Exploring concepts in science with an emphasis on futurism and space exploration, along with a healthy dose of science fiction. You could have a human overmind with, say, the sub-mind of Ohio, which was both a separateentity and part of the Earthmind at the same time, and how much so might fluctuate, asmight its membership, with some joining or leaving and involving themselves to varyingdegrees. A Space Elevator is hard to engineer on Earth, when it has to hold up its own weight forthousands of kilometers in Earth gravity. Another natural one could ultimately be the Sun getting hotter and brighter as it agescausing the inner Solar system to become inhospitable.
You can also potentially armor your spaceships up like tanks but needless to say that takesa lot of mass, something that's always to be avoided with spaceships, especially ground-to-spacevarieties as opposed to space-to-space. Or even just removing all the planets life could arise on, mining away all the elementsand sending them home. science and futurism with isaac arthur The faster something is moving, the less time you have to react to it and the more energyit has to do damage, but you can also see it further out and it's even more vulnerableto destruction by some small object just waiting in standby to flick into its path. That is an example of when you might have a doomed planet you can do nothing about buthave plenty of time to prepare for, even if it is absurdly improbable. The second novel from acclaimed sci-fi author Kurt Vonnegut, Jr., The Sirens of Titan sends the richest, most privileged man in 22nd century Earth on an interplanetary journey of self-discovery as a war between Earth and Mars looms. The same applies to any Star League, they've got no external threats in any situation wherethey can't remain unified just by light lag, since it implies war is very nearly impossibleon a galactic scale, but if such threats and wars were viable, so too would be a unifiedcivilization.