What Is a Meteor? (Meteoroid, Meteor, Meteorite — and How Fast They Fall)

Look up on a clear, dark night for long enough and you will eventually catch one: a thin, silent streak of light that flares and vanishes in under a second. We call it a shooting star, but there is no star involved. What you saw was a speck of rock or metal — often no bigger than a grain of rice — meeting the top of the atmosphere at a speed no human machine can match, and burning away in a flash of superheated air.

Meteors are one of the few genuinely universal sights in nature. Every culture on Earth has watched them; every night, somewhere, thousands streak down. And thanks to a worldwide network of small cameras, we can now do something people could only dream of a generation ago: see, on a map, where the meteors of last night actually fell.

Three words for one falling rock

The vocabulary trips people up, but it is simple once you see the pattern — it is the same object named for where it is.

A meteoroid is the object while it is still in space: a fragment of an asteroid or comet, drifting along its own orbit around the Sun. The vast majority are tiny, somewhere between a grain of sand and a small pebble. There are countless numbers of them threading through the inner Solar System.

A meteor is what happens when that meteoroid runs into Earth's atmosphere and burns up. The meteor is the streak of light — the event, not the rock. This is the thing you actually see. It is over in a fraction of a second because the meteoroid is moving so fast that it is destroyed almost the instant it enters the dense air.

A meteorite is the rare survivor: a piece large and tough enough that it isn't completely consumed, and reaches the ground where someone can pick it up. Only a small fraction of incoming meteoroids leave any meteorite at all — most vaporise entirely, kilometres up.

So the tidy version: meteoroid in space → meteor in the sky → meteorite on the ground.

Why they glow (it isn't friction)

The common explanation — that meteors heat up from friction against the air — is not really right. The true cause is compression. A meteoroid arriving at tens of kilometres per second is moving far faster than the air can get out of its way, so it violently compresses the air directly ahead of it. Compressing a gas heats it, and here the heating is extreme: the air in front of the meteoroid reaches thousands of degrees in an instant.

That blazing air, together with vaporised material boiling off the surface of the meteoroid itself, is what glows. The energy is also enough to knock electrons off the surrounding air molecules, leaving a narrow, briefly luminous ionised trail — sometimes visible for a second or two after the meteor itself has gone. In effect the rock punches a short-lived channel of white-hot plasma through the upper atmosphere.

The speeds are extraordinary

Here is the part that never quite lands until you see the numbers. Meteoroids hit the atmosphere at somewhere between about 11 and 72 kilometres per second. The lower figure is roughly 40,000 km/h; the upper is over a quarter of a million km/h. Even the slowest meteors are far outrunning any rocket humanity has built.

The reason for the range is geometry. Earth is itself hurtling around the Sun at about 30 km/s. A meteoroid that Earth catches up to from behind meets us gently, so it arrives slow. One coming straight at us, head-on, adds its speed to ours and screams in near the top of the range — which is why fast showers like the Leonids are famous for brilliant, fleeting meteors. The Meteor Map shows the measured entry speed of each meteor the network caught, so you can see this spread for yourself, night to night.

Showers and sporadics

Not all meteors are alike in where they come from.

Some belong to a meteor shower. Comets, as they loop around the Sun, shed a trail of dust and grit along their orbit. When Earth ploughs through one of these trails — which it does on the same dates each year — we get a shower: many meteors over a few nights, all appearing to fan out from a single point in the sky called the radiant. The Perseids in August and the Geminids in December are the best known.

The rest are sporadics — the steady background of random debris that arrives every night of the year from no particular direction and on no schedule. On a typical night, most of what a camera network records is sporadic, with showers layered on top when one is active. The map tags each meteor as a named shower or a sporadic, so a busy shower night looks visibly different from a quiet one.

Seeing where they fell

For most of history a meteor was a private, unrepeatable moment: you either happened to be looking or you missed it. That has changed. Networks of low-light video cameras, run by observatories and volunteers around the world, now watch the whole sky every night. When two or more cameras tens of kilometres apart record the same meteor, its path can be reconstructed in three dimensions — its real track over the ground, its height, its speed, and even the orbit it was on before it arrived.

The Meteor Map turns that firehose of detections into something you can browse: last night's meteors, each placed where it actually streaked, coloured by how bright it flared, and labelled with its shower and speed. It is the closest thing there is to a nightly weather map of the sky's oldest spectacle — and a reminder that even on an ordinary night, Earth is quietly sweeping up thousands of tiny travellers from space.