Pentcho Valev
2013-12-16 12:28:09 UTC
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Albert Einstein: "In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its result hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)."
Here Einstein deliberately confuses two meanings of "constancy of the velocity of light":
1. If the gravitational field is removed, the velocity of light stops varying with position and in this sense remains constant. But this constancy has nothing to do with "the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity".
2. "The constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity" implies that the velocity ("speed" would be more exact) of light relative to the observer does not vary with (is independent of) the speed of the observer. Yet it is easy to show that, if in a gravitational field the velocity of light "varies with position", then, in gravitation-free space, it varies with the speed of the observer.
Conclusion: What "we might think" is true: As a consequence of the fact that, in a gravitational field, the velocity of light "varies with position", the special theory of relativity and with it the whole theory of relativity is laid in the dust.
Pentcho Valev
Albert Einstein: "In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its result hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)."
Here Einstein deliberately confuses two meanings of "constancy of the velocity of light":
1. If the gravitational field is removed, the velocity of light stops varying with position and in this sense remains constant. But this constancy has nothing to do with "the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity".
2. "The constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity" implies that the velocity ("speed" would be more exact) of light relative to the observer does not vary with (is independent of) the speed of the observer. Yet it is easy to show that, if in a gravitational field the velocity of light "varies with position", then, in gravitation-free space, it varies with the speed of the observer.
Conclusion: What "we might think" is true: As a consequence of the fact that, in a gravitational field, the velocity of light "varies with position", the special theory of relativity and with it the whole theory of relativity is laid in the dust.
Pentcho Valev