> Such a species would now be using technology completely incomprehensible to, and likely undetectable by, humanity.
They are undetectable by us, but this isn't because of how good their technology is (though it may well also be that good), but simply because the universe is so large and the speed of light so slow. Even if their first "person" to create a powerful enough radio had the idea to beam a signal directly to earth, it still wouldn't have arrived. That signal would have been sent before I sun even started forming, so there is no reason for them to have had the idea, but even if they did anyway.
They are undetectable by us, but this isn't because of how good their technology is (though it may well also be that good), but simply because the universe is so large and the speed of light so slow. Even if their first "person" to create a powerful enough radio had the idea to beam a signal directly to earth, it still wouldn't have arrived. That signal would have been sent before I sun even started forming, so there is no reason for them to have had the idea, but even if they did anyway.