Electron and Universe: Difference between pages
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The '''Universe''' consists of the whole [[spacetime]] continuum in which we find ourselves, together with all the matter and [[energy]] within it. |
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The '''electron''' is a tiny subatomic [[particle physics|particle]] with one unit negative [[electric charge]]. The electron is one of a class of subatomic particles called [[lepton|leptons]] which are believed to be [[particle physics|fundamental particles]] (that is, they cannot be broken down into smaller constituent parts). |
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The Universe on its largest scales is studied by [[astronomy]], and especially by [[cosmology]]. The most important result, that the Universe is expanding, is derived from [[redshift]] observations and quantified by [[Hubbles law|Hubble's law]]. Extrapolating this expansion back in time, one arrives at a [[singularity]], a point in time when all distances in the universe were zero. This describes the [[Big Bang]] theory, the dominant model in cosmology today. The Big Bang is estimated to have happened about 15 billion years ago. |
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[[Atom]]s consist of a [[nucleus]] of [[proton]]s and [[neutron]]s surrounded by electrons. The [[mass]] of an electron is about 9.11 × 10<sup>-31</sup> kg, which makes a proton about 1800 times as heavy as an electron. |
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The effects of the Big Bang can be seen today by the fact that the farther [[galaxy|galaxies]] are away from us, the faster they are moving away from us. It can also be seen in the [[Cosmic Background Radiation|microwave background radiation]] which is the much-attenuated radiation that originated soon after the Big Bang. This background radiation is remarkably uniform in all directions, which cosmologist have attempted to explain by an initial period of rapid [[inflation]] following the Big Bang. |
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The electron has [[spin]] 1/2, which means it is a [[fermion]], i.e., follows the [[Fermi-Dirac statistics]]. |
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It is not known whether the Universe is finite or [[infinity|infinite]], though currenly an infinite Universe is favored. The ''observable universe'' however, consisting of all locations that could have affected us since the Big Bang given a finite [[speed of light]], is certainly finite. The ''lookback distance'' to the "edge" of the observable universe is about 15 billion [[light year]]s, meaning that light from the most distant objects we can see today has been travelling for 15 billion years. The ''present distance'' to the edge of the observable universe is larger, since the universe has been expanding; it is estimated to be about 48 billion light years. The observable universe contains about 10<sup>21</sup> [[star]]s, organized in about 10<sup>10</sup> [[galaxy|galaxies]], which themselves form [[groups and clusters of galaxies|clusters]] and [[supercluster]]s. |
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The [[antimatter]] counterpart of the electron is the [[positron]]. |
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The Universe has no boundary but may still be finite. This can be understood by a two-dimensional analogy: the Earth's surface has no edge, but nonetheless has a finite area. |
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When electrons move, free of the nuclei of atoms, and there is a net flow, this flow is called [[electricity]], or an [[electric current]]. This might be compared to a flock of sheep moving north together, while the shepherds do not. |
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Depending on the average density of matter and energy in the Universe, it will either keep on expanding forever or it will be gravitionally slowed and will eventually collapse back on itself. Currently the evidence seems to point to a universe whose expansion is accelerating, see [[accelerating universe]]. |
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So-called "static electricity" is not a flow of electrons at all. More correctly called a "static charge", it refers to a body that has more or fewer electrons than are required to balance the positive charge of the nuclei. When there is an excess of electrons, the object is said to be "negatively charged". When there are fewer electrons than [[proton|protons]], the object is said to be "positively charged". When the number of electrons and the number of protons are equal, the object is said to be electrically "neutral". |
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There is some speculation that multiple universes exist in a higher-level [[multiverse]]. For example matter that falls into a black hole in this universe could emerge as a big bang starting another universe, or the universe could ultimately collapse back into a "big crunch" which would rebound as a new big bang. However all such ideas are currently not testable and so cannot be regarded as anything more than speculation. |
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Revision as of 16:15, 19 February 2002
The Universe consists of the whole spacetime continuum in which we find ourselves, together with all the matter and energy within it.
The Universe on its largest scales is studied by astronomy, and especially by cosmology. The most important result, that the Universe is expanding, is derived from redshift observations and quantified by Hubble's law. Extrapolating this expansion back in time, one arrives at a singularity, a point in time when all distances in the universe were zero. This describes the Big Bang theory, the dominant model in cosmology today. The Big Bang is estimated to have happened about 15 billion years ago.
The effects of the Big Bang can be seen today by the fact that the farther galaxies are away from us, the faster they are moving away from us. It can also be seen in the microwave background radiation which is the much-attenuated radiation that originated soon after the Big Bang. This background radiation is remarkably uniform in all directions, which cosmologist have attempted to explain by an initial period of rapid inflation following the Big Bang.
It is not known whether the Universe is finite or infinite, though currenly an infinite Universe is favored. The observable universe however, consisting of all locations that could have affected us since the Big Bang given a finite speed of light, is certainly finite. The lookback distance to the "edge" of the observable universe is about 15 billion light years, meaning that light from the most distant objects we can see today has been travelling for 15 billion years. The present distance to the edge of the observable universe is larger, since the universe has been expanding; it is estimated to be about 48 billion light years. The observable universe contains about 1021 stars, organized in about 1010 galaxies, which themselves form clusters and superclusters.
The Universe has no boundary but may still be finite. This can be understood by a two-dimensional analogy: the Earth's surface has no edge, but nonetheless has a finite area.
Depending on the average density of matter and energy in the Universe, it will either keep on expanding forever or it will be gravitionally slowed and will eventually collapse back on itself. Currently the evidence seems to point to a universe whose expansion is accelerating, see accelerating universe.
There is some speculation that multiple universes exist in a higher-level multiverse. For example matter that falls into a black hole in this universe could emerge as a big bang starting another universe, or the universe could ultimately collapse back into a "big crunch" which would rebound as a new big bang. However all such ideas are currently not testable and so cannot be regarded as anything more than speculation.