“The average star is more than six billion years old. The Sun is 4.5 billion years old. So the average advanced civilization could be a couple of billion years more advanced than we are.”
True, however the galaxy is a dangerous place to hang out. Our solar system is on an offshoot of a spiral arm, about 3/4ths of the way from galactic center. A rather dull place, but there’s a good chance that either closer, or further away from GC is too violent and destructive for life to last long enough to evolve intelligence.
Add to that supernovas, that will sterilize a large area of space so relatively fast that a space vessel hundreds of times the speed of light would be needed to escape its wrath.
And there’s the next problem. If you go one way or another along the habitable band of the galaxy, you’re probably looking at anywhere from 200-500 light years before you encounter a habitable planet.
At best, you need a spaceship capable of 128 times the speed of light, and it will still take 1.56 years for just 200 light years. 256 times the speed of light for nine months of travel.
200 light years is not diddly in space travel. Beyond that the distances along the habitable band get significantly greater.
So I’m not particularly worried.
Remember, for someone that advanced -- billions of years more advanced than us -- we cannot conceive of their capabilities.
I believe the speed of light is the speed limit in our universe, just as Einstein said it was. But already, never mind billions of years from now, physicists are proposing ways around it.
Maybe they could travel here through the multiverse, or tunnel their way through a wormhole, or inflate a bubble of space around their ship and arrive here in a fraction of a second.
I've been meaning to read "The Killing Star." Ever read it? Heard it's pretty good. It's about the Earth getting clobbered by a non-explosive missle traveling at 99.99% the speed of light (think Rods of God on steroids) lobbed at us by a hostile alien civilization. The kinetic energy was so great that it sterilizes, or nearly sterilizes, the planet.