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Sunday, July 2

  1. page home edited Historical physics papers The purpose of this Wiki is to provide on-line translations of a few…

    Historical physics papers

    The purpose of this Wiki is to provide on-line translations of a few historical physics papers into English. In addition, I will add a few in-text links to appropriate reference sites. Talk pages may be used for short commentaries.
    As for now, anyone is allowed to improve and add texts, and this is even strongly encouraged.
    (view changes)
    1:39 am

Tuesday, September 20

  1. page Langevin1911 edited ... One may call pairs in space, the pairs of events [45] that have just been considered, whose se…
    ...
    One may call pairs in space, the pairs of events [45] that have just been considered, whose sequence in time has no absolute sense, but which, in an absolute manner, are distant in space.
    It is noteworthy that, if the spatial distance between two events can not be canceled, it reaches a minimum precisely for reference systems with respect to which the two events are simultaneous.
    ds2**
    invariant
    (dx2
    ds2 = invariant = (dx2 + dy2
    ...
    dz2) - c2dt**2c2dt2
    Hence the following statement:
    The spatial distance between two events that are simultaneous for a certain group of observers is shorter for them than for all other observers that are in any motion with respect to them.
    (view changes)
    7:24 am
  2. page Langevin1911 edited ... One may call pairs in space, the pairs of events [45] that have just been considered, whose se…
    ...
    One may call pairs in space, the pairs of events [45] that have just been considered, whose sequence in time has no absolute sense, but which, in an absolute manner, are distant in space.
    It is noteworthy that, if the spatial distance between two events can not be canceled, it reaches a minimum precisely for reference systems with respect to which the two events are simultaneous.
    ds2 = invariant = (dx2ds2**
    invariant
    (dx2
    + dy2
    ...
    dz2) - c2dt2c2dt**2
    Hence the following statement:
    The spatial distance between two events that are simultaneous for a certain group of observers is shorter for them than for all other observers that are in any motion with respect to them.
    (view changes)
    7:22 am

Thursday, September 15

  1. page Langevin1911 edited ... -> Native English speakers, please help improve the style and word choice. Note: as is hab…
    ...
    -> Native English speakers, please help improve the style and word choice.
    Note: as is habitual in old English texts, the word vitesse is consistently rendered "velocity". "Ligne d'universe" is rendered "world line" and "lois du monde", "laws of the universe".
    ...
    add paragraph numbersnumbers, as well
    ...
    in bold face;face (colour #300fa3); thus note
    THE EVOLUTION OF SPACE
    AND TIME
    (view changes)
  2. page Langevin1911 edited ... This group differs profoundly from the preceding concerning the transformations of space and t…
    ...
    This group differs profoundly from the preceding concerning the transformations of space and time.
    [37] One must make a choice: if we want to maintain an absolute value to equations of rational mechanics, to mechanical processes, as well as the corresponding space and time, then we must regard as false those of electromagnetism, renounce the admirable synthesis that I mentioned here above, go back in optics to for example an emission theory, with all the difficulties that it entails and which led to its dismissal, you see, more than fifty years ago. If instead we want to keep electromagnetism, we must adapt our mind to the new concepts that it requires for space and time and consider rational mechanics as having no more value than as a first approximation, more than sufficient however when it concerns motions whose velocity does not exceed a few thousand kilometers per second. Only electromagnetism, or the laws of mechanics that admit the same transformation group as the first, allow us to go further and take the dominating place that mechanism assigned to rational mechanics.
    5 [The world according to the new mechanics contrasted with classical mechanics]
    The world according to classical mechanics
    To better highlight the opposition between the two syntheses, it is easier to merge, as proposed by Minkowski, the two concepts of "space" and "time" into the more general concept of "world".
    (view changes)
  3. page Langevin1911 edited ... This group differs profoundly from the preceding concerning the transformations of space and t…
    ...
    This group differs profoundly from the preceding concerning the transformations of space and time.
    [37] One must make a choice: if we want to maintain an absolute value to equations of rational mechanics, to mechanical processes, as well as the corresponding space and time, then we must regard as false those of electromagnetism, renounce the admirable synthesis that I mentioned here above, go back in optics to for example an emission theory, with all the difficulties that it entails and which led to its dismissal, you see, more than fifty years ago. If instead we want to keep electromagnetism, we must adapt our mind to the new concepts that it requires for space and time and consider rational mechanics as having no more value than as a first approximation, more than sufficient however when it concerns motions whose velocity does not exceed a few thousand kilometers per second. Only electromagnetism, or the laws of mechanics that admit the same transformation group as the first, allow us to go further and take the dominating place that mechanism assigned to rational mechanics.
    5 [The world according to the new mechanics contrasted with classical mechanics]
    The world according to classical mechanics

    To better highlight the opposition between the two syntheses, it is easier to merge, as proposed by Minkowski, the two concepts of "space" and "time" into the more general concept of "world".
    The world is the set of all events: an event consists in that it happens or that there is something in a certain place at a certain moment. Given a reference system, that is to say a system of axes linked to a certain group of observers, an event is determined in terms of its position in space and time by four coordinates related to this reference system, three for space and one for time.
    ...
    What one can thus realise for space, the coincidence of two events in space by means of a suitable choice of reference system, we have seen that one can not achieve that for time, since the time interval of two events has an absolute sense, is measured in the same way in all reference systems.
    One has there an asymmetry that is habitually made between space and time but which the new conceptions make disappear: the time interval, just like [41] the distance in space becomes variable with the reference system, with the motion of observers.
    The world according to the new mechanics
    In the new conceptions, a single case exists and must exist where the change of reference system is ineffective: it is where the two events coincide in both space and time: this double coincidence must in fact have an absolute sense since it corresponds to the encounter of the two events and from this encounter may well emerge a phenomenon, a new event, which necessarily has an absolute sense. Retaking the previous example, if the two objects that exit the car through the same hole, leave it simultaneously, if their releases coincide in both space and time, this can result in collision, a breaking of objects; and the phenomenon of collision has an absolute sense, so that in any conception of the universe (electromagnetic or mechanic), the coincidence in both space and time, if it exists for a group of observers, can not be denied by another group, regardless of its motion relative to the first. For those who see the car pass by as well as for those who find themselves in the car, the two objects will have broken each other because they passed at the same time at the same point.
    Except for this very special case, it is easy to see that the electromagnetic design requires a major overhaul of the concept of world. The equations of electromagnetism imply in their habitual form that an electromagnetic disturbance, a light wave for example, propagates in the vacuum with the same velocity in all directions, equal to about three hundred thousand kilometers per second.
    (view changes)
  4. page Langevin1911 edited ... One may call pairs in space, the pairs of events [45] that have just been considered, whose se…
    ...
    One may call pairs in space, the pairs of events [45] that have just been considered, whose sequence in time has no absolute sense, but which, in an absolute manner, are distant in space.
    It is noteworthy that, if the spatial distance between two events can not be canceled, it reaches a minimum precisely for reference systems with respect to which the two events are simultaneous.
    ...
    dz2) - dt2c2dt2
    Hence the following statement:
    The spatial distance between two events that are simultaneous for a certain group of observers is shorter for them than for all other observers that are in any motion with respect to them.
    (view changes)

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