Explain the need to postulate the existence of dark matter in the universe.
Dark matter is a hypothetical type of matter distinct from ordinary matter such as protons, neutrons, electrons, and neutrinos.
Dark matter has never been directly observed; however, its existence would explain a number of otherwise puzzling astronomical observations.[1][2] The name refers to the fact that it does not emit or interact with observable electromagnetic radiation, such as light, and is thus invisible to the entire electromagnetic spectrum.
Although dark matter has not been directly observed, its existence and properties are inferred from unexplained mass in gravitational lensing calculations, which affects the motions of baryonic matter and light.[4]. It influences the universe's large-scale structure, the formation of galaxies, and affects the cosmic microwave background.
The standard model of cosmology indicates that the total mass–energy of the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy Thus, dark matter constitutes 84.5%[note 1] of total mass, while dark energy plus
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