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The vacuum chamber used to test for the presence of the chameleon field. Credit: Holger Muller

Physicists study ‘chameleon fields’ to better understand effects of dark energy

Dark energy is weird. We don’t know much about it yet. What we do know is that it makes up most of the energy and mass present in the universe. The atoms that make up us, the Earth and everything else we see is just a small portion of what’s actually in the universe. We also know that dark matter is responsible for the dispersal of galaxies across the universe. It has a repulsive characteristic that tends to push matter apart.

Physicists and astronomers have long been trying to explain it and one of ways this may be possible is by studying it in its natural environment. It is thought that its effects can only be measured in extremely low-density areas like between stars and galaxies. In order to study it here on Earth, physicist Paul Hamilton of the University of California, Los Angeles, recreated the conditions that might be present in intergalactic space. In doing this, Hamilton attempted to create a chameleon field. A chameleon field is a theoretical field that will exert an increasing force on matter as surrounding density decreases. This means it would exert almost no force in the ‘high’ density air that is Earth’s atmosphere but will exert force when density is very low like in areas between galaxies. The presence of chameleon fields has not yet been confirmed

To test the presence of chameleon fields, Hamilton and his team built a vacuum chamber with a pressure about 1 trillionth that of our atmosphere. In the chamber they placed atoms of cesium that were cooled to almost absolute zero to remove almost all motion except that that would be observed in the presence of gravity or of the chameleon field if it was present. They also placed an aluminum sphere inside the chamber, which would exert extra force on the atoms if the chameleon field were present.

By shinning a near infrared laser into the chamber, they could search for movement in the cesium atoms. Unfortunately, the only movement seen was due to the force of gravity and no effects from the chameleon field were detected. This doesn’t mean it isn’t present however. Hamilton and his team intend to continue their search for the elusive field.

The force of gravity on Earth is much stronger than that force of the chameleon field so it would be much easier to detect the force if the force of gravity were removed. One possible solution is to repeat the test on the International Space Station where the force of gravity is far weaker.

About Harry H

Harry H
Harry is currently studying biology and chemistry in University and hopes to go to grad school for evolutionary biology. He enjoys writing about sciences and sports and is a big fan of hockey and soccer. Some of his other interests are reading and rock climbing. Contact Harry: