Mass in universe
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Understanding the Mass of the Universe
Total Mass of the Universe: Key Estimates
The mass of the universe has been a subject of extensive research and debate. Eddington's calculations suggest that the universe contains approximately (10^{22}) stars, each with an average mass similar to our sun, leading to a total mass of around (2 \times 10^{49}) tons . This estimate is corroborated by the mass of protons and electrons in the universe, which also approximates to (2.55 \times 10^{49}) tons .
Cosmological Theories and Mass Parameters
Various cosmological theories, despite their differences, converge on a mass parameter of the order of (10^{55}) grams, equivalent to about (10^{79}) protons . This parameter is fundamental in Eddington's cosmology and appears as a 'fictitious mass' in Milne's theory, suggesting a common underlying principle in these models .
Mass Fluctuations and Density Parameters
The amplitude of mass fluctuations in the universe, denoted by (\sigma_8), is a critical factor in understanding the mass distribution. For a universe with critical density, (\sigma_8) ranges from 0.52 to 0.62, while for a spatially flat universe with (\Omega_0 = 0.2), it ranges from 1.25 to 1.58 . These values highlight the dependency of mass fluctuations on the cosmological density parameter.
Observable Universe and Dark Energy
The standard cosmological model, Lambda Cold Dark Matter (LCDM), assumes an infinite universe. However, some researchers argue for a finite universe with a mass of approximately (6 \times 10^{22}) solar masses, which negates the need for dark energy or a cosmological constant . This model interprets cosmic acceleration as a measurement of the gravitational radius of the universe.
Measuring the Mass of the Cosmos
The mass of the cosmos on gigaparsec scales can be measured by examining the maximum in the areal radius on the past null cone. This maximum provides a measurable characteristic of the cosmos and is sensitive to the bulk cosmological parameters . This approach offers a unique method to connect cosmic geometry with observations.
Evolution of the Concept of Mass
The concept of mass has evolved significantly, from Newton's laws to Einstein's theories, and further with the discovery of the Higgs boson. Recent developments suggest that rest-mass energy is likely the gravitational binding energy of a particle within our gravitational horizon . This perspective interrelates various interpretations of mass through the lens of general relativity.
Microphysical Derivations and Cosmology
Microphysical arguments have been used to derive the overall mass of the universe, linking cosmological parameters with the constants of nature and elementary particles . This approach highlights the connection between the microscopic world and cosmological phenomena.
Challenges in Determining Cosmic Mass Density
Determining the average mass density of the universe, parameterized by (\Omega), remains a significant challenge. Despite decades of research, (\Omega) is still uncertain by a factor of five, primarily due to the elusive nature of dark matter and its distribution relative to observable galaxies . Advanced numerical simulations and new methods, such as analyzing redshift-space distortions, are being developed to improve these measurements.
Conclusion
The mass of the universe is a complex and multifaceted topic, with estimates ranging from the mass of stars to the intricate distribution of dark matter. While significant progress has been made, many questions remain, particularly regarding the precise relationship between dark matter and observable galaxies. Ongoing research and advanced methodologies continue to refine our understanding of the universe's mass and its implications for cosmology.
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