[HN Gopher] The most powerful cosmic ray since the oh-my-god par...
___________________________________________________________________
The most powerful cosmic ray since the oh-my-god particle puzzles
scientists
Author : WithinReason
Score : 127 points
Date : 2023-11-26 11:09 UTC (11 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| Aardwolf wrote:
| I see this all over the news, not only on HN. But the signal was
| detected in May 2021. What makes this newsworthy now instead of
| then?
| sandworm101 wrote:
| A slower news cycle. In recent days US politics and the various
| wars have hit relatively steady states. So the news outlets are
| casting out for interesting science content, stuff that doesn't
| require math to understand.
| exegete wrote:
| The findings were published now in a scientific journal and not
| then.
| moh_maya wrote:
| Perhaps because the peer-reviewed paper was published only
| recently (23rd Nov) - while not a perfect system (see the
| recent issues with the retraction of the super-conductivity
| paper by Nature), I think it not a bad thing that journalists
| are covering such reports once they have undergone the peer-
| review process - however flawed it may be, and not just based
| on the university or research group published press-release
| announcing the results before the peer-review process is
| complete.
|
| [1] https://www.science.org/doi/10.1126/science.abo5095
| jordanpg wrote:
| Also, while the final result can be simply stated in a
| headline, performing the analysis that rules out all known
| sources of error is very, very difficult and can take years
| to validate.
| ivan_gammel wrote:
| 320 EeV = 3.2e20 eV ~ 50 J ~ energy required to lift 5 kg by 1 m
| or energy sufficient to warm a cup of water from 0degC to 40degC
|
| Edit: to launch 100t of payload to LEO with Starship you will
| need ~60 millions of such particles, a tiny fraction of the
| number of protons in human DNA.
| Szpadel wrote:
| I wonder what impact on eg human body such particle would have.
| would it just go through or boil some cells? could someone
| unlucky hit by such particle just drop dead?
| pletnes wrote:
| Probably pass through while generating secondary radiation
| also powerful enough to leave the body. Nothing you'd notice.
| Might cause cancer but so could other cosmic rays or
| radioactive rocks you encounter day to day.
| nine_k wrote:
| The particle won't dissipate all its energy inside the body,
| so likely it won't even hurt you noticeably. It it hit you
| eye though you'd likely see a very bright flash.
|
| 50 J is about as much as an airsoft gun pellet carries; not
| going to hurt you even if it manages to dump all its energy
| on your body.
| closewith wrote:
| Airsoft is typically ~1 J. Even the most powerful are below
| 5 J.
|
| 50 J is enough to hunt small pests in an air rifle. Easily
| enough to injure or blind a human.
| jfengel wrote:
| You wouldn't notice it. The energy is sufficient, but the
| momentum is too small. Energy goes up with square of velocity
| and momentum just linearly, so this particle gets more of its
| energy from velocity and less from mass compared to a
| macroscopic object. The result is lowish momentum.
|
| It probably hits a water molecule and the heat is quickly
| dissipated. You don't recoil because the momentum is small.
|
| It might kill a few cells, but far smaller than the ordinary
| cycle of life. So any effect is swamped.
| bjelkeman-again wrote:
| I cup of water would be about 2dl (200g), with the specific
| heat capacity of water being (4.18 J/gdegC, or 4180 J/kgdegC) I
| think 50 J is not enough.
| ivan_gammel wrote:
| Yes, thanks, I did a napkin calculation but apparently missed
| it by orders of magnitude.
| necroforest wrote:
| What's an order of magnitude between friends?
| falserum wrote:
| Any chance that 1Cal == 1kCal have influenced the
| calculation?
| ivan_gammel wrote:
| Could be. Last time I touched thermodynamics was 20 years
| ago, may have used wrong number from the table.
| nine_k wrote:
| A cup of water is 0.2 kg. Water specific heat is 4200
| J/kg*degC, so it takes about 840 J to heat a cup of water by
| 1degC. 50 J is not going to make any noticeable difference.
|
| OTOH a tennis ball is about 0.06 kg, so from e = m*v^2/2 would
| give about 41 m/s, a good serving that you will definitely feel
| if it hits you.
| dustingetz wrote:
| removed
| MattRix wrote:
| huh? You'll feel cold tea, that's all. You can't detect a
| change of 0.05C
| IAmGraydon wrote:
| There's a lot wrong here, starting with the energy of the newly
| discovered particle. The particle in question had an energy of
| 240 EeV, which comes to 38.45 J.
| ivan_gammel wrote:
| By accident I used the energy of OMG particle which is also
| mentioned in the article, but it is not completely wrong --
| it's the same order of magnitude as the new one, so it still
| can be used to understand how much is that.
| fallingknife wrote:
| That would only get you to 3km. 20K to get to 100t * 3000 to
| get you to 3km. Would need another 100x to get to orbital
| height. But that's trivial compared to the energy you will need
| to get up to orbital speed. And then there's gravity drag.
| melagonster wrote:
| the link of research article is not work now.
| JKCalhoun wrote:
| I wonder how complicated those detectors are and if amateurs
| could set up backyard detectors and contribute to cosmic ray
| detection.
| spacecadet wrote:
| Great Question. I dabble in some back yard Radio Astronomy, but
| now you have me wondering this too.
| getoffmycase wrote:
| Put a DSLR in the freezer with a long exposure time.[1] Instant
| cosmic ray detector. [1]
| https://www.reddit.com/r/astrophotography/comments/m1w4wv/i_...
| IAmGraydon wrote:
| For those who might be considering doing this, don't unless
| you're ok with destroying the camera.
| CamperBob2 wrote:
| How does it destroy the camera?
| IAmGraydon wrote:
| Most DSLRs are designed to withstand down to 0C. Most
| freezers are around -20C. You risk damage to the battery,
| condensation on interior components, contraction and
| mechanical damage of components with tight tolerances,
| etc.
| taylorportman wrote:
| I wonder if there is a common substance that could be scanned
| for historical interactions - like some salt flats.. that might
| preserve, like film, a history of energetic anomalies.
| eesmith wrote:
| One such is a Miyake event.
| https://en.wikipedia.org/wiki/Miyake_event
|
| > an observed sharp enhancement of the production of
| cosmogenic isotopes by cosmic rays. It can be marked by a
| spike in the concentration of radioactive carbon isotope 14C
| in tree rings, as well as 10Be and 36Cl in ice cores, which
| are all independently dated.
|
| Wood and ice are pretty common. :)
|
| I don't know if there are other examples.
| maxnoe wrote:
| It's relatively easy to detect cosmic rays if you are happy
| with secondary muons that are produced in the atmosphere when a
| high energy cosmic ray is absorbed.
|
| Detectors are relatively cheap and come out of the box for
| citizen science projects, this project is relatively well
| known: http://www.cosmicwatch.lns.mit.edu/
|
| For high energy cosmic rays, you need to observe many of these
| secondary particles that are produced during the absorption
| with high temporal resolution, few nanoseconds, to be able to
| tell anything about their properties.
|
| There are essentially five or so detection principles for
| measuring cosmic rays at the ground, and many observatories
| combine multiple techniques.
|
| First, you can observe the secondary particles that reach the
| ground, mainly muons and electrons. This is possible either
| using water tanks with photosensors inside detecting Cherenkov
| light or using scintillators like in the project I linked
| above.
|
| Then you can also detect very short and faint light that is
| also emitted in the air shower. This also comes in two
| variants: Cherenkov light is emitted in a cone around the
| charged particles and results in a "light pool" of roughly 250m
| diameter on the ground. Fluorescence light is emitted in all
| directions. We build optical telescopes with extremely fast and
| sensitive cameras to detect Cherenkov or fluorescence light.
|
| Last, there is also radio emission from air showers, you can
| detect with antennas.
|
| Auger in Argentina combines water tanks, scintillators and
| fluorescence telescopes and is investigating adding in radio
| antennas.
|
| Telescope Array, the experiment which measured this event here,
| is using scintillators and fluorescence telescopes.
| eternauta3k wrote:
| > Auger in Argentina combines water tanks, scintillators and
| fluorescence telescopes and is investigating adding in radio
| antennas.
|
| Any thoughts about surviving the next 4 years?
| troymc wrote:
| Pierre Auger Observatory is a project with scientific
| collaborators from all over the world. The initial
| construction costs were shared by 15 different countries.
| Ongoing work and upgrades are paid by a variety of
| international funding sources. To get some sense of that,
| see [1] and the Acknowledgements section of journal papers
| arising from work there, such as [2].
|
| [1] https://www.auger.org/collaboration/funding-agencies
|
| [2]
| https://iopscience.iop.org/article/10.3847/1538-4357/acc862
| fllsdf wrote:
| Not that hard, Marco Reps, an excellent maker YouTube channel
| has a video on how to create one
| https://www.youtube.com/watch?v=PCB8nv4fatc
| antognini wrote:
| There are a couple of apps that let you detect cosmic rays on
| your smartphone. (One example: https://cosmicrayapp.com/)
|
| They basically keep the camera shutter closed and look for
| streaks on the camera CCD.
| somenameforme wrote:
| It's really easy to build a basic visible cosmic ray detector -
| they're called cloud chambers. Here [1] is a random video, but
| you can find countless sources just searching for 'how to build
| a cloud chamber.'
|
| If you haven't seen one of these before, it might sound more
| cool in paper than in practice. Cosmic rays are absurdly
| abundant to the point that dozens to hundreds are passing
| through you per second. So a cosmic ray detector ends up
| turning more into something like a really neat art show than a
| search for a signal. Of course there is the search for 'the big
| one', but somehow it's not quite so romantic when you're
| getting plowed by these guys constantly.
|
| [1] - https://www.youtube.com/watch?v=gt3Ad5_Z5IA
| cozzyd wrote:
| The scintillator detectors are quite simple, but you need a
| whole ton of them working together to be useful.
|
| The fluorescence detectors are more complicated.
| dist-epoch wrote:
| Can someone explain why this particle couldn't have been
| gravitationally accelerated by taking a turn around a super-
| massive black hole just on the edge of the event horizon? Is
| there a limit to how much acceleration a black hole can give?
| WendyTheWillow wrote:
| The article says there are no known quasars in the area of
| space where the energy is seemingly from, or at least that's my
| interpretation.
|
| So yeah it could be from a black hole, just an unknown one. Or
| it's from a different region of space than we think, and our
| math is off.
| maxnoe wrote:
| Mass is of a single particle is extremely small (proton has a
| mass of 1.6e-27 kg), speed is very high and already very close
| to the speed of light at all but the lowest energies, so
| gravity "assists" are not really anything with which you can
| gain energy.
|
| These are charged particles (protons and fully ionized heavier
| nuclei), so electromagnetism is a much more efficient way to
| reach high energies.
|
| All currently proposed mechanisms for cosmic ray acceleration
| involve turbulent plasmas and shock fronts that reflect
| particles magnetically, giving them a small bump in energy each
| time [1] or rotating magnetic fields [2] in sufficiently
| extreme environments.
|
| [1] https://en.wikipedia.org/wiki/Fermi_acceleration
|
| [2]
| https://en.wikipedia.org/wiki/Centrifugal_acceleration_(astr...
|
| Gravity just doesn't play a direct role for accelerating
| charged particles, it's much too weak compared to the
| electromagnetic force for a charged particle.
| saiya-jin wrote:
| So, a pulsar would do the trick? How far back do we simulate
| movement of milky way and all galaxies around to say for sure
| they come from an 'empty' place? I think our local
| supercluster look quite a bit different say 1 billion years
| ago
| eesmith wrote:
| The particle is traveling at a whisker under the speed of
| light.
|
| If I read things correctly, it's only a few light-days
| behind what the light would be after 1 billion years.
|
| So what we see should (as we we understand it) look like
| the conditions where/when it achieved its tremendous speed.
| ars wrote:
| That's not how gravitational acceleration works.
|
| If the particle accelerates towards black hole it will
| decelerate when the leaves the black hole.
|
| To actually accelerate and keep it, you need a third particle.
| In a spaceship that third particle is the fuel.
|
| In a solar system that third particle is the planets
| interacting with their sun.
|
| My post is telling you what's needed without explaining it at
| all, please watch some YouTube videos to actually understand
| it.
| NegativeK wrote:
| You can extract energy from a rotating black hole via
| slingshotting around it.
|
| But it's not an amount relevant to this discussion.
| pixl97 wrote:
| So, I'd say it's a little more complicated than this even.
|
| There are orbitals around black holes where particles could
| maintain stable orbits for long periods of time. Now when you
| get a complex environment around said black hole with lots
| matter attempting to infall but not having the correct
| momentum you will get a lot of interaction between particles
| of different velocities, hence why we actually see black
| holes at all. you get matter crashing into each other
| releasing gamma rays and such. From these interactions alone
| you can get gravitational particle acceleration.
|
| It just gets more complicated from here as you add magnetic
| field interactions.
| sacrosanct wrote:
| > Oh-My-God particle
|
| Interesting that scientists choose the G word when announcing new
| discoveries. I know even atheists say 'Oh my god' even though
| they're non believers. There's no getting away from the word God,
| religious zealot or not. It's here to stay I'm afraid.
| WendyTheWillow wrote:
| Lots of scientists are religious firstly, and secondly naming
| things is hard!
| alex201 wrote:
| The 'Oh-My-God particle' refers to an actual observation made
| in 1991, which is known by this name. Besides, not all
| scientists are atheist.
| falserum wrote:
| > here to stay I'm afraid.
|
| Nothing to be afraid. Just accept people as they are. (Even if
| you do not want to join them)
| notbeuller wrote:
| They don't specify which god - perhaps one of the Eldritch
| horror type gods is being invoked and awoken!
| eesmith wrote:
| Your conclusion suffers from several issues.
|
| From the link: "The scientists nicknamed the particle
| 'Amaterasu', after a Japanese Sun goddess."
|
| Shall we conclude the Japanese Sun goddess is here to stay too?
|
| Various devout Christians consider "Oh my God" to be contrary
| to the third commandment: Exodus 20:7 "You shall not take the
| name of the LORD your God in vain, for the LORD will not leave
| him unpunished who takes His name in vain."
|
| Madalyn Murray O'Hair, "America's Most Hated Woman" due to her
| advocacy of atheism, would say "oh my God" because it triggers
| Christians. https://youtu.be/pu5cqoSbeJA?t=832 .
| lamontcg wrote:
| Irony exists. And I thought you weren't supposed to take the
| "Lords" name in vain in an irreverent manner as well.
| idlewords wrote:
| The big deal about these events is that, if you reasonably assume
| that it's a proton, then it violates a bound called the Greisen-
| Zatsepin-Kuzmin limit. Anything going that fast should be
| energetic enough to interact with the cosmic microwave
| background, which is hugely blueshifted in its frame of
| reference. The GZK is a kind of cosmic speed limit over long
| distances.
|
| So anything this energetic would need have a nearby source (in
| astrophysical terms) so it doesn't have time to slow down. But
| when we trace these things back, we see bupkus in the direction
| it came from.
|
| This means there is either (almost certainly) interesting new
| astrophysics, or (with tiny probability) new particle physics
| involved. Whatever is giving individual protons the energy of a
| thrown baseball is probably something worth studying.
| willis936 wrote:
| I'm relatively lay in astrophysics. Could the origin not be
| galactic magnetic field lines between Earth and the galactic
| nucleus? Like the magnetic mirror between Earth and the Sun but
| much larger.
| smueller1234 wrote:
| To our best understanding, particles of such high energy do
| not originate in our own galaxy. We don't have a good
| understanding of what exact process might be putting this
| much energy into a single particle, but the commonly accepted
| acceleration mechanisms of, eg., supernovae don't reach
| anywhere near these energies.
|
| GP also said "nearby source (in astrophysical terms)" which
| in this case is code for "could be over 100 million light
| years".
| unsupp0rted wrote:
| Or a nearby emanation source we can't readily detect?
| bee_rider wrote:
| I think that might fall under
|
| > This means there is either (almost certainly) interesting
| new astrophysics,
|
| possibly. An emanation source they can just barely pick up is
| a mystery they can puzzle out, right?
| newZWhoDis wrote:
| Probably a leaky warp reactor on a passing starship :)
| araes wrote:
| Honestly, still mildly crazy. If:
|
| - Whatever Star Trek says about warp reactors (matter /
| antimatter reaction) is valid. Reacts "some" amount of
| matter/antimatter every second.
|
| - Klingon Bird of Prey can maintain an effectively infinite
| cloaking time from a human observation perspective, so it can
| be nearby.
|
| - Warp reactor "occasionally" leaks (1% of 1% of 1% of
| reactions? I dunno...) so we might actually detect something.
| "Slightly" imperfect shielding.
|
| - Problem: 5E1 J for OMG Particle (people say its a proton).
| 1.8E14 J for 1 gram of matter / antimatter annihilation.
| Except: 1 Proton = 1.6726231E-24 g. Proton rest mass energy
| is 1.503E-10 J. So the particle is more energetic than a
| Proton / Antiproton annihilation event (by a lot). It's been
| upshifted More than 100,000,000,000 from the rest mass
| energy.
|
| - It "might" work if the one proton escaping represented a
| single proton gaining enough energy to overcome reactor core
| shielding confinement, which, in my opinion, seems somewhat
| plausible physics by Star Trek standards.
|
| - PS: Personal guess is a Q-Clearance [3] experiment at a DOE
| lab we deny exists.
|
| [1]
| https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)
|
| [2] https://en.wikipedia.org/wiki/Proton
|
| [3] https://en.wikipedia.org/wiki/Q_clearance
| ricksunny wrote:
| To the casual HN reader - my recommendation to you is to
| neithet laugh at nor dismiss out of hand analyses such as
| this (even as logic intrinsic to them merits as much
| picking apart as any other analysis one sees everyday on
| HN).
|
| Robin Hanson's description of long-lived stars (usually
| strongest in infrared - i.e. the 3 stars our eyes lack the
| spectral response to see for every 1 star that we do see
| when looking into the night sky) _significantly_ updated my
| priors on the likelihood of intelligent, non-human life
| roaming about the cosmos.
|
| https://youtu.be/cQq2pKNDgIs?t=1210 (timestamped)
|
| tl;dr: Red-dwarf stars have been around -- with all that
| goes with that.. -- for much, much longer than our sun.
| captainmuon wrote:
| I wonder if it could be a background source that we don't
| understand. Maybe some freak coincidence where particles come
| in in exactly the right angles to fake a hyperenergetic photon.
| Or somebody messing with laser pointers. Or birds or whatever.
|
| I used to work in particle physics, and never shared the
| confidence of my colleagues in rare events. If you just have
| 3-4 signal events, considering the expected number of events,
| you might _statistically_ have a discovery. But you can 't be
| sure how your detector is going to behave for those extreme
| events, because you have no benchmark. You have to assume a
| proton is a proton, an electron is an electron, and no weird
| things happen at high/low energies and angles (or that you
| understand how things change).
|
| It is even worse if you are trying to disprove some specific
| model. You see no events of a certain kind. Does that mean you
| disproved the model, or that your setup (detector, triggers,
| event selection ...) is just blind in this very narrow part of
| the parameter space?
| jp57 wrote:
| I assume that limit accounts for the time dilation, too. At the
| speed the particle was traveling it wouldn't have had much time
| in its reference frame to interact with the background
| radiation, even blue-shifted as it would be, right?
| idlewords wrote:
| Yeah, the model does account for it, and the time dilations
| are nuts. For the Oh-my-god particle (a similar early
| detection), I remember that it would have crossed a billion
| light years in what it perceived as a day.
| whoopdedo wrote:
| > either interesting new astrophysics or new particle physics
|
| Or measurement error which historically has been the most
| frequent explanation of these rule-breaking observations.
| Someone else will look at the data and notice an anomaly which
| once accounted for will make everything fit within expected
| models.
| lamontcg wrote:
| In this case though they've been observed over the past 30
| years at at least 4 different detectors, which provides
| independent confirmation across multiple different research
| groups. It is very unlikely to be a "oops we didn't plug the
| cable in firmly" kind of situation. It would need to be
| something fundamental about the design of these detectors,
| which has been replicated four independent times, which has
| completely escaped the notice of physicists for >3 decades
| (which includes 3 decades worth of grad students incentivized
| to take a look at the problem with fresh eyes and make a name
| for themselves by explaining it all away).
| emmelaich wrote:
| How different are those detectors? Is it possible they
| share a common or similar design?
| lamontcg wrote:
| > It would need to be something fundamental about the
| design of these detectors, which has been replicated four
| independent times, which has completely escaped the
| notice of physicists for >3 decades
| a_wild_dandan wrote:
| What initial speed must the proton have for consistency with
| our observed final "dragged down" speed (assuming some ballpark
| galactic distance)? Alternatively, could a "clump" of particles
| have smashed into our detector? Whatever the new physics winds
| up explaining this bonkers momentum, it'll be fascinating.
| cozzyd wrote:
| It would certainly be convenient for me if it is a proton,
| given the experiments I work on (protons at the highest
| energies -> more ultrahigh energy neutrinos -> maybe my
| experiments will see something!), but, unfortunately for me, I
| don't think we know that. Nuclear species composition can
| typically only be done statistically, and it looks like this
| wasn't even measured in the fluorescence detector, which would
| give the best measurement of the penetration depth of the
| particle in the atmosphere (the best handle on particle id).
| In,the journal article, which admittedly I've just skimmed,
| they give direction reconstructions giving different species
| assumptions (and Milky Way models, which are important for
| heavier nuclei) and say that while they can exclude a photon
| (which... would be weird!), without data from the fluorescence
| detector, they can't tell the difference between a proton and a
| heavier nucleus.
|
| Though given how TA mass-composition measurements turn light at
| the highest energies, they may perhaps privately argue it's
| likely a proton. But, alas, Pierre Auger Observatory would
| argue otherwise. I'll ask Toshihiro what he thinks next time I
| see him...
|
| It is intriguing that the smaller TA has seen more high-energy
| events than the bigger PAO. Maybe there really are big
| differences between the northern and southern hemisphere at
| play here...
| idlewords wrote:
| If Santa handed you a hundred billion dollars or so to study
| this stuff, what would be your dream detector?
| cozzyd wrote:
| Probably a integrated in-ice Cerenkov + radio neutrino
| detector with a giant cosmic ray detector (scintillators +
| water cerenkov tanks + fluorescence detectors + radio) on
| top, perhaps with some fluorescent/radio detectors deployed
| on tethered aerostats to look for upgoing air showers from
| taus. Sort of like IceCube Gen2 Radio on steroids,
| mishmashed with Auger and ANITA/PUEO/EUSO-SPB. Both in
| Antarctica and in Greenland to get both hemispheres. But
| there are arguments for other types of detectors too, and
| perhaps I'm not thinking big enough since 100 Billion is
| several orders of magnitude above what is probably
| reasonable :)
| rthomas6 wrote:
| Could it be a small black hole orbiting the sun?
| alister wrote:
| > _Cosmic rays with energies of more than 100 EeV are rarely
| spotted -- fewer than one of these particles arrives on each
| square kilometre of Earth each century._
|
| How do they explain detecting such a particle at all? I would
| assume that the surface of the Earth has much less than 1 square
| kilometer worth of detectors, so on average they shouldn't have
| detected any 100 EeV particles since the invention of cosmic-ray
| detectors.
| itishappy wrote:
| They detect a cascade of secondary particles created from the
| collision of cosmic rays with the upper atmosphere. There are a
| lot more of them.
|
| https://en.wikipedia.org/wiki/Air_shower_(physics)
|
| https://en.wikipedia.org/wiki/Cosmic-ray_observatory
| eesmith wrote:
| It uses photomultiplier tubes to record interactions of the
| cosmic rays with a good-sized chunk of atmosphere, plus
| detectors for the shower of particles when a cosmic ray
| interacts with the air.
| https://en.wikipedia.org/wiki/Telescope_Array_Project says it
| uses "a 762 km2 grid array with 1.2 km between each unit".
|
| > The Telescope Array project ... is designed to observe air
| showers induced by ultra-high-energy cosmic ray using a
| combination of ground array and air-fluorescence techniques.
| ... When a cosmic ray passes through the Earth's atmosphere and
| triggers an air shower, the fluorescence telescopes measure the
| scintillation light generated as the shower passes through the
| gas of the atmosphere, while the array of scintillator surface
| detectors samples the footprint of the shower when it reaches
| the Earth's surface.
|
| See also
| https://en.wikipedia.org/wiki/High_Resolution_Fly%27s_Eye_Co...
| , an earlier version.
|
| We have other observaatories which are also pretty big, in the
| km-sized range.
|
| There's IceCube, a neutrino detector observing events in a
| cubic kilometer of ice, at
| https://en.wikipedia.org/wiki/IceCube_Neutrino_Observatory .
|
| And KM3NeT, under construction will be a neutrino detector
| using several cubic km of ocean,
| https://en.wikipedia.org/wiki/KM3NeT. It is the next generation
| after ANTARES,
| https://en.wikipedia.org/wiki/ANTARES_(telescope) .
| smueller1234 wrote:
| And the largest cosmic ray observatory, Pierre Auger
| Observatory in Argentina clocks in at around 3000 km^2.
| https://en.wikipedia.org/wiki/Pierre_Auger_Observatory
|
| A very different and really neat concept that hasn't become
| real yet is JEM EUSO, a telescope that would be mounted on a
| space station, pointed at Earth, would detect air showers via
| fluorescence like Auger's fluorescence telescopes do on the
| ground. This could theoretically cover a much larger area
| than traditional CR observatories.
| https://en.wikipedia.org/wiki/JEM-EUSO
| maxnoe wrote:
| We have instrumented much, much more area than a square km.
|
| The largest instrument to observe cosmic rays is the Pierre
| Auger Observatory in Argentina, which has detectors placed on
| an area of over 3000 km2.
| prpl wrote:
| Fluorescence detectors are volumetric though only operate
| during moondown at night, and in the case of both Auger and TA,
| are paired surface detectors. Auger uses more water tanks with
| a PMT lined with Tyvek and detect electronic and muonic
| secondary particle components for the EAS. TA has scintillation
| detectors with PMTs, which are polyvinyl toluene sheets
| embedded in a steel casing. In both cases, they have individual
| triggers, usually around 1 MIP (minimum ionizing particle),
| which will trigger communication to a tower, which would then
| poll nearby detectors for events greater than 1/3 MIP.
|
| Or, at least this is how it was setup 15 years ago. Both
| experiments have added new fluorescence and surface detectors
| since then.
| nealabq wrote:
| A century is about 3 billion seconds, and Earth's surface area
| is about half-a-billion square kilometres, so one of these hits
| Earth about every 6+ seconds.
| loufe wrote:
| Kurzgesagt recently uloaded a video on hypethetical interplantary
| weapons (https://www.youtube.com/watch?v=tybKnGZRwcU) which is
| the only reason I even know what the OMG particle is.
|
| They described an "Ultra Relativistic Electron Beam" which
| theoretically could travel much closer to the speed of light than
| the OMG particle. I'm left wondering if the proximity to the pure
| speed of light has any bearing on total delivered energy when
| comparing different particles.
| qubex wrote:
| You're often taught that E= _m_ c2 but the fuller equation is
| actually E2= _m_ 02c4+ _p_ 2c2 where _p_ is the momentum, so at
| high speeds mass fades into irrelevance and the velocity
| component of momentum becomes dominant.
|
| EDIT in classical physics _p_ = _mv_ so you might wonder what
| I'm banging on about when mass appears linearly on both sides
| and on the first term is multiplied by c4 whereas in the second
| only by c2. However relativistic momentum is classical momentum
| adjusted by the Lorenz transformation g=1 /[?](1-[ _v_ /c]2 so
| it actually dominates in the limit when _v_ tends to c.
|
| EDIT 2: the latter works out to be _sigh_ c3 _vm_ 0/[?](c2- _v_
| 2) and it grows without bound as _v_ -c so that's the pedantic
| answer. The first term is linear the second term is anything
| but.
| mitthrowaway2 wrote:
| E = mc2 is the full equation if 'm' is the relativistic mass,
| which grows with velocity. E2=m02c4+p2c2 is the full equation
| if 'm0' is the rest mass.
| cylinder714 wrote:
| John Walker (of Autodesk) wrote this excellent piece on the Oh-
| My-God Particle:
|
| https://fourmilab.ch/documents/OhMyGodParticle/
| qubex wrote:
| > _one per kilometre squared per century_
|
| Okay so build a hundred km2 (10 km per side) observatory and
| you've got yourself a 'telescope' to the same degree that super-
| kamiokande is sometimes described as being a "neutrino
| telescope".
| maxnoe wrote:
| That's exactly the kind of detector that observed this event.
| It's been done. Multiple observatories exist that have
| effective observation areas of hundreds to thousands of square
| kilometers. Pierre Auger Observatory in Argentina is more than
| 3000 km2
| mensetmanusman wrote:
| Could these be a source of cancer if one hits you?
| saagarjha wrote:
| It would be unlikely that they hit you because they'll plow
| through the atmosphere first. You might get hit by a byproduct,
| though.
| cozzyd wrote:
| Cosmic rays are certainly a source of cancer (though,
| strangely, lack of cosmic rays is also potentially problematic;
| see
| https://www.frontiersin.org/articles/10.3389/fmicb.2017.0017...
| )
| johndunne wrote:
| If we're talking about a single proton, and looking back at the
| direction the proton came from, we see nothing; what are the
| chances the proton passed close enough to a black hole to deflect
| it a significant angle from its original path, eventually landing
| on earth?
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