I would add that there are a series of planetary system-wide risks that appear only for civilizations traveling within their solar systems but do not affect other solar systems. These include artificial giant planet explosions via initiating nuclear fusion in their helium and lithium deposits, destabilization of the Oort cloud, and the use of asteroids as weapons.
More generally speaking, any spacecraft is a potential weapon, and the higher its speed, the more dangerous it becomes. Near light-speed starships are perfect weapons. Even a small piece of matter traveling at very high velocities (not necessarily light speed, but above 100 km per second, as I recall) will induce large nuclear reactions at the impact site. Such nuclear reactions may not produce much additional energy but will cause significant radioactive contamination. They could destroy planets and any large structures.
Additionally, space colonization will likely develop alongside weapon miniaturization, which could ultimately result in space-based grey goo with some level of intelligence. Stanisław Lem’s last novel, “Fiasco,” seems to address this concept.
I would add that there are a series of planetary system-wide risks that appear only for civilizations traveling within their solar systems but do not affect other solar systems. These include artificial giant planet explosions via initiating nuclear fusion in their helium and lithium deposits, destabilization of the Oort cloud, and the use of asteroids as weapons.
More generally speaking, any spacecraft is a potential weapon, and the higher its speed, the more dangerous it becomes. Near light-speed starships are perfect weapons. Even a small piece of matter traveling at very high velocities (not necessarily light speed, but above 100 km per second, as I recall) will induce large nuclear reactions at the impact site. Such nuclear reactions may not produce much additional energy but will cause significant radioactive contamination. They could destroy planets and any large structures.
Additionally, space colonization will likely develop alongside weapon miniaturization, which could ultimately result in space-based grey goo with some level of intelligence. Stanisław Lem’s last novel, “Fiasco,” seems to address this concept.