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The Sun seen through the Earth in “neutrino light” (2007)
- kmm 6y agoSince fusion is only happening in the center of the Sun, and the outer layers are almost entirely transparent to neutrinos, this is actually a direct image of the solar core. Which makes it even cooler imo.
- yummybear 6y agoSo they can use this image to directly measure the width of the core?
- lopsidedBrain 6y agoTo an extent. I'm actually curious about its angular resolution.
- 0PingWithJesus 6y agoIn principle yes....although the specifics of the physics involved kinda make the question itself not well posed. There is no hard boundary to the core of the sun. The "core" is by definition where nuclear fusion reactions occur. However, those reactions don't just stop at a certain radius...but instead just occur at a lower and lower rate. So even if you could determine with 100% precision where a neutrino came from within the sun, you would still measure some exponential-like decay as a function of radius. But to add even more complexity there's ~10 different nuclear processes within the sun that produce neutrinos. Those processes all have different radial profiles. So even if you measure with 100% accuracy the radial profile of neutrinos associated with one or two nuclear processes...you still haven't really measure the core of the sun...you've just measured it for a few specific reactions. And for the neutrinos produced by many of the reactions this method cannot work, those neutrinos are too low in energy to provide direction information. And beyond that there are a handful of nuclear reactions that occur within the sun that don't produce neutrinos. So there doesn't really exist any way to measure the radial profile of those nuclear processes. And this all assume you can perfectly tell where the neutrino came from within the sun, which is also impossible. There will always be some relatively poor "resolution associated with your ability to place a neutrinos origin. Here is the "hard" physics limit to your angular resolution for a relatively high solar energy neutrino...it only gets worse as the energy goes down https://i.imgur.com/h3n8c4V.png https://i.imgur.com/h3n8c4V.png. But getting to even that resolution is impossible b/c an interaction will only produce so many photons from Cherenkov radiation (think 100s of photons). Then it becomes a statistics problem...what's the best angular resolution you could possibly achieve given an average number of photons that's around (say) 500. It ends up the answer is "pretty good" but far from perfect. And all of that is assuming the electron scattered from the solar neutrino will travel in only one direction...that's extremely untrue, the electron will always bounce off of other electrons & atoms after scattering. This multiple-scattering leads to even worse angular resolution. Here's a paper on the subject if you'd like further detail https://arxiv.org/pdf/1606.02558.pdf https://arxiv.org/pdf/1606.02558.pdf
- sudhirj 6y agoMost lines of this kind are drawn based on some value we agree on, not any intrinsic rule in physics. The boundary of the atmosphere, earth's crust, the extent of the solar system, etc.
- cp_mlreef 6y agoThank you for sharing! Extremly interesting and mind boggling - what a time to be alive!
- frumiousirc 6y agoAbsolutely not. The angular resolution is nowhere near good enough. Every time the Internet regurgitates this link it is misinterpreted by essentially everyone that comments on it.
- ahazred8ta 6y agoThe core is about 20% of the width of the sun, so about 0.1 degree wide as seen from Earth.
- zyxzevn 6y agoThe circle in the centre of the image is much wider than the sun. Sadly, we can not see any meaningful imagery from it.
- gabrielfv 6y agoThat's impressive. But I'm also curious as to what other applications this setup can be useful for, because that looks to be one hell of an expensive operation. It's awesome to see such things actually happening.
- zuzun 6y agoIt was initially used to observe proton decay. By not detecting a decaying proton in the water tank, they could place the mean lifetime of a proton above 10^30 years.
- jjk166 6y agoWhile not done with neutrinos (at least not yet), a very similar setup is used for stufying geological structures. Usually either cosmic rays or muons produced by cosmic ray collisions are detected and depending on the number of detections over time, the density of the rock they pass through can be determined. By filtering the energy of the particles, you can look at radiation directionally (particles coming straight down have more energy than those that come at a shallower angle). You can have a detector next to a volcano and get an "x-ray" of that volcano. Neutrino detectors can also "see" active nuclear reactors. One could imagine using a detector located outside of a suspect nation to validate their claims with regards to nuclear nonproliferation (ie that they're not running their reactors overtime to produce more plutonium than they report).
- TallGuyShort 6y agoSo I understand how they can detect the presence of a neutrino, but how do they trace that back to form the image? Is the Cherenkov radiation directional?
- idlewords 6y agoYes.
- 0PingWithJesus 6y agoThe process behind this measurement is that the neutrino hits an electron in the detector. That electron will (with relatively high likelihood) travel in the same direction as the incident neutrino. The Cherenkov radiation produced by the electron is emitted in a cone shape along the direction of travel. The photo-detectors observe the Cherenkov light and through some well tuned algorithms the electrons direction is "reconstructed". Super-K has no doubt spent significant effort improving & evaluating their reconstruction algorithms. Once you have the reconstructed electron direction there's almost no hope that you can reconstruct the incident neutrino direction...but that's generally okay, b/c you can usually just assume the neutrino traveled exactly parallel to the electron (i.e. directly away from the sun). But that's sometimes wrong which is (partly) why you see a lot of "fuzz" around the solar core in the image.
- credit_guy 6y agoIsn't this image a bit circular then (pardon the pun)? The "hot" pixels in the middle represent the electrons with a direction perfectly aligned with the direction to the Sun, while the cool-blueish outside pixels are a representation of the electrons traveling at an angle? Circular in the sense that you know where the Sun is, and are looking in that direction, and the electron trails are just confirming that. Is this image telling us anything new? Can this method be used for any type of observation? Or it simply serve as observation in the opposite direction: knowing where the neutrinos come from, you can infer in what cone the bounced electrons can move? A fun thought: if one day, a secret organization starts running an undisclosed nuclear fusion reactor, will it show up on this "photo"?
- Ciantic 6y agoI'm not very well versed on the physics, but every time neutrinos come up, I wonder when can we establish a data link that goes through the earth, instead of around it. When neutrinos can be captured and emitted with good ability, and they can go through the earth, then how feasible it is to build a data link with them from between let's say Japan and US? It's not possible today of course, because it would have been done already.
- whatshisface 6y agoIt's possible today but not economically practical. You could get low-latency messages, but you would miss most of the bits coming through.
- Ciantic 6y agoInteresting, care to elaborate more? I haven't found that it's even possible with long distances like that. If corporates are literally blowing holes to mountains to get faster and more direct data links between trading places. Then it sounds like just a question of time when the technology matures enough (if it's possible already).
- Evidlo 6y agoHere's an article about communicating with neutrino beams: https://blogs.scientificamerican.com/observations/message-encoded-in-neutrino-beam-transmitted-through-solid-rock/#:~:text=Neutrinos%20are%20having%20a%20moment.&text=Neutrinos%20have%20been%20proposed%20for,screen%20out%20most%20other%20particles https://blogs.scientificamerican.com/observations/message-en.... In short, they were able to achieve about 0.1 bps with hardware that costs hundreds of millions of dollars.
- ClumsyPilot 6y agoAlso note that the distance transmitted is a mere kilometer. Carrier pigeons are more practical
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- k2xl 6y agoQuestion from someone who has no physics background - they mention the neutrino can go "faster than speed of light" - how is that possible?
- jameskilton 6y agoI think you're talking about "the electron is accelerated at a speed greater than the speed of light in water"? The "in water" is the important bit. Light travels [as measured in a straight line] slower in water due to bouncing off of the water molecules. It's not that light itself is slow it just takes light longer to make it through the water because it takes a longer path.
- lopmotr 6y agoIt's not taking a zig-zag path like you imply. That would be scattering and it would end up in a random direction.
- w1 6y agoIt goes faster than the speed of light _in water_. While the speed of light in a vacuum is fixed, light will pass slower through different mediums (i.e. it goes slower in water than air, which is how you get refraction).
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- lekanwang 6y agoYou can't go faster than the speed of light in a vacuum. But, you can definitely go faster than light in a medium. Speed of light in water, for example, is around 0.75c.
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- idlewords 6y agoThere's a fun paper on how you could use a particle accelerator to blow up nuclear weapons in their silos from the other side of the planet with a neutrino beam. There would be no defense against this (highly fanciful) countermeasure. https://arxiv.org/pdf/hep-ph/0305062.pdf https://arxiv.org/pdf/hep-ph/0305062.pdf
- andbot 6y agoGood luck generating a 1000 TeV neutrino beam with that flux. Currently, humanity is at 6.5 TeV for protons, which are easily acceleratable because they're charged. Neutrinos have to be produced through a fixed target collision setup which translates only a small fraction of the original energy into neutrinos. So I dare to predict that by the time we can have such a beam we have wiped ourselves out with nuclear bombs.
- spacemark 6y agoNot to mention you'd have to know where to aim your neutrino beam...
- ISL 6y agoWow. I've never seen a paper like it. At the surface level -- if you kick a core hard enough with enough neutrinos, sure, it'll probably initiate -- the argument seems plausible. My expertise doesn't let me go deeper than that. The moral implications of such a device are fraught. To use it is to detonate the very weapons that one should not detonate.
- mhh__ 6y agoThere is probably a lot more scientific research like this buried away in the vaults of the superpowers. Even more if you include the "scientific" research done by programs like MK-ULTRA (most files where successfully destroyed AFAIK). For example, when Project Orion was being seriously considered the scientists had to find ways of making large quantities of fairly powerful nuclear weapons cheaply and quickly. Based on something Freeman Dyson said, I think they succeeded to some extent, but that secret now has died with the scientists who worked on it. There has to be a lot of writing squirrelled away somewhere, because there are restrictions like "You agree to obtain a validated export license when exporting if this product is incorporated into the design, development, production, or other activities related to chemical weapons, biological weapons, nuclear weapons, or ballistic missiles." but no available literature on how these packages may actually be used in this context. (https://welsim.com/download https://welsim.com/download) One of the reasons Nuclear Testing is now very uncommon is because computers and software are now advanced enough to simulate them accurately. And yet, despite that, there is no "Nuclear Weapons design: A modern approach" available for public consumption. These are worked on by physicists so someone must be wasting time by writing books somewhere.
- devin 6y agoShould the article’s title on HN reflect its publication date? (2007)
- rydre 6y agoCan we use this principle to decrease the latency between continents over the internet? Like transmitting data via artificially generating neutrinos and sending them directly from say Asia to Latin America? There has to be a way, no? I'm not a physics guy so it would bee be better if someone with domain knowledge could chime in.
- bognition 6y agoThe challenge is detecting neutrinos is very hard. The image in the article required a 500d exposure.
- _jal 6y agoSure. Your 'NICs' would be rather expensive[1] and you'd need to minimax bandwidth vs. error correction for the number of detection misses. [1] Here's a picture of one: https://amp.businessinsider.com/images/5b23cd9d1ae66220008b5296-2732-1366.jpg https://amp.businessinsider.com/images/5b23cd9d1ae66220008b5...
- phinnaeus 6y agoAlso note this is only the receiver, you'd need another device of similarly massive scale to transmit.
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- The5thElephant 6y agoI don't think we can detect enough neutrinos to make this work. The reason it works with the Sun is the massive number of neutrinos it generates and exposing over 500 days since even then so few are detected.
- pphysch 6y agoArticle says the image is from a 503 day exposure--it doesn't say how, if at all, the nighttime data is decoupled from the daytime data. Perhaps it is something like "technically 0.0001% of this image might be from nighttime readings".
- rwmj 6y agoThe detector is deep underground (1000m) so it always goes through a bit of the earth. But they can easily select only the parts of the raw data which correspond to neutrinos going through the whole earth by only using detections which happened at night, local time. I guess they didn't mention this because it's obvious?
- ClumsyPilot 6y agoThere is no nighttime, nutrinos go straight through stars and planets.
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- frumiousirc 6y agoThere is in principle a day-night effect which may be measured. The electron flavor component of the neutrino can be enhanced or diminished by the presence of matter.
- JuettnerDistrib 6y agoFor neutrinos there is no nighttime. The neutrinos are captured when they need to travel the maximum distance through the earth. That way, there are fewer other particles that need to be distinguished from neutrinos.
- 0PingWithJesus 6y agoThis article is quite old but a more recent measurement from the same experiment (Super-K) used a 1600 day dataset. Of that 1600 days of exposure 860 "days" were nights. So it's pretty close to half and half. (Cite: Section V-B, bottom left of page 22, of https://arxiv.org/pdf/1606.07538.pdf https://arxiv.org/pdf/1606.07538.pdf ) The daytime data and night time data are decoupled quite easily. Whenever an event is recorded by the detector you just make sure a timestamp is associated with the event. Then you use that timestamp to determine the location of the sun at the time of the event. If the sun is below the horizon it's "night" and if it's above the horizon it's day.
- wcoenen 6y agoThe abstract of this paper is one of the funnier descriptions I have come across about how hard it is to stop a neutrino: https://journals.le.ac.uk/ojs1/index.php/pst/article/view/859 https://journals.le.ac.uk/ojs1/index.php/pst/article/view/85...
- dfee 6y ago> We find that a thickness of 34000 light years would be necessary if a sheet of osmium were used, whereas neutron star matter could achieve this at 189 km thickness. We conclude that a neutrino sail is not a practical method of propulsion. Not practical, hmm?
- short_sells_poo 6y agoI think that even if we ignore the practicality of building it, at that thickness the neutron star material would immediately collapse into a black hole :)
- jbay808 6y agoThe osmium, too!
- ur-whale 6y agoNew theory: maybe black holes are scrapped alien neutrino detectors?
- dmurray 6y agoHow about a whole system of neutron stars, in orbit around each other, separated by vacuum, arranged for a given straight-line path in order that at any point in time that path intersects at least 189 km worth of neutron stars? Is this possible? I'm considering a loose definition of the word "possible" here, but could such an arrangement exist without collapsing to a black hole under gravity or being torn apart by centrifugal force?
- praveen9920 6y agoI wonder if there were there any attempts to observe the rest of the universe with this kind of equipment considering there are n number of neutrino sources. It could reveal the general shape of the universe or center of universe.
- 0PingWithJesus 6y agoThe Ice Cube experiment has done that exact thing. Here's the most recent publication from them on that subject, https://arxiv.org/abs/1910.08488 https://arxiv.org/abs/1910.08488. Here's a slight older but perhaps more digestible result from them https://icecube.wisc.edu/news/view/449 https://icecube.wisc.edu/news/view/449
- hinkley 6y agoThere was a detector that had a catastrophic failure during construction, and I am thinking it was this one. Anyone recall that story? Effectively, a bad unit cracked, and because they were submerged in a fluid, it created a shock wave that caused other units to crack, which caused more units to crack. They had to replace some large percent of the sensors and it set them back something like a year.
- 0PingWithJesus 6y agoYou are correct, that happened to the Super-K detector in the early 2000s. It's briefly mentioned here https://en.wikipedia.org/wiki/Super-Kamiokande#History https://en.wikipedia.org/wiki/Super-Kamiokande#History
- c-smile 6y agoThe most interesting fact on the image (IMO) is that the halo is clearly elliptical, why? Is the image aligned to the "main" ecliptic plane of Solar system or rather to Sun's rotation plane (7.25° from those) ?
- 0PingWithJesus 6y agoI think what you're seeing is either a random noise fluctuations, or perhaps a result of the coordinate system they're using for that image. If you take a look at a similar, more up to date, image from Super-K that uses more data you don't see any sort of elliptical nature. http://www-sk.icrr.u-tokyo.ac.jp/sk/physics/image/image_solarnu/solpic_1500d_2_1.jpg http://www-sk.icrr.u-tokyo.ac.jp/sk/physics/image/image_sola...
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- linuxhansl 6y agoDo we know how many neutrinos were registered during the 503 days? I'd be curious about the resolution of this image. Also, in order to cause the Cherenkov radiation, the neutrino has interact at least with an electron, I wonder about the percentage of the number of neutrinos interacting with the water in this vs. the number of neutrinos that interacted with Earth on the way. Not anything practical... I'd just be curious.
- 0PingWithJesus 6y agoFor their more recent data they reported seeing ~32000 solar neutrino events over a 1600 day dataset (cite: top-right of page 13 https://arxiv.org/pdf/1606.07538.pdf https://arxiv.org/pdf/1606.07538.pdf). Their detector nowadays is more sensitive than it was when the OP was published so I would estimate the image comes from probably around 5000 neutrino events. And I don't know any specific numbers but you can be sure a large amount more of neutrinos interacted with the air/rock between the Sun and Super-K than interacted in the detector volume. But that number (whatever it is) is still tiny compared to the total flux (which is ~5 million per square centimeter per second). And that's of just the "high energy" type neutrinos that Super-K is sensitive to. The lower energy varieties are more like 10 billion per square centimeter per second.
- fallingfrog 6y agoHow do you image neutrinos? I mean if you’re imaging the sun with light you’d use a pinhole camera, for normal images lenses or mirrors, but if neutrinos go straight through the whole planet how do you make a lens for that? Or a pinhole camera? Edit: I see that someone else asked a similar question, the answer being that you image electrons that have been knocked loose by neutrinos, which is much easier.
- saagarjha 6y ago> much easier Well, that's relative ;) It still takes hundreds of highly-sensitive detectors and many tons of hyperpure water to detect neutrino reactions.
- bepBoo 6y agoThe real story here, is that we likely have a very good understanding of what North Korea and Iran, each, have accomplished with their nuclear programs, based on what these neutrino detectors and LIGO experiments notice. LIGO being dual-use sensitive to ground vibration, and teams of neutrino detectors capturing and triangulating sudden directional showers of particles from special places around the globe, shot directly through the planet, into their chilled water tanks.