‘Chameleon’ forces remain elusive in a new dark energy experiment

A chameleon-like pressure that shifts its nature based mostly on its setting may clarify a significant physics quandary: how the mysterious substance referred to as darkish power is compelling the cosmos to broaden sooner and sooner. But 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 fundamental 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. In the sparseness of house, 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 may drive the accelerating growth of the universe with out disagreeing with measurements on Earth.

But it’s a problem to suss out such a changeling pressure. On Earth, says astrophysicist Jianhua He of Nanjing University in China, “it’s very, very tiny. That’s the most difficult part.”

So He and colleagues designed a detector to seek for a refined fifth pressure. A wheel with plastic movies connected 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 fashion, however because of the machine’s design, it ought to be a lot weaker than a chameleon pressure.)

The staff was in a position to rule out a class of chameleon theories. In the long run, the researchers hope to enhance their outcomes by chilling their machine to permit for extra delicate measurements.

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