What is the best explanation to the Fermi Paradox?
We're the first and/or only intelligent life in our light cone
The aliens are already here
The "Grabby Aliens" hypothesis
Intelligent life is doomed to destroy itself
Something makes interstellar expansion incredibly impossible
Something else

Parallel to this market, but with different options.

And I'm stealing the criteria:

"Resolves when a solution to the Fermi Paradox is widely agreed upon in the scientific community in response to empirical evidence."

For context, the "Grabby Aliens" hypothesis is here for those who haven't heard of it:

Get Ṁ600 play money
Sort by:

another factor militating against longer planet durations is hydrogen escape. If a planet is massive enough to hold on to its hydrogen for billions of years, it will rarely have a thin enough atmosphere for light to reach the surface, and without photosynthesis your raw energy available for evolving life is reduced by at least 6 orders of magnitude

@JonathanRay and the probability of evolving intelligent life on a planet is probably not just a power-law on time, but a power law on the product of time*area*energy*otherconditions. Suboptimal planets (e.g., no light reaching the surface) can basically be ignored as having a negligible chance of evolving intelligent life.

@JonathanRay Yet another argument against longer lived planets creating grabby aliens is that they won't have enough U-235 to get any fission chain reaction started after ten billion years, and fission is probably the only good way to power interstellar travel. They might be able to bootstrap it with an accelerator and a fast breeder reactor with a very high breeder ratio, but that's so deep down the tech tree without any breadcrumbs along the way.

The dark forest hypothesis seems like a reasonable explanation: why put the effort into constructing a giant transmitter it it creates a large X-risk for you.

The longer-lived low-mass stars are flare stars incompatible with life because their luminosity varies over too wide of a range (multiple orders of magnitude) So it's a bit misleading for the grabby aliens paper to proceed from the assumption that the average star lives for 5 trillion years. To get out of the flare star range you need at least 0.6 solar masses which leads to a star lifespan of only 35 billion years.

Presently, we can only perceive ourselves as purely deterministic animals with no unique extent into the quantum multiverse. If there was an unavoidable multiverse ethics that concluded ‘grabby aliens’ was undesirable then by choice all aliens would, in almost every branch, look inward rather than expand outwards.

If building misaligned AI were a common failure mode for alien civs we ought to see some utilitronium shockwaves spreading out at significant fractions of the speed of light. D-T fusion with a Q-factor of infinity has a theoretical maximum specific impulse of about 10% c (any other kind of fusion being much worse) and U-235 fission would have a theoretical maximum specific impulse of 3% c. By the classical tsiolkovsky equation you need a ship that's 99.3% fuel to get to half the speed of light. Seems likely that even a superintelligent AI would not be able to make its utilitronium shockwave go faster than 80% of the speed of light.


The Great Filter:

@Gigacasting most alien civilizations as smart as us would be increasing their intelligence via breeding, biotech, information technology, or other means