[quietpain]

I suggest we add its origin to the SETI list.

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.

[EForEndeavour]

Would this be the Dark Forest Hypothesis [1], with the added twist that the hidden civilizations are so advanced that they've "cloaked" themselves such that they only show up as what we currently interpret as dark matter?

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...

[simne]

> Dark matter interacts only gravitationally and is currently the leading explanation for things like galaxy rotation curves

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.

[choilive]

Shouldn't we be able to detect the civilizations that have been broadcasting EM radiation before they got quiet? Whether they went silent voluntarily or involuntarily - unless every single technologically advanced civilization had the foresight to develop cloaking before becoming spacefaring (which seems unlikely) we should be able to detect their signals within some window of time.

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.

[hdivider]

Regarding an ET source: some key questions to consider:

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.)

[trilbyglens]

So uh, 27% of the mass of the _universe_ is being cloaked by civilizations? Literally in all directions, distributed evenly throughout all of visible space? Seems extraordinarily unlikely.

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...

[jareklupinski]

> cloaking of extraterrestrial civilisations

> 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...

[simne]

To cloak from so weak civilization as we, need to just hide electromagnetic emissions, as we cannot detect distant objects which don't emit anything EM to our direction.

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).