Tag: helium-3

A new source of cosmic rays?

The International Space Station carries a suite of instruments conducting scientific experiments and measurements in low-Earth orbit. One of them is the Alpha Magnetic Spectrometer (AMS), which studies antimatter particles in cosmic rays to understand how the universe has evolved since its birth.

Cosmic rays are particles or particle clumps flying through the universe at nearly the speed of light. Since the mid-20th century, scientists have found cosmic-ray particles are emitted during supernovae and in the centres of galaxies that host large black holes. Scientists installed the AMS in May 2011, and by April 2021, it had tracked more than 230 billion cosmic-ray particles.

When scientists from the Massachusetts Institute of Technology (MIT) recently analysed these data — the results of which were published on June 25 — they found something odd. Roughly one in 10,000 of the cosmic ray particles were neutron-proton pairs, a.k.a. deuterons. The universe has a small number of these particles because they were only created in a 10-minute-long period a short time after the universe was born, around 0.002% of all atoms.

Yet cosmic rays streaming past the AMS seemed to have around 5x greater concentration of deuterons. The implication is that something in the universe — some event or some process — is producing high-energy deuterons, according to the MIT team’s paper.

Before coming to this conclusion, the researchers considered and eliminated some alternative explanations. Chief among them is the way scientists know how deuterons become cosmic rays. When primary cosmic rays produced by some process in outer space smash into matter, they produce a shower of energetic particles called secondary cosmic rays. Thus far, scientists have considered deuterons to be secondary cosmic rays, produced when helium-4 ions smash into atoms in the interstellar medium (the space between stars).

This event also produces helium-3 ions. So if the deuteron flux in cosmic rays is high, and if we believe more helium-4 ions are smashing into the interstellar medium than expected, the AMS should have detected more helium-3 cosmic rays than expected as well. It didn’t.

To make sure, the researchers also checked the AMS’s instruments and the shared properties of the cosmic-ray particles. Two in particular are time and rigidity. Time deals with how the flux of deuterons changes with respect to the flux of other cosmic ray particles, especially protons and helium-4 ions. Rigidity measures the likelihood a cosmic-ray particle will reach Earth and not be deflected away by the Sun. (Equally rigid particles behave the same way in a magnetic field.) When denoted in volts, rigidity indicates the extent of deflection the particle will experience.

The researchers analysed deuterons with rigidity from 1.9 billion to 21 billion V and found that “over the entire rigidity range the deuteron flux exhibits nearly identical time variations with the proton, 3-He, and 4-He fluxes.” At rigidity greater than 4.5 billion V, the fluxes of deuterons and helium-4 ions varied together whereas those of helium-3 and helium-4 didn’t. At rigidity beyond 13 billion V, “the rigidity dependence of the D and p fluxes [was] nearly identical”.

Similarly, they found the change in the deuteron flux was greater than the change in the helium-3 flux, both relative to the helium-4 flux. The statistical significance of this conclusion far exceeded the threshold particle physicists use to check whether an anomaly in the data is really real rather than the result of some fluke error. Finally, “independent analyses were performed on the same data sample by four independent study groups,” the paper added. “The results of these analyses are consistent with this Letter.”

The MIT team ultimately couldn’t find a credible alternative explanation, leaving their conclusion: deuterons could be primary cosmic rays, and we don’t (yet) know the process that could be producing them.

Physicists observe long-expected helium superfluid phase

Physicists have reported that they have finally observed helium 3 existing in a long-predicted type of superfluid, called the ß phase.

This is an important discovery, if it’s borne out, for reasons that partly have to do with its isotope, helium 4. Helium 4 is a fascinating substance because the helium 4 atom is a boson – a type of particle whose quantum properties and behaviour are explained by rules called Bose-Einstein statistics. Helium 3, on the other hand, is a fermion, and fermions are governed by Fermi-Dirac statistics.

Bosons and fermions have one important difference: bosons are allowed to disobey Pauli’s exclusion principle, and by doing so they can assume exotic states of matter rarely found in nature, with many unusual properties.

For example, when helium 4 is cooled below a certain temperature, it becomes a superfluid: a liquid that flows without experiencing any resistance. If you poured a superfluid into a bowl, it will be able to climb the walls of the bowl and spill out without any help. But helium 3 atoms are fermions, so they are bound to obey Pauli’s exclusion principle and can’t become a superfluid.

At least this is what physicists believed for a long time, until the early 1970s, when two independent groups of physicists found – one in theory and the other in experiments – that helium 3 could indeed enter a superfluid phase, but at a temperature 1,000-times lower than the critical temperature of helium 4. The theory group, led by Anthony Leggett at the University of Sussex, had in fact made a significant discovery.

Today, we know that the flow of superfluid helium 4 is analogous to the flow of electrons in a conventional superconductor, which also move around as if they face no resistance from the surrounding atoms. Leggett and co. found that the theory used to explain these superconductors could also be used to explain helium 3 superfluidity. This theory is called Bardeen-Cooper-Schrieffer (BCS) theory, and the materials whose superconductivity it can explain are called BCS superconductors.

Electrons are fermions and cannot ‘super-flow’. But in a BCS superconductor that has been cooled below its critical temperature, some forces in the material cause the electrons to overcome their mutual repulsion (“like charges repel”) and pair up. These electron pairs, while being made of two individual fermions, actually behave like bosons. Similarly, Leggett and co. found that helium 3 atoms could pair up to form a bosonic composite and super-flow.

Over many years, physicists used what they had learnt through these discoveries to expand our understanding of this substance. They found, among other things, that superfluid helium 3 can exist in many phases. The superfluidity would persist in each phase but with different characteristics.

Superfluid helium 3 was first thought to have two phases, called A and B. The temperature-pressure plot below clearly shows the conditions in which each phase emerges.

Credit: E.V. Thuneberg, Encyclopedia of Condensed Matter Physics, 2005

When physicists subjected superfluid helium 3 in its A phase to a strong magnetic field, they found another phase that they called A1, whose atom-pairs had different spin characteristics.

In 2015, a group of researchers led by Vladimir Dmitriev, at the P.L. Kapitza Institute for Physical Problems, Moscow, discovered a fourth phase, which they called the polar, or P, phase. Here, they confined helium 3 in a nematic aerogel and exposed the setup to a low magnetic field. Aerogels are ultra-light materials that are extremely porous; nematic means its molecules were arranged in parallel. The aeorogel in the Dmitriev and co. experiment was 98% porous, and whose pores “were much longer than they were wide” (source). That is, the team had found that the shape of the container in which helium 3 was confined also affected the phase of its superfluidity.

In August 2021 (preprint), the same team reported that it had observed a long-expected-to-exist fifth phase called the ß phase.

They reported that they took the setup they used to force superfluid helium 3 into the P phase, but this time exposed it to a high magnetic field. According to their paper, they found that while the superfluid earlier moved into the P phase through a single transition, as the temperature was brought down, this time it did so in two steps. First, it moved into an intermediate phase and then into the P phase. The intermediate is the ß phase.

(If this sounds simple, it wasn’t: the discoveries were each limited by the availability of specially designed instruments capable of picking up on very small-scale changes unavailable to the naked eye. Second, researchers also have had to know in advance what changes they should expect to happen in each phase, and this requires the corresponding theoretical clarity.)

The temperatures at which the phase transition between the two polar phases differ as the magnetic field strength increases. The gap between the two phases is bridged by the ß phase. Source: https://doi.org/10.1103/PhysRevLett.127.265301

I have considerably simplified helium 3’s transition from the ‘normal’ to the superfluid phase in this post. To describe it accurately, physicists use advanced mathematics and associated concepts in high-energy physics. One such concept is symmetry-breaking. When a helium 3 atom pairs up with another to form a bosonic composite, the pair must have a ‘new’ spin and orbital momentum; and their combined wavefunction will also have a ‘new’ phase. All these steps break different symmetries.

There’s a theory called Grand Unification in particle physics, in which physicists expect that at higher and higher energies, the three fundamental forces that affect subatomic particles – the strong-nuclear, the weak-nuclear and the electromagnetic – will combine into a single unified force. Physicists have found in their mathematical calculations that the symmetries that will break in this super-transition resemble those broken by helium 3 during its transition to superfluidity.

Understanding helium 3 can also be rewarding for insights into the insides of neutron stars. Neutron stars are extreme objects – surpassed in their extremeness only by black holes, which exist at the point where known theories of gravitational physics collapse into meaninglessness. A few lakh years after a neutron star is born, it is expected to have cooled sufficiently for its interiors to be composed of superfluids and superconductors.

We may never be able to directly observe these materials in their natural environment. But by studying helium 3’s various phases of superfluidity, we can get a sense of what a neutron star’s innards could be like, and whether their interactions among themselves and the neutrons on the surface could explain these objects’ still-mysterious characteristics.

Featured image: The liquid helium is in the superfluid phase. A thin invisible film creeps up the inside wall of the cup and down on the outside. A drop forms. It will fall off into the liquid helium below. This will repeat until the cup is empty – provided the liquid remains superfluid. Caption and credit: Alfred Leitner, public domain.

Firstpost’s selfish journalism

I’m sure you’ve heard of the concept of false balance, which is based on the conviction that there are two sides to every story even when there aren’t or when it’s not clear to anyone what the other side is. I’m also sure you’re aware of how journalism based on false balance can legitimise fake news and pseudoscience, as we used to see so often with climate change until the mid-2010s.

The problem with believing there exists a balance between two viewpoints where there is actually none is rooted in the belief that both points are equally valid, which in turn is rooted in ignorance and/or prejudice. However, it would appear there is another form of false-balance reportage that is rooted in selfishness and/or apathy – one where a publication publishes an article that, at some point, acknowledges that A and B are not equally valid but whose headline and lede declare that they are. Here’s a fresh example from Firstpost:

The lede goes thus:

After months of delay in its launch, the Indian Space Research Organisation (ISRO) said that the country’s second moon mission — the Rs 800 crore ‘Chandrayaan-2’ — is designed to hunt for deposits of Helium-3 — a waste-free nuclear energy that could answer many of Earth’s energy problems.

Chandrayaan 2 isn’t going to prospect the Moon for helium-3, or any other potential sources of clean energy for that matter, if only because we don’t have the wherewithal to use such materials to produce energy. Second, the problem with C2, as with many of ISRO’s space science missions at the moment, is that there is no roadmap. I don’t know what or who Firstpost‘s sources were for it to have pieced together this BS.

However, after talking about this as if any of it made sense, the article quotes my article in The Wire to say “even if we are successful in bringing back huge deposits of Helium-3 from the moon, we are far away from having the technology to harness it”.

So what has Firstpost done here? a) It reignited the pseudo-debate over ISRO’s non-existent plans to mine the Moon for helium-3; b) it re-legitimised Sivan’s, and others’, ridiculous point of view that India should lead the way in this endeavour; and, most importantly, c) it cashed in on the fallacy even as it suggested it may have recognised that the helium-3 story is erected entirely on speculation and daydreams.

In effect, this is nauseatingly selfish and, insofar as it is journalism, apathetic. It does not have the public interest in mind; in fact, it completely disregards it. And in case someone demands to know how I can claim to know better than K. Sivan, who claimed last year that it’s important for India to be at the forefront of helium-3 mining, only that anecdote about what Bertrand Russell – a staunch atheist – would say should he come face to face with god comes to mind: “Well, I would say that you did not provide much evidence.”

Do your bit, broaden your science menu

If you think a story was not covered by the media, it’s quite likely that that story didn’t feature in your limited news menu, and that it was actually covered by an outlet you haven’t discovered yet. In the same vein, saying the entirety of India’s science media is crap is in itself crap. I’ve heard this say from two people today (and some others on Twitter). I’ll concede that the bulk of it is useless but there are still quite a few good players. And not reading what they are writing is a travesty on your part if you consider yourself interested in science news. Why I think so is a long story; to cut it short: given what the prevailing distribution mechanisms as well as business models are, newsrooms can only do so much to ensure they’re visible to the right people. You’ve got to do your bit as well. So if you haven’t found the better players, shame on you. You don’t get to judge the best of us after having read only the worst of us.

And I like to think The Wire is among the best of us (but I can’t be the final judge). Here are some of the others:

  1. The Telegraph – Among the best in the country. They seldom undertake longer pieces but what they publish is crisp and authoritative. Watch out for G.S. Mudur.
  2. Scroll – Doesn’t cover a lot of sciencey science but what they do cover, they tend to get right.
  3. The Hindu – The Big Daddy. Has been covering science for a long time. My only issue with it is that many of its pieces, in an effort to come across as being unafraid of the technicalities, are flush with jargon.
  4. Fountain Ink – Only long-form and does a fab job of the science + society stories.
  5. Reuters India – Plain Jane non-partisan reportage all round.

I’m sure there are other publishers of good science journalism in India. The five I’ve listed here are the ones that came quickest to mind and I just wanted illustrate my point and quickly get this post out.

Note: This is the article the reactions to which prompted this post.

Featured image credit: Hans/pixabay.

Auditing science stories: Two examples from the bottom rungs

There are different kinds of science stories. I don’t just mean the usual long-form, short-form stuff. I mean there are qualitatively different kinds of stories. They inhabit a hierarchy, and right at the bottom is getting something wrong.

Like the way Livemint did on April 20, 2017, reporting that ISRO had plans to mine resources from the Moon to help manage India’s energy needs. ISRO has no such plans. The report’s author, Utpal Bhaskar, is likely referring to comments made by the noted space scientist Sivathanu Pillai at the Observer Research Foundation’s Kalpana Chawla Space Policy Dialogue 2017, held in March. Pillai had said mining helium-3 from the Moon was possible – but he didn’t say anything about ISRO planning such a thing. India TV then quoted Livemint and published a report of their own, not a detail changed.

Right on top of getting something wrong on the quality hierarchy is the act of reporting something that doesn’t deserve to be – the way The Guardian did, also on April 20. Ian Sample, the newspaper’s science editor, published a piece titled ‘No encounters: most ambitious alien search to date draws a blank’. What he seems to make no big deal of is mentioned – to be fair – in the first paragraph, but without playing up its significance in this context: Breakthrough Listen, the search mission, has been online for only a year.

And in this time, nobody expected its odds of finding anything would be noticeable. I’d say the deeper flaw in the story is to pay heed to the fact that this is humans’ most ambitious project of this kind yet. Well, so what if it is? It’s still not big enough to have better odds of finding anything in its first year of ops (the story itself says how they used one telescope last year and that it scanned 629 stars – both puny numbers). In other words, this is a null result and no one expected anything better. At best, it should’ve been a tweet, a status update for the records – not a news report suggesting disappointment. So in a way Sample’s effort can be construed as a null result reported wrong.

Finally, I will not speculate if Sample, who’s probably attending the Breakthrough Discuss conference (also being live-cast through Breakthrough’s Facebook page) on April 20-21, has been obligated by the organisers to publish a report on the subject – but I will say I’m tempted to. 😉 And I recommend just following Paul Gilster’s blog if you’re interested in updates on the Breakthrough Initiatives.

Featured image: The Green Bank radio telescope, West Virginia. Credit: NRAO/AUI, CC BY 3.0.