Dark Matter & Dark Energy: The Invisible Forces Shaping the Universe

by Sayohn J

Published 3rd of April

The universe is vast and mysterious, and despite centuries of scientific exploration, much remains unknown. Among the greatest enigmas in modern astrophysics are dark matter and dark energy, two unseen forces that make up approximately 95% of the universe (NASA). While dark matter binds galaxies together, dark energy accelerates the universe’s expansion. Understanding these forces is crucial for comprehending the fundamental nature of the cosmos. 

Dark matter is an invisible substance that does not emit, absorb, or reflect light, making it impossible to observe directly. Scientists infer its existence through its gravitational effects on visible matter. In the 1930s, Swiss astronomer Fritz Zwicky first proposed the concept of dark matter when he noticed that galaxies in the Coma Cluster moved in a way that suggested the presence of unseen mass (Zwicky). Later, astronomers Vera Rubin and Kent Ford provided further evidence by studying the rotational speeds of galaxies, which remained constant even in their outer regions; contrary to what Newtonian physics predicted (Rubin & Ford). This anomaly suggests that an unseen form of matter provides additional gravitational pull.

Despite its crucial role in shaping galaxies, the true nature of dark matter remains a mystery. Scientists have proposed several candidates, including Weakly Interacting Massive Particles (WIMPs) and axions, but direct detection efforts have yet to succeed (Bertone and Hooper). Ongoing research using underground detectors and particle accelerators aims to uncover its properties.

Dark energy, on the other hand, is responsible for the accelerating expansion of the universe. In 1998, two independent teams of astronomers studying distant supernovae discovered that the universe's expansion was speeding up rather than slowing down, as previously thought (Riess et al.; Perlmutter et al.). This acceleration implies the existence of a repulsive force counteracting gravity. Dark energy is suspected to make up about 68% of the universe and is often associated with the cosmological constant, a term introduced by Albert Einstein in his general theory of relativity (Einstein). However, alternative explanations have also been proposed, such as quintessence, a dynamic field that evolves (Peebles and Ratra).

The study of dark matter energy remains one of the most exciting frontiers in physics. Advanced telescopes, such as the James Webb Space Telescope and the upcoming Euclid mission, aim to provide more insights into these cosmic mysteries. As research continues, scientists hope to uncover the true nature of these invisible forces and their role in the universe’s evolution.

Works cited:

Bertone, Gianfranco, and Dan Hooper. "A History of Dark Matter." Nature, vol. 468, 2010, pp. 389-393.

Einstein, Albert. "Cosmological Considerations in the General Theory of Relativity." Sitzungsberichte der Königlich Preußischen Akademie der Wissenschaften, 1917.

NASA. "Dark Energy, Dark Matter." NASA Science, 2021, https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy.

Peebles, P. J. E., and Bharat Ratra. "The Cosmological Constant and Dark Energy." Reviews of Modern Physics, vol. 75, no. 2, 2003, pp. 559-606.

Perlmutter, Saul, et al. "Measurements of Omega and Lambda from 42 High-Redshift Supernovae." The Astrophysical Journal, vol. 517, no. 2, 1999, pp. 565-586.

Riess, Adam G., et al. "Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant." The Astronomical Journal, vol. 116, no. 3, 1998, pp. 1009-1038.

Rubin, Vera C., and W. Kent Ford Jr. "Rotation of the Andromeda Nebula from a Spectroscopic Survey of Emission Regions." The Astrophysical Journal, vol. 159, 1970, pp. 379-403.

Zwicky, Fritz. "On the Masses of Nebulae and of Clusters of Nebulae." Astrophysical Journal, vol. 86, 1937, pp. 217-246.