The existence of an energy field that permeates all of time and space is the best explanation for why the cosmos is expanding at an increasingly rapid rate. It is known as dark energy. If dark energy does exist, we don’t know what it is, and we are not positive that it does. One intriguing idea implies the presence of a particle and associated force that may interact with matter, albeit very weakly, and was put forth in 2003. This is the fictitious fifth force and “chameleon” particle. But a recent study has demonstrated that it is improbable that such a force exists.
Gravitation, electromagnetism, and the strong and weak nuclear forces, and these are the four fundamental forces of nature. This chameleon force would be very weak close to Earth but would be sensed in less dense areas, such as intergalactic space, depending on the density of the area. The capacity to alter in various surroundings is where the term “chameleon” originates.
“Despite significant efforts in laboratory experiments and astrophysical observations, earlier testing have not been accurate enough to draw firm judgments about the viability of these hypotheses. The so-called chameleon theory, which the authors, led by a group at Nanjing University, described in their paper published in Nature Physics, “describes an ultra-light scalar field that couples to normal-matter fields and leaves measurable effects that are not explained by the four fundamental interactions, a so-called fifth force.
The research team utilized a wheel with plastic films attached that spun past another film resting on a levitating force sensor made of graphite to see if the unexplained connection could be observed. For the spinning films to exert a periodic force on the levitating film, dragging it up and down, the chameleon theory—which states that the chameleon force would exert less force in a dense environment—must be true.
The instrument was enclosed in a faraday cage to prevent electric fields from affecting the measurement of the distance between the two masses. But even though it was 100 times more sensitive than earlier detectors, it was unable to discover any anomalies.
In their report, the scientists stated, “We find no evidence for the fifth force suggested by chameleon models. Our findings indicate the reliability of laboratory experiments for future revelations of the nature of dark energy, conclusively ruling out the basic chameleon model as a contender for dark energy. A wide variety of fundamental physics topics could be studied using the methods created here.
The results reject most of the chameleon theories for dark energy, but the team is working to improve the system by cooling it to extremely low temperatures. This might be used to look more closely at the chameleon theory and other theories explaining dark energy.