I really love this thread. First time posting in here (I think), but I saw this post and it's reminded me of some of my recent smoke sessions. Usually I sit in front of my fireplace, so that the smoke and odor can go right up the chimney. I listen to classic rock and just chill. My thoughts have been returning more and more to the history of our planet.
Being an engineer, I truly admire science and scientists. I'm also impressed with how much they are able to infer from our planetary/cosmic history. Yet, it's still all based on our current set of knowledge. There's so many things which can't be known that the possibilities are endless.
For instance, I had the thought recently that it's entirely possible that Earth wasn't always the 3rd rock from the sun. What if originally the sun was a tad bit smaller such that there was another planet between the sun and Mercury (not necessary for this theory, but interesting). If the sun were smaller, our planet would have been much colder than it is now, and Venus could have been at the perfect conditions for life. In fact, it could have been home to an advanced civilization which died out once the Sun went through it's changes and grew bigger, possibly engulfing the planet between Mercury and the Sun. With conditions on Venus as they are, any evidence of past life would be completely wiped out or unattainable at this point. Who's to say that this doesn't occur again in the future, making Mars the goldilocks planet and making Earth very similar to Venus-conditions? Maybe that civilization on Venus, knowing it's end time was near, helped to populate the Earth with the beginnings of life?
Another thought I've had relates to the quote above. Dinosaurs roamed the Earth for millions of years. Specifically, 248 to 65 million years ago. So for 183 million years, dinosaurs populated and roamed the Earth. Yet all we have from those millions of years of life, are a handful of fossils. Human civilization has been around for, what, 4,000 years? Yes, we've advanced greatly in that time, but if we were wiped out tomorrow, what would be left of us after 1 million years? Not much. So who knows how many advanced civilizations have come and gone in the 65 million years since the dinosaurs were around. If they only last a few thousand years each, then I wouldn't expect much to be left around to find if after 183 million years of life we only have a few dinosaur fossils.
Sorry for the rambling. I'll be back at the fireplace this evening, thinking again about all this. Stay high.