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74 Science & technology ► green heating is anyone s to play for. The usual suspects (assuming any electricity supplied is generated using appropriately carbon -tree means) Include electric im. mersion heaters, heat pumps (devices that work a bit like refrigerators in reverse, in that they extract heatfrom a buildingssur- roundings and then pump it into that building), and burning hydrogen instead of natural gas. Engineers at a small British company called Heal Wayv, though, think they have another contender: microwaves. The principle is the same as in a micro- wave oven. Many molecules, water includ- ed, are electrically dipolar. This means they havea positive charge at one end and a negative one at the other. They will there- fore rotate to align themselves with a strong electromagnetic field. If that field is oscillating, as is the case with electromag- netic radiation such as microwaves, then the molecules themsehrs will oscillate too--tiumping and Jostling their neigh- bours as they do so, and thus creating heat. But there is more to building a micro- wave boiler than simply repurposing the parts used for an wen, says Phil Stevens, one of Heat Wayv's founders. Most micro- wave ovens employ magnetrons --chunky devices built by surrounding a cathode with a carefully shaped anode that is de- signed to produce electromagnetic radia- tion of a specific frequency. with the help of a pair of big chipmakers, Heat Wayv has come up with a solid-state device that per- forms the same job. but which fits on a W - square -centimetre silicon chip. Arrays of these devices beam micro- waves into water in a boiler, heating it up. The pipes that carry the water are also made of microwave -sensitive materials, as is the insulation that lags them. And a heat exchanger recycles residual waste warmth. The upshot, says Mr Stevens, is a boiler that is about 96% efficient. The best exist- ing gas boilers rarely exceed go96. Efficiency mattems, because the move away from gas may mean higher heating bills. Electricity generated from fossil fuels is necessarily more expensive than the fu- els themselves. In Britain, at the moment, a given amount of energy delivered as elec- tricity costs three or fourtimes as much as the same amount delivered by natural gas. Switching to renewables is unilkely to change that much. Though the 'fuel" in- volved (wind or sunlight) is free, other cosmarenftPn higherthan forconvention- al power stations. Forced by taw to switch from gas, then, customers will surely have theft eyes on the cost. Heat Wayv argues its technology offers advantages overrival methods. Immersion heaters most tun continuously to deliver water at a suitable temperature. That often warms water which is never used. By con- trast and like existing gas boilers, micro- waves heat water quickly enough to pro - vide it only when itis needed. Heatpumps, too, havedrawbacks. Their efficiency plummets on cold days, when they are needed most. They are also bulky. And they generate water that is warm rath- er dun hot, often requiring the retrofitting ofbigger radiators orunderfloor heating Hydrogen, meanwhile, must either be extracted from natural gas or created by running electrical currents through water. Both processes are inherently inefficient Comments on the Draft CAP 2.0 2021.12.22 The Economist April lath 2ozi and the former is hardly green Also, the infrastructure needed to produce and de- liver hydrogen in quantity does not yet (and may never) exist Hear Wayv hopes to be producing mi- crowave boilers for sale by 2024, in time for the first sage of the government's ban. Hr Stevens says the idea has attracted In- terest from most of Britain's big housebuil- ders. Soon, perhaps, microwaves may heat people's water as well as their food. n Model misbehaviour For the second time in a month, an anomaly in the laws of physics has been noted u Ho oanrar¢ti thatr' ltus was the Wreactian, tamous in particle - physics circles, of Isidor Isaac Rabi wthe discovery of the muon. ltabi, a Nobel laureate who helped America develop the atom bomb, was reflecting physicists' general surprise that muons, which are, to all intents and purposes, just heavy and unstable versions ofelectrons, actu- ally exist. To an orderly physicist's mind they somehow seemed superflrmus to Nature's requirements. Establishing the muon's nature was, though, an important part of the creation ofwhatis known as the Standard Model of particle physics This. along with Einstein's ge iteral theory of relativity (actuallya theory of gravity), is one of the two foundation stones on which modern physics is built. Yet the Standard Model is known to be incomplae for several reasons, one of which is precisely the fact that itdoes not yet embrace gravity. So it seems fitting that an answer to Rabi s question, and with it a path to an explanation of physics beyond the Stan- dard Model, may now have been opened A magnetic moment by a measurement made on mucins. The study in question, called Mucin g -a, used a superconductingstorage device (pictured) to look at the magnetic behaviour of mucins. Experiments con- ducted with this machine at Brookhaven National Laboratory, in NewYorkstate, in the rggos, had suggested an anomaly in such behaviour—a deviation of about os% from theoretical predictions about the way that muons should spin in mag- netic fields—butwithout sufficient statistical power to be sure. If this anom- aly were real, it would suggest that an unknown force was tugging on the mu - on in the experiment To have another go at finding oat, the storage device was shipped to ferintlab, outside Chicago, in 2ot3. There, it was linked to equipment which gave it more oomph. This boost has, indeed. con- firmed the previous result—though irritatingly not quite unambiguously enough for physics' finicky require- ment,. These demand "five sigma" of significance (five standard deviations from the mean, for the mathematically indined). The new data, added to the old, and announced onAprU ift give only - 4.2 sigma. That nevertheless, suggests there is only one chance in 4o,000 that the result is a fluke. This is the second time in a month that a group of physicists has published a result which might lead beyond the Standard Model, for on March 23rd re- searchers on a project being conducted at caRN, home ofthe large HadronCollid- er, theworld's largest particle accelerator, pulled a similar sutprise. Their wort involved the deny of particles called a -mesons into electrons, muon and their antimatter equivalents. Again, the details are of yet quite as statistically robust as might be desired. But two such findings in short order give hope that the hunt for physics beyond the standard Model may soon run its quarry down