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Atomic orbitals are basic building blocks of the atomic orbital model (or electron cloud or wave mechanics model), a modern framework for visualizing submicroscopic behavior of electrons in matter. In this model, the electron cloud of an atom may be seen as being built up (in approximation) in an electron configuration that is a product of ...
The spatial region from which we can receive light is called the observable universe. The proper distance (measured at a fixed time) between Earth and the edge of the observable universe is 46 billion light-years [50] [51] (14 billion parsecs), making the diameter of the observable universe about 93 billion light-years (28 billion parsecs). [50]
The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave—a wave form that does not move relative to the nucleus. This behavior is defined by an atomic orbital , a mathematical function that characterises the probability that an electron appears to be at a particular location ...
Initially, Earth was believed to be the center of the Universe, which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars. [1] After the acceptance of the heliocentric model in the 17th century, observations by William Herschel and others showed that the Sun lay within a vast, disc-shaped galaxy of ...
In Aristotle's fully developed celestial model, the spherical Earth is at the centre of the universe and the planets are moved by either 47 or 55 interconnected spheres that form a unified planetary system, [19] whereas in the models of Eudoxus and Callippus each planet's individual set of spheres were not connected to those of the next planet ...
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, H 2), and the formation of H II regions.
The densest molecular clouds have significantly higher pressure than the interstellar average, since they are bound together by their own gravity. When stars form in such clouds, especially OB stars, they convert the surrounding gas into the warm ionized phase, a temperature increase of several hundred.
The chronology of the universe describes the history and future of the universe according to Big Bang cosmology.. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level.