This is an image of lightning.
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Photograph provided courtesy of Steve Albers
Sound Waves vs. Light Waves
You see a flash of lightning across the night sky. Five seconds later,
your hear the rumble of thunder. If lightning and thunder come from the
same source, then why don't they occur at the same time?
Actually, they do occur at the same time. The time difference that
you sense is due to the way sound and light travel. Light travels
extremely fast (300,000,000 m/s). In fact, it is faster than anything
else. Sound travels at a measly 343 m/s through air. Therefore we can
see light in an instant, but it takes a while to hear thunder.
Sound has another disadvantage because it tends to bounce off molecules
in the air. This makes the sound travel in all different directions.
The further away the source of the sound is, the more the sound gets
distorted.
Therefore, when you hear rumbling thunder, the lightning bolt was far
away. When you hear a crack or boom of thunder, the lightning bolt is
close to you (<100 m).
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