I’m not the poster you’re asking this of, but the reasons why a seemingly empty universe are concerning basically all boil down to “it indicates that the universe is hostile to civilization specifically, or to life in general.”
If the universe is neutral or friendly to civilizations, then we should expect to find someone out there in fairly short order. The universe is so large, even if there’s only a one in several billion chance of a particular solar system birthing a civilization, there should be a few others besides us already in the Milky Way.
If there’s not anyone else, the best case is that we are simply the first (this is my personal bet). Worse scenarios include civilizations simply fail and die after some time, or that one “predator” civilization kills off any other civilizations it finds before they can become a threat.
As Arthur C. Clark said: Either we're alone or we're not. Both are equally scary.
To think that with billions of stars, each with at least one planet, intelligent life only happened on one planet (the Earth) means intelligent life is super rare, even if life in general happens on many planets.
This means if we get hit by an asteroid or don't get passed the Great Filter, the only ones who "think" about this universe and give a meaning to it will be gone forever.
I suspect that intelligence is an inevitable evolutionary step once a nervous system is in place. Nearly all animals have evolved towards increasing intelligence.
The rough idea is that the galaxy seeming insanely quiet could potentially imply that it's rare for life to reach a level which we can easily detect; space-faring, multi-planetary, capable of astro-engineering, etc.
If that is the case, it might be that there is a "Great Filter" which tends to knock these civilizations back into their stone age, or kill them outright. Maybe it's nuclear weapons, or grey goo, or biological experiments that break containment, or an AI that decides to kill its makers, or even just conventional wars that stunt their growth, etc. Generally, some kind of technological development or societal event that leads to that civilization going/staying dark to the galaxy.
The potentially worrying question is: have we passed the Great Filter? Or is it still somewhere in our future? There are any number of things that might kill or stunt humanity in its crib, before we spread out far enough to be able to persist.
And even then, how long is it going to be before a nuclear holocaust on Earth would no longer effectively cripple humanity, even if we've colonized the solar system and could nominally survive it? Or imagine AI-infused grey goo that spreads throughout the solar system.
Yes, although there are more esoteric alternatives to the Great Filter. For example, the idea that our universe is a simulation and the number of sapient species is deliberately limited by the controllers to few or perhaps just us.
They also both posit the existence of a supreme being. Either an all powerful god, or an all powerful sysadmin.
I’d go further and say they require such a being, despite us having reason to believe such a being is not compatible with our understanding of how the universe actually works.
Just as the existence of an all powerful eternal being doesn’t seem compatible with what we know about what’s possible in the universe, I have severe doubts that a simulation of the fidelity we observe in our existence is practical to build in our universe.
I have severe doubts that a simulation of the fidelity we observe in our existence is practical to build in our universe.
It certainly isn't. You can't simulate three atoms using two atoms. There's no reason another universe has to abide by the same rules as ours, though. It's not something anybody should actually worry about but it's about as scientific an idea as string theory is.
>The potentially worrying question is: have we passed the Great Filter?
As a biologist I'd love it if they found life (that was totally seperate from Earth life) somewhere else in the solar system, but if we do it's one less great filter.
Oh no, that’s even worse. If life is ubiquitous in the universe, it means we would expect intelligent technological life to be even more common than otherwise. The absence of such civilisations, despite weak filters at the “low end” of the Drake equation, implies an even more dangerous and inescapable filter in the high end of the equation where we are now, that wipes out later stage civilizations.
If the universe is neutral or friendly to civilizations, then we should expect to find someone out there in fairly short order. The universe is so large, even if there’s only a one in several billion chance of a particular solar system birthing a civilization, there should be a few others besides us already in the Milky Way.
If there’s not anyone else, the best case is that we are simply the first (this is my personal bet). Worse scenarios include civilizations simply fail and die after some time, or that one “predator” civilization kills off any other civilizations it finds before they can become a threat.