Yeah, I should have specified that my comment was with respect to manned aircraft/spaceships/and so on.@dmgtz96 8.5years would be a long time indeed to travel to our nearest star, but remember we as humans have craft traveling for decades before it reaches the destination, so no reason why advanced races wouldn't send out unmanned craft for extended periods of time. Although as you say, the closest lifeform might be 50 or 1000 light years away, which would put the number very high
Interesting, hadn't heard of Fermi's paradox but I had heard of the Drake equation.Isn't the opposite true? I'm talking about Fermi's Paradox, in which states that the size of the Universe is so large and the age so old that mathematically we should be seeing countless civilizations succeed in interstellar travel (however fast that may be). These would be active or relics. The fact that we haven't is a mathematical paradox.
The Kepler telescope findings helped produce an estimate of 40 billion planets in the habitable zone, and this was from 2013. Number is likely higher now. That's just the Milkway alone. 40 billions planets with millions upon millions of years to produce multiple intelligent lifeforms. We went from horse and carriage to rover on mars in little over 100 years. Its microscopic time to achieve space travel.
Here's the link to the wiki article on possible explanations for Fermi's paradox. My money is on "It is the nature of intelligent life to destroy itself" based on how humanity is doing right now. "Periodic extinction by natural events" is also plausible. With COVID I wouldn't be surprised if other intelligent civilizations were wiped out by some kind of virus instead of the reasons mentioned in the article.
Your comment about the 40 billion planets in the Milky Way needs context. For reference, once you consider rogue/orphan planets the Milky Way is estimated to have 10^15 - 10^19 planets. For the lower number, 40 billion is just 0.004% of all planets in the galaxy. For the higher number, 40 billion is negligible. Further, the Milky Way has a radius of 129,000 light years based on recent research (previous researchers had calculated ~52 thousand lightyears). Even though 40 billion habitable planets exist in the Milky Way, they are a negligible amount of the total planets in the galaxy, and they are far enough away from us to never reach us during the microscopic time our civilization has existed.