In the quest to decipher the mysteries of the cosmos, a highly sensitive experiment named LUX-ZEPLIN (LZ) has been recently used in the United States to detect dark matter in the universe. Scientists, while studying the effects of dark matter on the movement of stars in the cores of certain galaxies, discovered that the out-of-plane bending can be explained through dark matter halos in barred galaxies.
Understanding Dark Matter
Dark matter is made up of uncharged particles and since these particles don’t emit light, an electromagnetic phenomenon, they are referred to as “dark.” Despite their lack of visible presence, they possess mass akin to normal matter and engage in interactions through gravitation. It’s interesting to note that the visible universe is a result of various interactions among the four fundamental forces – Strong nuclear force, Weak nuclear force, Electromagnetic force, and Gravitation working upon particles. However, all matter only comprises 5% of the entire visible universe, with the rest being a combination of dark matter and dark energy.
The challenge lies in detecting any particle which interacts with gravitational force due to its extremely weak nature. This characteristic makes the gravitational force less understood relative to the others.
Dark Energy – A Theoretical Concept
Dark Energy, unlike Dark Matter, is yet an unproven concept. It is an expected form of energy that applies a negative, repulsive force, thus functioning in the opposite direction of gravity. It was put forth to explain the attributes of distant types of supernovae, indicative of the universe expanding at an ever-increasing rate. Much like Dark Matter, Dark Energy is inferred from measurements of gravitational interactions between celestial objects, but not explicitly observed.
Differentiating Dark Matter and Dark Energy
While dark matter serves as a binding force that holds the universe together due to its interactive nature with gravity, dark energy serves as a repulsive force or an anti-gravity that slows down the universe’s expansion. When it comes to their respective power, dark energy outweighs dark matter by accounting for around 68% of the universe’s total mass and energy. Dark matter, on the other hand, accounts for just 27%, leaving the remaining 5% to all the ordinary matter that we can see and interact with daily.
Proof of Dark Matter
The existence of dark matter is strongly supported by indirect evidence visible at various distance scales. A significant discrepancy between observed star speeds and their estimated figure as we move outwards from the center of the galaxy suggests a large presence of dark matter. Additional supporting evidence can be found in observing the universe at different levels, such as the atomic level, galaxy clusters, and even larger distances where the entire universe can be mapped and studied.
For instance, when two galaxies merge to form bullet clusters, the resultant structure could only be scientifically explained through the existence of dark matter.
Detecting Dark Matter: A Pending Mystery
Although neutrinos would have been ideal for detecting dark matter, their lightweight nature proves unhelpful. Several other proposed entities include the Z boson’s supersymmetric companion, a particle that mediates the electro-weak interaction. However, no viable particle has been found that can interact with gravity and is also detectable using current technology on Earth.
The UPSC Civil Services Examination
In the context of modern scientific research, relevant subject matter pertaining to ‘IceCube’, a particle detector located at the South Pole was present in the 2015 examination. The IceCube Neutrino Observatory is deeply nestled inside Antarctic ice and spreads over a cubic kilometer. It was specifically engineered to identify and track high-energy neutrinos. Weakly Interacting Massive Particle (WIMP) dark matter could be gravitationally captured by massive objects like the Sun and accumulate in its core. The products of this annihilation decay into neutrinos, which could be observed by IceCube as an excess of neutrinos from the direction of the Sun.
Last Modified: February 15, 2024