How big is the unknown universe
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The Vastness of the Unknown Universe
Understanding the Scale of the Universe
The universe is an incredibly vast and complex entity, far beyond the comprehension of the human mind. The observable universe alone spans approximately 46 billion light-years in every direction, a distance determined by how far light has traveled since the Big Bang4. This immense scale is difficult to grasp, especially when considering that even the smallest known objects in the universe, such as elementary particles, are dwarfed by the enormity of cosmic structures2.
Comparing Cosmic and Terrestrial Scales
To put the size of the universe into perspective, consider that the difference in scale between an elementary particle and the observable universe is around 10^402. This staggering difference highlights the vastness of the cosmos. Even within our own galaxy, the Milky Way, there are stars so large that millions of Earths could fit inside them3. The total number of stars in the universe is often compared to the number of grains of sand on all the seashores of the world, emphasizing the sheer number of celestial bodies that exist3.
The Concept of Infinity in the Universe
One of the most profound questions in cosmology is whether the universe is finite or infinite. This question has intrigued scientists and philosophers for centuries. Some theories suggest that the universe might bend in such a way that distant galaxies are actually closer than they appear, potentially implying a finite but unbounded universe2. However, the exact nature of the universe's size remains one of the greatest mysteries in science6 7.
Early Universe and Dark Matter
The early universe was nearly smooth and homogeneous, with tiny fluctuations in matter distribution that eventually led to the formation of structures. These fluctuations, influenced by the unknown nature of dark matter, resulted in the creation of Earth-mass dark-matter haloes, which are stable and numerous within the Galactic halo5. Understanding these early structures is crucial for comprehending the overall scale and evolution of the universe.
Conclusion
The universe's size and complexity are beyond human comprehension, with distances measured in billions of light-years and scales that dwarf even the largest terrestrial objects. Whether the universe is finite or infinite remains an open question, but the observable universe alone is vast enough to inspire awe and wonder. As we continue to explore and understand the cosmos, each discovery brings us closer to unraveling the mysteries of the unknown universe.
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Most relevant research papers on this topic
10 million unknowns: is it that big? [computational electromagnetics]
ScaleME successfully solved a large-scale electromagnetic scattering problem with nearly 10.2 million unknowns, proving its ability to handle massively parallel multilevel fast multipole algorithms.
Highly CitedThe 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.
PreprintIs 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.
Earth-mass dark-matter haloes as the first structures in the early Universe
Earth-mass dark-matter haloes, about as large as the Solar System, were the first structures to form in the early Universe, and their stability against gravitational disruption suggests they could be bright sources of -rays.
Highly CitedTHE 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 aril 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
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
Optically dark massive galaxies
This discovery may help solve some of the mysteries surrounding the formation and evolution of massive galaxies in the early universe.
Mapping the Universe
Large coherent structures in the universe, such as the "Great Wall," challenge our current understanding of the universe's origin and evolution.
Highly Cited