[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/10230\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EHow to make a nuclear clock tick\u003C\/h2\u003E\u003Cp\u003EThorsten Schumm is a clockmaker, but not the kind who sits at a workbench covered with springs and cogs, a magnifying loupe jammed into one eye. No, he is making a timepiece that is in an entirely different league.\u003C\/p\u003E\n\n\u003Cp\u003EAtomic clocks may sound familiar enough \u2013 but if Schumm\u2019s research goes to plan, it could result in a nuclear clock. And far from just telling the time, it could help crack some of the universe\u2019s most closely guarded secrets.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018This is still a dream,\u2019 said Schumm, a professor at the Vienna University of Technology in Austria. \u2018No one knows how to do it.\u2019\u003C\/p\u003E\n\n\u003Cp\u003EHe intends to change that and, in the process, to shed light on some of the fundamental forces of nature.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003ESplit second\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003EA clock can be based on anything that oscillates at regular intervals and can be read. The first clocks were mechanical. Many wristwatches today use the electromechanical oscillations of a quartz crystal.\u003C\/p\u003E\n\n\u003Cp\u003EBut clock technology moved up a gear in the 1950s with the advent of atomic clocks.\u003C\/p\u003E\n\n\u003Cp\u003EAtoms are made up of a nucleus surrounded by an orbiting cloud of electrons. The tick of an atomic clock depends on the \u201cquantum transitions\u201d these electrons make.\u003C\/p\u003E\n\n\u003Cp\u003EIt works like this. Electrons can absorb a packet of energy, which moves them from a \u201cground state\u201d to an \u201cexcited state\u201d of higher energy. Then they can fall back to the ground state, releasing that packet of energy on their way down.\u003Cbr \/\u003E\n\u003Cbr \/\u003E\n\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\r\nIt is something that has never been done before.\r\n\r\n\r\n\r\n\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EProfessor Ekkehard Peik, ThoriumNuclearClock\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\n\n\u003Cp\u003EThese energy transitions occur with a particular frequency that can be used for timekeeping. This all happens astonishingly fast.\u003C\/p\u003E\n\n\u003Cp\u003EFor instance, one second is officially defined as 9 192 631 770 oscillations of an energy packet that excites a caesium-133 atom.\u003Cbr \/\u003E\n\u003Cbr \/\u003E\nAtomic clocks are so precise because they produce an awful lot of oscillations, or ticks. So, if the readout mechanism misses one or two of them, it generally isn\u2019t much of a problem when there are more than 9 billion per second.\u003C\/p\u003E\n\n\u003Cp\u003ENuclear clocks are different. The tick wouldn\u2019t depend on electrons but rather on the vibrations of the nucleus itself. These\u0026nbsp;are many times faster than the ticks of the electron transitions.\u003C\/p\u003E\n\n\u003Cp\u003EBut, as Schumm says, work continues on getting a nuclear clock up and running.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cb\u003EHappy coincidence\u003C\/b\u003E\u003C\/p\u003E\n\n\u003Cp\u003EHe got interested in solving this nuclear mystery partly out of serendipity.\u003C\/p\u003E\n\n\u003Cp\u003EIt turns out that a rare isotope of the element thorium-229 is by far the easiest material from which a nuclear clock might be built. That\u2019s because it is thought to have the slowest ticks of any nucleus. Plus, the institute where Schumm works is one of the few places that can access this material.\u003C\/p\u003E\n\n\u003Cp\u003EThorium-229 isn\u2019t naturally occurring. It is produced only through the nuclear decay of certain types of uranium.\u003Cbr \/\u003E\n\u003Cbr \/\u003E\nThe Vienna University of Technology has an agreement with Oakridge National Laboratory in the US that allows it to obtain some thorium-229 from leftover uranium used in nuclear tests decades ago.\u003C\/p\u003E\n\n\u003Cp\u003EIt wasn\u2019t lost on Schumm that his first name and the name of the element are both derived from the mythical Norse god, Thor.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018That tickled me,\u2019 he said.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003EIt\u2019s about time\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003ESince 2020, Schumm has been conducting basic research on creating a nuclear clock under the EU-funded \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/856415\u0022\u003EThoriumNuclearClock\u003C\/a\u003E\u0026nbsp;project running until early 2026.\u003C\/p\u003E\n\n\u003Cp\u003EHe and his colleague Professor Ekkehard Peik of Germany\u2019s National Metrology Institute in Braunschweig share the project\u2019s role of principal investigators, along with Marianna Safronova from the University of Delaware in the US and Peter Thirolf from LMU Munich in Germany.\u003C\/p\u003E\n\n\u003Cp\u003ETo set a nuclear clock ticking, it needs a nudge with a laser set to exactly the right energy level. But for most nuclei, the energy frequency required is nowhere near accessible with current laser technology.\u003C\/p\u003E\n\n\u003Cp\u003EThorium-229 is one of the largest stable nuclei that exist. It was thought it could adopt a state with a very low energy that current lasers could reach \u2013 though no one really understands how or why it does this.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018To begin with, it wasn\u2019t even really clear that this state of thorium-229 existed,\u2019 said Schumm.\u003Cbr \/\u003E\n\u003Cbr \/\u003E\n\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003EGoing from atoms to nuclei isn\u2019t about getting a better clock.\r\n\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EProfessor Thorsten Schumm, ThoriumNuclearClock and CRYSTALCLOCK\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\n\n\u003Cp\u003ENow it\u2019s known that it does exist. In 2020, Schumm and his colleagues published \u003Ca href=\u0022https:\/\/journals.aps.org\/prl\/abstract\/10.1103\/PhysRevLett.125.142503\u0022\u003Ea measurement of the isotope\u2019s energy level\u003C\/a\u003E. Since then, they have continued to build on that knowledge.\u003C\/p\u003E\n\n\u003Cp\u003EAll of that opens the way to testing the clock for real. Schumm and his fellow researchers have been working on building a laser that is custom-designed to tickle the thorium at exactly the right frequency.\u003C\/p\u003E\n\n\u003Cp\u003ESoon they plan to direct this laser at some trapped thorium atoms for the first time in a bid to start them ticking.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018We are very excited about the outcome of this experiment because it is something that has never been done before,\u2019 said Peik. \u2018We and others have tried related experiments with thorium-229 in the past without success. This time we feel we are much better prepared.\u2019\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003ECrystal clear\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003EFor those experiments, the thorium atoms will be held in atomic traps \u2013 a very finicky business. So, while ThoriumNuclearClock was already under way, Schumm also lead a two-year EU-funded project called \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/882708\u0022\u003ECRYSTALCLOCK\u003C\/a\u003E, which aimed to develop a simpler design and readout mechanism for a nuclear clock.\u003C\/p\u003E\n\n\u003Cp\u003EThe idea here was to grow a crystal consisting of calcium fluoride and have a scattering of thorium-229 atoms distributed through the material. This provides a solid material that is far easier to work with than the atomic traps.\u003C\/p\u003E\n\n\u003Cp\u003ESchumm and his colleagues, including Dr Tomas Sikorsky, published \u003Ca href=\u0022https:\/\/arxiv.org\/pdf\/2211.05445.pdf\u0022\u003Ea paper demonstrating that these thorium-doped crystals could be grown in 2022\u003C\/a\u003E. The next step will be to start working out how the tick of these crystals can be read.\u003C\/p\u003E\n\n\u003Cp\u003ESchumm says that a technique called nuclear tomography could be adapted for this purpose and the whole process would be much easier than using thorium atoms in traps.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003EForces of nature\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003EThis is worth all the bother not because more precise clocks are needed but rather because humankind\u0027s fundamental understanding of how reality works can be tested.\u003C\/p\u003E\n\n\u003Cp\u003EThe best theories of physics explain that the universe has four fundamental forces: gravity, electromagnetism, the weak nuclear force and the strong nuclear force. The strength of these forces is known and those numbers are often referred to as fundamental \u201cconstants\u201d.\u003C\/p\u003E\n\n\u003Cp\u003EBut it isn\u0027t know whether the strength of these forces has been, and will always be, the same. There are indications that the forces were much stronger in the distant past, close to the Big Bang, and they may even still be changing by the merest amount.\u003C\/p\u003E\n\n\u003Cp\u003EAtomic and nuclear clocks may make it possible to put that to the test. The tick of an atomic clock is predominantly affected by the strength of electromagnetism, so if the speed of the tick began to change that would suggest a drift in the underlying force.\u003C\/p\u003E\n\n\u003Cp\u003EHowever, electromagnetism is very weak, so atomic clocks, despite their breathtaking precision, may never be able to pick up any change to it.\u003C\/p\u003E\n\n\u003Cp\u003ENuclear clock ticks are, by contrast, influenced by the strong force. So, if and when a working nuclear clock were to be created, it could be used to monitor whether there are any changes to the strong force over periods of time.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018Going from atoms to nuclei isn\u2019t about getting a better clock,\u2019 said Schumm. \u2018In fact, it\u2019s likely that the first nuclear clock won\u2019t be as good as the best atomic clocks. The point is more about having a completely new kind of technology that could basically test the strong force.\u2019\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cem\u003EResearch in this article was funded via the EU\u2019s European Research Council and previously under Future and Emerging Technologies Open (FET Open) as well as via the Marie Sk\u0142odowska-Curie Actions (MSCA). 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