I was thinking tonight of the things needed to have a technological civilization arise from the primordial dust. And the rules that apply for us, apply for aliens as well. I believe intelligent life is as rare as gold in the universe. A number of factors come into play, I’ll make a list.
When the universe was born, the constituents of that universe were hydrogen and helium. Great for making stars, bad for making rocks, metals, proteins, hydrocarbon chains… you know, the ingredients of life. Stars were born, however, big ones that had short lifespans in stellar terms. Boom! They’d supernova, many collapsing into the black holes that potentially form the heart of galaxies today. In the process of exploding and collapsing, they produced the elements of the periodic table. Including carbon, the most important atom for life. It took billions of years to synthesize these elements in the hearts of stars and spread them across the nascent galaxies, incorporating them into new stars. By the time we got to the third generation of stars, the metalicity of those stars was sufficient to form rocky bodies, aka terrestrial planets when the proto nebula collapsed and formed a star. After 9 to 10 billion years of existence, the universe was diverse enough in the elements to create our Sun, which was born with a planet we later came very much to need. Earth.
It’s entirely possible that because of the metalicity stars need to create terrestrial planets that are metal rich like Earth, we are among the first civilizations to arise in the universe. It takes time to build up lots of iron.
A Lucky Collision:
Shortly after the new Earth was formed, a rocky body named Thea slammed into the planet. It hit at precisely the right angle that didn’t allow it to shatter both worlds, but did allow Earth’s gravity well to retain much of the ejecta. The result: The Moon. The Moon is remarkable. When it was born it was a mere 15,000 miles above the surface of our planet, it’s been receding since the beginning. Tides a mile high inundated the coasts, mixing molecules, providing water to lifeless lagoons and ponds. And, as a side benefit, the gravity of the Moon prevents the Earth’s axis from tilting much more than it does now. Without that stabilization, the planet’s axial tilt can swing wildly, creating dramatic and devastating climate events that would make it difficult for life to arise, and probably impossible for multi-cellular life to exist. Don’t believe me? Imagine the Earth with an 85 degree axial tilt. The northern hemisphere would be in the sunlight for months, then a day/night cycle, then months of darkness. The temperature under full sun would skyrocket, under months of darkness it would plummet to 3 digits below zero. What animal or plant survives that? Now imagine a species that does survive trying to rise to intelligence, agriculture, trade, technology, flight, etc. Without the Moon it’s unlikely anything like life as we know it would be here.
A Lucky Neighborhood:
One gamma ray burster, one star passing too close and pulling planets out of orbit, one supernova nearby, a black hole going active near us… none of that has happened in the billions of years the Sun has been shining and feeding life on this planet. Or, if any of them did, they happened early enough that life recovered. It’s possible some of the early extinction events were gamma ray bursters, but we don’t know. What we do know is that such events are so rare evolution has time to operate. Because we’re in a quiet neighborhood of the galaxy. Light on stars, and light on threatening objects. Good for us now, although it might make it more difficult for when we become star farers.
We’re lucky for Jupiter too. That giant has swept objects that could threaten us with dinosaur level impacts so successfully they happen over millions of years, instead of thousands. We’ve seen it. Just search Jupiter impact on Google and see.
A Lucky Mix:
There are numerous examples of what I mean here, let’s talk about just one however. Water. What if the Earth had twenty times as much water? There’d be no land, or at most just a few islands. Nothing for technological civilization to work with. What if is had 1/20th as much water? We’d have a desert planet that looks more like Mars than our green world. That water came from somewhere, maybe it’s a function of the type of star we formed around, or maybe it’s because Jupiter scooped up the excess. Either way, we got the mix just right. Lucky indeed.
A Lucky Size:
Imagine if we were a super-earth. With surface gravity of 2-3G. Life would probably evolve just fine. Even technological life might. But would they go to space? Probably not. To get off the Earth our rockets are 95% fuel to get to 11.2 kilometers per second and reach escape velocity. That’s at 1G. One a 10 Earth mass super Earth with twice the diameter of our planet that number changes dramatically to 25 kilometers per second. I don’t know the fraction of a percent payload could be for such a world, but if it was even possible to get a satellite into orbit, the payload would be tiny compared to the rocket and fuel. Payload certainly wouldn’t be 5% of the weight of our rockets. More like .05% (again, just a guess, I don’t know the formula for this, but we know it’s much less than Earth if you can get to orbit at all.
Just a few reasons.
These are just a few of the reasons I think technological spacefaring civilizations are very rare. Others, such as the heat in our core maintaining tectonic activity is also vital. And our fluid core creating a magnetosphere. There are so many things that if one was different we’d not be here. So Drake’s equation might want to consider that number, the number of life bearing planets which give rise to technological civilizations is quite low I expect.
All just my opinions, and I might be very wrong. But it’s why, in the Dark Seas Series, humanity doesn’t meet any aliens from our universe.