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Oct 7th 2021

REFRIGERATORS AND air-conditioners are old and clunky technology, and represent a field ripe for disruption. They consume a lot of electricity. And they generally rely on chemicals called hydrofluorocarbons which, if they leak into the atmosphere, have a potent greenhouse-warming effect. Buildings central-heating systems, meanwhile, are often powered by methane in the form of natural gas, which releases carbon dioxide, another greenhouse gas, when it is burned, and also has a tendency to leak from the pipes that deliver itwhich is unfortunate, because methane, too, is a greenhouse gas, and one much more potent than CO2.

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One potential way of getting around all this might be to exploit what is known as the thermoelectric effect, a means of carrying heat from place to place as an electric current. Thermoelectric circuits can be used either to cool things down, or to heat them up. And a firm called Phononic, based in Durham, North Carolina, has developed a chip which does just that.

The thermoelectric effect was discovered in 1834 by Jean Charles Peltier, a French physicist. It happens in an electrical circuit that includes two materials of different conductivity. A flow of electrons from the more conductive to the less conductive causes cooling. A flow in the other direction causes heating.

The reason for this is that electrons are able to vibrate more freely when pushed into a conductive material. They thereby transfer energy to their surroundings, warming them. When shunted into a less conductive one, electrons vibrations are constrained, and they absorb energy from their surroundings, cooling those surroundings down. An array of thermoelectric circuits built with all the high-conductivity materials facing in one direction and all the low conductivity ones in the other can thus move heat in either direction, by switching the polarity of the current. For reasons buried in the mathematics of quantum physics, the heat thus flowing does so in discrete packages, called phonons. Hence the name of the firm.

The thermoelectric effect works best when the conductors involved are actually semiconductors, with bismuth and tin being common choices. Fancy cameras contain simple cooling chips which use these, as do some scientific instruments. But Phononics boss, Tony Atti, thinks that is small beer. Using the good offices of Fabrinet, a chipmaker in Thailand, he has started making more sophisticated versions at high volume, using the set of tools and techniques normally employed to etch information-processing circuits onto wafers made of silicon. In this case, though, the wafers are made of bismuth.

The results are, admittedly, still a long way from something that could heat or cool a building. But they are already finding lucrative employment in applications where space is at a premium. At the moment, the fastest-growing market is cooling the infrared lasers used to fire information-encoding photons through fibre-optic cables, for the long-distance transmission of data. They are also being used, though, in the 5G mobile-phone base stations now starting to blanket street corners, to keep the batteries of electric vehicles at optimal operating temperatures, and as components of the optical-frequency radar-like systems known as LIDAR, that help guide autonomous vehicles.

The crucial question from Mr Attis point of view is whether semiconductor-based thermoelectronics can break out of these niches and become more mainstream, in the way that semiconductor-based electronics and lighting have done. In particular, he would like to incorporate heat-pumping chips into buildings, to provide them with integral thermoregulation.

In their current form, thermoelectric chips are unlikely to replace conventional air conditioning and central heating because they cannot move heat over the distances required to pump it in and out of a building in bulk. But they could nonetheless be used as regulators. Instead of turning a big air-conditioning system on or off, to lower or raise the temperature by the small amounts required to maintain comfort, with all the cost that entails, thermoelectric chips might tweak matters by moving heat around locally.

Phononic has already run trials of such local-temperature-tweaking chips in Singapore, in partnership with Temasek, that countrys state-run investment fund. In 2019 SP Group, Singapores utility company, installed eight of the firms heat pumps, which comprise an array of chips pointed down at people, pumping heat out of the air above them, on the boardwalk on Clarke Quay in the city. Phononic claims the devices lowered the temperature in their vicinity by up to 10C and, as a bonus, consequently reduced humidity by 15%. If that can be scaled up, it would certainly be a cool result.

This article appeared in the Science & technology section of the print edition under the headline "Cool thinking"

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A novel way to heat and cool things - The Economist

Oct 9th 2021

THE NOBEL prizes, whose winners are announced this month (see Science), may be the worlds most coveted awards. As soon as a new crop of laureates is named, critics start comparing the victors achievements with those of previous winners, reigniting debates over past snubs.

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A full account of why, say, Stephen Hawking was passed over will have to wait until 2068: the Nobel Foundations rules prevent disclosure about the selection process for 50 years. But once this statute of limitations ends, the foundation reveals who offered nominations, and whom they endorsed. Its data start in 1901 and end in 1953 for medicine; 1966 for physics, chemistry and literature; and 1967 for peace. (The economics prize was first awarded in 1969.)

Nomination lists do not explain omissions like Leo Tolstoy (who got 19 nominations) or Mahatma Gandhi (who got 12). But they do show that in 1901-66, Nobel voters handed out awards more in the style of a private members club than of a survey of expert opinion. Whereas candidates with lots of nominations often fell short, those with the right backerslike Albert Einstein or other laureatesfared better.

The bar to a Nobel nomination is low. For the peace prize, public officials, jurists and the like submit names to a committee, chosen by Norways parliament, that picks the winner. For the others, Swedish academies solicit names from thousands of people, mostly professors, and hold a vote for the laureate. On average, 55 nominations per year were filed for each prize in 1901-66.

Historically, voters paid little heed to consensus among nominators. In literature and medicine, the candidate with the most nominations won just 11% and 12% of the time; in peace and chemistry, the rates were 23% and 26%. Only in physics, at 42%, did nomination leaders have a big advantage. In 1956 Ramn Menndez Pidal, a linguist and historian, got 60% of nominations for the literature prize, but still lost.

However, voters did make one group of nominators happy: current and future laureates. Candidates put forward by past victors went on to win at some point in the future 40% more often than did those whose nominators never won a Nobel. People whose nominators became laureates later on also won unusually often. This implies that being accomplished enough to merit future Nobel consideration was sufficient to gain extra influence over voters.

In theory, this imbalance could simply reflect laureates nominating stronger candidates. However, at least one Nobel winner seems to have boosted his nominees chances, rather than merely naming superstars who would have won anyway.

According to the Nobel Foundations online archive, all 11 of Einsteins nominees won a prize. Some were already famous, like Max Planck; others, like Walther Bothe, were lesser-known. In two cases, his support seems to have been decisive.

In 1940 Einstein supported Otto Stern, a physicist who had already had 60 nominations. Stern won the next time the prize was given. Similarly, Wolfgang Pauli, whose exclusion principle is central to quantum mechanics, had received 20 nominations before Einstein backed him in 1945. He got his prize that same year.

Source: Nobel Foundation

This article appeared in the Graphic detail section of the print edition under the headline "Noblesse oblige"

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The best way to win a Nobel is to get nominated by another laureate - The Economist

It all started with a bang. During an unimaginably brief fraction of a second, the embryonic universe ballooned in size with unimaginable swiftness. In a flash, dimples of imperfection stretched into cosmic scars and locked in the universe we experience today, a milieu filled with galaxies, stars, planets, and humans.

The circumstantial evidence for this origin story, known as inflation, is overwhelming. It has inspired a generation of cosmologists to write papers, teach classes, and publish textbooks about the sundry ways inflation could have played out. And yet, a smoking gun remains elusive: Ancient ripples in spacetime should have left a particular imprint on the sky, but searches have repeatedly come up short.

A group of astronomers known as the BICEP/Keck collaboration leads the hunt for these primordial gravitational waves. On Monday the researchers released their latest results, the culmination of years of painstaking labor in one of the harshest places on Earth. Once more, they found no sign of their quarry. If an inflating universe reverberated with gravitational wavesas most cosmologists still fully expect it did it must have done so in a rather subtle way.

The simplest flavors, we are right now ruling out, says Clem Pryke, an astrophysicist at the University of Minnesota and member of the BICEP/Keck collaboration. [This result] is killing previously very popular theories of inflation.

[Related: What did the universe look like just after the big bang?]

The oldest light in the universe has been streaming through space for more than 13 billion years, ever since the cosmos cooled enough to become transparent. Astronomers have precisely mapped this Cosmic Microwave Background (CMB) and used it to learn that the universe was, and has remained, strikingly uniform overall. The CMB indicates that when the universe was just 380,000 years old, it had nearly the same density of matter everywhere. And today, astronomers see galaxies in every direction.

But the CMB is ever so slightly clumpy, and it clumps in a special way. Dense and thin spots come in all sizes, from very small to very large. Today we see a related pattern, from single galaxies to giant mega clusters of them.

How did the universe get this way? Inflation winds back the clock even further, attempting to explain how lumps of all sizes developed during the cosmoss first 0.00000000000000000000000000000000001 of a second. During this period, the minuscule universe seethed with energy, and quantum theory ruled the day. In the quantum realm, nothing holds perfectly steady. Subatomic jitters continuously introduced tiny flaws into the inflating universe, tweaking the density of substances that would eventually become light, matter, dark matter, and more. The growing universe continuously stretched these blemishes, even as newer, smaller fluctuations kept appearing, resulting in blips of all sizes. Eventually, the CMB recorded the final product. Inflation naturally produces lumpiness of exactly that type, Pryke says.

Or so the story goes. Inflation has become the leading theory of the birth of the cosmos because it explains exactly what astronomers see when they study the large-scale patterns formed by matter, dark matter, and more.

But one pattern has eluded them. The fabric of spacetime itself cannot hold perfectly still at the quantum scale, and inflation should have stretched those initial tremors into proper waves just as it did with matter and everything else. These primordial gravitational waves would have left faint fingerprints in the CMB, specific whorls in the light known as B-mode polarization. Astronomers have the capability to directly detect these whorls today, if the pattern is prominent enough, but have yet to find any.

Frustratingly, the universe is awash in materials that shine in a similarly whirly way. The BICEP team triumphantly announced the discovery of primordial gravitational waves in 2014, for instance, only to later learn that they had picked up the dim heat glow of dust grains streaming along the magnetic fields that fill the space between stars in the Milky Way.

The BICEP/Keck collaboration has now spent years refining their methods and building a series of telescopes at the south pole, where the crisp and arid air offers a crystal-clear view of the cosmos. Their newest results blend data from the last three generations of their Antarctic telescopes with other experiments.

For more than a decade, they have increased the number of sensors from dozens to thousands. And crucially, they have expanded the set of colors in which they observe, from one wavelength to three. Any B-mode swirls in the CMB, which fills the entire universe, should show up evenly in all wavelengths. Polarization that comes through more strongly at different wavelengths, however, can be blamed on local dust.

The key measure of how much inflation rattled the universe goes by the name tensor-to-scalar ratio, or r to those in the field. This single number describes how forcefully space time rippled compared to other fluctuations. An r of zero would imply that inflation didnt rock the fabric of the cosmos at all, suggesting that cosmology textbooks might need to rip out their first chapter.

BICEP/Keck observations have successively lowered the ceiling for primordial gravitational waves, showing that r should be smaller than 0.09 in 2016 and less than 0.07 in 2018. With the latest results, published in Physical Review Letters, the collaboration states with 95 percent confidence that r should be less than 0.036, a value that makes one commonly studied class of inflationary models impossible.

The shrinking limit for gravitational waves has obliged theorists to crouch lower and lower, but plenty of riffs on the general theme of inflation still fit comfortably below the new BICEP/Keck roof. The situation is getting cozy though, and if the limit falls below 0.01, many inflation researchers will start to sweat.

Its pretty hard to get a value less than that in any basic textbook model of inflation, theorist Marc Kamionkowski of John Hopkins University told Physics Today in 2019.

[Related: Wait a second: What came before the big bang?]

The nearly hundred members of the BICEP/Keck collaboration plan to reach that level of precision in a matter of years. They are currently building a new array of four telescopes, which should allow for a measurement of r up to three times as precise. By the end of the decade, a mega-collaboration between BICEP/Keck and other CMB teams known as CMB-S4 should get a few times more sensitive still, limiting r to roughly 0.001.

Many cosmologists hope that primordial gravitational waves will show up in one of these ever-sharper images of the CMB, proving that theorists really do have a handle on the universes initial bang. If not, the theory may languish in limbo a bit longer. It would take an r ten times lower still to cull most straggler inflationary models, and that would require experimentalists like Pryke to once again come up with even better ways to measure the nearly imperceptible ripples theorists forecast.

From an experimental point of view, it just seems unobtainable, he says. But when I got into the business 20 years ago, measuring B modes at all seemed ridiculous.

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A key part of the Big Bang remains troublingly elusive - Popular Science

HENRIETTA, N.Y (WROC) According to the Rochester Institute of Technology, Mishkat Bhattacharya, an associate professor at RITsSchool of Physics and AstronomyandFuture Photon Initiative, proposed a new method for detecting superfluid motion in anarticle published inPhysical Review Letters.

Bhattacharyas theoretical team on the paper consisted of RIT postdoctoral researchers Pardeep Kumar and Tushar Biswas, and alumnus Kristian Feliz 21 (physics). The international collaborators consisted of professors Rina Kanamoto from Meiji University, Ming-Shien Chang from the Academia Sinica, and Anand Jha from the Indian Institute of Technology. Bhattacharyas work was supported by aCAREER Award from the National Science Foundation.

The laser is shined through the superfluid in a minimally destructive manner, and the system can then read how the superfluid and light react, so the subatomic movements can be observed and studied.

This new research represents the first time that scientists will be able to get a closer look at how this seemingly-physics-defying moves. As scientists understand this wonder-liquid, they can start to harness it to make incredibly efficient power generation.

Bhattacharyas measuring method can also be used in quantum information processing.

So, clearly, theres a lot going on there. Lets break it down.

A superfluid is a gas or a liquid that can move without viscosity, or internal friction.

This means that the particles dont jostle each other, Bhattacharya said. Theyre not elbowing each other, or colliding.

Water for example has a very low viscosity. Its easy to imagine how quickly and smoothly water flows, compared to a highly viscous fluid, like maple syrup.

Its difficult to imagine, but a superfluid has zero internal friction.

This means that it slows down at an incredibly slow rate, meaning that once the gas or liquid is set in motion, its nearly impossible to stop. It also means that this movement of the particles doesnt lose energy like other processes of friction.

Slamming the brakes on your car introduces a lot of friction, and everyone knows that there is a lot of sound and heat that is given off. That is the release of energy when friction is applied. Superfluids dont have this.

This unusual trait can be harnessed practically if an electrical current is applied to it.

If you can get something to flow, its like current going around in a circle, Bhattacharya said.

That means that unlike normal electrical circuits that get incredibly hot when they are used to capacity, these atomtronic circuits with superfluid dont.

We dont really understand the physics of this, Bhattacharya said.

Part and parcel with this lack of understanding is that the only known superfluids like liquid helium only reach that state when they are supercooled. Needless to say, our cell phones would be massive and unusable if they needed a supercooler to use them.

Bhattacharya says that if someone can discover a superfluid that works at room temperature, they would not only win a Nobel prize, but they would revolutionize technology as we know it.

He says tests in Germany have shown that this technology admittedly with the supercooled superfluid can power entire towns in an economically feasible way.

Youd have to ask a computer scientist, Bhattacharya said when asked how much more powerful our phones would get. But it would be reasonable to say one hundred or one thousand times more powerful.

The challenge in creating a room temperature superfluid is that as Bhattacharya alluded to, physicists dont quite understand how superfluids really work, beyond the visually observable macro effects, like seeing it infinitely loop in a closed circuit, or the creep effect of liquid helium.

But to begin to understand how superfluids work, Bhattacharya and his team decided they needed a way to measure its subatomic movement, using quantum physics.

If you think about the particles of which the fluid is made, as little balls, it is impossible to explain what it is, without realizing that it also acts as a wave, he said.

So since an electrically charged superfluid circuit acts more like a wave rather than a particle, because of its lack of friction and electrical charges, it becomes a quantum object. Which means then that even the incredibly weak pressure force of a light wave will destroy the object, making it impossible to observe.

Bhattacharya and his team worked their way around this problem, by calibrating their laser light source to be a different wavelength than the superfluid that they are observing.

This minimally destructive method allows them to observe the incredibly small effect that the laser has, and by studying that wiggle, they can begin to determine how superfluid moves.

Once they understand how it moves, they can begin to figure out how to engineer a superfluid that stays in that state at room temperature.

Interestingly, this measuring method also has that application.

Scientists have begun to encode information on a paritcular kind of quantum particular that wiggles in a particular way. That can not only storage vast amounts of information, but move information at the speed of light.

Bhattacharya says that fiber optics does this is some manner, but the optics are too impure to move at that speed, and even the most advance fiber optics need signal boosters and repeaters at fairly regular intervals.

While quantum light processing made need those as well, the information would still be moving at the speed of light.

But his measuring technology can begin to more precisely measure the quantum wiggle, allowing them to figure out how to store the information longer.

It started at 1 millionth of a second, Bhattacharya said. Its now up to 60 seconds of storage. Thats seven orders of magnitude greater.

With Bhattacharya and his team on it, we may have those 1,000 times stronger cell phones in no time.

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RIT professor and team discover new method to measure motion of superfluids - RochesterFirst