<img src=”https://www.molwn.com/wpcontent/uploads/2022/08/Extendedtestswiththelevitatedforcesensorfindnoevidence.jpg” alt=”Les proves ampliades amb el sensor de força levitat no troben proves de la cinquena força” title=”Esquema de l’experiment. a, La “cinquena força” del camp camaleònic és generada per vuit pel·lícules primes (mases font) de poliimida amb un gruix de 75 μm, espaiades igualment en una placa giratòria. El sensor de força consisteix en una peça de grafit pirolític, levitada diamagnèticament en una trampa magnetogravitatòria i una pel·lícula de 12,5 μm de gruix (massa de prova) del mateix material que les masses font a la part superior sostinguda per una vareta de vidre. La trampa magnetogravitatòria es col·loca en una cambra de buit amb aïllament del soroll sísmic. La distància entre la massa de prova i les masses font és de 390 μm. La rotació de les masses font i el moviment del sensor de força són controlats per sistemes òptics, amb els senyals òptics detectats pel fotodíode 1 i el fotodíode 2, respectivament. El requadre mostra un esquema de la detecció del desplaçament del sensor de força. b, Les masses font giratòries generen una “cinquena força” periòdica Fcham que actua sobre la massa de prova. S’utilitzen una fina finestra de blindatge elèctric amb un gruix de 0,5 μm i un blindatge magnètic per protegir les forces electrostàtiques i magnètiques de fons. c, El camp ϕ al llarg de l’eix z central en dues fases de rotació diferents. Les corbes vermelles i blaves indiquen els casos amb i sense una pel·lícula de massa font per sobre de la massa de prova, respectivament. L’esquema no és a escala sinó per visibilitat. Crèdit: Nature Physics (2022). DOI: 10.1038/s41567022017069″ width=”800″ height=”530″/> Scheme of the experiment. a, The “fifth force” of the chameleon field is generated by eight thin films (source masses) of polyimide with a thickness of 75 μm, equally spaced on a rotating plate. The force sensor consists of a piece of pyrolytic graphite, levitated diamagnetically in a magnetogravitational trap and a 12.5 μm thick film (test mass) of the same material as the source masses on top held by a rod of glass The magnetogravitational trap is placed in a vacuum chamber with seismic noise isolation. The distance between the test mass and the source masses is 390 μm. The rotation of the source masses and the movement of the force sensor are controlled by optical systems, with the optical signals detected by photodiode 1 and photodiode 2, respectively. The inset shows a schematic of the displacement detection of the force sensor. b, The rotating source masses generate a periodic “fifth force” Fcham acting on the test mass. A thin electric shield window with a thickness of 0.5 μm and a magnetic shield are used to protect the background electrostatic and magnetic forces. c, The ϕ field along the central zaxis in two different rotation phases. The red and blue curves indicate the cases with and without a film of source mass above the test mass, respectively. The diagram is not to scale but for visibility. Credit: Physics of nature (2022). DOI: 10.1038/s41567022017069
A team of researchers from Nanjing University, working with two colleagues from the University of Science and Technology of China, have conducted new tests of the chameleon theory and reported a failure to find any evidence of a fifth force. They have published their article in the journal Physics of nature.
Previous research has suggested that there is a mysterious force acting on the universe, called by theoretical physicists dark energy, it was theorized as a way to explain why the universe is expanding at an accelerated rate. Despite many efforts, no one has been able to prove that dark energy exists. A theory called the chameleon theory suggests that objects affected by gravity can behave in a way that fluctuates depending on factors in their environment. The theory includes the idea of a chameleon field as a fifth force. The theory has been hotly debated because it directly contradicts the theory of general relativity, which states that gravitational forces are expected to be constant.
In this new effort, the researchers sought to prove or disprove the theory using a levitated force sensor: a wheelshaped device with attached plastic fins that spins past a thin film sitting on top of a piece of magnetically levitated graphite. The base below the graphite is held in place by springs. The goal is to test the idea that gravity exerts different amounts of force depending on the density of the objects around it. In a broad context, the chameleon field would exert less force in a dense environment like an individual planet than it would over a large, less dense swath of space. If a fifth force exists, then the spinning films should exert a periodic force on the levitating film.
After running the experiment several times, the researchers found no evidence that the spinning fins affected the levitated film, which, they say, rules out the chameleon theory as a candidate explanation for dark energy. They also suggest that their methodology highlights the need for robust, laboratorybased evidence as a means of verifying or discrediting theoretical research. They suggest their methodology could be used in other endeavors as well.
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Peiran Yin et al, Levitation Force Sensor Experiments Challenge Dark Energy Theories, Physics of nature (2022). DOI: 10.1038/s41567022017069
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Summons: Extended tests with levitated force sensor find no evidence for fifth force (2022, August 26) Retrieved August 27, 2022, from https://phys.org/news/202208levitatedsensor – evidence.html
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