What if sound was as fast as light?

If sound were a million times faster - at the speed of light - humans would not be able to survive the terrifying impact of the sound waves.

Compared to light, which travels at 300,000 kilometers per second, sound waves are very sluggish as they travel through the air at just 0.3 kilometers per second. That's why we see lightning before we hear thunder. So what happens when the speed of sound suddenly increases by a million times, which is about as fast as light?

Humans will not be able to survive when the speed of sound is equal to the speed of light.

At that time, people will hear thunder at the same time as lightning flashes. However, lightning will look very unusual.

Sound waves are composed of particles, each moving just enough to collide with the next. This creates areas of higher and lower densities in the waves, according to George Gollin, a professor of physics at the University of Illinois. Think of rainbow springs (slinky springs) - as this toy moves, the loops of wire continuously pinch in and out again. Sound waves are similar. At low speeds the change in density is imperceptible, but at the speed of light it is completely different.

"During a thunderstorm, the air will be very humid, the sound waves go through and squeeze everything, then spread out and the pressure drops significantly," Gollin said. Pressure corresponds to temperature, so the sudden drop in air pressure after thunder causes the moist air to freeze. As a result, humans would see lightning through a thick fog of ice crystals.

With lightning speed, the sound in our world will change completely. For example, a voice whose pitch is so loud that it cannot be heard. "Even your dog can't hear its owner," said William Robertson, a professor in the department of physics and astronomy at Middle Tennessee State University.

Human vocal cords produce sound by creating standing waves, acting like heavy ropes attached to the wall in a gym. When the practitioner shakes them fast enough, the waves begin to oscillate up and down without seeming to travel along the rope. As the rope is shaken faster and faster, the number of waves - or frequency - increases. Similarly, as the sound waves generated by a person's larynx accelerate, they also increase in frequency.

With sound waves, increased frequency means increased pitch. For example, sound waves travel through pure helium three times faster than through air. Thus, inhaling helium makes the human voice sound like a cartoon character. If the audio were to speed up a million times, the results would be much more dramatic.

Orchestral instruments need a redesign if the speed of sound is to increase a million times.

The orchestra would suffer catastrophically, Robertson commented. Wind instruments work similarly to the vocal cords in humans, the sound moving back and forth inside the cavity of an oboe or trumpet, creating a standing wave. Humans would have to engineer wind instruments a million times longer to keep them in tune with violins and cellos. The reason is that when the speed of sound traveling through air changes, the velocity in the string remains the same.

However, humans could not have survived to experience these dramatic changes as even the slightest sound of the flute would cause everything around to explode into pieces.

Light travels in electromagnetic waves, which are not made of matter. But sound waves are composed of particles colliding with each other. A molecule traveling at the speed of light would have near infinite energy, says Gollin. It will blow up every particle it encounters, sending electrons away, and creating a "rain" of matter and antimatter - particles produced in extremely high-speed collisions and possessing the as opposed to material. "The effects then will be spectacular," said Gollin.