On the compatibility between the ether hypothesis and Einstein's definition of simultaneity
论以太假定与爱因斯坦同时性定义的兼容性

摘要

狭义相对论所遗留下来的最大问题在于：晚期的爱因斯坦明确承认存在作为光速媒介的以太，并称之为“广义相对论以太”，并且明确宣称以太假定与狭义相对论不矛盾，但是爱因斯坦并没有通过其对于狭义相对论的修正做到这一点。仔细分析爱因斯坦狭义相对论的原始理论可以发现：爱因斯坦对于同时性的定义可以被重新理解为与以太假定不矛盾：爱因斯坦在其最初论文中，通过对于同时性的定义实际上可以理解为定义了特殊的真空以太坐标系，并与绝对运动系相区别，如此才能合乎逻辑地理解同时性的相对性问题。但爱因斯坦一生对于同时性的定义共有三个不同的表述，有不同的和互相区别的内涵，其中第一个同时性定义只能被理解为是与以太假定一致的，其余的同时性定义并非如此。如果我们要将爱因斯坦的这三个同时性定义理解为是一致的和有意义的，必须将洛伦兹变换重新建立在以太假定的基础上才有可能。通过笔者给出洛伦兹变换的新推导方式，更清晰地实现了这个目标，或展现了新的物理图像。在这个物理图像中，洛伦兹变换涉及的两个参照系都可以被理解为是真空以太系，因为对于它们都定义了相对于以太的光速不变，但是当其中的任何一个参照系被理解为是真空以太系的时候，另一个系就必须是绝对运动系，这样的理解也与爱因斯坦的初衷一致：即洛伦兹变换涉及的两个参照系都可以符合同时性定义。但是，这种理解还需要补充解释才是恰当的：两个参照系不能同时符合同时性定义，当其中一个系被理解为符合同时性定义的时候，另一个系必然不符合同时性定义。这样理解的逻辑合理性在洛伦兹变换的新推导方式中清晰显示出来：即不能将光速看作是沿着X轴传播的同一束光，而应当将光速看作是两束，分别沿着两个参照系的Y轴和Y'轴传播。这样理解的洛伦兹变换就摆脱了光速相对于任意参照系的不变性，而只剩余相对于以太系的不变性。这样得到的洛伦兹变换就被重新置于以太假定的基础之上，于是我们也就完成了对于狭义相对论解释的范式转换，为获得更强的狭义相对论的逻辑自洽性奠定了基础。最后通过分析区分爱因斯坦没有区别的时间的同时性与同步性所造成的问题，得出的结论是：狭义相对论的相对时间观不需要否定牛顿的绝对时间观，而只是补充了绝对时间观：牛顿的绝对时间观与狭义相对论的时间观的关系其实是如同光速不变与光速的周期可变那样的关系。

Abstract

The most significant problem left unresolved by special relativity is this: In his later years, Einstein explicitly acknowledged the existence of an ether as the medium for light speed, which he termed the "general relativistic ether," and categorically declared that the ether assumption does not contradict special relativity. However, Einstein never achieved this through his modifications to special relativity. A careful analysis of Einstein's original theory of special relativity reveals that his definition of simultaneity can be reinterpreted as being consistent with the ether assumption. In his seminal paper, Einstein's definition of simultaneity can in fact be understood as defining a special vacuum ether coordinate system, distinct from absolute motion systems—only through such an interpretation can the relativity of simultaneity be logically comprehended. Yet throughout his life, Einstein presented three different formulations of simultaneity with distinct and separate connotations. The first formulation can only be understood as consistent with the ether assumption; the remaining formulations are not so. If we are to interpret these three definitions of simultaneity as consistent and meaningful, the Lorentz transformation must be reconstructed on the foundation of the ether assumption. Through the author's novel derivation of the Lorentz transformation, this goal is more clearly achieved, revealing a new physical picture. In this picture, both reference frames involved in the Lorentz transformation can be understood as vacuum ether systems, since for each the invariance of light speed relative to the ether is defined. However, when either reference frame is understood as the vacuum ether system, the other must necessarily be an absolute motion system. This interpretation aligns with Einstein's original intention: that both reference frames in the Lorentz transformation can satisfy the definition of simultaneity. Nevertheless, this understanding requires supplemental clarification to be appropriate: Both reference frames cannot simultaneously satisfy the definition of simultaneity. When one frame is understood to satisfy it, the other necessarily does not. The logical validity of this interpretation becomes evident in the new derivation of the Lorentz transformation: Light speed cannot be regarded as a single beam propagating along the X-axis, but must be considered as two beams propagating along the Y-axis and Y'-axis of the two reference frames, respectively. The Lorentz transformation thus understood sheds the invariance of light speed relative to arbitrary reference frames, retaining only invariance relative to the ether system. The resulting Lorentz transformation is thereby reestablished on the foundation of the ether assumption, completing a paradigm shift in the interpretation of special relativity and laying the groundwork for achieving greater logical self-consistency. Finally, by analyzing the problems arising from Einstein's failure to distinguish between temporal simultaneity and synchronization, we conclude that special relativity's relativistic concept of time does not necessitate rejecting Newton's absolute time concept, but merely supplements it. The relationship between Newton's absolute time and special relativity's time concept is actually analogous to the relationship between the invariance of light speed and the variability of light's period.