Questions tagged [fermi-paradox]

"If extraterrestrial intelligence exists, why have we found no evidence?", first defined as a paradox by Enrique Fermi and colleagues, after estimating based on various facts that an advanced civilization has had time to colonize the entire galaxy many times over.

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Why is the Fermi paradox' assumptions so strong? Do they even need to be?

The Fermi paradox first states that it is highly likely that intelligent lives have existed on planets long ago. As in, not just on one planet, but on billions of planets. Then the paradox goes on and ...
Art's user avatar
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What is the most accepted explanation to the Fermi paradox by the scientific community? [closed]

If there is no "most accepted" explanation, then what would be the most scientifically probabilistic explanation to the Fermi paradox? The Fermi paradox, named after Italian-American physicist ...
A-ar's user avatar
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What percentage of the universe's galaxies are within our reply-lightcone before they're Hubble-flow expanded away too far to reply? [duplicate]

Because of the Hubble constant, how far can we now send a signal and still be in range to hear an immediately-issued (the moment they receive a signal) reply? And what percentage of today's visible ...
math's user avatar
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Copernican principle based question about ET

As mentioned, I'm following the Copernican principle for this line of questioning. Yes I've considered and read many other possibilities, but this question is for Copernican-style answers ONLY. Your ...
Nomadyn's user avatar
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Is there good estimates/measures on the variables that make up the Fermi paradox?

Here's what I've got: Universe size: Milky way is 100,000 LY wide. Nearest galaxy is 2.2m LY away. Number of stars: about 300,000,000,000 in the Milky way. 100,000,000,000 galaxies. Age of ...
dwjohnston's user avatar
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Is a combination of 'space is big' and 'humans haven't been around long' a good solution to the Fermi paradox?

The Fermi paradox is basically that: There are billions of stars, life is probably abundant throughout the universe. Even though it may take tens of thousands or millions of years for life on other ...
dwjohnston's user avatar
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Could unexpectedly high levels of interstellar space debris be the Great Filter?

I've heard (though I can't find the source) that sufficiently large interstellar space debris has the potential to destroy spacecraft, and that there is considerable uncertainty about how much of a ...
Kelmikra's user avatar
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Could Von Neumann probes be forbidden by technological limitations?

The famous Fermi paradox asks an important question: if space-faring civilizations exist and are not extremely rare, why are they not already here? Von Neumann proposed a probe, that flies to nearest ...
Irigi's user avatar
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