If I understand correctly, these particles are entering the earth from space around, say, the North Pole, and the coming out the other side in Antarctica?
If so, is it only out of Antarctica? Would that mean they are coming from a specific direction in space?
Why can't we observe them simply as they come out of space? Is there something about the process of moving through the earth that makes them more detectable?
These may be stupid questions, feel free to vote this down..
Edit: if I understand correctly it seems like it's happenstance and ANITA just happened to be above Antarctica when the cosmic rays shot up through it on those particular occasions, I think
I think it's because both detectors are using the deep ice sheet as part of neutrino detection experiments.
ANITA is listening for Askaryan radiation created by neutrino's traveling through ice (from the wiki, I know as much as you). And IceCube is looking for flashes of light created when a neutrino interacts with ice.
Disclaimer: I work on ANITA. Also I need to go to bed, so I'm writing this really fast so it probably doesn't make sense.
ANITA is a radio telescope attached to a balloon looking for broaband impulsive radio emission in Antarctica.
The main purpose is to look for the Askaryan emission from neutrinos interacting in the ice. The Askaryan emission is just the coherent version of the same process (Cerenkov radiation) that produces the flashes of light in IceCube (basically at long wavelengths you can't resolve the charges in a cascade and see a fast moving current density-- there's a negative charge excess because positrons can annihilate with atomic electrons). To detect this Askaryan emission, you need a dense dielectric material (if not dense, no target mass, if not dielectric, then RF won't propagate). Antarctica happens to be both the place you do long duration ballooning (due to all-day sunlight and favorable wind patterns that keep you over land) and the place with the most ice.
However, the events discussed here were produced by another channel. ANITA can also see RF emission from cosmic-ray extensive air showers (EAS). The RF emission here mostly comes from the splitting of charges in the showers by the Earth's magnetic field. Because in Antarctica, the magnetic field is approximately vertical, this produces horizontally polarized emission. Because ANITA is so high up (~40 km), EAS development from cosmic rays occurs below the payload, so the most common way for us to observe EAS's from cosmic rays is for the emission to bounce off the ice (because it's very forward-beamed). We can also see atmosphere-skimming showers that miss the ice entirely. As expected, the events that bounce off the ice have a polarity flip compared to the events that miss the ice.
The strange events discussed here look like EAS's from air showers, but the RF emission clearly points at the ice and there is no polarity flip from reflection, so the events look like very-energetic upward going air showers. There's no good way to explain upward going air showers in the Standard Model at these energies and observed angle (at lower energies or more grazing angles, tau neutrinos make it through the earth, which can decay to make upward-going air showers). So either there is something wrong with the measurement (we can't think of anything, but we're trying!), we got really unlucky with anthropogenic backgrounds (we think this is very unlikely), or there might be some new physics.
For this detection channel, there isn't too much special about Antarctica, just that we're on a balloon looking down so we can see stuff coming from below. The ice could potentially offer a slight enhancement compared to rock, but that's probably not so important. Other observatories looking for upward going showers from tau neutrinos (Pierre Auger) only look at very grazing incidence. There are proposals using fluorescence instead of radio emission (e.g. JEM-EUSO, and the SPB-EUSO balloon mission) that could do more or less the same thing.
Thank you, I've been working with microwave wireless transceivers for 20 years now and feel like you're explained what's going on. (I'm not really going to understand the physics)
Also a bit gobsmacked you can get Cerenkov radiation in air. On reflection I shouldn't be.
For the Askaryan channel you want a dense dielectric material (dense to have a big target, dielectric so tht radio can propagate). On Earth, that means glacial ice, sand or salt. Antarctica has a lot of ice.
Unrelated - are you accepting public pull requests for your AnitaFramework project on GH? From a quick glance there are some resource leaks and some such, should be easy to patch up.
We don't have any policy on this really. Like most experiments we are highly manpower-constrained, so I can make no general guarantees about timeliness to respond, but I don't see any problem with it. I'd probably be the one to deal with it anyway :)
I'm not sure what you mean exactly by bounce particles, but I think the answer is probably that at these highly relativistic energies, particles don't really bounce (what would they decay off of) or decay backwards (in the lab frame).
It’s also a matter of signal to noise. Not very many things (other than neutrinos) are detectable when you point a detector straight down into the earth. Contrariwise, you’re swamped with signal when you point a detector at space.
I ask in ignorance, but: could these particles actually have come from space in the normal way (i.e. from above the South Pole) and then just been reflected back up from several meters or so below the surface? That would, on its face, seem to resolve the question about strong vs. weak interaction: they’d be strongly interacting particles that happened to interact and ricochet straight back.
The particles can't be reflected like that. We do see reflected radio emission from (presumably) cosmic ray air showers, but the polarity of the signal undergoes a sign flip on reflection. These signals are peculiar because they are definitely coming from the ice but don't have the sign flip one would expect for a reflection.
Thanks for the answer! Apologies if this question betrays my ignorance further, but what would happen if a signal were reflected twice? Would the polarity flip back?
Yeah, or if it reflected off an interface going from high refraction index to low (e.g. reflecting off an under-ice cavern or something). These are possibilities, but 1) the reflection is far away, so for this to be coherent, it probably must be some massive feature, and 2) ANITA also had a trailing balloon with a calibration pulser from which we could observe both direct and reflected pulses, and from that pulser, we never saw evidence of the reflected pulses not being flipped in polarity. Of course, that did not probe every region of ice and all incident angles, but it seems like if such a strange reflection were likely, we likely would have seen it there.
Nonetheless, we are working on simulating reflections off various ice models to see if we can come up with a plausible optics explanation (like pathological sastrugi).
If the radio emission was generated by an air shower in Earth's magnetic field, it's something we can model (and we've seen many other events that are probably reflected air showers so we can check consistency).
What angle are these particles hitting the detector as it may well be possible these are particles are not traveling thru the entire planet and just a traveling in a chord (a line thru a circle that does not pass thru the centre) and as such, traveling thru far less of the planet.
Then there is the aspect that due to the size and the stated interaction with other matter that they are deflected from their original trajectory and could very well appear to be arising from directly below, giving the appearance of passing right thru the planet when they are not.
So very much possibly explained with what we already know about said particles.
The two relevant events had RF emission from 27 and 35 degrees below the horizontal. If interpreted as emission from upward-going EAS, then the particle would be within a degree or so of that. So they don't go all the way through the Earth, but through a chord long enough that, if our shower energy estimate (which, admittedly, is fraught with peril, we have an order of magnitude errors on that), no standard model particle could have made it through (yes, at high energies, the Earth is opaque to neutrinos).
Stopped reading there. I hate that a lot of pop-science articles suggest that the foundations of natural sciences are so shaky that a new finding can turn them upside-down. I've lived together with 50-60 social scientists in a small community during my student years, and I found that they don't have the slightest idea about how thoroughly e.g. special and general relativity have been tested in controlled experiments and every day when they use gps in their smartphones. For them these theories may be true, but who knows? I find it really sad that media that are supposed to bring sciences closer to non-scientists fail this way.
The foundations are shaky. Of course it's an easy rhetoric tool to use by journalists, but often they are not wrong, if those claims turn out to be true.
That's not so much a crack in the foundation as it is a patch of dirt next to the foundation.
To get an idea of what happens to old physics when new physics is discovered, realize that Newton's laws are still correct, and can be derived from QM. That's what you get when you do a good job of actually checking the truth with experiments. All theories have implicit tolerances embedded within the known precision of the experiments used to confirm them, and with these tolerances you can say "Newton's laws are right" without denying other, finer details. Similarly, scientists 1000 years from now will agree with everything we presently know about the Standard Model, because all of our beliefs are tempered by how closely we know our experiments are looking.
>Quantum entanglement
I should add that entanglement isn't "shaky" at all, it was predicted from the start and has been observed in countless experiments to date.
On one hand, on some scales, Newtonian mechanics is correct "enough" to give results that work, and so in that sense it is just incomplete in that its domain is restricted. On the other, relativity and QM change everything. These new theories may reduce to Newtonian mechanics given certain assumptions, but Newtonian physics assumes things about the structure of spacetime that are fundamentally incorrect (e.g. velocity is not additive). In this sense, one can fairly say that Newton's mechanics are not just incomplete or missing some fine details, but wrong.
I think there is more to the foundations than just the best numbers we can come up with for a given experiment. Our numbers for the gravitational constant, for example, are pretty similar (if more precise) to the numbers in 1891, but the setting in which that number is completely changed. There is no aether, no absolute space, velocities don't add (even though it's "mostly" right on most scales we experience and measure, it is false), space and time get mixed up, etc. Those were all pretty foundational ideas just over a hundred years ago.
>There is no aether, no absolute space, velocities don't add
There are two categories of things in that list: statements that had implications beyond what they had confirmed (the medium of light, the absoluteness of space) and an approximation (the addition of velocities.) Unsurprisingly the metaphysical interpretation of physics has not stood up to refinements in physics. The physics, however, remains true to within the bounds they knew. Likewise, the interpretation of physics is likely to change quite a bit over the next 1000 years, even 100. That's why you should never put too much stock in pop-sci articles that try to tell you that the universe is made of this-or-that. Fortunately on the philosophical side we now all realize that the interpretations are just humanizations of the knowledge itself, and are not knowledge themselves.
It's very successful, but It's known to be incomplete, so this is why this article is interesting because it can point to a new theory that alter or event replace the standard model. Also, I linked to the cosmological constant problem, which to me looks like a gaping hole in the theory.
It's amazing that all this math can describe the world we live in and help build us all the modern gadgets we see:
It's not exactly known to be incomplete although everyone hopes it is, there are a few theoretical extensions to it like SUSY but currently all of them have failed to produce any tangible experimental results.
We thought that the LHC would quickly find physics beyond the standard model but alas it has found nothing which is a problem for many theories that want to replace or even substantially expand on it as many of their prediction were proven to be false.
At this point i would find it very unlikely that we will replace the standard model completely most likely scenario is that we will find an extension to it which will be proven correct and at this point it seems the model we have will not be extended as much as it was thought so previously.
It would require an extremely drastic discovery to essentially push the standard model out of it's current generalised state.
And the cosmological constant is not a gaping hole in any theory it's a problem for some its not a huge or (even a small) problem in the standard model if you want to find the biggest true problem with it currently you should look into neutrinos which are supposed to be massless according to the standard model but have a small non-zero mass in reality.
There are a few solutions to this problem both within the current model as well as extensions which range from a massless sterile neutrino to super symmetry and to a secondary mechanism through which particles may gain mass other than the Higgs field.
There are no more 'revolutions' left for physics? And I'm not talking about tomorrow but imagine a 1000 years from now. It seems a bit arrogant to assume that.
I also dislike the pseudo pop-science, but the visceral close mindedness is just another side of that coin imo.
"overhauled" is not the same as "broken". It's bit arrogant to assume that all those GPS measurements that pinpoint our location will one day be proven wildly incorrect. They clearly aren't. They might be refined, but are not all that wrong. Even Newtonian physics is under many circumstances a close approximation of reality.
> living in a mental world of absolute rights and wrongs, may be imagining that because all theories are wrong, the earth may be thought spherical now, but cubical next century, and a hollow icosahedron the next, and a doughnut shape the one after.
> What actually happens is that once scientists get hold of a good concept they gradually refine and extend it with greater and greater subtlety as their instruments of measurement improve. Theories are not so much wrong as incomplete.
> Even when a new theory seems to represent a revolution, it usually arises out of small refinements. If something more than a small refinement were needed, then the old theory would never have endured.
The point isn't that you get a few more significant figures of accuracy on a slightly larger set of problems, but that you use completely new tools, techniques, and ideas to tackle completely new classes of problems.
Heliocentrism isn't a "refinement" of geocentrism. It's a completely new way of understanding the universe. The fact that you can make geocentrism work if you make your epicycles complicated enough doesn't change the fact that it's conceptually incorrect, and not a useful way to think about the solar system.
Likewise GR isn't a "refinement" of Newton. It drives a tank through the middle of the Newtonian world view and burns it to the ground. Then it says "New physics, this way" and off it goes, thinking about phenomena that are literally inconceivable in a Newtonian universe.
You can consider GR a more accurate refinement for certain problems only. There's a limited set of problems - large in everyday human terms, but extremely limited in cosmological terms - where Newton gives you all the accuracy you want.
But if your understanding stops there, you're missing the point of these revolutions. They're not about improved accuracy, they're about new world views that give access to entirely new problem classes.
You literally cannot imagine these problems if you consider Newton as a mostly correct foundation and GR as a kind of philosophical epicycle added to it later.
When Asimov says that "the model of a flat earth is nearly right, it's only wrong by 8 inches per mile" it's supposed to be an outrageous statement - the earth is not flat, that way of understanding is completely incorrect, and the (Newtonian level) correct model can help you solve new problem classes such as travel to the moon.
He's making the point of how the existing understanding can't give wildly wrong answers which are ready to be "upended", or else it would not have persisted. The understanding can be upended, sure. But the new theory has to account for everything existing.
GR (amongst other things) is a generalisation of Newton's law of universal gravitation, Newton's laws can be accurately derived from both QM and from GR with the PPN framework being the most common tool which derives it's parameters from the predictions set by GR.
Newtonian gravity works perfectly well in weak fields so it is not "wrong" but rather it's just not a generalised theory.
A good way to look at it is that the laws govern the flow rate in a pipe are not a good generalisation of the behaviour of fluids in motion but they are as sure as hell good for calculating how liquid will flow in a pipe.
And wile GR tied everything together the signs that Newtonian laws were not a generalised theory predate Einstein in fact the Lorenz Transformation which serves as the basis for GR pretty much proved that as if the speed of light must taken as a constant and be finite which as defined by Newtonian physics then we get variable length and time.
So no GR to Newton isn't the same as Heliocentrism to Geocentrism if anything is that Geocentrism didn't actually work even with the math and observation we had.
The Greeks understood the Helicentric model quite well and even considered stars as distant suns the only problems with their models were primarily due to measurement errors for example Aristarchus's measurements were wrong by a few degrees but that was enough to alter the distance and size ratio of the moon and the sun to being about 20 times which what the greek calculated from being about 400 times which is what we've eventually measured correctly when we had better tools.
Uh, all your examples illustrate the core fact that our current theories are pretty close (to within many decimal places, usually) and that anything new isn't going to completely upend our expectations, even if it posits a completely new way of looking at things.
As the OP said, its not about upending expectations about precision of measurement.
After all you can make the geocentric model infinitely precise with enough epicycles, it can match all and every earthbound observation to any degree of precision.
That does not change the fact that it is fundamentally wrong.
It’s quite possible to have an understanding of something that works in some situations but does not explain every situation. I would say that we have mathematics models of fairly large portions of physics but they are limited because they can’t explain how gravitation works. We can describe how we see it working but not explain how and why it works. I think there will always be new more complete models that encompass more and more of what we cannot explain.
>They might be refined, but are not all that wrong. Even Newtonian physics is under many circumstances a close approximation of reality.
They might become wrong; we assume that the laws of physics are fixed and immutable, that they have operated unchanged for all time so far and will continue to operate unchanged for the rest of time. Some physics acknowledges that that they may change at the edges of time, but it may also be the case that they are subject to sudden radical shifts.
Depends on what you define as the laws of physics.
We have cases where the laws of physics break for example singularties and it’s generally accepted that at certain energy levels forces can join or split for example during and shortly after the Big Bang the it’s assumed that all of the forces were joined together.
There is also the Higgs field which is not clear if it can change states or not and if it has done so at any period in the past which is not directly observable.
In fact the laws of physics “changing” is one of the possible answers to how the matter anti matter symmetry broke in the first place and allowed the universe as we know it to form.
However ofc any global change in any of the “fundamental” laws/constants will end all existence as we know it.
> There are no more 'revolutions' left for physics?
Sounds like how people were talking around the turn of the last century. Then came special and general relativity and quantum physics in about 20 years' time. Not to mention similar revolutions in math.
Physicists would love for some observation to end up breaking physics as we know it.
They know that 99,999/100,000 times something strange is observed, it turns out to be no big deal.
The day something breaks the Standard Model, physicists will cheer and begin a beautiful renaissance... and another... and another.
But can intelligent creatures in a simulation ever understand the scope and rules on which their simulation is based? Or can they only get closer and closer to the substrate, with a hard limit on ever modeling the details?
The answer is no. Gödel's incompleteness theorem is interesting here as it states that within a given axiomatic system, there are facts that are true but not provable within that same axiomatic system.
Another way to think about it is that if we are part of a set of fundamental rules that make up a simulation, it's impossible for us to prove everything about that system.
If the creatures within a simulation can make contact with the creatures (or physics) outside it, then perhaps they can look in from the outside, to get all the information necessary for any proof?
Well, maybe you shouldn't have stopped reading. A particle that is not described by the standard model DOES "break physics as we know it." That phrasing is typical of science journalism hyperbole, but it is accurate in this case.
Perhaps my exact point didn't get through well. I find that exactly this kind of phrasing is what's bad, because I fear that it isn't interpreted as "new physics" or "overhalued physics" as in cozzyd's or SideburnsOfDoom's comments, but rather "look, scientists from Newton through Einstein were proved wrong". And the big issue is when this is followed by the thought "How can we know scientists aren't wrong about [insert issue here]?"
There are like dozens of hypothesized particles outside of the standard model. The standard model is not the be all and end all of physics as we know it.
Doesnt general relativity only predict the right thing if you allow for 90% of the universe to be made of dark matter/energy that is only detectable as deviations from from the predictions of GR?
No. (No, it predicts right things locally; no, dark energy is not in conflict with GR; and probably no on the scale of galaxies, with some assumptions).
We can (and do) test General Relativity to exquisite precision in the solar system.
Those tests constrain the local density of any sort of effectively undetectable matter which includes among other things the (thermal) cosmic neutrino background, lots and lots of relativistic neutrinos, and a fair amount of ultrarelativistic neutrinos (like those that ANITA studies).
Effective undetectability is a function of current technology versus the goodness of estimate of (high) flux of the particles; we can spot small numbers of GZK-interaction neutrinos (with various observatories, including ANITA), we can spot small numbers of Super-KK neutrinos (mostly because we know the path they follow), we can spot small numbers of solar neutrinos (there are A LOT of them and we also know what direction they're coming from), but we have no real hope right now of spotting relic neutrinos (since as we take the momentum to zero, we lose the ability to spot recoil interactions; the emitted photons get drowned out by the CMB; the cosmic neutrinos are also travelling in random directions, like the cosmic photons).
If we take the local density of any of these neutrinos way up, their gravitational effects in the solar system (and indeed in similar systems we can study with various different telescopes) will be pronounced, and straightforward to study with General Relativity.
We do see pronounced gravitational effects at the scale of galaxies; one way to explain them is to add a thin dust of slow-moving mass where the dust motes remain on extremely stable orbits (implying no heating from (photon) radiation, no cooling by emitting (dark? photon? whatever) radiation, and no collisions with ordinary matter dust).
Dark matter is extremely sparse at the scale of star systems -- but then star systems are extremely sparse at the scale of large galaxies! (Likewise, the interstellar medium is extremely sparse, but there's a lot of space among the stars!) Low-interaction is easy enough; Earth is highly opaque to ultrarelativistic neutrinos, but as you take the momentum of the neutrinos down, Earth becomes highly transparent to them (so do telescopes and other instruments, alas, which is why they are hard to observe). (Standard-model) neutrinos are too light to stay in the places where the gravitational effects are observed -- gravitational interactions with the ordinary mass of the galaxy would kick them away. So something else is needed. The question is what, microscopically, it is. However, wishing the gravitational effects away doesn't work, and neither does modifying General Relativity (at least not so far).
In the standard cosmology, Dark Energy is precisely a component of the Einstein Field Equations of General Relativity (it's literally \Lambda, the cosmological constant). So it is entirely the opposite of being in conflict with General Relativity. The research question is mainly why it takes on the value it does, and whether it does so in any sort of spacetime-position-dependent way.
Nothing to take away from your point, but the harsh fact about much of physics especially the modern kind is built on 'Models'. Most of it still remains true in that Model, even if a new Model shows totally different set of truths.
Albert Einstein himself said this about Entropy:
A theory is the more impressive the greater the simplicity of its premises, the more different kinds of things it relates, and the more extended its area of applicability. Therefore the deep impression that classical thermodynamics made upon me. It is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts.
Michelson-Morley experiment was did with precision of up to 1E-17(!) and found nothing. Distance to Alpha-Centaur is just 4E16 meters. But then LIGO performed roughly the same experiment with precision of 1E-18 and found waves.
One of the reasons that many 'pop-science articles' get things wrong is that they're seldom written by scientists. Scientists who venture into popular writing can be looked down on as 'glory-hounds' by their colleagues. (E.g., George Gamow.)
So it's not entirely the journalist's fault if they don't have the credentials to simplify things adequately without distorting something.
Hey now, not that long ago, we assumed that the universe had C, P, and T symmetry, but after looking closely at the weak force, have found that our universe only maybe has CPT symmetry. We could still find out that CPT symmetry is bunk.
If so, is it only out of Antarctica? Would that mean they are coming from a specific direction in space?
Why can't we observe them simply as they come out of space? Is there something about the process of moving through the earth that makes them more detectable?
These may be stupid questions, feel free to vote this down..
Edit: if I understand correctly it seems like it's happenstance and ANITA just happened to be above Antarctica when the cosmic rays shot up through it on those particular occasions, I think