Dark energy. It’s a difficult concept to understand, and it’s even more difficult to explain, even though scientists believe that dark energy makes up over 68 percent of all the energy in the entire universe. Theoretical physicists believe that dark energy may be the antithesis of gravity. While gravity is a force that we tend to think of as “sticking” objects of mass together, dark energy is believed to counteract gravity, causing the universe to expand.
Going back to 1998, scientists used the Hubble Space Telescope and came to the conclusion that the universe is expanding outwards, like a giant balloon. Scientists also determined that the rate at which the universe is expanding is constantly speeding up. Now, scientists believe that the force that is “pushing” to universe to expand is what they are calling “Dark Energy.”
But what is Dark Energy, and why can’t we see — or detect — it?
In 2004, Justin Khoury from the University of Pennsylvania posited that the reason that we can’t see or detect Dark Energy is because it intentionally hides from us. That may seem a bit farfetched when you first read it, but it is really not. Khoury first coined the term “chameleon particles,” meaning that the particles that make up Dark Energy appear in different ways depending on their environment, or, as in the case of Dark Energy, depending on the density of the surrounding mater.
Khoury posed that in a laboratory setting, when the chameleon particles in Dark Energy are totally surrounded by “regular” matter, the particles wouldn’t have much influence or effect on their surroundings. However, Khoury said, in space, where the distance between masses of matter in the form we normally recognize is often light years apart, the chameleon particles contained in Dark Energy react by exerting much, much more influence, effectively causing the universe to expand.
Now, some experiments being performed may let us know if chameleon particles actually do exist in dark matter. A team of scientists led by a postdoctoral fellow at the University of California at Berkeley, named Paul Hamilton, are measuring the forces at work on a “falling cesium atom.” Another experiment being performed by another collaboration of universities are looking at how dark energy may interact with an atom’s electron.
Thus far, the results of both series of experiments have not been able to pinpoint the existence of the chameleon particles that are surmised to make up dark energy, but the work continues.
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