This question comes up quite often, and the answer is that it is possible for meteors to appear to be at very low altitude, however it's only an
illusion that occurs since our eyes/brains can't judge distance well when it comes to a light source in the sky (although there may be some
exceptional circumstances where this might be possible that Il'll get on to later).
We also know that the vast majority of meteors completely "burn up" (it's actually a process known as "ablation" that is responsible for the
light/heat produced) at altitudes of around 80-100 km. They are usually the size of grain of sand, or perhaps rice. Brighter meteors or fireballs (a
meteor that is brighter than the planet Venus), are usually a bit larger, perhaps the size of a pebble, or even a football in some cases.
Even these larger meteoroids are not very good at penetrating our atmosphere very deeply, which is a good thing since they are surprisingly common.
When a meteoroid first encounters our atmosphere, it's a bit like a diver belly flopping from 100m, and that is just the "wispy" upper part of our
atmosphere. Lower down, at around 40 km the atmosphere is effectively like a concrete barrier to all but the largest/hardest meteors, and these are
very rare.
In perhaps 99.9999% of cases, where meteorites do make it below 40km and reach the ground, they will have ceased to be luminous for a good few minutes
before reaching the ground, since the atmosphere slows them down so rapidly. In many of these cases the meteoroid is traveling so fast initially, that
is simply disintegrates (most meteoroids are actually composed of quite fragile material) in a bright flash, which is what happened in at least 3
"major" events covered here on ATS in the last 6 months or so:
Massive object crashes over Edmonton, Canada
UFO - meteor like object with sonic boom above Dallas and Austin Texas!
A few meters planetoid will hit Earth
Check out the video footage, in the first two threads especially.
Getting back to the topic at hand,
this page explains in a bit more detail about why meteors can
appear to be closer to the ground than they actually are.
This diagram should help you visualize what is going on:
Basically, the lower down in the sky (or closer to the horizon) a meteor appears to be, the further away it probably is. In the exceptional cases
where this is not the case, and a meteor is still luminous, and less than 1km away from you, unless you're within diving distance of a bunker, that
would probably be the last thing you ever saw.
It's worth mentioning what happened in 1908, when what is thought to be a fragment of a comet exploded somewhere between 5 and 10 km above
Tunguska, devastating
an estimated 2150 square km and
knocking down 80 million trees!
Related reading, that should answer all your other questions:
Seen a swift/very swift moving light (colored or white) in the sky?
Hope that answers all your questions, if not, then feel free to ask...
Happy meteor observing
[edit on 29-3-2009 by C.H.U.D.]
