Bizarre Particles Keep Flying Out of Antarctica's Ice

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.

Further reading from Dr Asimov: https://chem.tufts.edu/answersinscience/relativityofwrong.ht...

> 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.

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.

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.

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.

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.