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.
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.
> 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.
You confused PHYSICS definition with ASTRONOMY definition, they are different.
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.
We have confusing and extremely sophisticated context. It involving wide spectrum of less complex contexts. Physics and astronomy, depend on from what direction we look on it.
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.
Humanity just very short time have instruments to hear sky.
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 :)
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.)
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...
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).
This journal is published by "American Association for the *** Advancement of Science ***". Jesus. You can't make up this sort of irony. Open collaboration, peer efforts and all that altruist nonsense requires you having the access. No access - no science for you. Beat it.
I respectfully disagree. Bringing this issue up again and again is important even though it has almost nothing to do with the topic being discussed. They had so many options "SharedAI", "CommonAI", "ResponsibleAI", "WorldAI" - but chose the only adjective that does not reflect what they are doing. It muddles waters. It makes it more difficult for the real OpenAI organization to form (what name should they adopt - "RallyOpenAI"? "TheOpenAI"?)
Yes I know the arguments they used to defend their choice but I don't find them convincing.
In reading the article that was the same sentence I copy-pasted to bring back here for discussion. Anyone have an idea what the reporter garbled into "faster than the speed of light?" I guess just "nearly the speed of light"?
As someone else has said, the article should say "faster than the speed of light in air".
The Guardian article says:
> Some charged particles in the air shower travel faster than the speed of light, producing a type of electromagnetic radiation that can be detected by specialised instruments.
> One such instrument is the Telescope Array observatory in Utah, which found the Amaterasu particle.
The Telescope Array actually has two different types of instrument for detecting the particles. Fluorescence Telescopes and Scintillation Detectors.
According to the paper the "fluorescence detectors were not operating at the time (owing to bright moonlight)". Instead the particles were detected by the plastic scintillator surface detectors.
Oh that makes a lot of sense. That actually makes a nice image for the train-wreck of cascading particle collisions that happens. Air is dense enough its impossible to move that fast thru it. But the particle hits the air moving that fast. Result: fireworks that can be detected.
Perhaps it's a reference to a relativistic quirk having to do with cosmic rays. When a high-energy cosmic ray hits the atmosphere, it can create a meson or something. This sub-atomic particle isn't stable and has a tiny half-life, really it is mostly just an intermediary mid-way through the feynman diagram of the cosmic particle collision interaction, where the actual result is a typical output of stable electrons or neutrinos or what have you.
It gets weird because you see evidence of these mesons or whatever way down below the part of the atmosphere where cosmic rays impact. Like, if you multiply the half life of the meson with the speed of light, you get a result that should be way shorter than the actual distance you see mesons (or what have you) actually traveling. Depending on how you look at it, it's like the mesons are traveling faster than the speed of light given how far they're going before decaying.
It turns out these particles are traveling so close to the speed of light that the passage of time is different for the particles than an observer on earth. Their half-life duration occurs within their frame of reference, which is different than ours. So even though the particle was traveling at (fake numbers) 1 kilometer a second and traveled 3 kilometers, it only had a lifespan of 1 second. It plays out this way because 3 seconds on earth transpired during the particle's 1 second in its own frame of reference and thus we saw it travel 3 kilometers during the particle's own 1 second, despite the speed of light being just 1 kilometer per second. So depending on how you look at the numbers it can seem like it was 3x faster than the 1km/s speed of light.
I realize this almost of creates more (and bigger) questions than answers.
I'm not a particle physicist, but as I understand it, it wouldn't be very exciting to be hit by this because even if it interacted with you, the shower of particles produced would be so energetic that they'd nearly all come right out of the other side of you and go deep into the Earth before hitting anything else. One atom gets smashed, and one molecule gets excitingly altered but that's all in a day's work for biology.
It's a bit like how the depth where the energy is deposited of radiotherapy gets deeper with increasing energy. Past a certain energy (hundreds of MeV), most of the energy ends up being delivered somewhere behind you. This particle is hundreds of billions times more energetic than that radiation.
I think there's a high chance that no atom in the human would get hit. Just thinking of the photo of the sun that was taken through whole earth. There are thousands of particles from outer space each day passing our bodies without interaction.
Much likely, nothing at all! The more energy a particle gets, the smaller the probability of interacting with anything.
And if it does interact in your head... nothing at all! At such an energy, it is so tiny that at most one electron or one nucleon (i.e. proton or neutron) will get the thrill of its life and find itself leaving precipitously your body in order to smash, a few nanoseconds later, into the planet behind you. You won't notice, and the Earth won't either.
As an example, and admittedly in a completely separated energy range: neutrons emitted by uranium have to be slowed down in order to keep the reaction going at the desired speed.
If you don't slow them down, they'll just traverse other uranium nuclei and the reaction will only proceed with its natural speed (half-life of billion of years).
That's why you need a minimum mass of uranium for a nuclear explosion: you need neutrons to traverse a certain thickness of material before it gets slow enough to excite other nuclei
The observations of the Amaterasu particle increased over the years, coming from an apparently empty region of space. A minor science mystery. Then one day, the feint glow of a body was seen, just outside the solar system. It's trajectory was odd, foreshortened and the light was blue-shifted and of a very strange spectrum. Almost like an engine pointing our way, decelerating. "Time to lay out the welcome mat," the astronomer said, with mingled excitement and fear.
I assume any particle like that can only be detected by a single sensor in one location. How do you verify that this isn't some sort of noise artifact in your system?
It creates a cascade of secondary particles that are detected over an array of sensors. In this case, the shower triggered 23 detectors, which are part of 507 stations arranged in a square grid. The stations are spaced by 1.2 km, giving a total effective area of 700km^2
While traveling through the atmosphere, they create particle showers over large areas, which can be reliably detected. There's even the citizen science project called CREDO [1] that relies on volunteers using their smartphone camera sensors as particle detectors.
Since no one knows what's the source, here's a dumb question: we are unable to detect dark matter, right? Is it possible that the Local Void isn't actually void, just contains a lot of dark matter?
Add on question: can dark matter emit high-energy particles?
This questions could not be answered by current science. Could only make guesses.
For first, most current answer, we just know, something exists in Universe, which we could not see directly, but have mass and so emit some gravitation, which influence moving of other objects, which we could see.
For second, even worse. We only know, we cannot SEE anything in void, but this just mean, something could be there, but we cannot detect it with our current technology, nothing more.
When we cannot se anything, and we have not before encountered such phenomenon, we could only speculate on fantastic theories.
That aspect of the Three Body Problem really irritated me. Maybe I just like my sci-fi harder than that. But saying the aliens could turn ordinary protons into magical supercomputers with near unlimited powers to manipulate matter... Gah! I hated it.
Same. They had so much technology that could have trivially solved most of their problems - especially the titular one! - and instead they decided to do a weird psyop on a few hundred people four light years away.
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.