How can I explain why meteors glow without saying friction?

Many textbooks and websites say meteors glow because of friction with the air. That is a simplification that can create misconceptions.

What really happens. A meteoroid travels at 11 to 72 kilometres per second, far faster than sound. It cannot push air out of the way smoothly. Instead, air piles up in front of it in a thin layer and is compressed extremely rapidly. Compressing a gas heats it, as you can feel when pumping up a bicycle tyre and the pump warms. At meteor speeds, the compression is so extreme that the air reaches thousands of degrees, becomes ionised and glows. This hot gas also heats the meteoroid's surface, which melts and vaporises.

Why friction is misleading. Friction suggests surfaces rubbing together, like sandpaper on wood. At meteor speeds, the main effect is the shock wave and compression, not rubbing. Most of the heating comes from the hot compressed gas.

Demonstrations. - Let pupils feel a bicycle pump warm up as they pump. - A fire piston, a sealed tube in which a plunger is pushed down rapidly, can ignite a small piece of char cloth by compression alone. This should be done by a teacher with appropriate safety precautions.

Similar examples. Spacecraft re-entering the atmosphere need heat shields for the same reason. The glowing plasma around them is caused by compression heating.

Language. It is fine to mention that air resistance slows the meteoroid, but emphasise compression as the cause of heating.

This helps pupils build accurate models of energy transfer.

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