This is a collection point for such information.
I keep a running list of reasons why Earth-Humanity are unique in the Universe. Here is my partial list. It’s incomplete and merely presents food for thought.
Earth is unique. We read about these immense numbers of galaxies, stars and planets and just *know* that there are other “earths” out there. But it will become more and more evident and publicly accepted that Earth is exceedingly unique. The list continues to grow regarding factors that make it so, but here are a few.
• Sol is singular, not a binary star system. It’s estimated up to 1/2 of solar systems are binary. This cuts the number of possible stars for Sol like systems by 2/3s.
• Sol’s position in the galaxy is out in an arm away from the chaos of inner galaxy turmoil.
• Sol’s wave path as the Milkyway revolves allows it to miss much of the disruptions in the galaxy. (Local bubble)
• Earth’s distance from Sol, Goldilocks zone, LOTS of liquid water.
• Earth’s neighbors, Jupiter’s asteroid cleaning.
• Earth’s impact from Theia resulting in a much denser iron/nickel core.
• Earth’s extensive magnetosphere (due to this larger than normal magnetic core).
• Luna’s very large size and its influence on Earth’s rotational / axial stability, not to mention tides (tide pools enhance life generation possibilities).
• The asteroid belt delivering asteroids, comets and meteors and their H2O and elements.
Here are some chemical aspects of Earth that make it unique
• Earth’s H20 to land ratio.
• Earth’s land distribution (large continents, not islands).
• Earth’s high quantity of radioactive elements within the planet interior.
• Volcanism continuously recycling minerals and elements.
• Early life starting 3.5bya, clearing the oceans of toxins.
• The tilt of Earth providing seasons.
• Ozone without which DNA would be rendered inert.
• The transition of prokaryotic to eukaryotic life.
And here are some reasons why Man is unique on this Unique earth.
• 2.5 billion years of hydrocarbon deposition.
• Humanity’s survival through and benefit from disease, we are robust.
• The decimation of prior dominant classes of animals and the rise of mammals.
• Fire both its discovery and the existence of burnable material for boosting our nutritional uptake and our ability to manipulate elements.
• Broad variety of available metals useful for life and industry and eventually the construction of communication capabilities.
• The configuration of the continents that gave rise to grasses that gave rise to agriculture.
• The existence and development of draft animals without which agriculture would not have arisen.
• Humanity had to survive, and in general, avoid having its electricity systems (generation, grid, transformers) being devastated by CMEs (coronal mass ejections).
And no doubt many more.
We are unique.
• I agree that the numbers favor life, lots of life, in the Universe. What I’ve tried to explore, over the years of gathering this list, is that the trek of humanity to the stage we enjoy today is one of tenuous happenstance. I find that many folks I’ve spoken with haven’t examined the special situational sequence of events and configuration of planetary, ecological, and geological factors that humans leveraged to get to this point in our evolution.
Take trees for instance. Where would humanity be if it were not for the existence and diversity of trees? The implications are manifold. If there are alien intelligences out there living on planets where trees or their substitute, do not exist… could they discover fire? Build shelter? Build ships? Construct tools and machinery of thousands of kinds? Produce charcoal for smelting? Produce methanol as a fuel? I realize that such a statement is highly anthropocentric. But still, imagine humanity without the ability to leverage wood as a resource. Wither wood, would we have ever reached the state we thrive in today?
It’s factors like that, in that list as well as others I’ve identified, that simply invite one to step back and think about how incredible humanity’s path to technological advancement really is.
• As I alluded to, the argument for life vs intelligent, electromagnetic capable life are two different things. Lots of life — sure. Intelligent life? Who knows. I simply list factors which many people do not take into account when examining humanity as an EMC (electromagnetic capable) species. A similar species to us would have to have enjoyed similar serendipity. That’s all my point is trying to provide. For instance, fuel for fire is necessary to smelt the metals that an EMC life-form might leverage to build their technology. Not to mention the fact that such metals must be readily available. Things like that.
• What’s unfortunate about SETI is that it’s focused on radio. It appears that even for humans, radio is a transition technology. The recent fervor regarding directed energy propulsion — lasers — to push tiny space craft out to the stars speaks of using lasers to communicate to and from said space capsules. If we’re already looking to use lasers to talk between us and our crafts or our colonies then it would seem we need to start to switch SETI over to capturing pulsed light transmissions; if we want to starting “listening” to aliens who might be using light to talk.
• Theia’s impact delivered more than just iron and nickel to Earth’s core (producting an extra large magnetosphere) but also (probably) delivered additional carbon, nitrogen and sulfur — chemicals which, like oxygen and hydrogen, are volatile and tend to get boiled off during a planet’s accretion phase (forming from the solar system’s proto-disc).
• Tidally locked planets and moons would lose their magnetosphere (the dynamo engine within a molten cored planet). Without this magnetic shield solar and cosmic radiation would ravage any life that had arisen on the planet.