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DID I ACTUALLY SEE A FIREBALL LAND NEAR ME?

People frequently report that they have not only seen a bright meteor (a "fireball") in the sky, but that they've actually seen it LAND near them on the ground! But however convincing such a sight may seem to be, it is actually vanishingly unlikely! To understand why, we will have to talk right up front about what we know to be true regarding meteors and meteorites... For example, we know that the shooting stars we normally see are actually VERY high up in our atmosphere - they generally become visible at altitudes of 80 kilometers or more. And of course, if you aren't DIRECTLY under the meteor, you will see it at an angle, from much further off along our globe... Second, we know that even bright meteors are usually from very small particles: one the size of a house might light up the sky like a second sun! And because of the tremendous energy that a desk- or basketball-sized meteoroid generates when it "belly-flops" into our atmosphere at over 30,000 mph, we know meteors almost NEVER survive atmospheric entry! We also know that these small particles - especially the ones which come from the meteor showers - are usually NOT very dense. Instead of thinking of them as little rocks or sand grains, the best analogy for them seems to be "Cosmic Dustbunnies", or even "Celestial Cotton Candy". :) Because of the the small size and low density of meteor- shower meteors - even the very brightest ones - it's no small wonder that a meteorite has NEVER been definitely associated with a meteor shower! Instead, the kind of large, hard, dense matter that could survive earth's atmosphere is generally theorized to come from some where else - most likely, the rocky "asteroids" between the planets. And these objects are no more common during meteor showers than they would be at any other time of year. -- Finally, re: seeing a fireball apparently land nearby, there are a few tricky things to keep in mind. These "tricks" trip up essentially every non-meteor observer who is lucky enough to see one of these bright meteors: folks like mathematicians, engineers, and even professional (non-meteor) astronomers! First, it is basically impossible for someone to "see" how far away an object is based only on perspective, UNLESS they also know the TRUE SIZE of that object! The reason we're so used to believing we can judge distances is that everything we see on the ground has a known size. But objects in the sky, and especially unfamiliar ones, can play real tricks on us here! (For example, basically all of us "see" the moon and sun as being larger when near the horizon than when they're high in the sky. But in fact, they're not at all!) Second and even more importantly, meteorites do not "burn" all the way down to the ground! Instead, they "flame out" at a high altitude - usually at least 30km - and then go into what's called dark flight. Essentially, after falling below 30km, they become mere "falling rocks"! By the time they finally reach the ground at "normal" falling velocities, several minutes after "flaming out" and becoming invisible, they're generally not even very warm! NOTE: The purpose of this page is not to discourage you from reporting what you believe you saw! But it is important when you see an amazing event like a bright meteor, to have some context for understanding it. And again, if you're confused, you aren't alone! Practically every fireball report sent in by non-meteor-watchers - no matter their background - describes the object witnessed as having landed "a few yards away", "in the next field", "next town over", maybe "a county or two over", etc. This is true even when the same object has been witnessed by many other people hundreds of miles further downflight! Last of all, let me say that meteor science is NOT completely known... It is just possible that you may have seen something unique in our understanding (so far) of meteors - a flaming meteoritic particle, which actually remained "on fire" somehow all the way down to the ground! No one can say this is "impossible", but do keep in mind that the realistic chances of there actually being anything there on the ground are vanishingly small... Anyway, for those privileged to see a truly bright meteor, it's to be hoped that the above information, coupled with the thrill of the actual event, is enough to pique your interest in learning more about meteors. If so, this site and many others on the Web are a great starting point!

Clear skies!
Lew Gramer <dedalus@alum.mit.edu>