Dark matter refers to a hypothetical form of matter that does not interact with electromagnetic radiation, making it invisible and unable to be directly observed. It is called "dark" because it does not emit, absorb, or reflect light, and therefore cannot be detected using traditional astronomical methods. Yet, it exerts a gravitational influence on visible matter, contributing to the structure and dynamics of the universe at large scales. Dark matter is believed to make up a significant portion of the total matter in the universe, but its exact nature and composition remain unknown.
Dark matter is a term used in cosmology and astrophysics to refer to matter that cannot be directly observed by humans. It is distinct from normal matter that interacts with light and other forms of electromagnetic radiation. Dark matter does not emit, absorb, or reflect light, making it invisible and difficult to detect using traditional observational techniques. Its presence is inferred through its gravitational effects on visible matter and the structure of the universe. Therefore, among the given options, the most accurate definition of dark matter would be "energy that humans cannot observe directly."
The definition of dark matter is energy that humans cannot observe directly. It is different from other forms of matter because it does not emit, absorb, or reflect any electromagnetic radiation, such as light or radio waves. Dark matter is so named because it does not interact with light, making it invisible and difficult to detect using traditional telescopes or instruments. Scientists have inferred the existence of dark matter based on its gravitational effects on visible matter and structures in the universe. While it cannot be directly observed, its presence is inferred from its gravitational influence on galaxies, galaxy clusters, and the large-scale structure of the universe. So, the correct option among the given choices is: energy that humans cannot observe directly.
