How big is observable universe

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The Size of the Observable Universe

Observable Universe Size: 46 Billion Light-Years

The observable universe is defined by the maximum distance from which light emitted since the Big Bang can reach us. According to current cosmological models, this distance is approximately 46 billion light-years. This boundary, known as the cosmic horizon, represents the furthest extent of the observable universe2 3.

Geometry and Volume of the Observable Universe

The observable universe can be modeled as the surface volume of a 3-sphere. Using this model, the radius of the observable universe is calculated to be around 46.27 billion light-years, which aligns with the accepted figures. The volume of the observable universe is significantly larger than the Hubble volume by a factor of 12 pi3.

Constraints on the Universe's Geometry

The global geometry of the universe, whether it is infinite or finite, is a subject of ongoing research. If the universe is wrapped into a flat hypertorus, the fundamental domain must be at least 0.4 times the diameter of the observable universe. This constraint applies to all compact, orientable flat spaces, suggesting that the observable universe is a significant fraction of the total universe1.

Large-Scale Structure and Observability

Recent studies have focused on defining key observables of the large-scale structure of the universe within a general relativistic framework. These include redshift perturbations, weak lensing shear, magnification, and the observed number density of tracers. These observables help in understanding the structure and scale of the universe4.

Numerical Simulations and Observational Data

Advanced numerical simulations, such as the DEUS "Dark Energy Universe Simulation" Full Universe Run, have provided detailed insights into the formation and evolution of the universe's largest structures. These simulations, which involve billions of particles and extensive computational resources, support observational programs aimed at mapping the distribution of matter and galaxies5.

Finite or Infinite Universe?

The question of whether the universe is finite or infinite remains unresolved. Current data suggest that the universe's curvature is very close to flat, implying a lower limit on the total volume. Based on the latest cosmological parameters, there are at least 21 observable universe-sized patches similar to ours, with the potential for many more beyond our observational capabilities9.

Conclusion

The observable universe spans approximately 46 billion light-years in radius, encompassing a vast volume filled with galaxies, stars, and other cosmic structures. While the exact nature of the universe—whether finite or infinite—remains a topic of scientific inquiry, current models and simulations provide a robust framework for understanding its immense scale and complexity.

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Most relevant research papers on this topic

Is the Universe infinite or is it just really big

The fundamental domain of the universe must be at least 0.4 times the diameter of the observable universe, limiting compact cosmologies based on hexagonal prisms.

1998·42citations·Janna Levin et al.·Physical Review D

Physical Review D ··DOI

Is the universe infinite or just very big

The cosmic horizon is about 46 billion light-years, and it's a three-dimensional equivalent of the 2D-horizon people see on Earth.

2015·0citations·M. Campbell·New Scientist

New Scientist ··DOI

Determining the Radius of the Observable Universe Using a Time-Scaled 3-Sphere Model of the Universe

The observable universe has a radius of 46.27 billion light years and a volume larger than the Hubble volume, with the observable universe acting as a time-scaled 3-sphere model.

Preprint

2016·0citations·James A. Tassano·viXra

viXra ··DOI

Large-scale structure observables in general relativity

This paper reviews key observables of the large-scale structure of the Universe, including redshift perturbation, distortion of cosmic rulers, and observed number density of tracers, in a general relativistic context.

2014·34citations·D. Jeong et al.·Classical and Quantum Gravity

Classical and Quantum Gravity ··DOI

First-ever full observable universe simulation

The first-ever full observable universe simulation provides unique information on the formation and evolution of the largest structure in the universe, supporting future observational programs.

2012·14citations·J. Alimi et al.·2012 International Conference for High Performance Computing, Networking, Storage and Analysis

2012 International Conference for High Performance Computing, Networking, Storage and Analysis ··DOI

The Scale of the Universe in Perspective

The universe is a very large place, with objects like brown dwarfs being millions of times larger than humans, and its exact nature remains unknown.

Preprint

2020·0citations·Pelobello·viXra

viXra ··DOI

Size of the Observable Universe

The observable universe has a radius 0.7% smaller than previously estimated, due to the expansion of space and the finite age of the cosmos.

2016·11citations·Paul Halpern et al.

·DOI

Observability of the size of the universe

The size of the universe can be observable in principle if our universe is multiple connected, as the spectrum detected by an accelerating monopole detector is altered by a periodic boundary condition.

1989·1citation·O. Abe·Physics Letters B

Physics Letters B ··DOI

HOW MANY UNIVERSES DO THERE NEED TO BE

There are at least 21 universes with the same volume as ours, but we cannot know the number of observable universes beyond 105 patches.

2006·2citations·Douglas Scott et al.·International Journal of Modern Physics D

International Journal of Modern Physics D ··DOI

THE SIZE OF THE UNIVERSE

Before we can discuss the size of the universe it is necessary to define exactly what we are talking about. Astronomers have in the past been somewhat loose in their use of the word "universe.'' About ten years ago one of the much-discussed topics of the day was the "theory of island universes" universes in the plural ! A universe in that discussion was what we now call a galactic system, a stellar system like our own. As I am using the word tonight, there is only one universe, which contains all these systems, and everything that can be observed and that we can think of as being observable, either now or in the future. The universe is the whole of all things that exist in the physical or outer world. The next question to be considered is : has the universe any size at all? This question, whether the universe is of finite size or infinite, has occupied the minds of some of the greatest of mankind ever since science was born. There exists a delightful little tract, written by Archimedes, the greatest of Greek mathematicians, about 200 b.c. It is called "On the Grains of Sand" and is cast in the form of a letter addressed to the king of Syracuse. It begins as follows : "There are those who think, King Gelo, that the number of grains of sand is infinite ; that is, the grains of sand not only in the environs of Syracuse and the rest of Sicily, but also in all parts of the world whether inhabited or uninhabited. Others think that it is not infinite, but that no number can be named so large that it would exceed the said number of grains of sand. It appears that those who think so would still less be able to imagine

1932·3citations·W. Sitter·Publications of the Astronomical Society of the Pacific

Publications of the Astronomical Society of the Pacific ··DOI

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