# Difference between revisions of "Einstein:Book chapter 04 - The Galileian System of Co-Ordinates"

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==4: The Galileian System of Co-Ordinates== | ==4: The Galileian System of Co-Ordinates== | ||

− | <p class="NOINDENT">{{Boldword|A|S}} is well known, the fundamental law of the mechanics of < | + | <p class="NOINDENT">{{Boldword|A|S}} is well known, the fundamental law of the mechanics of <span class="PERSON">Galilei</person>-<span class="PERSON">Newton</person>, which is known as the ''law of inertia'', can be stated thus:</p> |

− | A body removed sufficiently far from other bodies continues in a state of rest or of uniform motion in a straight line. This law not only says something about the motion of the bodies, but it also indicates the reference-bodies or systems of co-ordinates, permissible in mechanics, which can be used in mechanical description. The visible fixed stars are bodies for which the law of inertia certainly holds for a high degree of approximation. Now if we use a system of co-ordinates which is rigidly attached to the earth, then, relative to this system, every fixed star describes a circle of immense radius in the course of an astronomical day, a result which is opposed to the statement of the law of inertia. So that if we adhere to this law we must refer these motions only to systems of co-ordinates relative to which the fixed stars do not move in a circle. A system of co-ordinates of which the state of motion is such that the law of inertia holds relative to it is called a "Galileian system of coordinates." The laws of the mechanics of < | + | A body removed sufficiently far from other bodies continues in a state of rest or of uniform motion in a straight line. This law not only says something about the motion of the bodies, but it also indicates the reference-bodies or systems of co-ordinates, permissible in mechanics, which can be used in mechanical description. The visible fixed stars are bodies for which the law of inertia certainly holds for a high degree of approximation. Now if we use a system of co-ordinates which is rigidly attached to the earth, then, relative to this system, every fixed star describes a circle of immense radius in the course of an astronomical day, a result which is opposed to the statement of the law of inertia. So that if we adhere to this law we must refer these motions only to systems of co-ordinates relative to which the fixed stars do not move in a circle. A system of co-ordinates of which the state of motion is such that the law of inertia holds relative to it is called a "Galileian system of coordinates." The laws of the mechanics of <span class="PERSON">Galilei</person>-<span class="PERSON">Newton</person> can be regarded as valid only for a Galileian system of co-ordinates. |

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## Revision as of 20:22, 8 July 2016

Albert Einstein: **Relativity: The Special and the General Theory**

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## 4: The Galileian System of Co-Ordinates

**AS** is well known, the fundamental law of the mechanics of Galilei</person>-Newton</person>, which is known as the *law of inertia*, can be stated thus:</p>
A body removed sufficiently far from other bodies continues in a state of rest or of uniform motion in a straight line. This law not only says something about the motion of the bodies, but it also indicates the reference-bodies or systems of co-ordinates, permissible in mechanics, which can be used in mechanical description. The visible fixed stars are bodies for which the law of inertia certainly holds for a high degree of approximation. Now if we use a system of co-ordinates which is rigidly attached to the earth, then, relative to this system, every fixed star describes a circle of immense radius in the course of an astronomical day, a result which is opposed to the statement of the law of inertia. So that if we adhere to this law we must refer these motions only to systems of co-ordinates relative to which the fixed stars do not move in a circle. A system of co-ordinates of which the state of motion is such that the law of inertia holds relative to it is called a "Galileian system of coordinates." The laws of the mechanics of Galilei</person>-Newton</person> can be regarded as valid only for a Galileian system of co-ordinates.
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