[zaphirplane]

Why does the distance change the dynamic? So what if the species trying to exterminate you are 500 light years away, you think they should ignore it ? Maximum travel speed of an extermination weapon in 100,000 years of of science may very much be impressive or even magical by today’s standards

[cedilla]

The distance completely changes the dynamic. If I tell you there's a crazy axe murderer in your house, you should be afraid. If I tell you there's a crazy axe murderer on Venus, how afraid are you?

And unless we are completely wrong about physics, the maximum speed of a weapon will be the same as it today - very close to 1c.