Astronomical Distances

Reading about the Voyager 1 probe leaving the solar system got me thinking about the unbelievable distances there are in outer space. Voyager 1 was launched 36 years ago and only now has it left the solar system, despite the fact that it's traveling over 17 km a second (or around 62,000 km/hr).

This got me tinkering with some calculations to try to convey how big astronomical distances are. Back in elementary school you may have done a project where the earth was a small size and then had to determine how far away the other planets were. Let's do something like that again.

If you shrank the universe such that the Earth was a tiny dot only a quarter of a millimeter in diameter (so the entire Earth shrunk to the size of a dot you can barely see):

• The Sun would be 2.9 meters away (and it would only be 2.7 cm in diameter)
• Pluto has a very elliptical orbit but on average it would be around 114 meters away.
• The next nearest star, Proxima Centauri, would be 786 kilometers away. Not meters, kilometers.

(remember, the Earth is the size of a dot you can barely see)

• The star Sirius would be 1595 kilometers away.
• The Orion Nebula would be over 250,000 km away.
• And the Andromeda Galaxy would be 473 million km away!

And that’s why it takes probes like Voyager 1 a long time to get anywhere -- the distances are unbelievably big. It will take tens of thousands of years for the probe to reach another star system.

Sometimes I feel sci-fi books and TV shows do a lousy job at capturing this vast emptiness. Most get around the distances with tricks like “warp” or “hyperspace” travel, or some other way to quickly traverse the distance such as wormholes. A few recognize the long time it will take to cross interstellar distances so use things like suspended animation for travelling. I suppose it wouldn't make for an exciting book if it was all about hurtling through empty space for your entire lifetime.

Anyway, I’m thrilled to have been around for the momentous occasion of the first man-made object to leave the solar system.