rover49 wrote:
Don't forget, we are seeing some of these planets as they were thousands, if not millions of years ago, so they may be as different now as earth is compared to the dinosaur era.
The furthest away we have so far been able to find is only about 20.000 light years, but the point isn't quite that. IF we ever get a signal from taht planet, then it was sent using technology those aliens had 20,000 years ago. Which would suggest that they are scarily more advanced now.
Of course, once we develop the technology to see planets million of light years away,we may find an early-Earth clone, but irritatingly would be unlikely to ever know whether intelligent life developed similarly there as here, and whether there are aliens at a similar stage of evolution similarly looking at the discovery of a planet orbiting Sol and wondering the same thing.