Dear William,
One fallacy that is continuing for about a century is the notion that a light pulse has to bounce back from an object for its measurement and this disturbs the object. Measurement is a process of comparison between similars. You measure length by comparing it with the length of a scale. You measure area or volume or density by comparing it with the area or volume or density of suitable unit. Thus, light, which moves at a constant speed, can be used to measure only the speed of something by comparing its distance at some intervals through the reflected light. In all other cases it can be used only as an aid to ocular perception and not measurement. We see objects in their own or reflected light. To disturb the object, light pulse should have either mass or energy. Since photon is mass less, we can consider only its energy. But this energy is being applied to all - including the measuring device and the person doing the measurement. You may argue, the light pulses are different for the observer and the object of measurement. But then velocity of light being same, its effect will be same. When we measure something on Earth, we ignore the effects of gravitation, air pressure, etc, since it is common to all. Similarly, the light energy should be ignored as it is common to all. Otherwise we will land in problem.
For example, let us consider the measurement of length of a moving rod. Two possibilities of measurement suggested by Mr. Einstein in his 1905 paper were:
(a) "The observer moves together with the given measuring-rod and the rod to be measured, and measures the length of the rod directly by superposing the measuring-rod, in just the same way as if all three were at rest", or
(b) "By means of stationary clocks set up in the stationary system and synchronizing with a clock in the moving frame, the observer ascertains at what points of the stationary system the two ends of the rod to be measured are located at a definite time. The distance between these two points, measured by the measuring-rod already employed, which in this case is at rest, is the length of the rod"
The method described at (b) is misleading. We can do this only by setting up a measuring device to record the emissions from both ends of the rod at the designated time, (which is the same as taking a photograph of the moving rod) and then measure the distance between the two points on the recording device in units of velocity of light or any other unit. But the picture will not give a correct reading due to two reasons:
• If the length of the rod is small or velocity is small, then length contraction will not be perceptible according to the formula given by Einstein.
• If the length of the rod is big or velocity is comparable to that of light, then light from different points of the rod will take different times to reach the recording device and the picture we get will be distorted due to different Doppler shift. Thus, there is only one way of measuring the length of the rod as in (a).
Here also we are reminded of an anecdote relating to a famous scientist, who once directed two of his students to precisely measure the wave-length of sodium light. Both students returned with different results - one resembling the normally accepted value and the other a different value. Upon enquiry, the other student replied that he had also come up with the same result as the accepted value, but since everything including the Earth and the scale on it is moving, for precision measurement he applied length contraction to the scale treating the star Betelgeuse as a reference point. This changed the result. The scientist told him to treat the scale and the object to be measured as moving with the same velocity and recalculate the wave-length of light again without any reference to Betelgeuse. After sometime, both the students returned to tell that the wave-length of sodium light is infinite. To a surprised scientist, they explained that since the scale is moving with light, its length would shrink to zero. Hence it will require an infinite number of scales to measure the wave-length of sodium light!
Some scientists we have come across try to overcome this difficulty by pointing out that length contraction occurs only in the direction of motion. They claim that if we hold the rod in a transverse direction to the direction of motion, then there will be no length contraction. But we fail to understand how the length can be measured by holding the rod in a transverse direction. If the light path is also transverse to the direction of motion, then the terms c+v and c-v vanish from the equation making the entire theory redundant. If the observer moves together with the given measuring-rod and the rod to be measured, and measures the length of the rod directly by superposing the measuring-rod while moving with it, he will not find any difference because the length contraction, if real, will be in the same proportion for both.
The fallacy in the above description is that if one treats "as if all three were at rest", one cannot measure velocity or momentum, as the object will be relatively as rest, which means zero relative velocity. Either Mr. Einstein missed this point or he was clever enough to camouflage this, when, in his 1905 paper, he said: "Now to the origin of one of the two systems (k) let a constant velocity v be imparted in the direction of the increasing x of the other stationary system (K), and let this velocity be communicated to the axes of the co-ordinates, the relevant measuring-rod, and the clocks". But is this the velocity of k as measured from k, or is it the velocity as measured from K? This question is extremely crucial. K and k each have their own clocks and measuring rods, which are not treated as equivalent by Mr. Einstein. Therefore, according to his theory, the velocity will be measured by each differently. In fact, they will measure the velocity of k differently. But Mr. Einstein does not assign the velocity specifically to either system. Everyone missed it and all are misled. His spinning disk example in GR also falls for the same reason.
Mr. Einstein uses a privileged frame of reference to define synchronization and then denies the existence of any privileged frame of reference. We quote from his 1905 paper on the definition of synchronization: "Let a ray of light start at the "A time" tA from A towards B, let it at the "B time" tB be reflected at B in the direction of A, and arrive again at A at the "A time" t'A. In accordance with definition the two clocks synchronize if: tB - tA = t'A - tB."
"We assume that this definition of synchronism is free from contradictions, and possible for any number of points; and that the following relations are universally valid:--
1. If the clock at B synchronizes with the clock at A, the clock at A synchronizes with the clock at B.
2. If the clock at A synchronizes with the clock at B and also with the clock at C, the clocks at B and C also synchronize with each other."
The concept of relativity is valid only between two objects. Introduction of a third object brings in the concept of privileged frame of reference and all equations of relativity fall. Yet, Mr. Einstein precisely does the same while claiming the very opposite. In the above description, the clock at A is treated as a privileged frame of reference for proving synchronization of the clocks at B and C. Yet, he claims it is relative!
There are similar fallacies in the principle of equivalence that gives rise to the Russell's paradox of set theory. Hence, in your formative years, please do not believe whatever is taught to you. Apply your intelligence to understand the concept logically. Otherwise question it irrespective of who proposed it.
God bless you.
basudeba