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A chameleon-like pressure that shifts its nature based mostly on its setting might clarify a serious physics quandary: how the mysterious substance referred to as darkish power is compelling the cosmos to increase sooner and sooner. However a brand new experiment casts doubt on some chameleon theories, researchers report August 25 in Nature Physics.
The chameleon pressure can be a fifth sort of pressure past the essential 4: gravitational, sturdy, weak and electromagnetic. And like a chameleon altering its colours, the hypothetical fifth pressure would morph relying on the density of its environment. In dense environments like Earth, this fifth pressure can be feeble, camouflaging its results. Within the sparseness of area, the pressure can be stronger and long-ranged.
This pressure would end result from a chameleon discipline — an addition to the identified fields in physics, akin to electrical, magnetic and gravitational fields. A chameleon discipline with these morphing properties might drive the accelerating expansion of the universe with out disagreeing with measurements on Earth.
But it surely’s a problem to suss out such a changeling pressure. On Earth, says astrophysicist Jianhua He of Nanjing College in China, “it’s very, very tiny. That’s probably the most tough half.”
So He and colleagues designed a detector to seek for a delicate fifth pressure. A wheel with plastic movies hooked up spins previous one other movie sitting on a magnetically levitated piece of graphite. If a chameleon pressure actually exists, the movies spinning by would trigger a periodic pressure on the levitating plastic, pulling it up and down. (Gravity additionally acts this manner, however due to the gadget’s design, it must be a lot weaker than a chameleon pressure.)
The group was in a position to rule out a class of chameleon theories. Sooner or later, the researchers hope to enhance their outcomes by chilling their gadget to permit for extra delicate measurements.
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