The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
https://en.wikipedia.org/wiki/Great_Filter
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, “If life is so easy, someone from somewhere must have come calling by now.”
https://en.wikipedia.org/wiki/Fermi_paradox
Personally I think it’s photosynthesis. Life itself developed and spread but photosynthesis started an inevitable chain of ever-greater and more-efficient life. I think a random chain of mutations that turns carbon-based proto-life into something that can harvest light energy is wildly unlikely, even after the wildly unlikely event of life beginning in the first place.
I have no data to back that up, just a guess.
AFAIK there is no known energy source that would keep a generation ship powered for the duration of an interstellar flight.
The person to whom you responded is half right. The speed of light is half of the barrier to interstellar travel. Entropy is the other half.
Would you need a power source? If you aim your ship correctly, then put everything alive into cryo, the ship could go completely dark, vent all heat and become a frozen rock. Then after [very long time] the ship enters the vicinity of a different star and can be reactivated and unfrozen using solar energy. You dont need energy to maintain cryo if the whole ship is at 1° kelvin.
(Of course that relies on cryo sleep being possible)
Or synthetic life. (Robots)
Only if they can be turned off (same as the cryo sleep). The whole ship either has to have enough energy to last potentially 100000 years (no theoretical power source exists like that) or enter a state of 0 energy consumption. Solar/radiation collectors dont work if you are to far from a star. Synthetic life still needs energy
Well, that depends on how far you’re going. If you pick a nice close target, let’s say 3 light years away, you can potentially get there pretty quickly. With fusion propulsion systems you could make the trip is something like 70 years, coasting most of the way. I’d need to check the math to get exact numbers, but I recall fusion allowing for pretty reasonable trip times.
But if you can survive for hundreds or thousands of years, then solar sails become an option. Then it becomes a materials science problem of how thin can you make a sail that will still hold together. The greater the sail to payload ratio, the faster you go.
Also, you’d need to know for certain that the planet you’re sending your generation ship to is habitable for your species. While this may be technologically trivial for a society that can build a functional generation ship, the timescales for such projects (literally hundreds or even thousands of years from the launch of the probe to the yes/no signal) makes it extremely difficult to actually organise.
Lol we get to the planet and find it was obliterated by a gamma ray burst 50 years ago
Or just send a lot of ships and hope one or two find something good.
That and you won’t even know if the destination civilization is still there by the time you arrive.
Plus isn’t the rate of expansion of the universe increasing? So at some point, even going at light speed, your destination will recede faster than you can travel.
Not really. Galaxies are pretty stable, stars orbit around the central black hole in the galaxy. You can absolutely travel between stars in the same galaxy, even if it takes a thousand years.
just reverse entropy
INSUFFICIENT DATA FOR A MEANINGFUL ANSWER
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