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On the other hand, in 1912 the Finnish mathematician Karl Fritiof Sundman proved that there exists a series solution in powers of t1/3 for the 3-body problem.[6] This series converges for all real t, except for initial conditions corresponding to zero angular momentum. (In practice the latter restriction is insignificant since such initial conditions are rare, having Lebesgue measure zero.)

On the other hand, in 1912 the Finnish mathematician Karl Fritiof Sundman proved that there exists a series solution in powers of t1/3 for the 3-body problem.[6] This series converges for all real t, except for initial conditions corresponding to zero angular momentum. (In practice the latter restriction is insignificant since such initial conditions are rare, having Lebesgue measure zero.)

另一方面，1912年芬兰数学家**Karl Fritiof Sundman**证明了三体问题存在一个 {{math|''t''^1/3}}幂次方的级数解。除了对应于角动量为零的初始条件外，这个级数对所有实数t都收敛。

另一方面，1912年芬兰数学家 卡尔·弗里蒂奥夫·桑德曼 Karl Fritiof Sundman 证明了三体问题存在一个 {{math|''t''^1/3}}幂次方的级数解。除了对应于角动量为零的初始条件外，这个级数对所有实数t都收敛。

An important issue in proving this result is the fact that the radius of convergence for this series is determined by the distance to the nearest singularity. Therefore, it is necessary to study the possible singularities of the 3-body problems. As it will be briefly discussed below, the only singularities in the 3-body problem are binary collisions (collisions between two particles at an instant) and triple collisions (collisions between three particles at an instant).

An important issue in proving this result is the fact that the radius of convergence for this series is determined by the distance to the nearest singularity. Therefore, it is necessary to study the possible singularities of the 3-body problems. As it will be briefly discussed below, the only singularities in the 3-body problem are binary collisions (collisions between two particles at an instant) and triple collisions (collisions between three particles at an instant).

Unfortunately, the corresponding series converges very slowly. That is, obtaining a value of meaningful precision requires so many terms that this solution is of little practical use. Indeed, in 1930, David Beloriszky calculated that if Sundman's series were to be used for astronomical observations, then the computations would involve at least 108000000 terms.[7]

Unfortunately, the corresponding series converges very slowly. That is, obtaining a value of meaningful precision requires so many terms that this solution is of little practical use. Indeed, in 1930, David Beloriszky calculated that if Sundman's series were to be used for astronomical observations, then the computations would involve at least 108000000 terms.[7]

但不幸运的是，对应的级数收敛得非常慢。也就是说，为了获得一定精度的值需要很多级数项，这样的解法并没有什么实际用途。的确，在1930年，David Beloriszky计算出，如果将Sundman级数用于天文观测，则计算将至少涉及10^{{{val|8000000}}}项。

但不幸运的是，对应的级数收敛得非常慢。也就是说，为了获得一定精度的值需要很多级数项，这样的解法并没有什么实际用途。的确，在1930年，大卫·贝洛里奇 David Beloriszky计算出，如果将Sundman级数用于天文观测，则计算将至少涉及10^{{{val|8000000}}}项。

==特殊的求解方法==

==特殊的求解方法==

In 1767, Leonhard Euler found three families of periodic solutions in which the three masses are collinear at each instant. See Euler's three-body problem.

In 1767, Leonhard Euler found three families of periodic solutions in which the three masses are collinear at each instant. See Euler's three-body problem.

1767年，**Leonhard Euler**提出了三个周期解系列，其中三个质量在每个瞬间共线。

1767年， 莱昂哈德·欧拉 Leonhard Euler提出了三个周期解系列，其中三个质量在每个瞬间共线。

1772年，拉格朗日（Lagrange）找到了一系列解，其中三个质量在每个瞬间形成一个等边三角形。这些解决方案与Euler的共线解一起构成了三体问题的中心配置。这些解决方案对于任何质量比均有效，并且质量沿开普勒椭圆形运动。这四个族是唯一有明确解析公式的已知解决方案。在圆形受限三体问题的特殊情况下，这些解决方案在与原边一起旋转的框架中观察时，变为称为L₁, L₂, L₃, L₄和L₅，并且叫做拉格朗日点，其中L₃, L₄是拉格朗日的对称解的实例。

1772年，拉格朗日 Lagrange找到了一系列解，其中三个质量在每个瞬间形成一个等边三角形。这些解决方案与欧拉的共线解一起构成了三体问题的中心配置。这些解决方案对于任何质量比均有效，并且质量沿开普勒椭圆形运动。这四个族是唯一有明确解析公式的已知解决方案。在圆形受限三体问题的特殊情况下，这些解决方案在与原边一起旋转的框架中观察时，变为称为L₁, L₂, L₃, L₄和L₅，并且叫做拉格朗日点，其中L₃, L₄是拉格朗日的对称解的实例。

在1892年至1899年的工作中，**Henri Poincaré**建立了无穷有限三体问题的周期解，以及将这些解法继续推广到一般三体问题的技巧。

在1892年至1899年的工作中，亨利·波因加 Henri Poincaré建立了无穷有限三体问题的周期解，以及将这些解法继续推广到一般三体问题的技巧。

1893年，迈塞尔提出了现在所说的毕达哥拉斯三体问题：将比例为3：4：5的三个质量置于3：4：5直角三角形的顶点处。Burrau在1913年进一步研究了这个问题。1967年，Victor Szebehely和C. Frederick Peters利用数值积分理论建立了这个问题的最终逃逸模型，同时找到了附近的周期解。

1893年，迈塞尔提出了现在所说的毕达哥拉斯三体问题：将比例为3：4：5的三个质量置于3：4：5直角三角形的顶点处。布鲁 Burrau在1913年进一步研究了这个问题。1967年，维克多·塞贝赫利 Victor Szebehely和 C、 弗雷德里克·彼得斯 C. Frederick Peters利用数值积分理论建立了这个问题的最终逃逸模型，同时找到了附近的周期解。

20世纪70年代，**Michel Hénon**和 '''Roger A. Broucke'''各自找到了一套解决方案，这些解决方案构成了同一系列解决方案的一部分: Broucke–Henon–Hadjidemetriou族。在这个家族中，这三个物体都具有相同的质量，可以表现出逆行和直行两种形式。在、Broucke的一些解中，两个物体遵循同样的路径。

20世纪70年代，米歇尔·赫农 Michel Hénon和 罗杰A.布鲁克 Roger A. Broucke各自找到了一套解决方案，这些解决方案构成了同一系列解决方案的一部分: 布鲁克-赫农-哈德吉德梅特里奥

1993年，[[圣塔菲研究所]]的物理学家'''Cris Moore'''提出了一种零角动量解，该解适用于三个相等质量围绕一个八字形运动。这种方法在2000年由数学家'''Alain Chenciner'''和'''Richard Montgomery'''证明。在数值上证明了该解对于质量和轨道参数的小扰动是稳定的，这增加了在物理宇宙中可以观察到这种轨道的可能性。但有人认为不太可能发生这种情况，因为稳定​​性的范围小。例如，1993年，圣达菲研究所的物理学家克里斯·摩尔（Cris Moore）在数字上发现了一个零角动量解，该解的三个相等质量围绕一个八字形运动。[12]它的正式存在后来在2000年由数学家Alain Chenciner和Richard Montgomery 证明。[13] [14]在数值上证明了该解对于质量和轨道参数的小扰动是稳定的，这增加了在物理宇宙中可以观察到这种轨道的可能性。但是，由于稳定​​性的范围小，因此不太可能发生这种情况。例如，二元-二元散射事件导标号-8轨道的概率估计为1%的一小部分。

1993年，[[圣塔菲研究所]]的物理学家克里斯摩尔 Cris Moore提出了一种零角动量解，该解适用于三个相等质量围绕一个八字形运动。这种方法在2000年由数学家'''阿兰·契纳 Alain Chenciner'''和'''理查德·蒙哥马利 Richard Montgomery'''证明。在数值上证明了该解对于质量和轨道参数的小扰动是稳定的，这增加了在物理宇宙中可以观察到这种轨道的可能性。但有人认为不太可能发生这种情况，因为稳定​​性的范围小。例如，1993年，圣达菲研究所的物理学家克里斯·摩尔在数字上发现了一个零角动量解，该解的三个相等质量围绕一个八字形运动。[12]它的正式存在后来在2000年由数学家Alain Chenciner和Richard Montgomery 证明。[13] [14]在数值上证明了该解对于质量和轨道参数的小扰动是稳定的，这增加了在物理宇宙中可以观察到这种轨道的可能性。但是，由于稳定​​性的范围小，因此不太可能发生这种情况。例如，二元-二元散射事件导标号-8轨道的概率估计为1%的一小部分。

In 2013, physicists Milovan Šuvakov and Veljko Dmitrašinović at the Institute of Physics in Belgrade discovered 13 new families of solutions for the equal-mass zero-angular-momentum three-body problem.

In 2013, physicists Milovan Šuvakov and Veljko Dmitrašinović at the Institute of Physics in Belgrade discovered 13 new families of solutions for the equal-mass zero-angular-momentum three-body problem.

2013年，贝尔格莱德物理研究所的物理学家Milovan uvakov 和 Veljko dmitra inovi 发现了等质量零角动量三体问题的13种新的解族。

2013年，贝尔格莱德物理研究所的物理学家 米洛万·乌瓦科夫 Milovan uvakov 和 维利科·德米特拉·伊诺维 Veljko dmitra inovi 发现了等质量零角动量三体问题的13种新的解族。

In 2015, physicist Ana Hudomal discovered 14 new families of solutions for the equal-mass zero-angular-momentum three-body problem.

In 2015, physicist Ana Hudomal discovered 14 new families of solutions for the equal-mass zero-angular-momentum three-body problem.

2015年，物理学家 Ana Hudomal 发现了14种等质量零角动量三体问题的新解族。

2015年，物理学家 安娜·胡多马尔 Ana Hudomal 发现了14种等质量零角动量三体问题的新解族。

In 2017, researchers Xiaoming Li and Shijun Liao found 669 new periodic orbits of the equal-mass zero-angular-momentum three-body problem.[17] This was followed in 2018 by an additional 1223 new solutions for a zero-momentum system of unequal masses.[18]

In 2017, researchers Xiaoming Li and Shijun Liao found 669 new periodic orbits of the equal-mass zero-angular-momentum three-body problem.[17] This was followed in 2018 by an additional 1223 new solutions for a zero-momentum system of unequal masses.[18]

2017年，研究人员Xiaoming Li 和Shijun Liao发现了669个等质量零角动量三体问题的新周期轨道。2018年，不等质量的零动量系统又增加了1223个新解。

2017年，研究人员 李晓明 Xiaoming Li 和 廖世俊 Shijun Liao发现了669个等质量零角动量三体问题的新周期轨道。2018年，不等质量的零动量系统又增加了1223个新解。

In 2018, Li and Liao reported 234 solutions to the unequal-mass "free-fall" three body problem.[19] The free fall formulation of the three body problem starts with all three bodies at rest. Because of this, the masses in a free-fall configuration do not orbit in a closed "loop", but travel forwards and backwards along an open "track".

In 2018, Li and Liao reported 234 solutions to the unequal-mass "free-fall" three body problem.[19] The free fall formulation of the three body problem starts with all three bodies at rest. Because of this, the masses in a free-fall configuration do not orbit in a closed "loop", but travel forwards and backwards along an open "track".

===数值方法===

===数值方法===

Using a computer, the problem may be solved to arbitrarily high precision using numerical integration although high precision requires a large amount of CPU time. In 2019, Breen et al. announced a fast neural network solver, trained using a numerical integrator.[20]

Using a computer, the problem may be solved to arbitrarily high precision using numerical integration although high precision requires a large amount of CPU time. In 2019, Breen et al. announced a fast neural network solver, trained using a numerical integrator.[20]

==历史==

==历史==

The gravitational problem of three bodies in its traditional sense dates in substance from 1687, when Isaac Newton published his Principia (Philosophiæ Naturalis Principia Mathematica). In Proposition 66 of Book 1 of the Principia, and its 22 Corollaries, Newton took the first steps in the definition and study of the problem of the movements of three massive bodies subject to their mutually perturbing gravitational attractions. In Propositions 25 to 35 of Book 3, Newton also took the first steps in applying his results of Proposition 66 to the lunar theory, the motion of the Moon under the gravitational influence of the Earth and the Sun.

The gravitational problem of three bodies in its traditional sense dates in substance from 1687, when Isaac Newton published his Principia (Philosophiæ Naturalis Principia Mathematica). In Proposition 66 of Book 1 of the Principia, and its 22 Corollaries, Newton took the first steps in the definition and study of the problem of the movements of three massive bodies subject to their mutually perturbing gravitational attractions. In Propositions 25 to 35 of Book 3, Newton also took the first steps in applying his results of Proposition 66 to the lunar theory, the motion of the Moon under the gravitational influence of the Earth and the Sun.

The physical problem was addressed by Amerigo Vespucci and subsequently by Galileo Galilei; in 1499, Vespucci used knowledge of the position of the Moon to determine his position in Brazil. It became of technical importance in the 1720s, as an accurate solution would be applicable to navigation, specifically for the determination of longitude at sea, solved in practice by John Harrison's invention of the marine chronometer. However the accuracy of the lunar theory was low, due to the perturbing effect of the Sun and planets on the motion of the Moon around the Earth.

The physical problem was addressed by Amerigo Vespucci and subsequently by Galileo Galilei; in 1499, Vespucci used knowledge of the position of the Moon to determine his position in Brazil. It became of technical importance in the 1720s, as an accurate solution would be applicable to navigation, specifically for the determination of longitude at sea, solved in practice by John Harrison's invention of the marine chronometer. However the accuracy of the lunar theory was low, due to the perturbing effect of the Sun and planets on the motion of the Moon around the Earth.

Amerigo Vespucci和随后的Galileo Galilei提出了三体问题; 1499年，Vespucci利用对月球位置的了解来确定自己在巴西的位置。因为这种方法适用于导航，特别是在海上确定经度，1720年代该方法变得非常技术实用。事实上确定经度的问题被John Harrison发明的航海经线仪所解决。但是，由于太阳和行星对月球绕地球运动的干扰作用，月球理论的准确性很低。

亚美利哥·韦斯普奇 Amerigo Vespucci和随后的 伽利略·伽利雷 Galileo Galilei提出了三体问题; 1499年，韦斯普奇 Vespucci利用对月球位置的了解来确定自己在巴西的位置。因为这种方法适用于导航，特别是在海上确定经度，1720年代该方法变得非常技术实用。事实上确定经度的问题被 约翰·哈里森 John Harrison发明的航海经线仪所解决。但是，由于太阳和行星对月球绕地球运动的干扰作用，月球理论的准确性很低。

Jean le Rond d'Alembert and Alexis Clairaut, who developed a longstanding rivalry, both attempted to analyze the problem in some degree of generality; they submitted their competing first analyses to the Académie Royale des Sciences in 1747.[21] It was in connection with their research, in Paris during the 1740s, that the name "three-body problem" (French: Problème des trois Corps) began to be commonly used. An account published in 1761 by Jean le Rond d'Alembert indicates that the name was first used in 1747.

Jean le Rond d'Alembert and Alexis Clairaut, who developed a longstanding rivalry, both attempted to analyze the problem in some degree of generality; they submitted their competing first analyses to the Académie Royale des Sciences in 1747.[21] It was in connection with their research, in Paris during the 1740s, that the name "three-body problem" (French: Problème des trois Corps) began to be commonly used. An account published in 1761 by Jean le Rond d'Alembert indicates that the name was first used in 1747.

建立了长期竞争关系的Jean le Rond d'Alembert和Alexis Clairaut都试图以某种普遍性来分析该问题。他们于1747年向皇家科学研究院提交了他们的第一批竞争分析。在1740年代的巴黎，“三体问题”（法语：Problèmedes trois Corps）这个名字开始被普遍使用，与他们的研究有关。Jean le Rond d'Alembert于1761年发布的文章表明该名称最早于1747年使用。

建立了长期竞争关系的 让·勒朗·达朗贝尔 Jean le Rond d'Alembert 和 亚历克西斯·克莱奥特 Alexis Clairaut都试图以某种普遍性来分析该问题。他们于1747年向皇家科学研究院提交了他们的第一批竞争分析。在1740年代的巴黎，“三体问题”（法语：Problèmedes trois Corps）这个名字开始被普遍使用，与他们的研究有关。让·勒朗·达朗贝尔 Jean le Rond d'Alembert于1761年发布的文章表明该名称最早于1747年使用。