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# See the speed of sound

By Kyle Hill

Queen’s performance at Live Aid 1985 was only 20 minutes, but it lived on forever. Propped up by an infectiously enthusiastic Freddie Mercury and Brian May’s screaming  guitar, the performance has gone on to be regarded as one of the best rock concerts of all time. If you haven’t seen it (above), take a little break to appreciate this supernova of a show.

The other thing you’ll notice is the crowd. They are in near-perfect unison, signing along and gesturing with Mercury’s mesmerizing gyrations. The audience was so in sync, in fact, that the only thing separating their movement was the speed of sound itself.

Watch the GIF below. Can you see the rapid, pulsing ripples that radiate through the fist-pumping masses? This is much faster than an organized wave like you’d see during a baseball game. No one is coordinating the movement, so what is going on?

A little math might help. The venue, Wembley Stadium, goes about 115 yards deep. The time it takes wave in the crowd to go from Mercury to the back of the stadium is maybe 0.3 seconds (a rough approximation). Dividing these two values results in a wave velocity of 340 meters per second. That’s almost exactly Mach 1, or the speed of sound.

Think about that! What you are actually seeing is thousands of people reacting reflexively the show, and what pops out is a wave moving at Mach 1. The people are a visual representation of Queen’s music–a unbridled manifestation of sound. It could only have happened at a show like this, yet another testament to Mercury and the band.