Composition of matter in the universe
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Composition of Matter in the Universe
Overview of Universe Composition
The universe is composed of several distinct components: dark matter, dark energy, baryonic (ordinary) matter, and radiation. These components play crucial roles in the structure, evolution, and ultimate fate of the universe.
Dark Matter: The Invisible Mass
Dark matter constitutes a significant portion of the universe's mass, estimated to be around 26.8% . Unlike ordinary matter, dark matter does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects on visible matter, radiation, and the large-scale structure of the universe Turner1991Freese2017. Observational evidence for dark matter includes galaxy rotation curves, gravitational lensing, and the Cosmic Microwave Background (CMB) . There are several candidates for dark matter particles, including axions, neutralinos, and sterile neutrinos, which are being investigated through various experimental approaches Turner1991Mullat2015.
Dark Energy: The Mysterious Force
Dark energy is an even more enigmatic component, making up approximately 68.3% of the universe . It is responsible for the accelerated expansion of the universe, a phenomenon first observed in the late 20th century. The nature of dark energy remains one of the most profound mysteries in cosmology, often described as a form of antigravity Seife2005Freese2017. Theoretical models and observational data, such as those from the Planck Mission, support the existence of dark energy, but its exact properties and underlying mechanisms are still under intense investigation .
Baryonic Matter: The Ordinary Stuff
Baryonic matter, which includes protons, neutrons, and electrons, constitutes only about 4.9% of the universe . This is the matter that makes up stars, planets, and all known life forms. Despite its relatively small proportion, baryonic matter is crucial for the formation of galaxies and other cosmic structures. The distribution of baryonic matter is influenced by the gravitational pull of dark matter, leading to the formation of cosmic voids and dense regions along their boundaries .
Radiation: The Energy of the Universe
Radiation, including photons and neutrinos, is another component of the universe. While its contribution to the total energy density of the universe is relatively small today, it played a significant role in the early universe, particularly during the era of Big Bang nucleosynthesis, which led to the formation of the first atomic nuclei .
Theoretical Models and Observations
The composition of the universe is supported by various theoretical models and observational data. The spatially-flat, Einstein-de Sitter model, for instance, is supported by structure formation theories, the temporal Copernican principle, and inflationary models . Observations from the Sloan Digital Sky Survey and other cosmological surveys provide constraints on the average matter content and the growth rate of cosmic structures, further refining our understanding of the universe's composition .
Conclusion
The universe is a complex and dynamic system composed of dark matter, dark energy, baryonic matter, and radiation. While significant progress has been made in understanding these components, many questions remain, particularly regarding the nature of dark matter and dark energy. Ongoing and future experiments aim to shed light on these mysteries, potentially leading to groundbreaking discoveries in cosmology and particle physics.
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Most relevant research papers on this topic
Constraints on Cosmology and Gravity from the Dynamics of Voids.
The dynamics of cosmic voids constrain the average matter content and growth rate of structure in the universe, and no deviations from Einstein's general relativity are found in the data.
A Physico-Chemical Approach To Understanding Cosmic Evolution: Thermodynamics Of Expansion And Composition Of The Universe
The expansion of the universe accelerated due to dark energy at 7.25 x 109 years, and dark matter is identified as a plasma form of matter similar to that which existed before recombination and during reionization.
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