Dark energy has puzzled scientists for long, despite the known fact that it make up over 68% of all the energy in the entire universe. According to theoretical physicists, dark energy is exactly opposite to gravity.

They say that gravity acts to stick objects of mass together, whereas dark energy counteracts gravity, causing the universe to expand.

With the help of the Hubble Space Telescope, scientists concluded in 1998 that the universe was expanding outwards, like a massive balloon. They also claimed that the rate of expansion was burgeoning, and now believe that dark energy is responsible for pushing the universe to expand.

Justin Khoury from the University of Pennsylvania said in 2004 that Dark Energy can’t be seen because it intentionally hides itself from us. Khoury also said that chameleon particles, the particles that make up Dark Energy, appear in different ways depending upon their environment. In the case of Dark Energy, density of the surrounding is a factor that plays a role.

Chameleon particles wouldn’t have much influence or effect on their surroundings in a laboratory setting when the regular matter totally surrounds the particles in Dark Energy. However, in space, the chameleon particles contained in Dark Energy react by exerting much, much more influence, effectively causing the universe to expand. The distance between masses of matter is often light years apart in space.

Scientists are now performing new experiments to figure out if chameleon particles actually do exist in dark matter. They are also trying to see how dark energy may interact with an atom’s electron.