Our solar system is big. To understand just how big, consider the giant planet Jupiter, which dominates the sky for much of the night. It’s low in the east as night falls and high in the south by about midnight. It shines brightest for the year, far outdoing all the other planets and stars in the night sky.
Jupiter shines so brightly right now in part because it’s closest to Earth for the year — just 390 million miles away. Of all the solar system bodies visible in our sky, only the Sun, Moon, and three other planets are closer.
Even so, on the human scale, that’s an incredibly vast distance. At a zippy highway speed of 75 miles per hour, it would take almost 600 years to get there. And it would take almost two years at the speed at which Apollo astronauts traveled to the Moon.
The only thing that can travel between planets quickly is light. Moving at a zippy 11 million miles every minute, it crosses the immense gulf between Earth and Jupiter right now in just 35 minutes. So as you gaze at Jupiter tonight, keep in mind that you’re seeing the giant planet as it looked 35 minutes earlier.
That’s not a problem for skywatching, but it can be a problem for missions to the planet. If something goes wrong, it takes more than an hour for a message to reach home and a response to get back to a spacecraft. So when trouble strikes, missions to Jupiter and beyond are designed to shut down and wait for instructions from home — a long way away.
Script by Damond Benningfield, Copyright 2013