Seeing Back Billions of Years

Scientists estimate that the universe is 15 billion years old. By looking far out into space, they can see the past in other places, because light takes time to reach us. An event that happened on the sun nine minutes ago will just be now visible to us. Astronomers have recently discovered a place so far away that it dates back to almost the beginning of the universe. What we see today happened 14 billion years ago.

Radio Waves and Snowflakes

In a 1980 television show, popular astronomer Carl Sagan said, “All of the radio waves from space ever studied equal less than the power of a single snowflake hitting the ground.”

That wasn’t quite true then, but it was close. Today, with many more radio telescopes and many more years of collecting astronomical radio waves, the total power of all the waves studied from space is still much less than the energy your body used while you read this post.

Astronomer Carl Sagan, public domain via Wikimedia Commons


I’ll bet you don’t know what an orrery is! It is one of those things you see in museums that model the solar system. The sun and the planets are made out of various size balls held on wires, and they circle around like the hands of a clock.

Orreries are hopelessly out of scale. In reality, if the sun was three feet (one meter) in diameter, the earth would be the size of a pea. The pea would be circling the three-foot sun on a wire 100 feet (30 meters) long. This whole thing, with the pea-size earth, and with all the other planets would be over ninety miles (145 kilometers) in diameter.