The Fermi Paradox does not involve faster-than-light travel.
"We still have this problem of what DNA was doing for that approximately two and a half billion years—the overwhelming majority of the history of life on Earth. Why didn’t it evolve at all during that time? What’s going on?"
Those early single-cell organisms were evolving!
1. The creation of life seems to be easy as the first life appeared very close to earth formation, in a very hostile environment (unless that seeding of life was done intentionally).
2. Sexual reproduction seems hard - it took 2.5B years to evolve, despite the significant evolutionary advantage
3. Plants and animal seem hard again - it took another billion years after sexual reproduction.
After plants and animals appeared, things seemed to accelerate, so for example you could say that having an intelligent species take over the world seems inevitable.
The problem is that those timescales are getting close to the entire lifespan of earth. Within a few hundred million years we expect the oceans to boil and all life to die. So even on earth, with a single sample, it appears that we are incredibly lucky to reach where we reached.
Personally, if I had to bet on an early filter, I'd go for the eukaryotic transition. Not so much the "having a nucleus" part, more the "dealing with genes at scale" part, because it requires so much machinery so low in the stack with so many knock-on effects and such a long payoff horizon. It's like the single-thread to multi-thread transition, except instead of everyone agreeing that multi-thread was the future and merely struggling to get there, we instead had a situation where everyone was trying to eat (literally, as in cannibalize) the proponents of multi-thread if their programs failed to go faster per dollar of hardware.
"In about one billion years, the solar luminosity will be 10% higher than at present. This will cause the atmosphere to become a "moist greenhouse", resulting in a runaway evaporation of the oceans."[2]
If we're talking about manned-space travel, the acceleration needed to get to anything approaching the speed of light would itself take months, if not an entire year.
So that's two years of travel just accelerating and braking. And to the next nearest star, you will probably be traveling at speed for somewhere around 3 years. I'm just assuming that you'd travel half a light year accelerating and braking. It's likely wrong. But I also suspect it's generous.
That's 10 years round trip to get to our closest neighbor.
And yes, while time dilation would cause those on the vessel to experience far less time than that, the people on Earth will still experience every minute of those ten years. It's also about 9 years before you even get a message. Because at least the information can be sent at SOL without having to worry about killing the messenger. 5 years to get there, 4 years to send a message back.
And some people will say "well, what about Von Neumann probes". Well, that still has the problem of at least a decade long wait to see if you have any return on that investment. And it assumes that we can develop artificial intelligence to the degree that such probes are possible. Which is a big leap considering we don't even really know what intelligence or conscience even is. We know what it can do, but we don't know how either works.
So, in order to colonize the galaxy, a civilization needs to be able to dedicate enormous resources to projects where the potential payoff, if any, are going to be at least a decade away. And to have developed technology far surpassing anything we have at the current moment. To have figured out very fundamental questions about exactly what life is.
Yeah. I'm not surprised we haven't seen any extraterrestrial life. The universe is simply too vast.
If a vessel can be made that survives travel durations of thousands of years, and the passengers likewise, then they're adapted for life in interstellar space, and won't see much point in expending a lot of energy to go far down a gravity well to a hostile environment. Telescopes are fine for observation. There's plenty of stuff in Kuiper belts. The locals won't be interesting until they get out to their own Kuiper belt anyway.
> Although he was not the first to consider this question, Fermi's name is associated with the paradox because of a casual conversation in the summer of 1950 with fellow physicists Edward Teller, Herbert York and Emil Konopinski. While walking to lunch, the men discussed recent UFO reports and the possibility of faster-than-light travel. The conversation moved on to other topics, until during lunch Fermi allegedly said suddenly, "But where is everybody?" (although the exact quote is uncertain)
My understanding is that due to the expansion of the universe, all the galaxies are moving away from each other. The rate at which they move away from each other is directly proportional to the distance between them (the Hubble Constant), because space itself is expanding. Kind of like if you lined up a bunch of deflated balloons next to each other and inflated them at the same rate.
At some point, around 13-15 billion light years away, galaxies are actually moving away from us faster than the speed of light. Also, because their "velocity" is proportional to the distance, they're actually accelerating away from us.
With each year, more things reach a "velocity" where they're moving away from us faster than the speed of light, and will never be reachable without faster than light travel.
Thus the Fermi Paradox only makes sense if you consider it likely that interstellar aliens could travel faster than the speed of light. If FTL travel is impossible, then a timer was started on the day the universe was created, counting down the seconds until our galaxies were moving away from each other too fast for contact to ever be possible. In that case, the Fermi Paradox is a paradox no more. It's entirely possible other life does exist, it's just physically impossible for us to contact each other.
The Fermi Paradox has come to be the term describing the more general lack of alien detection, but it's only a "paradox" if we expect to be able to detect aliens. That expectation is only reasonable if aliens produce enough activity close enough to us that we would be able to observe it. If FTL is possible, that assumption is an unequivocal yes. Without FTL, it's infinitely more contentious.