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Olbers' paradox, described by the German astronomer Heinrich Wilhelm Olbers in 1826 and earlier by Johannes Kepler in 1610 and Halley and Cheseaux in the 18th century, is the paradoxical observation that the night sky is dark, when in a static infinite universe the night sky ought to be bright. This is sometimes also known as the "dark night sky paradox". An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ...
Categories: Astronomers stubs | 1758 births | 1840 deaths | German astronomers | German physicists | Lists of asteroids ...
The oldest surviving photograph, Nicéphore Niépce, circa 1826 1826 (MDCCCXXVI) was a common year starting on Sunday (see link for calendar) of the Gregorian calendar (or a common year starting on Tuesday of the 12-day-slower Julian calendar). ...
Johannes Kepler Johannes Kepler (December 27, 1571 – November 15, 1630), a key figure in the scientific revolution, was a German mathematician, astrologer, astronomer, and an early writer of science fiction stories. ...
// Events January 7 - Galileo Galilei discovers the Galilean moons of Jupiter. ...
Edmond Halley (sometimes Edmund, October 29, 1656 – January 14, 1742) was an English astronomer, geophysicist, mathematician, meteorologist, and physicist. ...
Categories: Astronomers stubs | Swiss astronomers | 1718 births | 1751 deaths ...
(17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ...
A physical paradox is an apparent contradiction relating to physical descriptions of the universe. ...
Infinity refers to several distinct concepts which arise in theology, philosophy, mathematics and everyday life. ...
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Assumptions
If the universe is assumed to be infinite, containing an infinite number of uniformly distributed luminous stars, then every line of sight should terminate eventually on the surface of a star. The brightness of a surface is independent of its distance, so every point in the sky should be as bright as the surface of a star. The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ...
For stars to appear "uniformly distributed" in space they must also be uniformly distributed in time, because the further away one looks, the older is what one sees. On an infinite scale, this means the universe must be infinitely old with no dramatic changes in the nature of stars in that time.
Kepler saw this as an argument for a finite universe, or at least for a finite number of stars, but the argument is not convincing, as will be shown below.
Explanations One explanation attempt is that the universe is not transparent, and the light from distant stars is blocked by intermediate dark stars or absorbed by dust or gas, so that there is a bound on the distance from which light can reach the observer. However, this reasoning does not resolve the paradox. According to the first law of thermodynamics, energy must be conserved, so the intermediate matter would heat up and soon reradiate the energy (possibly at different wavelengths). This would again result in uniform radiation from all directions, which is not observed. This article needs to be updated. ...
The first law of thermodynamics, a generalized expression of the law of the conservation of energy, states: the increase in the internal energy of a system is equal to the amount of energy added to the system by heating, plus the amount added in the form of work done on...
The explanation of the paradox to gain the most scientific consensus points to the finite speed at which light travels through space. Given its finite speed, the light from the most distant star cannot have travelled a further distance, measured in light years, than the star itself is old. This explanation was first offered in 1848 by poet and writer Edgar Allan Poe, who observed: A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ...
1848 is a leap year starting on Saturday of the Gregorian calendar. ...
This daguerreotype of Poe was taken less than a year before his death at the age of 40. ...
- "Were the succession of stars endless, then the background of the sky would present us an uniform luminosity, like that displayed by the Galaxy -–since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all."[1]
Holding the universe to be approximately 13.7 billion years old, the furthest expanse that light could have possibly travelled since its creation is an equal number of light years. Thus, even if every infinite trajectory into space from the earth eventually passes through a star in the farthest regions of the universe, the light of all such stars beyond the maximum distance in which light has travelled since the origin of the universe will remain beyond visibility from earth. yes indeed.
Resolutions The paradox is resolvable in a variety of ways.
If the universe has existed for only a finite amount of time, as the prevalent Big Bang theory holds, then only the light of finitely many stars has had a chance to reach us yet, and the paradox breaks down. Alternatively, if the universe is expanding and distant stars are receding from us (also a claim of the Big Bang theory), then their light is redshifted which diminishes their brightness, again resolving the paradox. Either effect alone would resolve the paradox, but according to the Big Bang theory, both are working together, although the finiteness of time is the more important effect. Some see the darkness of the night sky to be evidence in support of the Big Bang theory. According to the Big Bang theory, the universe emerged from an extremely dense and hot state (bottom). ...
Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared to that of the Sun (left). ...
According to the Big Bang theory, the universe originated in an infinitely dense and physically paradoxical singularity. ...
Even without the Big Bang theory and its redshift evidence, we may establish the finite age of the universe (in its present form) by a mathematical evaluation of hydrogen. Assume that the amount of mass in stars divided by the total amount of mass in the universe is nonzero. After some length of time, any given star will convert too much hydrogen into helium (or heavier elements) to continue nuclear fusion. From this we conclude that in unit time, the amount of hydrogen converted into helium by a given star divided by the star's mass is nonzero. Combining this with the earlier statement, we conclude that the amount of hydrogen converted into helium by stars as a whole divided by the mass of the universe is nonzero. There is no known process that can return heavier elements to hydrogen in the necessary quantities, and any would probably violate the second law of thermodynamics. Therefore, the amount of time needed for stars to convert all of the hydrogen in the universe into helium is finite, and it will never change back. After this, only heavier-element-burning stars will exist (and these will die when they hit iron, an event known as the heat death of the universe). This hasn't happened yet, so either the universe is of finite age, it has undergone major changes in its history, or there exists some highly exotic process (for which no direct evidence exists) that produces hydrogen to keep it going. Italic textLink titleLink titlelink titlelink titleBold text General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...
The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ...
Thermodynamics (from the Greek thermos meaning heat and dynamis meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ...
General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ...
The heat death is a possible final state of the universe, in which it has reached maximum entropy. ...
A different resolution, which does not rely on the Big Bang theory, was offered by Benoit Mandelbrot. It holds that the stars in the universe may not be uniformly distributed, but rather fractally like a Cantor dust, thus accounting for large dark areas. It is currently not known whether this is true or not, although recent satellite studies have found the cosmic microwave background radiation is isotropic to 1 part in 10000. Beno t Mandelbrot was the first to use a computer to plot the Mandelbrot set. ...
The boundary of the Mandelbrot set is a famous example of a fractal. ...
Cantor dust, named after the mathematician Georg Cantor, is the two-dimensional version of the Cantor set. ...
In cosmology, the cosmic microwave background radiation (most often abbreviated CMB but occasionally CMBR, CBR or MBR) is a form of electromagnetic radiation discovered in 1965. ...
Isotropy (the opposite of anisotropy) is the property of being independent of direction. ...
There are dim stars, light absorbing gases, and light pollution. Only the brightest stars actually make it through the atmosphere and are visible.
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