I've often wondered how the development of space by humankind would have played out if we didn't have the moon. The size ratio of the moon to the earth is quite large compared to other known planet-moon systems, and it hangs in the sky as a very obvious reminder that there is somewhere to go if you could throw yourself off the surface of the planet. Wouldn't the idea of spaceflight seem much more boring if all you could do easily was get into orbit? It might not even seem like traveling at all.
A recent study reports that
binary-star planetary systems may be equally likely as single star systems to develop. As far as the geometry, the Space.com article
three possibilities, based primarily on the distance separating the stellar pair. A close in pair might have a planetary system orbiting the center of gravity of the two stars, (giving you a Tatooine sunset). A pair with medium separation may be too unstable for planetary formation at all. And the third option is that the two stars may orbit far enough apart that they each have their own planetary systems in orbit around them.
It's this third option that I find most intriguing. Just as the Moon hangs tantalizingly close, in our sky, just asking to be flown to, imagine there was another entire solar system, a second sun 3-4 times the distance to pluto away. A good distance to be sure, but much more within reach than even Alpha Centauri. A tempting distance, especially if there were planets in it's
habitable zone.
How much more eager would we be in that scenario to develop a real long-distance spaceflight capability? If there were colonies, the politics of the added distance would make it a much different dynamic than an outpost on Mars. Interesting stuff.
