free.) | > Ultimately, I consider myself to be reasonably smart. | | Try education as well.
You first. You've certainly made more factual errors in this thread (and presented them more authoritatively, I might add) than I have.
In any event, this thread has certainly taken on a life of it's own, a life totally unrelated to R/C. We really should let it die. (Yes, I know, I'm contributing to it too.)
Ob R/C related:
Anybody know what this plane is?
http://mclaren.frenzy.com/~dougmc/RC/mystery-plane1.jpg
It's got a 6' wing span (and no dihedral), and an 0.40 OS MAX FP engine. (Sounds like it's a bit underpowered.) Got it off of a local freecycle list. Needs some work, but it's not in that bad of shape.
I suspect it's a Telemaster, but I'm not sure.
--
Doug McLaren, snipped-for-privacy@frenzy.com
"Only drug dealers and software companies
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Doug, you could have saved face by simply utilizing a wormhole to deposit the meteorite at the top of the atmosphere. LOL!
----- Original Message -----
<snip some wordy ass stuff>
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Doug McLaren wrote:

I was answering the proposition that there were certain places and speeds a meteor could arrive from that would make it encounter the earth at a slow speed. There are none. As you have described 11Kps is a minimum.
The fact that they may indeed get slowed down by friction is not part of what I was addressing. But they won't get slowed by friction AND arrive cool.
That 11KPS has to go into heat of some sort although its true to say that one the surface melts that is ging to get ripped off pretty fast. leaving the inner part cooler than it might have been (latent heat of evaporation and all that stuff).

Why?
Its interesting.

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...

Hah, like it collided with a slightly smaller meteor that was LEAVING the earth?

That makes one of us ;)
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No. Like it was moving slowly and in a straight perpendicular path to the earth. If the object is moving too slowly to orbit it would get sucked in by earth's gravity and if going staight in would only accelerate to terminal velocity.
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Sport Pilot wrote:

If it was moving that slowly, it wouldn't be anywhere near the earth. To get to that position in the solar system it has to have a speed equivalent to the earths speed round the sun, and if it was essentially in a similar orbit as the earth it would have been sucked into the earth or moon years ago.
Objects falling slowly towards the earth have nonexistent orbital paths. Therefore they cannot exist except as objects that have been thrown up from the earth, like a ball...
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The Natural Philosopher wrote:

to
get
To
essentially
earth
paths.
up
I was talking about speed relative to the earth. Of course it would be moving very fast relative to the sun, and extremely fast relative to the universe.
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Sport Pilot wrote:

So was I dear boy. Do the maths.
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An object simply can not be traveling close to the earth and in an orbit parallel to the earth and at the same speed as the earth. As TNP said no such orbits exist. If you "threw" an object into such an orbit it would accelerate towards the earth according to the normal Newtoniun laws of gravity. If the object started out say 50 miles from the surface of the earth it would hit the upper atmosphere with a velocity of a few thousand miles per hour. If it were farther out it would hit the upper atmosphere even faster. There simply is no way for an object to enter earths gravity field from a distance of even a million miles and not be going about 25000 miles per hour unless that object is equipped with a rocket to slow it. Forget about terminal velocity. It does not exist in a vacuum.
By the way, talking about speed relative to the universe itself is meaningless. There is no fixed point in the universe that is at rest. You can define any point you wish to choose in the universe as being at rest. But that is not the same thing as what you are saying.
It is also a scientific fact that meteors are often cool or even cold on the surface very shortly after impact. Recall that they come from outer space where the temp is just above absolute zero. Roughly minus 473 deg F as I recall. While the surface is usually melted by atmospheric friction the time that it takes the meterorite to travese the atmosphere is far too short for the whole object to be heated unless the meteroite is fairly small. In which case it is usually burned up before impact and nothing hits the earth other then dust. And if it is fairly large and does not break up in the atmosphere it will have so much energy on impact that it will vaporize itself as well as a bunch of the dirt/rock where it hits. That is what killed the dinosaurs. A big one hit that turned the whole earth into a fireball briefly. So only underground critters survived. And not many of them by the way.
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flyrcalot wrote:

Thank you for saying what I was trying to, so much better.
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Flyrcalot, Actually the universe isn't known to be moving (though it may well be moving relitive to other universe's) and has a fixed center.
And I do recall that it is possible for an object to fall slowly to earth. slowly is also relative but the example of a few thousand miles per hour probably would qualify. Terminal velocity is the velocity it reach's after it hits the earth, simply the velocity it would reach if dropped from a plane, many metorites do not slow down to terminal velocity.
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Sport Pilot wrote:

The concept is meaningless. Moving relative to what?
(though it may well be

What other Universes? The Universe (Uni=one veerse = something or other) is by definition 'all there is'

Not true if its 'dropped' from something higher than the earths atmosphere, and even less true if its 'dropped' from somewhere around the orbit of mars.
If it has enough kinetic energy to get to mars at all, it gains a huge potential energy as it falls back towards the sun.
THERE IS NO ORBITAL PATH THAT WILL ALLOW OF AN OBJECT TO BOTH BE OR HAVE BEEN IN THE VICINITY OF MARS AND BE AT LESS THAN PHENOMENAL SPPEED IN THE VICINITY OF THE EARTH. Full stop. Period. End of pseudo scientic babble by those who haven't actually bothered to understand basic physics.

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Oh, now we are talking about Mars? Thought it was just the possibility of entering the atmosphere without actually burning. I don't know where I read it but I do recall it is possible for this to happen, but with the caviate that the speed that which burning or melting occures is different for each material. But also very very improbabable.
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