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#87791 11/24/02 10:52 PM
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I have a question to ask:

Did anybody other than myself notice that the fireballs did not move in a consistent direction?

I am beginning to doubt my sanity. I've been reading everything I can put my hands on about the Leonid showers, and the reading would indicate that the movement is consistently in one direction, which is logical.

But that is not what I observed last week.

If anyone carefully noticed the direction of the the various appearances, and also noticed that they moved in various directions, please post here.

Best regards,
DubDoubting her sanity


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do you mean that the fireballs themselves changed direction as they fell, or that they came from several areas of the sky? (but flying straight)



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I observed some that fell directly into our western field area--skywise.

The moon was...maybe north or northwest. I didn't notice any that fell over in the area of the moon.

Many seemed to moved west.

But I could have sworn I saw several move eastward. No joke.

I keep running that mental tape of the morning I watched. I looked all over the sky, trying to catch them because their appearances were so very, very brief.

What I thought I was seeing was an appearance of a seam opening in the sky--beyond or behind the stars, so it seemed--a seam ripping open quickly then disappearing--and that seam seemed to open from east to west often, but also from south to east or even west to east.




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I am pretty ignorant about astronomy, but since the Earth is passing through a fairly
wide spread cloud of the particles, could not Earth's gravitation change aangle of entry of
metiorites enough to be noticeable?


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I have always understood that they can move in most any direction once they enter the atmosphere. the earth is basically flying through a band of comet flotsam and jetsam, and the small particles can be influenced by atmospheric conditions.

I don't think you were seeing things!

the last good shower I saw was in the late seventies, and they were flying all around. I wonder whatever happened to Kathy...



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The principle is that while they may seem to move in any direction from the point of view of the observer, they radiate from a common point of origin.

If you had a piece of graph paper and an accurate plot of their various trajectories, and you extended the lines backwards, you would find a point of convergence [edit: divergence, actually]. In this case - somewhere the constellation Leo, which is the reason they are called Leonids.

(One of my early Astronomy One lab assignments was to do exactly that, though I think it may have been the Perseids [August], not the Leonids.) I'm starting to sound like you, Bill! :-)


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Dear wofahulicodoc: It seems to me that there would be three factors involved:
1.the trajectory of the particles themselves,
2.the motion of the earth along its orbit
3.the rotation of the earth

It must be a bit like an automobile driving through a cloud of insects.

Of these I would expect Earth's motion along its orbit to the the greatest.
I wonder if Earth's gravitation pull has enough time to have much effect


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More than three, I'm sure, and it isn't really a "point" of origin either but rather a "region" of sky. Nevertheless the con/divergence is noted consistently, because the speed of the meteors dwarfs the other influences.

Think about the absence of Doppler effect on radio signals in a moving car. Even though the speed is not 186,000 miles per second but 186,000 miles-plus-88-feet per second (driving toward the transmitter at 60 mph), it really doesn't show up anywhere.



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I wonder how the "beam" of meteorite particles stays so relatively constant over such long
periods of time.


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the particles are detritus of comets which have followed an orbit for thousands if not millions of years. those orbits remain fairly constant, so the buildup of particles and the regular shedding of new material continues.

pretty cool...



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Dear etaoin: I should think comet orbits would be limited in size or they would be totally
disturbed by passing near some high mass object.


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well, of the several sites I've just explored, this one seems to have the most info:

http://www.amsmeteors.org/showers.html

this is good too:
http://www.astronomynotes.com/solfluf/s8.htm

there is so much information out there, I'll need to take the week off to get through only a small portion of it!



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From the link you gave, etaoin, the frequency of flashes is influenced somewhat by rotation
of earth:Over the course of a night, it will be noticed that more sporadic meteors can be
seen in the hours before sunrise than in the hours after sunset. This is due to the motion
of the Earth as it revolves around the sun, with the leading edge (morning side) of the Earth
encountering more meteoroids than the trailing edge (evening side). In general, 2 to 3 times
as many meteors can be seen in the hour or so just before morning twilight, than can be
seen in the early evening. Additionally, the numbers of random, or sporadic meteors will
also vary from season to season, due to the tilt of the Earth on its axis and other factors.
As a general rule, about 2 to 3 times as many sporadic meteors can be seen in the early
fall (September) as can be seen in the early spring (March). Together,these two effects
can generate a fluctuation in the hourly rate of sporadic meteors by a factor of 4 to 9 times,
over the course of the year.

But difference in trajectories that Wordwind was interested in seems to be quite small.


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But difference in trajectories that Wordwind was interested in seems to be quite small. ~ wwh

Maybeso Bill, but I saw a website (NASA maybe) where the visual simulation of the (then) upcoming leonids showed them streaking in different directions from a central, but large sector of the sky. To me the relative motions, as you have outlined, would all come into play, but the size of the shotgun scatter pattern of these cometal pieces of rocks as they follow the path of their orbit would be the determining factor inasmuch as what direction their fall would take relative to an observer on earth. That is, if the scatter pattern was larger than the diameter of earth the fact that the individual positional extremes would still be directed towards the single atom at the center of the earth (Hi Hogwash) and that would insure that they would be viewed as streaking in different directions by an observer at any point on earth.

Well. It could not be otherwise and still be within our current understanding of what is.



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Well, a big thank you! to all of you! You've put my mind to ease. I wasn't seeing things.

Now my children here at school, upon hearing me say I'd seen a couple green fireballs, told me that they'd also seen blue and red, which I did not observe. The only colors I saw were green, gold, and white.


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The only picture I could find showing different trajectories was taken as a time exposure
witha fish eye lens, which showed tracks at angles due to distortion and time difference.



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Here's you a picture:
http://antwrp.gsfc.nasa.gov/apod/ap021127.html

There's some time lag due to this being thirty one-minute exposures but I don't think there is any noticeable directional distortion caused by that.

Think of what it looks like to be driving into a snow storm and the snow is coming at you; if you are going fast enough that your motion is the main component, the snow will appear to be radiating from a point somewhere in front of you. How far off directly in front of you will depend on the speed and direction of the snowfall. This is pretty much the same thing as what is happening in the meteor shower.

What? You don't drive in the snow in Virginia? Well, you oughta try it sometime. It's fun.


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Who said I don't drive in snow in Virginia? I drive all over the place when it snows in Virginia. Driving in snow is one of my favorite things in the whole world to do. 4WD is the thing that makes it all possible. You know I must be crazy about driving in snow in Virginia just to have a 4WD that I use approximately 1.5 times a year.

And thanks, Fald, for the fantastic!!! photograph! That really does show a little of what I thought I was seeing. How very, very exciting to see that time-lapse photograph! I cannot wait till the next big meteor shower so now I'll know what to look for--even though W'On has told us that this is the biggest we'll see for another 30 or so years.




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Fascinating thread! Thanks to everyone!

Here's the official Nasa Leonid site (and be sure to click on Leonids Live over in the left column, then "Photographs" > "Image gallery" for 445 Leonid meteor images from 27 different countries!):

http://leonid.arc.nasa.gov/



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