Expert Knowledge Trivia Quiz

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5. Sound bite

The “Mach numbers” that are often used to measure aircraft speeds are based on the speed of sound. Mach 2 is double the speed of sound, Mach 3 is treble the speed of sound, and so on. At about what Mach number does light travel?

A) Mach 90
B) Mach 9,000
C) Mach 900,000
D) Mach 90,000,000

Your answer was correct!

The speed of light in air is about 300 million metres per second. At sea level in moderate temperatures, sound travels at some 333 metres per second, about 900 thousand times slower.

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