Think about the following questions as you watch the video

1. 00:42 At what distance does a sound wave from the human voice run out of energy?
2. 02:09 What does electromagnetism do for sound?

00:12: NARRATOR: Human vocal cords produce sound
00:15: by disturbing the molecules in the air around them.
00:18: Iceberg, straight ahead!
00:23: NARRATOR: The molecules begin to vibrate in a distinct pattern
00:27: known as a sound wave.
00:30: Engine, full stop!
00:33: NARRATOR: The farthest a human voice can travel
00:35: is about 600 feet
00:38: before the sound wave runs out of energy.
00:41: If we want to communicate over longer distances,
00:45: our voices have to hitch a ride on another type of wave
00:51: that relies on a force almost as old as the universe.
00:57: Big History brings in astrophysics
01:00: to connect us back to the beginning of time.
01:14: (explosion)
01:18: The Big Bang: the birth of all the matter and energy
01:23: that will ever exist in the universe
01:26: and the forces that govern how it all works.
01:30: CLIFFORD JOHNSON: The forces of nature we know now
01:34: began to distinguish themselves and separate out.
01:36: One of the forces that resulted from that process
01:39: is electromagnetism.
01:47: NARRATOR: Electromagnetism gives sound a way to travel
01:50: that's more powerful than air molecules
01:52: bumping into each other:
01:54: radio waves.
01:57: These waves are transmitted
01:59: by the vibration of electric and magnetic fields,
02:03: and unlike the simple sound wave,
02:05: radio waves can travel vast distances.
02:09: NASA's Voyager 1 spacecraft
02:12: can send radio transmissions to Earth
02:15: from the very edge of the solar system,
02:18: 12 billion miles away.
02:21: So a cell phone extends the reach
02:25: of the sound waves our voices make
02:27: by converting them into radio waves