One of my pet theories is that the Fermi paradox is due to cloaking of extraterrestrial civilisations. We’re not entitled to observing them, and as a result the mass and energy of the universe doesn’t add up. Hence black matter and black energy.
Aside: dark matter and dark energy are pretty distinct concepts by my reading [2]. Dark matter interacts only gravitationally and is currently the leading explanation for things like galaxy rotation curves (visible mass is far too low to support observed disk rotation speeds, so non-luminous, i.e., "dark" matter must exist to make up the difference) and gravitational lensing by galaxies (again, visible mass is too low to produce observed lensing). Dark energy is, well, something that accelerates the expansion of the universe.
[1] https://en.wikipedia.org/wiki/Dark_forest_hypothesis
[2] https://science.nasa.gov/astrophysics/focus-areas/what-is-da...
Humans also have been broadcasting EM out into space for a bit now.. so either these hostile aliens are on their way right now, they are too far away to have detected us yet, or they don't exist.
Visual observations exists much longer, but they are limited to just our galaxy, Milky way (more distant sources are not bright enough to see them with naked eye).
And even most obvious mask ideas (and development), which we see on our current sci-tech stages, very fast move spectrum to infrared, which is near impossible to observe via thin atmosphere. And even now, I hear about developments of laser cooling, which could emit extreme amounts of heat into some direction, where nobody will see it.
For example, now Earth communications conversed to Ultra high frequencies and very high gain antennas (3G, 4G, 5G, emit only very narrow beam to receiver and are very short range), and to fiber-optic communications, which emit just infrared from heat. Also, Ultra high frequencies very quickly absorbed by moisture, so also effectively converted to heat infrared.
So, right question should be, how much time industrial civilization emit observable to others emissions.
And imagine, what could alien civilization learn about Earth from locations, where clouds are rare, as others they could not hear :)
Not exact. For so weak technologically civilizations such our Terrestrial, now could not detect many distant objects which does not emit EM spectrum.
For example, only small fraction of known planets outside our Solar system, seen on telescopes directly, most others detected by indirect means - measuring difference of speed of star (by Doppler shift), or measuring changes of brightness of star, when big planet eclipse star (most cases partially).
In many cases, planets orbits are not so fortunate to us to detect them, and these planets for us are dark matter also.
To be exact, for us "normal" matter are only classic stars and some other objects like Black holes when they "eat" something.
Astronomers already made calculations, based on assumption, that Solar system is more or less typical (we know approx weights of matter of Sun, Planets, Asteroids, Star dust, etc), and seen, that all we know could been about half of dark matter, but other half we could not explain, and this is huge number.
"Dark matter" has a technical meaning in astronomy, and this is not it.
For ASTRONOMY, dark matter is just what they could not see, but have gravitation features. And as I said, for astronomy, ~50% of dark matter is nothing special, but for example, only extreme models could suggest tens of thousands Black holes (to fill 50% of emptiness), because of this, they conclude, that exists something other matter which we don't know.
For PHYSICS, technical meaning of dark matter is special type of matter.
Good that we found understanding on this.
What kind of technology would produce such ultra high energy particles?
What would they use such technology for?
Can a technological source be inferred from the data we already have?
It could also 'just' be a new particle which behaves differently than anything on the board. (Would still be a VERY strange particle though for sure, and still leaves open the question of what produced it.)
Also, how do they erase their early radio signals after they have been emitted? Civilizations don't go from zero to dark mater cloaking capable without a few intermediate steps...
> as a result the mass and energy of the universe doesn’t add up
wouldnt something smart enough to put up a cloak know that they should put up something to replace the missing data?
i mean... i would hope...
Even recent stealth technologies know from late 1970th, how to hide from radio waves reflections and how to hide visual reflections and how to hide infrared emissions (slot nozzle, directed where no observer).