[HN Gopher] Record-breaking neutrino is most energetic ever dete...
___________________________________________________________________
Record-breaking neutrino is most energetic ever detected
Author : lnauta
Score : 222 points
Date : 2025-02-12 16:52 UTC (1 days ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| cylinder714 wrote:
| The article references the "Oh-My-God particle, the most
| energetic particle yet encountered. Here's the late John Walker's
| excellent piece on that:
|
| https://fourmilab.ch/documents/OhMyGodParticle/
| epistasis wrote:
| > These calculations involve some elementary but easy to mess
| up algebra and some very demanding numerical calculations for
| which regular IEEE double precision is insufficient. If you'd
| like to double-check these results, be sure to use a multiple
| precision calculator with at least 30 significant digits of
| accuracy.
|
| So you're saying my iPhone built-in calculator app is going to
| have problems....?
|
| Time to whip out dc on the terminal.
| jiggawatts wrote:
| https://www.wolframalpha.com/
| Onavo wrote:
| Or ChatGPT to output Julia code
| eq_ind wrote:
| > So you're saying my iPhone built-in calculator app is going
| to have problems....?
|
| Your Android phone's built-in calculator app, however, will
| not. :^)
|
| https://dl.acm.org/doi/pdf/10.1145/3385412.3386037
| pixelpoet wrote:
| That was indeed excellent reading, thank you.
| pfdietz wrote:
| If I understand correctly, the interaction length of such an
| energetic neutrino in rock is only in the tens of kilometers.
| jihadjihad wrote:
| The Nature paper itself can be found here [0], for those curious.
| Was just published today.
|
| 0: https://www.nature.com/articles/s41586-024-08543-1
| ziddoap wrote:
| Ars Technica has an article, as well, with some additional
| context/explanation.
|
| https://arstechnica.com/science/2025/02/most-energetic-neutr...
|
| And an interesting, somewhat related, video from PBS Space Time
| exploring how supernovas act as particle accelerators (but don't
| quite explain particles like this one or the 'Oh My God'
| particle):
|
| https://www.youtube.com/watch?v=2sSNWIJbV3Q
| dr_dshiv wrote:
| Neutrinos "interact with regular matter so rarely that it's
| estimated you'd need about a _light-year of lead_ to completely
| block a bright source of them. Every one of us has _tens of
| trillions_ of neutrinos passing through us every second, but
| fewer than _five_ of them actually interact with the matter in
| our bodies in our entire lifetimes."
|
| They have 1/500,000 the mass of electrons. They interact only
| through the super short range weak force (and gravity). Nearly
| 5% of fission energy is expressed in neutrinos.
|
| And, they may be their own antiparticles, meaning they can
| potentially annihilate each other.
|
| Wild that these things can carry so much energy!
| ricksunny wrote:
| >Every one of us has tens of trillions of neutrinos passing
| through us every second, but fewer than five of them actually
| interact with the matter in our bodies in our entire
| lifetimes."
|
| Oh, but those five...
| lubujackson wrote:
| Next time I trip over nothing I am blaming those "darn
| neutrinos messing up my knee!"
| cozzyd wrote:
| The funny thing is a km^3 scale detector like km3net or
| icecube has roughly the same mass as all humans combined
| defrost wrote:
| Equally hilarious, the Kalgoorlie Super Pit has a volume
| of 3.15 cubic kilometers.
|
| That's a single, albeit large, gold mining pit and a
| fraction of the even greater volume excavated by humans
| looking for shiny stuff.
| Someone wrote:
| We mine about a cubic mile of oil _every year_
| (https://en.wikipedia.org/wiki/A_Cubic_Mile_of_Oil).
| That's 4 km3.
| steveoscaro wrote:
| These rare interactions with matter are also a cause of
| concern in voting machines, right? Or at least it was a
| concern at one point. A random bit being flipped or
| something.
| dtgriscom wrote:
| Other types of particles interact much more frequently. But
| yes: bits do get flipped (even with ECC memory).
| tasty_freeze wrote:
| It is mostly a problem of DRAM memory cells, though
| theoretically with enough energy it could flip SRAM cells
| to or override the driver of a given wire. It is not
| specific to voting machines.
|
| But the main source is from cosmic rays and local radiation
| sources in the ceramic packaging and/or decaying elements
| in the metal frame/leads/solder.
| irchans wrote:
| Interesting "fact" - The total amount of lead in the universe
| is a somewhat less than a cubic light year.
| sfn42 wrote:
| How could we possibly estimate that if we don't even know
| the size of the universe?
| insane_dreamer wrote:
| also reported in the NYT:
| https://www.nytimes.com/2025/02/12/science/astrophysics-univ...
| antognini wrote:
| For context, 120 PeV is about 10% the kinetic energy of a ping
| pong ball during typical play.
| lnauta wrote:
| One of the lead researchers in KM3NeT mentioned that the
| particle was emitting 2 horse power in light during detector
| transit. A typical body builder expends about 1 horse power
| while performing, so its 2 body builders in a single particle.
| A_D_E_P_T wrote:
| > _typical body builder expends about 1 horse power while
| performing_
|
| Close, but ackshually...
|
| Bodybuilders just oil up and pose in beauty pageants.
|
| 1 horsepower is basically one 250-pound bench press in one
| second. (550 foot pounds of work; the aforementioned bench
| press assumes a 2.2-foot stroke length.)
|
| Most bodybuilders and serious weight lifters can do that, but
| they can't keep it up for long.
| idlewords wrote:
| Neither could this neutrino.
| lnauta wrote:
| Ha, that made me laugh, thanks for the correction!
| h0l0cube wrote:
| So the neutrino is just doing a PB 1RM?
| 01HNNWZ0MV43FF wrote:
| It must have been a very short amount of time. 2 HP is 1,500
| watts, probably more light than all lightbulbs in my house
| combined.
| idlewords wrote:
| 1500 watts is about what an electric kettle uses.
| mr_toad wrote:
| American kettles. Kettles in hard core countries push
| 2300 to 2400 watts ;-)
| idlewords wrote:
| Slow-boiled water gives superior flavor!
| kevin_thibedeau wrote:
| Keeps the midichlorians from jumping out.
| moi2388 wrote:
| I always cook my water sous-vide
| wiredfool wrote:
| Meh, Lidl sells 3200w kettles.
| Daneel_ wrote:
| Where are the three phase models??
|
| Seriously though, a 15A kettle sounds great.
| SAI_Peregrinus wrote:
| Photonicinduction's 10-second kettle[1] managed about
| 10kW max (took around 5s to boil water) for a short time,
| 440V 23A. Then the resistance dropped, it went up to 16kW
| (426V 33A) and popped. 7-8kW (375V 19A to 400V 20A)
| seemed more sustainable.
|
| [1] https://www.youtube.com/watch?v=dDLw1Rx_cAI
| LargoLasskhyfv wrote:
| 2500W on 240V, single phase AC, 16A, German 'Schuko'-plug
| is normal. Or was. Some EU-regulation limits that to
| 2000, or even 1500W only now, for new devices, or
| something.
|
| Don't care. Still have the old ones, and whatever the
| electrician wired as '120V 3-phase AC' for the full US-
| style range in the US.
| sitharus wrote:
| UK 240V with 13A sockets, 3120W. Sounds like Lidl are
| rounding up.
| astrange wrote:
| American stove startups can do it in 40 seconds with ???
| watts by precharging a battery.
|
| https://www.youtube.com/watch?v=YdawGen0QPc
| lnauta wrote:
| The muon traverses a few hundred meters of detection volume
| very close to the speed of light, so in the order of one
| microsecond.
| rq1 wrote:
| Particle on steroids.
| zozbot234 wrote:
| Fun fact, a typical horse exerts about 1 horse power of
| usable work while performing. That's so weird, I'm sure
| almost no one would've been able to guess that - but it's
| true.
|
| (To be clear, that's sustained effort over time, not just
| momentary. Athletically trained humans can do about 1 HP of
| peak momentary effort, and around 0.3 HP if sustained over
| time.)
| mikepurvis wrote:
| And a horse can do quite a bit more in peak as well-- 1 HP
| is definitely meant to be the long term continuous output
| of a typical horse under load, especially a consistent load
| such as turning a millstone.
| loeg wrote:
| That's an all-day number. Peak HP/horse is somewhere in the
| 6-15 range.
| wiredfool wrote:
| Track cyclists (sprinters, world class) do 2KW+ peak for a
| few seconds at a time. That's potentially ~3HP. (and while
| doing so, average more than 70kph over a 200m distance)
| somat wrote:
| The funny thing is that a typical horse probably has closer
| to 2 or 3 horsepower and a big chonkin draft horse up to 4
| or 5 times.
|
| James Watt just picked the smallest possible value of horse
| when defining the unit so he could sell more steam engines.
|
| https://www.youtube.com/watch?v=7qxTKtlvaVE (donut, How
| Much Horsepower is a Horse?)
| m3kw9 wrote:
| Can we harvest that energy?
| AnimalMuppet wrote:
| This particle spread this energy through a volume of
| seawater a few km deep in the Mediterranean. It's going to
| raise the temperature of that volume a few billionths of a
| degree, if that. So, no, we can't.
| the_arun wrote:
| What if our existing solar panels are optimized to detect
| these? Then will it improve the quality of solar panels
| to capture more energy from sunlight as well? Sorry, I'm
| no expert in this - asking more of a curiosity.
| ars wrote:
| It's an enormous amount of energy packed into a single
| tiny particle.
|
| But it's still just a single tiny particle, so it's not a
| lot of total energy.
|
| It's like how you can lift a heavy weight for a second,
| but that's all you can do. You would need to be able to
| lift it for hours to be useful as a replacement for a
| crane. Same idea: Intensity vs total work.
| mr_toad wrote:
| If we had the ability to detect neutrinos in such a small
| volume as a solar panel they'd be _immensely_ valuable
| for communication - we'd be able to beam signals directly
| through the Earth, or through deep water.
| calebio wrote:
| Following that same line, if we had that ability, it
| would be useful for communicating to deep submarines like
| the U.S. used to do with Project Sanguine[0] and ELF
| waves :)
|
| [0] https://en.wikipedia.org/wiki/Project_Sanguine
| tadfisher wrote:
| Neutrinos interact extremely weakly with ordinary matter,
| which is why the detectors are typically huge volumes of
| water. Even then, the neutrinos interact with the
| purpose-built detectors on the order of one in a
| trillion. A neutrino power generator is not a feasible
| thing to build.
| TheOtherHobbes wrote:
| Unless you're next to an exploding star, in which case
| you have other problems/opportunities.
| tsimionescu wrote:
| There's nothing to optimize here, neutrinos just interact
| very very weakly with anything else because they don't
| carry charge (so no electrical interactions), don't carry
| color charge (so no nuclear interactions), don't carry
| weak charge (so no weak force interactions) and have tiny
| tiny masses, but they are still bosons (so don't act as
| field carriers like photons do, they're just regular
| matter). Their low chance of interacting with matter is a
| fundamental property of them, there's nothing you can do
| about it through technology, just like you can't create
| heavier electrons or weaker quarks.
| gus_massa wrote:
| > _don 't carry weak charge (so no weak force
| interactions)_
|
| Left neutrino have weak hypercharge, so they are produce
| by weak interactions and are detected using the weak
| interaction. And also gravity.
|
| Right neutrinos (if they exist) have no weak hypercharge
| so they only interact by gravity.
| tsimionescu wrote:
| Thanks for the correction!
| __MatrixMan__ wrote:
| It might improve the quality of neutrino astronomy to
| have the world's solar panels also be neutrino detectors.
| __MatrixMan__ wrote:
| Not for that particular neutrino, it's gone. But yes, my
| home (and yours) is being heated by neutrino power as we
| speak. It's not a significant enough amount of energy to
| make a dent in the utility bill however.
| Sharlin wrote:
| Most inefficient thermal power plant possible: utilize
| the difference in neutrino flux between the hemisphere
| that's open to space vs. the hemisphere where Earth is in
| the way.
|
| But now I'm wondering what percentage of the useful
| thermal power in a nuclear power plant is produced by the
| neutrinos created in the reactions (the infinitesimally
| small fraction that happen to interact with the matter
| within the reactor, that is).
| __MatrixMan__ wrote:
| On the contrary, it would have to be efficient indeed to
| do anything useful underneath all of the shielding that
| we'd need to keep those baser forms of radiation at bay.
| Gamma rays: yuck.
| whyenot wrote:
| So, 2,000 milliSchwarzeneggers if we use SI units?
| gattr wrote:
| Yes, but please observe SI rules [1]: it's
| millischwarzeneggers.
|
| > This means that they should be typeset in the same
| character set as other common nouns (e.g. Latin alphabet in
| English, Cyrillic script in Russian, etc.), following the
| usual grammatical and orthographical rules of the context
| language. For example, in English and French, even when the
| unit is named after a person and its symbol begins with a
| capital letter, the unit name in running text should start
| with a lowercase letter (e.g., newton, hertz, pascal) and
| is capitalised only at the beginning of a sentence and in
| headings and publication titles.
|
| [1] https://en.wikipedia.org/wiki/International_System_of_U
| nits#...
| jihadjihad wrote:
| Right, and it is this amount of energy _in a single particle_.
| A ping-pong ball is comprised of who-knows-how-many billions of
| particles, so the energy of any one particle is a fraction of
| the whole.
| grey413 wrote:
| A ping pong ball would be roughly 2 trillion trillion atoms,
| for reference
| GuB-42 wrote:
| Now, what will happen if you get hit by a ping-pong ball mass
| of 120 PeV neutrinos? 120 PeV is about 2e-16 grams, so a ping-
| pong ball will have about 1e16 of them.
|
| From nothing, to detectable, to lethal, to big boom?
|
| My intuition would be "detectable" but I don't know enough to
| do the maths.
|
| And by the way, I am using the mass-energy, not proper mass,
| because the question is crazy enough not to even consider what
| would be the mass of a neutrino.
| dahousecat wrote:
| Sounds like a great topic for an xkcd video
| bauruine wrote:
| There is a what if about it. https://what-if.xkcd.com/73/
| antognini wrote:
| The mean free path of neutrinos through lead is around one
| light-year. So, taking the thickness of the body to be 1/2 a
| meter, you would expect the probability of any individual
| neutrino to interact with the body to be ~5 x 10^-17. So
| you'd ballpark have around a 20--40% chance that a single
| neutrino interacts with your body. It would probably cause a
| localized radiation burn. Detectable, but probably not lethal
| unless you got really unlucky with where it hit you.
| pfdietz wrote:
| The mean free path of much lower energy neutrinos in lead
| is about a light year.
|
| The MFP of a 120 PeV neutrino in lead would be something
| like 10 kilometers, I think.
| cozzyd wrote:
| More like 100 km I'd think but yeah, the neutrino nucleon
| cross section gets much bigger at high energies
| queuebert wrote:
| Total energy of impact would be 120 PeV x 10^16 = 120 x 10^31
| eV = ~60 kilotons TNT, or 4 Hiroshimas.
|
| So BIG boom.
|
| Since the velocity is so close to the speed of light, you can
| think of this like the energy released by annihilating a ping
| pong ball made of antimatter.
|
| Edit: Commenter asked what would happen if they "hit", so I'm
| assuming a hypothetical 100% collision. But yes to stop 1/e
| of a neutrino beam with normal matter, you'd need a light
| year of lead.
| mppm wrote:
| > big boom
|
| The probability of interaction of neutrinos with matter
| increases with the energy. I've asked o1 to estimate the mean
| free path of a 120 PeV neutrino in water and it came up with
| 1000km. So let's say, conservatively, that 10^-7 of the total
| energy gets deposited in your body when the beam goes
| through. The mass equivalent of a ping pong ball is about
| 2.5x10^14 J, which gives us 2.5x10^7 J total, or about 6kg
| TNT equivalent. This is only an order-of-magnitude estimate,
| but it would definitely not be healthy.
| jl6 wrote:
| So, according to basic Ant-Man theory, if I were hit by one of
| these, it should be like getting all that (10% of a) ping pong
| ball energy concentrated in a tiny spot, causing me to fly
| backwards across the room?
| BobaFloutist wrote:
| I would expect it to be more likely to punch through skin
| than to actually propel you.
|
| But also neutrinos don't typically collide with things very
| easily, they're more likely to pass through you without you
| ever knowing.
| moffkalast wrote:
| Yeah there's no way it would be able to grip onto anything,
| probably more like the Bugorski case, where he stuck his
| head into a particle accelerator and a proton beam went
| right through his head.
| Aachen wrote:
| I was thinking the same though. It doesn't interact often,
| but if it randomly does annihilate with another particle in
| your body, at such a small scale (subatomic) that
| force/pressure just destroys anything in its path no? Like
| a paint flake hitting a space ship. Or is it more like
| "light" (since they're iirc their own antiparticle), which
| is then absorbed by surrounding matter and turns into heat?
|
| In the wrong spot, this sounds to me like it kills you?
|
| Nothing to be afraid of, of course, for the reason you
| mentioned. Just wondering, xkcd "what if" style
| parineum wrote:
| Isn't Ant-Man logic that he still has the same mass when he
| shrinks and, as such, can generate the same force?
|
| Unless you get thrown back by ping pong balls normally, I
| think you'd be fine.
| class700 wrote:
| And yet when he grows he still has enough strength to punch
| a leviathan out of the sky. I'm not sure there's such thing
| as ant man logic - It doesn't seem like it should result in
| strength both ways.
| voidUpdate wrote:
| His weight also changes with size, or doesnt, depending
| on what would be more convenient for the current scene
| s1110 wrote:
| Does this count as "Americans will measure with anything but
| the metric system"?
| UltraSane wrote:
| No, it is called giving context.
| MathCodeLove wrote:
| Does this count of "non-American's online will take any
| opportunity to shit on America"?
| tasty_freeze wrote:
| Are you implying that people who use the metric system have
| an intuitive sense of what 120 PeV means?
| scotty79 wrote:
| There's interesting "end of life" scenario. Nearby supernova
| exploding and sending so many high energetic neutrinos that
| even with their rare interactions they could mess up all
| chemistry that biology uses. And you wouldn't be able to
| shelter from it since the whole planet is basically transparent
| to them.
| ahazred8ta wrote:
| 120 PeV is 0.020 of a Joule, or 20 milliwatt-seconds.
| xarope wrote:
| the way I play ping pong (holding the paddle like an ice cream
| stick)? or the way a professional ping pong player plays (which
| probably means they are serving aces on me all day)?
| ziofill wrote:
| It's mentioned in the article that the highest energy ever
| recorded for a single particle was 320,000 PeV which is about 50
| joules, i.e. the energy of a golf ball at 100 mph @_@
| queuebert wrote:
| That was a cosmic ray proton, which has probably 10 billion
| times the mass of a neutrino and interacts much more strongly
| with normal matter. A nuclear juggernaut vs a ninja by
| comparison.
| cozzyd wrote:
| Most likely a heavier nucleus than a proton too
| adaml_623 wrote:
| Would a nucleus composed of multiple nucleons stay stuck
| together with that much energy? If it's zipping along and
| not interacting with the anything then sure but how did it
| get that much energy in the first place?
| cozzyd wrote:
| Yes, while there is a large amount of uncertainty, it is
| believed they the majority of the highest energy cosmic
| rays are nuclei of elements like iron. For people like
| me, in the business of finding high energy neutrinos (I'm
| not involved in km3net, btw), that's a bad thing since
| that means the highest energy cosmic rays convert less
| efficiently into neutrinos when interacting with the
| cosmic microwave background.
|
| How they got so much energy in the first place is kind of
| an open question. Generally it involves magnetic fields
| and shock fronts, getting a little kick each time (but
| yes, you also have to avoid disintegrating the nucleus in
| the acceleration environment!)
| dooglius wrote:
| It looks like they detected a muon and are inferring a neutrino
| from the fact it went through a lot of solid. Couldn't it be any
| other weakly-interacting particle though?
| Sniffnoy wrote:
| How? Quarks can't change into leptons. Charged leptons can't
| change directly into other charged leptons. And neither charged
| leptons nor hadrons are going to pass through such a quantity
| of matter, as you say. I mean I assume other cases are
| technically _possible_ but they don 't seem very _likely_...
| nxpnsv wrote:
| Nothing else that we know of would create a muon of that energy
| deep inside bedrock.
| AnimalMuppet wrote:
| Nit: As I read the article, they aren't sure that it went
| through _any_ solid. Went through a lot of seawater, though.
| And your argument still applies.
| cozzyd wrote:
| It could be beyond the standard model physics but no other
| standard model particle could work other than a neutrino.
| yapyap wrote:
| bit of a redundant title
| ge96 wrote:
| What's faster than satellite communication? Neutrinos baby
|
| Not even sure if that's worth doing, either create/emit or use
| encode data into them as they fly by to be received by someone
| else
|
| Edit: that's cool people have tried though
| queuebert wrote:
| Neutrinos can go straight through the Earth, yes, but since
| they have mass their velocity is less than c.
| mr_toad wrote:
| It's very close to c though, close enough that it beats
| sending a signal around the Earth.
|
| The drawback is the impractical size and cost of a receiver.
| cozzyd wrote:
| Come on, we gotta convince the finance bros to find
| building better neutrino beams and detectors.
| e3bc54b2 wrote:
| HFT peeps are Comfortable spending millions on custom
| high speed undersea cables to save few ms o'er request.
|
| How about saving few hundred ms across the earth?
| shagie wrote:
| That's covered in RFC 1217. https://www.rfc-
| editor.org/rfc/rfc1217.html
|
| Its in section 4: Jam-Resistant Underwater Communication
| PaulHoule wrote:
| Would have really been faster if this result was true
|
| https://en.wikipedia.org/wiki/2011_OPERA_faster-than-light_n...
|
| which was something that would have happened in
|
| https://en.wikipedia.org/wiki/Steins;Gate
|
| Funny the idea that the neutrino might be a tachyon never seems
| to go away. The best fit of OPERA results is within error bars
| of the speed of light but towards the superluminal side.
| Superluminal neutrinos of the energy they were generating with
| the kind of mass we expect wouldn't be going measurably faster
| than the speed of light.
|
| I visited the site of this experiment
|
| https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lar...
|
| where the best fit for the squared mass was just a tiny bit
| negative but within bounds of zero. There is the classic 1985
| Chodos paper
|
| https://www.academia.edu/27606971/The_neutrino_as_a_tachyon?...
|
| and people still keep writing papers about it
|
| https://www.mdpi.com/2073-8994/14/6/1172
|
| somebody is going to have to measure a positive mass squared to
| really put a stake in its heart.
| queuebert wrote:
| It's worth noting that we received the neutrinos from
| Supernova 1987a before the photons. We think that's because
| the photons have a difficult time escaping the ejecta cloud,
| while neutrinos stream away freely, but who knows ...
| PaulHoule wrote:
| Oddly another detector caught a burst of low energy
| neutrinos that came a few hours before the burst that
| everyone accepts was from 1987a
|
| https://www.sciencedirect.com/science/article/pii/S09276505
| 1...
|
| Low energy tachyons would go a little faster, but you've
| got the additional problem of explaining why neutrinos got
| emitted in a spectral line.
| queuebert wrote:
| That is weird. Is the conventional explanation a flash
| from one of the last fusion stages right before core
| collapse?
| PaulHoule wrote:
| The core collapse itself produces most of the neutrinos.
| All of these protons are squeezed together with electrons
| which produces neutrons and neutrinos.
| hammock wrote:
| We already do, so the conspiracy theory goes. In Antarctica
| bookofjoe wrote:
| >Observation of an ultra-high-energy cosmic neutrino with KM3NeT
|
| https://www.nature.com/articles/s41586-024-08543-1
| neals wrote:
| Anybody here able to tell me what it means? Where do neutrinos
| get their energy from? Is there a limit? Will this make my phone
| smaller? My microwave quicker?
| scotty79 wrote:
| I can answer last two questions with definite "no".
| thamer wrote:
| It took a few tries, but I got Wolfram Alpha to compute its
| velocity compared to the speed of light[1].
|
| I started with: sqrt(1-((1/(1+120 PeV /
| (neutrino mass * c^2)))^2))
|
| but it simply said "data not available". So I changed:
| 120 PeV to 120e15 * 1.602176634e-19 kg m^2 s^-2 neutrino
| mass to 1.25e-37kg speed of light to 299792458 m/s
|
| and finally it gave a numeric result:
| 0.999999999999999999999999999999999999829277971
|
| (that's 36 nines in a row). Pasting it in Google says the value
| is "1", which is... not far off.
|
| If you want details about the way this is calculated, I dug up
| the formula from an article I'd written about particle velocities
| in the LHC, back in 2008[2]. For comparison, their 7 TeV protons
| were going at 0.999999991 x c.
|
| [1]
| https://www.wolframalpha.com/input?i=sqrt%281-%28%281%2F%281...
|
| [2] https://log.kv.io/post/2008/09/12/lhc-how-fast-do-these-
| prot...
| davrosthedalek wrote:
| We don't know the neutrino's masses, so this is a lower limit
| for v (since the mass you used is an upper limit)
| wd776g5 wrote:
| I can see it came from your source but why is the neutrino mass
| specified in kg instead of g? why not 1.25e-34g?
| thamer wrote:
| The kilogram is the base unit of mass in the International
| System of Units (SI):
| https://en.wikipedia.org/wiki/SI_base_unit
|
| Time is in seconds, length in meters, temperature in kelvin,
| etc. A unit of energy like a joule is then defined using
| these base units, so 1 joule is 1[?]kg[?]m^2[?]s^-2.
| skissane wrote:
| > The kilogram is the base unit of mass in the
| International System of Units (SI)
|
| Arguably, an ugly wart, but one we are stuck with for
| historical reasons. The base units of the original metric
| system (metre and gram) were poorly proportioned for
| practical use, resulting in the two main
| scientific/engineering systems of metric units both
| choosing to prefix one base unit - the centimetre-gram-
| second (cgs) system chose to prefix the metre, the metre-
| kilogram-second (mks) system chose to prefix the gram, and
| eventually mks won out over cgs and evolved into SI.
|
| Whatever warts SI has, they are nothing compared to the
| chaos of the Imperial/customary system
| myrmidon wrote:
| > The base units of the original metric system (metre and
| gram) were poorly proportioned for practical use
|
| What is the dealbreaker here though? Because we have
| plenty of "poorly proportioned" SI units anyway; e.g. it
| would be much more practical to have megapascal,
| microfarad and megajoule as base units from an
| engineering pov (particle physicists might disagree;).
| skissane wrote:
| Pascal, farad, joule aren't base units, they are derived
| units.
|
| Ideally, the base units should be prefixless. Except for
| kilogram, they all are.
|
| Imagine a system exactly the same as SI, except instead
| of the kilogram, it had the kram, where 1 kram = 1
| kilogram... then the gram would be the millikram, the
| milligram would become microkram, the microgram would
| become the nanokram, etc... if you were starting from
| scratch, without any historical baggage, wouldn't such a
| system be superior? But of course, we aren't starting
| without historical baggage - almost everybody knows what
| a kilogram is, kram is a word I just now made up.
|
| I think some derived units being "poorly proportioned" is
| inevitable given the physics we have.
| myrmidon wrote:
| I understand what you mean-- I was just curious about why
| we could not just stick with gram-meter-second (since we
| have a bunch of "poorly proportioned" derived units
| anyway)...
| adrian_b wrote:
| Using the gram would not have removed the prefixes from
| all commonly used units.
|
| In the beginning, the liter was a much more frequently
| used unit of volume than the cubic meter.
|
| A liter was defined as the volume of a kilogram of water.
| In a system were the gram was the unit of mass, the
| corresponding unit of volume was the milliliter.
|
| Which of the gram and the kilogram or which of the
| centimeter and meter were chosen as the units of mass and
| length did not matter much for mechanical units, in the
| way they were used in practice in the 19th century.
|
| A definite choice of the base units has become important
| only after a bunch of new physical quantities have been
| defined for use in the theories of electricity,
| magnetism, heat and light, in the second half of the 19th
| century. When dealing with so many different physical
| quantities, not using unique base units would have caused
| too much confusion. While this necessity has been
| recognized, for many years 2 different choices for the
| base units were widespread, that based on meter-kilogram
| (used mostly by engineers) and that based on centimeter-
| gram (used mostly by theoreticians). Meter and kilogram
| were more typical for the sizes of practical machines,
| while centimeter and gram were more typical for the sizes
| of laboratory experiments.
| Sharlin wrote:
| If the base unit were gram, megapascals would be
| gigapascals, microfarads would be nanofarads, and
| megajoules gigajoules. Similarly a watt would be what's
| now a milliwatt and most "everyday" powers (except in
| electronics) would be kilowatts or megawatts.
| l33tman wrote:
| In particle physics you just use GeV (with varying powers)
| for most parameters :)
| dr_dshiv wrote:
| That's fast! But for how much energy? For comparison, the total
| energy from this one particle (0.0192 joules) is equivalent to
| keeping a 50 mW LED lit for a third of a second.
| octocop wrote:
| Why do they place the receiver in a large body of water, like the
| Mediterranean?
| tjpnz wrote:
| Neutrino interactions with nuclei of water produce charged
| particles which move faster than the speed of light in water
| (but slower than through a vacuum tube) creating a cone of
| light known as Cherenkov radiation, which is the optical
| equivalent to a sonic boom. This is projected onto a ring
| around the detector.
|
| Doesn't need to be submerged in a body of water as large as
| this. The Super-Kamiokande[0] detector for instance is located
| in a body of water inside a mountain.
|
| 0: https://en.m.wikipedia.org/wiki/Super-Kamiokande
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