Dark energy and dark matter are two mysterious components of the universe that together make up the vast majority of its mass-energy content, yet they are not directly observable through electromagnetic radiation like stars or galaxies. Here's a brief overview of each:
Dark Energy: Dark energy is a hypothetical form of energy that is thought to permeate all of space and is responsible for the observed accelerated expansion of the universe. This discovery, made in the late 1990s through observations of distant supernovae, was quite unexpected and remains one of the most significant mysteries in modern cosmology. Dark energy is believed to exert a negative pressure, causing the expansion of the universe to accelerate over time. Despite its name, "dark energy" is not well understood, and its nature remains a subject of active research.
Dark Matter: Dark matter is a form of matter that does not emit, absorb, or reflect electromagnetic radiation, making it invisible and detectable only through its gravitational effects on visible matter. Observational evidence for dark matter comes from studies of the motions of galaxies within galaxy clusters, gravitational lensing, and the large-scale structure of the universe. Dark matter is believed to make up about 27% of the total mass-energy content of the universe. While its exact nature is still unknown, various theoretical models suggest that dark matter may consist of exotic particles that interact very weakly with ordinary matter and light.
Together, dark energy and dark matter constitute the vast majority of the mass-energy content of the universe, with ordinary matter (the stuff we can see and interact with) making up only a small fraction (about 5%). Understanding the nature of dark energy and dark matter is one of the most significant challenges in modern astrophysics and cosmology, as it has profound implications for our understanding of the universe's past, present, and future evolution.
