Space is really, really big, and aliens are not magic. These are the two critical points to consider if you really want to think about UFOs as spacecraft from distant star systems. They are also the most important points to consider if you want to imagine humanity getting out of the solar system and building a Galactic Federation or (depending on your political inclinations) an Empire. The first point forces us to confront the insane distances between the stars. The second point forces us to deal with the physics problems involved in crossing those distances, even if we don’t know what their solution might be just yet. 

Let’s take a leap into the unknown but keep our science crash helmets on. The question we want to ask is this: If UFOs were spaceships from other star systems, then how might they (or us or anyone) cross the great interstellar void? The question is big enough that we must break it up into two parts. This week’s column will focus on the first part — getting a gut feeling for the real scale of the void.

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