Since 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.
In 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.
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.
Most 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.
> 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.
I 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 :)
How 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?
>How about a whole system of neutron stars, in orbit around each other
that's a neat idea. the orbital mechanics involved are pretty mind-boggling, but I guess a civilization that could create a system of neutron stars could probably deal with the math ;).
That's not someone harnessing neutrinos for their power, that's someone harnessing technobabble for it's ability to separate rubes from their money.
If I'm reading that paper above correctly, which despite its silly premise appears to have been seriously written (by undergrads, but the numbers pass the smell test), neutrinos have ~1/70th the power flux of solar anyhow, assuming you could catch all of them, which you can't.
Yeah I wondered about that. And their initial target application sounds pretty sketchy too. You have a brand new power source, you sell it to NASA first, not to Motorola, right?
From a little poking around it sounds like cosmic rays have a more useful power flux.
This thing is bizarre. It reads and looks like the standard "use trappings of actual science to sell bullshit", except they don't seem to be selling anything?
To be "charitable", maybe someone multiplied the solar neutrino flux/sqcm by their "maximum" energy (wikipedia numbers: 17e10 x 8e6 ~= 0.2w) and thought "that could power things!!!"
But more likely this is some sort of deliberate scam.
The science doesn't add up here. There are dozens of fluffy "this-will-save-the-world" articles without any substance which eventually led me to a single website that claims to represent a team working on that technology. That site seems to be seeking investors.
Without a miraculous scientific breakthrough the math doesn't add up. We don't know of any way to capture neutrons in a way that would provide meaningful power. For those reasons, I'll suggest this is more likely a scam than a sincere or realistic effort.
Why not communications? Neutrino-based communication is borderline ideal. A properly-aimed low-energy beam will make it to its target, obstructed or not.
Serious answer: because bandwidth is terrible. A transmitter the size of the LHC can only produce enough neutrinos (a few quadrillion per second) for a detector to receive a hundred per second or so. Accounting for noise, that means you can only achieve a few bytes per second at best, and again, that's with using the LHC to produce the neutrinos in the first place. With far less power you could instead use ultra-low frequency radio waves and still get better bandwidth.
I always thought neutrinos would be a much better medium for other civilizations sending out messages to the rest of the universe because of this fact. Radio waves like SETI is looking for attenuate at a significant rate and seem very primitive compared to harnessing neutrinos.
A physics paper I was actually able to fully comprehend. I'm happy this paper exists for no other reason than to make an amateur like myself feel they understand something.
I'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.
It's not impossible, but it's kind of absurd. Neutrinos are insanely hard to detect. You need immense detectors, and even you get only a ludicrously tiny fraction of the neutrinos passing through. You'd have to modulate it by turning on and off an immense nuclear power plant, so despite shaving off milliseconds of latency you still wouldn't be able to communicate fast.
There's no reason to expect any of that to become more practical any time soon. Neutrinos are too small, too fast, and too devoid of interaction to manipulate easily.
> You'd have to modulate it by turning on and off an immense nuclear power plant
A particle accelerator would be much more responsive.
The immense detectors on the other side would stay, and you'll need entire minutes just to get a single neutrino anyway (and then, how many do you need to be sure? at least 2, I imagine.)
We report on the performance of a low-rate communications link established using the NuMI beam line and the MINERvA detector at Fermilab.
The link achieved a decoded data rate of 0.1 bits/sec with a bit error rate of 1% over a distance of 1.035 km, including 240 m of earth.
We'd modulate this high-energy beam. Data bandwidth would likely be quite low, but in terms of latency, it should be the fastest.
A beam directly going through Earth (e.g. from North America to Asia) is definitely going to be faster than optical fibre (or satellite) links that have wrap around the Earth.
I'm assuming neutrinos are sparse in nature, which is 50,000 metric ton pool of water was needed to detect the neutrinos emanating from the sun. But if we artificially create a highly concentrated beam of many many neutrinos, even a 99.99% loss / non-detection rate shouldn't be problem. (Again, bandwidth would be low, but we are aiming to minimize latency.)
Unfortunately, not even then. Nowadays you generally neglect the latency of the physical act of receiving a bit and being sure whether it is a one or a zero because it is such a small amount of time compared to the other characteristics of the journey, but in this case you can't do that. The amount of time it will take to be sure whether it's a 1 or a 0 being sent will be dwarfed by the amount of time it would take to send a conventional TCP packet containing significantly more than one bit.
Note that while we neglect it, it still exists. If you zoom down to a small enough scale, you don't get a pristine series of ones and zeros, but a noisy voltage or light signal, and there can be plenty of attoseconds where the current voltage/light could correspond to either a 0 or a 1 coming in next.
> I'm assuming neutrinos are sparse in nature, which is 50,000 metric ton pool of water was needed to detect the neutrinos emanating from the sun.
No, that's not the reason. The reason is that they barely interact with anything, including detection equipment.
> even a 99.99% loss / non-detection rate shouldn't be problem.
"Two water-filled detectors of this type (Kamiokande and IMB) recorded a neutrino burst from supernova SN 1987A. Scientists detected 19 neutrinos from an explosion of a star inside the Large Magellanic Cloud – only 19 out of the octo-decillion (10^57) neutrinos emitted by the supernova." (from https://en.wikipedia.org/wiki/Neutrino_detector)
First, you have to modulate the source in such a way as to encode a message. I think we can rule out things that involve blocking the beam, so you'll have to adjust the generation power. You're gonna need a massively powerful nuclear reactor or particle accelerator or something to be at all possible to notice the message, so it will probably be pretty tough to modulate that much power at a frequency high enough to get any kind of decent data rate.
Then we need a detector. Since the article is about a massive and massively expensive detector being able to create sort of an image of the Sun after multiple years of observation, I'm not optimistic about that side. We can build a detector that can tell if a manmade beam is on or off, eventually. I'm not very optimistic about building a detector sensitive enough to detect subtle variations in the power of the beam. We're gonna have a real tough time getting a decent data rate.
Doesn't make much difference if 1 bit can be transmitted through the earth faster than an electric signal can make it around if the electronic one can send billions of bits in the time the neutrino detector takes to send two.
You can't make a directed neutrino beam because the direction they're emitted in a reaction is random. That includes particle accelerators which make neutrinos by colliding other particles. A single reaction product comes out in a random direction even though the momentum and energy of them all together are conserved.
> To create the neutrino beam, a beam of protons from the Super Proton Synchrotron at CERN was directed onto a graphite target. The collisions created particles called pions and kaons, which were fed into a system of two magnetic lenses that focused the particles into a parallel beam in the direction of Gran Sasso. The pions and kaons then decayed into muons and muon neutrinos in a 1-kilometre tunnel. At the end of the tunnel, a block of graphite and metal 18 metres thick absorbed protons as well as pions and kaons that did not decay. Muons were stopped by the rock beyond, but the muon neutrinos remained to streak through the rock on their journey to Italy.
Interesting, 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).
That's only two orders of magnitude away from a 100bps line, which would incur 10 ms latency due to the transmission method (in addition to the latency of the neutrinos actually having to get there), and that's for reliable communication.
Unreliable communication that gives you an advantage over mere chance 1% of the time can already be advantageous, you'll be right 51% of the time.
Blowing holes in miuntains is junior league for nuclear physics. The exact same factor that allows neutrinos to pass through a planet make them impossible to work with.
The detector here weighs 50,000,000kg, and still like 99.9..% of neutrinos pass though it without being detected - imagine that kind of signal loss in a data link.
This detector does not notice tiny amount of neutrinos produced at particle accelerators. It would have to placed right next to a 4GW nuclear powerplant to detect neurinos at any kind of reasonable rate.
The only man made source of neutrinos you could detect from another continent is a massive thermonuclear blast.
That image was captured over 503 days of exposure, with a detector the size of a swimming pool. I won’t claim it’s impossible, but I’ll give you fantastic odds against it in the next, say, twenty years.
All you need is one bit: silence -> neutral!, 0 -> buy!, 1 -> sell! Or two: 00 -> neutral!, 01 -> sell!, 02 -> buy!, 11 -> wait!
Plus error correction... When you add error correction and consider the number of missed bits and the need to retransmit / keep transmitting, it's probably not possible to realize a latency win here.
Think about it like this: the absolute vast majority of neutrinos pass through the whole planet without interacting with a single particle. One descriptive saying is that a neutrino can pass through 100 light-years of steel without interacting. This puts in context how hard it is to detect them (have them interact with your detector).
So your communication turns into some random string of detections where you never know if the absence of a detection means there was no neutrino, or it was just missed.
Perhaps, but if you consider the probability of missing an individual neutrino your error correcting scheme will have to be either very long or very clever because your odds of collecting the right neutrino at the right time will go down very quickly as the packet gets longer.
On top of that, if you used some kind of pulse scheme (i.e. morse code with neutrinos) it has to be slow enough to be detectable, but fast enough to beat the latency of a cable (let's say 100ms - speed of light + processing and errors) and also fast enough not to use enough power as to be unprofitable.
> > it's probably not possible to realize a latency win here
?
> On top of that, if you used some kind of pulse scheme (i.e. morse code with neutrinos) it has to be slow
"slow pulse" == long pulse. It will be "fast" in that it will go faster than the speed of light in fiberoptics and the path will be shorter, but it will be slower because error correction will demand a great deal of redundancy which, among other things, means long pulses.
I have the attention span of a hyperactive toddler so when I write HN comments I can end up responding to everything I've read in the comment tree, sorry.
You can easily send them through the earth because they are hard to detect: it’s two sides of how low their interaction is. What’s the point sending data that you cannot pick up? Femilab could probably modulate their bean to Oklahoma (or wherever the detector is located) but you can’t work up enough bandwidth for it to be worthwhile. Ever, for anything.
What about using neutrinos for interplanetary communication between ground bases on different planets? Since they are hard to be stopped by any kind of matter, it should be a good way of ensuring the link stays stable with only one base, instead of having 3 or 4 depending on Earth's location and day cycles.
Yottawatt level fusion power generation levels has been demonstrated at about 1% of solar output. Maybe those could be used in a pattern to send messages? ;-)
So 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?
The 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.
Isn'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"?
The detector does not "look" in any direction, it is in no way "pointed" at the sun. It records the direction of all events that occur within its volume. But once recorded they compare the direction of all events with the direction from the sun at the time of the event. The angle between the solar direction and the event direction is what makes up that image. If the neutrinos were not coming from the sun, the image would look like white-noise. Since there is a clear "peak" at the center you can make a good estimate about what fraction of events in your data set came from the sun. That amount is a direct measurement of nuclear processes going on with the sun over the course of the dataset...which is physically interesting. Here is the 1-D version of the neutrino "picture", https://i.imgur.com/7OmXXtn.png (cite: https://arxiv.org/pdf/1606.07538.pdf). You can tell quite clearly that there are many more events pointing away from the sun then are pointing back towards it. Exactly how much more is the interesting physics measurement done here.
All that being said, the specific shape of the "sun" in the image is influenced by many factors many of which are related to the detection mechanism and the detector itself...and don't tell you that much about the sun. Eventually (one hopes), detectors will improve to the point where the "shape" information of the image is reliable enough to extract interesting solar physics measurements from it.
P.S your fun thought on the detection of a fusion reactor is extremely on point. There exists a under-construction experiment in the UK called "Watchman" that hopes to detect a neutrino signature from a nuclear power plant being shut off and then being used to produce material for a nuclear weapon. The idea would be that you could observe activities of nuclear facilities in a "rouge nation". See here https://www.nytimes.com/2018/03/27/science/nuclear-bombs-ant... or here http://svoboda.ucdavis.edu/experiments/watchman/
There'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
Good 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.
Wow. 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.
There 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)
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.
Do 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.
For 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). 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.
I 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.
It 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).
You 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.
I got sidetracked reading about Oliver Heaviside, and noticed that it is claimed his theories allowed a 10x increase in transatlantic telegraph bandwidth...from 0.1 characters per minute to 1 character per minute.
I wonder how much more feasible it is to send information via neutrinos if 0.000000013 Mbps were considered reasonable speed.
Article 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".
This 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 )
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.
The 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?
For 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.
There 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.
How 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.
There 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.
Can 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.
I 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.
That'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.
While 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).
It 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.
I 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.
I 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_sola...
