In astrophysics and cosmology, invisible matter refers to forms of matter that do not interact with light or other electromagnetic radiation like visible matter
In astrophysics and cosmology, invisible matter refers to forms of matter that do not interact with light or other electromagnetic radiation like visible matter (like atoms and molecules) does. This invisible matter is often called "dark matter" and "dark energy," and they are two distinct concepts:
- Dark Matter: Dark matter is a hypothetical form of matter that does not emit, absorb, or reflect electromagnetic radiation, making it "dark" or invisible to telescopes and other instruments that rely on light. Despite being invisible, dark matter is thought to make up a significant portion of the mass in the universe, possibly as much as 27% of the total mass-energy content. It exerts gravitational forces on visible matter, galaxies, and galaxy clusters, helping to explain the observed gravitational interactions in the cosmos.
- There are various theories about the nature of dark matter particles, but they have yet to be directly detected. Scientists are actively conducting experiments and observations to understand dark matter better.
- Dark Energy: Dark energy is another mysterious and invisible component of the universe but fundamentally different from dark matter. Dark energy is believed to be responsible for the universe's accelerated expansion. Unlike dark matter, which has a gravitational attraction and tends to clump matter together, dark energy has a repulsive effect, causing the universe's expansion to accelerate.
- Dark energy is often associated with a cosmological constant or vacuum energy. Its exact nature remains a subject of intense research and debate among cosmologists.
These invisible forms of matter and energy play crucial roles in the large-scale structure and behaviour of the universe, and understanding them is one of the central challenges in modern astrophysics and cosmology. Their existence is inferred based on their gravitational effects and influence on the universe's expansion, but they remain elusive and mysterious regarding direct detection and characterization.