How old is the universe?
The universe is thought to be about 13 billion years old. By measuring the ages of the oldest stars and the rate at which the universe expands, scientists arrived at that number. They also measured the expansion by observing the doppler shift in light from almost all the galaxies which travel away from us and from each other. Galaxies travel faster the further they go. A galaxy will be so far away in the distant future that its light will not be visible to earth. The matter, energy, and everything in the universe was more compact last weekend than it is today.
The same can be said about any time last year, a million years ago, or a billion years ago. A little further back in time everything was the same place. The universe was not just one point. The universe expanded over time as space did. That the universe was not a dark empty space from which all matter sprang forth. Part of it is because it is full of space.
Spacetime
In general relativity the gravitational force is reimagined as the curvature of space time. It is not the result of a force deflecting a body from an ideal straight line but rather the body’s attempt to fall freely through a background that is curved by the presence of other masses.
It is a good approximation of the general relativity predictions when gravitational effects are weak. Average space is observed to be very nearly flat with a curvature close to zero. Spacetime also appears to have a simply connected topology in analogy to a sphere at least on the length scale of the observable universe. A cylindrical or toroidal topology may also exist as seen in two-dimensional space. The universe could also have a multi-dimensional global topology such as that of a sphere or a two-dimensional space. There is a multiplicity of dimensions in the universe as shown by string theory. It may also have multiple-dimensional topologies such as toroidal or cylindrical topologies of 2-dimensional space.
Physical properties
Gravitation is the most dominant of the four fundamental interactions. The gravitational forces’ effects are cumulative by contrast the effects of positive and negative charges tend to cancel each other. Both weak and strong nuclear forces decline rapidly with distance. Their effects are limited to subatomic length scales. Asymmetry may be related to the violation of the CP rule. There appears to be no net momentum or angular momentum in the universe which follows accepted physical laws if the universe is finite. The non-diversence of the stress-energy momentum pseudotensor is a Gauss law. The universe has no net moment of angular or tangential momentum and if it is finite it has no moment at all.
Age and expansion
The universe has grown monotonically since the Big Bang. Analyses of type II supernovae indicate that the spatial expansion is increasing.
It would collapse into a gravitational singularity when the universe is too dense. The best value of the age of the universe is 13.799 billion years if the model is correct. The universe and its contents have changed over time. The relative population of quasars and galaxies has changed and space itself has expanded. Due to this expansion scientists on earth can observe light from a galaxy 30 billion light years away even though the light has only traveled for 13 billion years. This expansion is consistent with the observation that light from distant galaxies has been redshifted the photons emitted have been stretched during their voyage to longer wavelengths and lower frequency. This has allowed it to grow for the last 13 billion years, giving time to form the universe.
Definition
The universe is defined as all space and time and its contents. The universe may refer to concepts such as the world and nature. It is often defined as the totality of existence, or everything that exists, everything that has existed, and everything that will exist. There are physical laws that influence energy and matter such as conservation laws and classical mechanics and relativity. The universe can include planets, moons, and star systems.
Historical conceptions
For the first time, the Greeks and Indians proposed theories of an impersonal universe governed by physical laws. Advances in astronomical observations and theories of motion and gravitational attraction led to more accurate descriptions of the universe over the centuries. Albert Einstein’s general theory of relativity in 1915 set the modern era in cosmology. Most modern cosmological theories are based on general relativity and more specifically the predicted big bang. It is possible to predict the origin, evolution, and conclusion of the universe as a whole quantitatively. Theories about the origin of the universe are known as cosmologies.
The universe is everything. It includes all of space, and all the matter and energy that space contains. It even includes time itself and, of course, it includes you. A billion galaxies in the observable universe are thought to have supermassive black holes at their center. Under your feet on the opposite side of the earth lies the unforgiving vacuum and radiation of space. Earth is a planet and part of the universe, just like the other planets. The environment near the surface of this planet is suitable for life and it just happens that some things live there. We will find out more about the universe and our place in it in this new era. It is the beginning of a new era in the history of the universe.
Composition
The dark matter that has not yet been identified accounts for 26.5 % of the contents. The dark energy that is causing the expansion of the universe to accelerate accounts for 68.3 % of its contents. Over the history of the universe, the proportions of all types of matter and energy have changed. The total amount of electromagnetic radiation in the universe has decreased by 1/2 in the past 2 billion years. The nature of dark energy and dark matter is not known at all. Dark matter and dark energy are distributed homogeneously throughout the universe over length scales longer than 300 million light years. The universe contains as many as 200 billion galaxies. The universe is bathed in highly isotropic microwave radiation that corresponds to a thermal equilibrium blackbody spectrum of roughly 2.72548 kelvins.
The Local Group of Galaxies is home to the Milky Way.
The universe is isotropic on significant scales larger than superclusters, meaning that the statistical properties of the universe are the same as observed from Earth in all directions. It is known as the cosmological principle that a large-scale universe is homogeneous and isotropic. This theory explains why the universe is so homogeneous and how it is cosmologically important. A universe that is both isotropic and homogeneously viewed looks the same from all vantage points and has no central point.
Support of life
According to the fine tuned universe hypothesis, the existence of observable life in the universe can only occur when certain universal fundamental physical constants lie within a very narrow range of values. If any of the fundamental constants were not slightly different, the universe would not have been able to support the establishment and development of matter, astrophysics, and life.
How has our view of the universe changed over time?
We humans have had little or no means of understanding the universe for countless lifetimes. Our ancestors instead rely on myth to explain the origins of everything they know. We have repeatedly leaped forward in our knowledge of the universe since then. Approximately a hundred years ago, astronomers first observed a group of galaxies beyond our own, and only a half century has passed since humans have sent spacecraft to other worlds.
When people began to investigate the nature of things a few hundred years ago, they were called natural philosophers instead of scientists. With ever-increasing technology and knowledge, and with no shortage of imagination, humans continue to lay the ground for the mysteries of the cosmos. But we have yet to send a space probe to even the closest of the billions of other star systems in the galaxy. No one has explored all the planets in our solar system.
The universe is around 11.4 billion years old, our solar system is 4.5 billion years old and humans have been around for a few thousand years. This means the universe has existed 56000 times longer than our species has. Almost everything that has ever happened to humans did so before they existed. In the meantime we wait for the cosmic to give us a hint.
Size and regions
The general theory of relativity states that the universe will never interact with ours in the lifetime of the universe due to the finite speed of light and the ongoing expansion of space. Some radio messages sent from Earth may not reach certain areas of space. The diameter of the observable universe is 93 billion light years and 2 billion particles. A typical galaxy’s diameter is 30000 light years (9198 parsecs) and the typical distance between two adjacent galaxies is 3 million light years (919.9 kiloparsecs). The distance from the edge of the Observable universe to the Earth is very close to the age of the universe, but this does not represent the distance at any given time because the Earth and the universe have since changed. The nearest sister galaxy to the Milky way is the Andromeda Galaxy.
Earliest conceptions of the universe
Even prehistoric people must have noticed that apart from a daily rotation now understood to arise from the spinning of the earth, the stars did not seem to move with respect to each other. Early nomads discovered that knowledge of the constellations could guide their travels and developed stories to help them remember the relative positions of the stars in the night sky. When nomads turned to farming, an intimate knowledge of the constellations served a new function in timekeeping ; in particular, it served to keep track of the seasons. During the course of a year, certain celestial objects moved forward and back in a narrow strip of sky that contained 12 constellations.
Multiverse hypotheses
For the different types of multiverses, Martin has developed a four-part classification scheme. Such multiverses are an example resulting from the chaotic inflation model of the early universe. The multiverse is a result of the many-worlds interpretation of quantum mechanics. Similar to quantum superposition and decoherence, parallel worlds are generated in this interpretation in which all the states of the wave functions are realized in separate worlds. The multiverse is a universal wave function in the many-world interpretation. It has been and continues to be a topic of much debate and multiple versions of interpretation exist whether scientifically meaningful probabilities can be extracted from this picture. Scientific multiverse models are different from concepts such as alternative plans of consciousness. It is composed of many distant events in our own universe. The nearest neighbour is a double exponential function larger than a googolplex.
It would be impossible to scientifically verify the existence of the same volume. It is possible to conceive of disconnected spacetimes of which each exists but is unable to interact with each other. Different universes are not connected to each other. According to one common terminology, each soap bubble of spacetime denotes a universe. Different galaxies are not connected to one another. Different universes are not necessarily connected in principle. As a group of separate soap bubbles, the concept of the multiverse can be visualized. The other unconnected universes may have different topologies of spacetime and different forms of matter. Other observers believe that each of several such bubbles created as part of chaotic inflation is a separate universe. In the present model, these universes all share a causal origin. Some have been put forward as possible explanations for the origin of the universe but they are purely speculative.
What is the universe made of?
Many of the observable matter in the universe takes the form of individual hydrogen atoms. In the molecule, two or more atoms share electrons. You have a sun like star if you collect 33,000 Earth masses of hydrogen and helium together. Planets, dwarf planets, ringlets, comets, and other particles are all collections of matter exhibiting different characteristics but obeying the same natural laws.
Particles
Elementary particles can be described as the forces that act on matter. These particles are sometimes described as fundamental because they have an unknown substructure. All elementary particles are currently best explained by quantum mechanics and exhibit wavelike behaviour whose behaviour has both particles like and wavelike aspects with different features dominating under different conditions. The standard model does not however accommodate gravity. The standard model is supported by the existence of particles that compose matter and quarks and their corresponding antimatter and force particles that mediate interactions with other particles.
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