Wednesday, June 20, 2012

Voyager is... Where Exactly?

Experts aren't sure if the Voyager spacecraft is out of our solar system yet or not. It's hard to tell, apparantly, because there's probably no well-defined border between our solar system (what's influenced by our sun's gravity) and interstellar space. What we do know is that it's extremely far away:
Voyager launched in 1977. Today, Voyager I is about 121 astronomical units away (one astronomical unit is equal to the rough distance from the Sun to the Earth). That is so far that it takes 16 hours for the radio signals it transmits to reach us. (Voyager II is about 22 astronomical units -- approximately seven years -- behind.) It is traveling at about 17 kilometers per second (38,000 miles per hour), propelled by the slingshot effect from flying by Jupiter and Saturn.
These distances are hard to fathom, although it is fun to try. Here's a more poetic take on the vastness of space from page 328 of Kim Stanley Robinson's 2312:
Sorry, but it's true. it has to be said: the stars exist beyond human time, beyond human reach. We live in the little pearl of warmth surrounding our star; outside it lies a vastness beyond comprehension. The solar system is our one and only home. Even to reach the nearest star at our best speed would take a human lifetime or more. We say "four light-years" and those words "four" and "years" fool us; we have little grasp of how far light travels in a year. Step back and think about 299,792,458 meters per second, or 186,282 miles per second--whichever you think you can grasp better. ... 
It goes on like that until you realize just how long it takes to travel with our existing technologies. It's a humbling grasp of the scope of existence.

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