In time possibly much more unusual and rare than in all of space-time, and given that the sun is a second generation star unless conditions are much better than they were here on Earth it may take a lot longer for (intelligent) life to develop than here. We may be 'early'.
So 'right now' we are probably rare in the sense that we are a space faring species that hasn't (yet) destroyed itself and that may happen only rarely, so rarely that there is never much or even any overlap in time between two species at that stage of development (or say, even the last 500 years or so if you want a larger window). That's 500 years to overlap across an extremely large population of stars and planets so it may happen but it is still a small chance.
But if you let go of the time requirement then I don't think it is all that rare for it to have happened multiple times.
Let me give one example of how important the Moon is: without the moon the tides would be very weak (just solar tides) and that would mean that there is no part of the world where aquatic life can easily evolve into amphibious life (no tides: no tide pools, so no half-way-house between land and water). It may still have happened but much slower.
And active tectonic plates cycle nutrient sediments that collect at the bottom of the ocean back up onto dry land. Without them all life would eventually migrate into deep water and below ground.
Have we decided if the moon affects tectonics or they are a happy coincidence?
You know, I'm not sure. Pangaea was 'only' 250 million years ago, but it sounds like there were 3 others - that we know of - and the oldest goes back more than a billion years?
I'm not sure whether tidal forces have a tiny or outsized affect on movement in the crust. Io is substantially affected by tidal forces, but that's a very different scenario.
We don’t know. We used to think it was critical because we thought life evolved in tide pools. Obviously no tide, no tide pools. That might be true, but now there’s good reason to believe that life started first in the deep depths of the ocean at magma vents. If that’s the case, maybe the moon isn’t essential.
The moon did shield us from many impacts however. All those massive craters were rocks that would have hit earth.
an interesting, albeit unsatisfactory solution to the Fermi parodox would be that we are a rare anomaly of a distant moon of comparable but lesser mass to the primary body, located in the inner solar system, but without tidal locking.
The latter two points might turn out to be extremely rare events.
I wouldn't call that a final solution to the paradox, though.
(Put on your tinfoil hats.)
Maybe the Earth-Moon system was engineered. The solar system came together from a nebular cloud 4.6 billion years ago. The great impactor hypothesis points to the mega-collision around 4.5 billion years ago. During the early days of the solar system, the system was very chaotic. By applying tiny-but-very-precisely-calculated forces in that system, you could cause an impact. Sure, it's many orders of magnitude above what humans have accomplished, but the gravity slingshots that got the Voyager missions out of the solar system are the same principle.
Dunno, seems crazy to think we are rare. Based on what exactly? Sure our radio signal has gone out 60-80 light years, which means nobody has replied within 30-40 light years of us.
There could be many 1000s of civilizations in the galaxy. Maybe we aren't that interesting to visit, especially since we always have a few wars going on, and we have nukes. Maybe they are watching us for anti-matter production, fusion, stopping burning fossil fuels, and a century of peace.
It seems like the circumstances of our planet's location and the moon and the resulting tides and temperatures are rare. And our evolutionary history seems very dependent on those.
The question is whether or not there are other good ways to end up with an abundance of complex life. We have no idea.
Would nukes be a concern to a civilization capable of interstellar travel? They'd almost certainly have access to technology capable of wiping us out. The more likely reason is that space is really big, and making interstellar voyagers is simply not worth the effort for most civilizations, if they do exist.
Maybe warlike species that destroy their planet are a dime a dozen and considered invasive species by the rest of the galaxy. They have enough interest to keep an eye on us with probes, but have no plans to visit or reveal themselves.
Maybe! Or they could have no concept of weaponry at all. How advanced would that be? I guess natural selection suggests we're most likely to encounter a hostile species, so maybe you are a lot closer to the truth than I imagine
2 trillion galaxies in the observable universe, each with hundreds of billions of stars on average. Those events better be extremely extremely rare.
To me it would be much more mind-blowing if our earth/moon system actually was a one in two hundred sextillion-ish event, than if the universe is teeming with life.
I'd also like to know. I supposed there must have been a lot of heat from the initial impact, tides must also happen inside the Earth, but I wonder how different the Earth would have looked like techtonically without the Moon?
No plate tectonics? So perhaps resurfacing event(s) like on Venus?
To me this question is in answer to the Fermi paradox, the great filter .. is it behind us? Its important to answer because if its not behind us, then; not wanting to be hyperbolic but, we are about to end.
Apparently most of the computer models of the early solar system doesn't result in rocky planets this close to the sun. And when it does there are constant meteor strikes. So we could be quite improbable. However considering the size and age of the universe, if the filter is behind us in the form of improbability, it should look to us as something that is impossible.
The "about to end" phrase is doing a lot of work there, unless you mean particularly 'soon on a geological time scale'.
Of course we could be a few hours from some autocratic idiot starting the last nuclear war, a few months from a terminal AI singularity, or a few years from a runaway climate or food web collapse. But, I see nothing in the Fermi Paradox requiring the end to be so soon. Even dozens of millenia is still the blink of an eye in geological or galactic time scales. Perhaps the filter is populating the solar system but not escaping to other star systems before the sun expands into a red giant?
If a tree falls on a planet 15 billion light years from Earth, does it matter to us? I think what really matters is how unusual are we in our galaxy and its neighbors.
"in the universe" could be read as "in general", which means specifying our galaxy and its neighbors implies a specific difference between our local conditions and conditions elsewhere that may not exist. Why import conditions?
I wouldn't assume uniformity until it is demonstrated. We already know beyond doubt that most galaxies are in far denser neighbors that ours is, and a few are in even more rural neighborhoods.
Also, for this question it really matters who we will ever meet, or could ever meet, even in artifact form, or vice versa. Galaxies far enough away are effectively in parallel universes for all intents except physics.
I'm interested in the answer universally, pardon the pun. Even if we never meet them in the distant future, I'd like to know that someone else is out there.
This is a never-ending series of questions. Is there a multiverse? Did life exist in universes before ours? Will life be created billions of years from now in our own universe?
- How much do we owe the moon & Theia for our existence?
- How unusual are we in the universe?