> aliens being here would imply FTL is possible
Why? There are plenty of stars within a sub-light-speed radius since events that could've announced us to the galaxy: advent of radio, first nuclear tests, etc.
Why? There are plenty of stars within a sub-light-speed radius since events that could've announced us to the galaxy: advent of radio, first nuclear tests, etc.
https://www.antipope.org/charlie/blog-static/2007/06/the_hig...
The odds someone is interested enough to spend truly mind boggling amounts of energy (literally moving hundreds of mountains worth) and hundred of years to check us out after one of those events - and not even say hi - is low. That they are also so close - also low. If they have some sort of magic drive tech (implied by the behavior of these drive sightings), then that changes the math a lot.
Most people mean ‘magic drive tech’ when they say FTL.
How could one even begin to make that kind of reasoning? Then the conclusion estimating the low probability is based on what? If I'd have to guess, I'd say otherwise - once a reasonably developed civilization (Kardashev type II and above) gets access to colossal amount of energy, there aren't that many things worth spending it (and attention in general) for. Life may or may not be plentiful around in the universe (it occured relatively shortly after Earth formation), but I'd bet sentient life is orders of magnitude more scarce, considering that it took billions for it to develop on Earth. That alone would make potential cradles for sentient life to be very interesting destinations to check once in a while. To provide here a relatable example, let's imagine a mostly desert continent, with a community living somewhere on its coast. At one point they develop enough capabilities to safely venture out in the desert and to make long journeys. How interested would they be in revisiting some oasis where they encountered some earthworms and small plants, and how interested would they be in revisiting a place (even across the continent, if that is what takes) with apes which happened to also exhibit some signs of primitive engineering?
P.S.: With all that, I still hope we're alone within a large enough vicinity, so we won't have to deal with anyone else for as long as our species exists.
There are roughly 1400 star systems within 50 light years of us [http://www.atlasoftheuniverse.com/50lys.html]
Which sounds like a lot. But there is estimated to be about 10 to 100 billion star systems in the Milky Way alone. So the odds that any of those stars are occupied by any excitijg neighbors is pretty low, unless the number of alien species+occupied star systems is mind bogglingly large. If there are 100 occupied star systems randomly dispersed in the galaxy meeting all these requirements, it would be one in 70,000 to 1 in 700,000 odds for instance.
Not great. And that is assuming a lot about how much energy they would be willing to expend. We’ve seen no evidence of anything resembling a Kardashev type civilization in the neighborhood.
If there is magic FTL tech, obviously everything is different. Also, who knows maybe we grew up next door to an equivalent to a intergalactic bus depot. That would also change things.
At least based on what we know now though, the tyranny of the rocket equation is rather complete, the distances involved in traveling between star systems so vast, and the energy requirements of even approaching C are so high that it is not a realistic thing to consider for life that works the way we do any time soon.
As for "we’ve seen no evidence of anything resembling a Kardashev type civilization in the neighborhood", although you're right, it's hardly useful to think in this frame. The available means that we had so far for observing anything in far away space were and still are pretty limited, for even inert phenomena. I'd say that counting on that to spot something sentient, where things are actively engineered, which may as well include engineering for the appearance itself, is overly optimistic.
If we’re trying to get something even somewhat defensible, there has to be some grounding on SOMETHING, or it’s all just fantasy.
If they spent 10k ly getting here, and the ungodly amount of energy and time it would take to do 20% of light speed over that distance, and they had since the great oxygenation event to notice us and get here (and have such a technological and energy advantage over us they were able to do it) - then why are they being seen randomly checking out military aircraft (not very smart or subtle it seems?) but never talk to anyone else? And show no other signs of existing?
Not impossible, but seems like a truly massive amount of energy and commitment of time over what far exceeds the timescales life as we know it works on to check out what could just be a puddle full of gooey algae for all they knew. And then potentially just sitting and watching for 100 million or a billion years.
At least seeing radio signals or a double flash from a nuke test means there is something like intelligent life?
Not really. Both of us were counting on current human knowledge, that our galaxy is this (light years) large, that the maximum speed is that of light and that an exponential amounts of energy is needed for each logarithmic increment of relativistic speed, that there is a working model for life based on what we call organic chemistry, that an atmosphere rich in a highly reactant element that is oxygen can not exist without something continuously producing it and what that could mean for an alien observer, all because, in the slim chance that we are the ones with technological head-start, that should serve as base ingredients for thinking about our long-term future external policy. I'm thinking if we are to become Kardashev type II (and above) civilization, what ought to be the best approach in dealing with an evolving galaxy? But yes, there are also aspects which are hard to think of now in more than hypothetical terms, like what would mean in practical terms to have access to (at least) a star's amount of energy and what it would be worth spending it on. To me, "to check out what could just be a puddle full of gooey algae" looks like a very important objective, and finding something underwhelming should be the desired result, safety wise.