Frequently Asked Questions
I think it Landed Nearby?
People often see a fireball meteor low in the sky, and assume it must have landed nearby. Unfortunately, the opposite is true!
Because meteors are around 100km above the ground and the Earth is a sphere, if you see them low on your horizon then they’re miles and miles away, right round the curve of the Earth. On the other hand if you see a fireball overhead, its much closer – though, unless its travelling straight downwards, its still likely to be many kilometres away.
This is called the Niniger Paradox, and you can see a nice explanation of it here.
Meteoroid, Meteor, Meteorite?
A meteoroid is the name for a bit of rock floating in space, generally orbiting the Sun. Big ones are callled asteroids.
A meteor is the bright flash that you see when a meteoroid enters the atmosphere and burns up. Again, big ones have their own name, and can be called either a fireball or a bolide.
And finally, if the meteor doesn’t burn up entirely and some lands on the Earth’s surface (or in the ocean which is more likely!), then it is a meteorite.
How Fast Are They?
Meteors are travelling at between 15 and 80 km/s – that’s 54,000 to 288,000 kilometres per hour! For comparison, a 737 passenger jet travels at about 800 kilometres per hour, and fighter jet might reach 2,500 kilometres per hour. This is one of the ways we can distinguish between meteors and aircraft – they’re going at least 20x faster!
A typical meteor could travel from London to Edinburgh in about ten seconds, and in the half-second that the average meteor shines for, it has travelled between seven and forty kilometres.
How Big are They?
The average meteor is about the size of a grain of sand, and weighs less than a gramme. They shine so brightly because they’re going so fast that they heat the air up so much it becomes a plasma and glows, in the same way that lightning heats up the air and makes it glow. Its not actually the rock thats glowing – its the air.
Most meteors burn up entirely. For a meteor to survive to become a meteorite, it must start out much, much bigger. A typical meteorite, weighing a few tens of grammes, started out as a one tonne meteoroid about one metre in diameter.