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Time dilation
is not due to uniform motion.
by John Doan
According to Einstein, when an object travels in high speed, its time would slow down due to an effect called time dilation. Everyone hears about it, knows all about it.
If I ask whether time dilation can be seen on clocks when they're brought back after the trip and compared to other stationary ones, everyone would say yes, of course. But the fact is, among those scientists who agreed with Einstein and wrote books explaining Einstein's time dilation to general readers, there're some who say no. Some say no, we can never see it on real clocks. Some say yes, we can. And some say nothing simply because they're scared to interpret it. Here is a sample of my imaginary Interview with Einstein:
....
Einstein said,
"I couldn't believe it. And they're those who claim they understand my theory?"
"Yes. They agree with you. They all say your theory is beautiful and correct and they try to explain so general readers can understand it. And I can't understand it. I feel like I'm cheated as I don't know whose relativity theory they try to show. My first impression was all Relativity books agreed that a traveling clock actually runs slower which shows on its reading after the trip, when compared to another stationary clock. That's what my teacher taught me in Year 12. And I believe most general readers think like me. But when I read again carefully, I find that they don't actually mean it. Many books even ignore that point, as if they were scared of it, and let readers misinterpret whatever they want (let's call it the first group). Only a few books specifically say about clocks reading, and when they do say, they say opposite things. One group says both clocks must show the same reading after the trip (let's call it the second group) and another group (let's call it the third group) claims the two clocks must show different readings after the trip."
"Show me."
9. "I'll give you three examples that three different authors (in the second group) suggest clocks readings always are same at rest, or interpreted that way by general reader.
In the textbook Physics, 1989 revised version, written by Prof. Richard Weidner of Rutgers University, the author explains how this time dilation equation drawn (page 868):
'This is the fundamental timedilation equation. Keeping straight the meaning of the terms in it is crucial. The time interval T_{o} is between two events that occur at the same location and are measured on the clock of an observer at rest at this location; T_{o} is termed the proper time (or rest time). On the other hand, T is the time interval between the very same two events but registered on the clock of an observer traveling at the speed of v relative to the location at which the two events take place (and who therefore sees the two events take place at different locations in his reference frame). Of course, the clocks of the two observers when compared at rest with respect to one another give identical readings.'
In another book Relativity written by Prof. Gerald Tauber in 1988, the author also used the same experiment with two identical clocks of light pulse to explain that clocks appear to run slow. He wrote: 'Two such clocks are constructed. One is kept on the ground, and the second is mounted in a fastmoving airplane or spacecraft. Both the observer on the ground and the pilot will obtain the same readings on their particular clocks. However, as seen from the ground, the path of the light in the moving clock  the one in the plane  will describe a zigzag (figure added). It is longer than the path of the stationary clock, because the airplane is moving horizontally. Since the speed of light is the same for both, the time between ticks of the moving clock is longer  the clock has slowed down. Exactly the same argument applies to the pilot of the spacecraft. To him the light pulse of the clock on the ground follows a zigzag path (but in the opposite direction). The clock has slowed down. The effect is mutual. Every observer finds that clocks in motion relative to him or her tick more slowly.'
(Figure 15.4)
In the third book Fearful Symmetry written by Prof. Anthony Zee in 1986, talking about Einstein's time and space, he wrote: 'Unfortunately, or perhaps fortunately, Einstein's theory does not offer a path to longevity. The lifetime of the train passenger is measured as longer by the station clock, but the lifetime experienced by the passenger, that is, as measured by the clock in the train, remains the same. In fact, since the very notion of relativity insists that neither the passenger nor the stationmaster has a status more special than the other, the lifetime of the stationmaster is also observed by the passenger as longer. Each perceives the other as having lived longer!'
Those are three examples from authors who suggest any time dilation in an uniform movement is a symmetric situation, any change would be all the same relative to the other observer, so all the clocks after the trip would show the same reading at rest. That is how it would be interpreted to readers. Is that what you mean when you say of time dilation? If that is the case, then forget your theory, people already know it and agree with it. What's the point to keep saying about time dilation, time appears to run slower in motion, clocks appear to run slower in motion, when all clocks moving relative to each other, at the end after the trip still show the same readings?
10. "Tell me the third group."
"An opposite interpretation is given in this third group. In the book 'About Time' written by Prof. Paul Davies 1995, the author denies that symmetry of time dilation in uniform movement, and he confirmed that time dilation can actually be seen on 'real clocks.' He mentioned about an experiment carried out in 1971 by J. Hafele and R. Keating with four atomic clocks placed in airplanes traveling around the world to prove the actual difference in time reading when clocks after the trip are brought back to compare with stationary clocks."
"What did the test show?"
"Before telling you about the test, do you agree with me your colleagues interpret different things about your theory? I'm not talking about those who agree and who disagree with you. I'm talking only about those who all agree with you, those physicists who claim they understand Einstein's theory, and who try to explain to general readers what Einstein's theory is all about. Why do they say opposite things about the most basic thing in your theory? Forget about how to prove your theory, people don't even know what you mean that time could run slower, let alone how to prove it. Do you mean two identical clocks moving away from each other would show different time at the end of the trip? That's all I need to ask. Yes or No, can you please tell me?"
11. "What about my original book about Relativity, what do you understand I'm saying in the book?"
"I'm not too sure. I think your book belongs to the first group which doesn't say much and readers more likely misinterpret it. For instance in your chapter 12 about The Behavior of MeasuringRods and Clocks in Motion, the best description I could find is this your statement: 'As a consequence of its motion the clock goes more slowly than when at rest.'
"What does it mean to you?"
"Actually, that's the question I want to ask you. What do you mean by that?"
"What if I say, I meant the clock in motion after the trip would show slower reading than the one at rest?"
"Then I would say either it doesn't make sense or you're selfcontradictory or you're wrong. Because how do we know which clock in motion and which one at rest when uniform motion is relative? Your first postulate states that the laws of mechanics must be the same for any freely moving objects regardless of their speed. That means in uniform motion, each object can be regarded in motion or at rest relative to the other. If no one is special than any other, how could you say this specific one is slower than the other? How could you justify such a thing that a > b and b > a?"
(Fig. 15.5)
"What if I say like Richard Weidner, I meant the clock in motion goes slower than the one at rest, but at the end of the trip both clocks show the same readings?"
"Then I would say forget it. What's the point to say clocks appear to run slower, when after all no clocks run slower? Exactly the same way looking at a small glass tank containing two goldfish, at some angle through refraction, you might see 5 fish, but what's the point to only trust your eyes saying there are now 5 fish, when you know after all there're only two?
(Fig.15. 6)
12. "Are you saying that time dilation never exists?"
"No, I never say that. It's just like you say Melbourne is in Australia. That is a true statement in 1997. To prove it, there could be hundred ways. If you're a mathematician you could use equations to prove it. But if you make a mistake in your calculation, your calculation is wrong, it doesn't mean your result is wrong, it doesn't mean Melbourne is not in Australia. The same thing when you try to prove time dilation here. You can make a mistake in your calculation about time dilation, but it doesn't mean time dilation cannot happen due to other causes. Time dilation (in your sense of clocks slowing down) might still happen due to change in gravitation, acceleration, temperature, biochemistry, etc,... But if you say time dilation happens due solely to uniform motion expressed in your equation than I think you're wrong."
"What is your point? Which causes time dilation?"
"I don't know. I haven't seen enough experiments. Also it's scientist's job to tell us what cause time dilation if there is such a thing and explain us how it happen. But if time dilation is real, together with length contraction, it can only make sense in a non symmetric situation. And as long as your first postulate says uniform motion is symmetric you can't have real time dilation nor length contraction caused by v in uniform motion."
13. "You reminded me of the twin paradox?"
"Yes, I want to ask you about that too."
"Go ahead."
"All 19 relativity books I've read, regardless how they interpret your concept of time dilation, they all say the twin puzzle is a non symmetric situation, so the traveling brother would come back younger than his twin remaining on Earth. Do you agree so with that statement? I couldn't find it in your book."
"What is the reason other books say it's not a symmetric situation?"
"They say the traveling brother has to accelerate, cruise along, slow down, then stop, turn around, accelerate, cruise again, then slow down and stop. Whereas his twin brother always remains rest at Earth."
"Don't you agree with that argument?"
"No. If one accelerates, he's not in uniform motion. Yes, it's true. But apart from those times, there's certainly a period (most of the trip) in which he travels in uniform motion relative to his twin, why can't we regard it as uniform motion just within that period then?
(Figure 15.7)
In your book you often use the example of a train in uniform motion relative to the station. Doesn't the train start, accelerate, cruise along, slow down and stop as well? But despite of that, you still can ignore those accelerated times, use only the part in which the train is traveling at speed v relative to the station, to call it uniform motion, and to carry out your experiments, to explain how time dilation and length contraction happens in uniform motion. Then why are we so difficult with the twins here? They say let's imagine a twin travels in a spaceship at the constant speed v relative to Earth, then when are we allowed to say it's traveling at constant speed of v? Never?
The point I want to make is we are not consistent in our argument. We're so obsessed with time dilation that we want to keep it by all means even at the cost of selfcontradiction. The fact is if we love time dilation concept so much we certainly can try it on many things else like gravitation, acceleration, temperature, electromagnetism, etc,.. as long as it's a non symmetric environment. But on uniform motion with the first postulate of relativity, time dilation is a nonsense. Regardless how fast he's traveling, no any twin brother would age slower just because of uniform motion."
(Fig. 15.8)
14. "Do you have any experiments to prove your point?"
"No. I don't need any experiments to prove it. Why should I need experiments just to understand the language we're talking? In fact I haven't said anything new. You're the one who wrote the theory of relativity. I don't understand it, so I have to try to understand what it is that you say. That's all I'm doing. You say time could run slower. I ask whose time could run slower? You say the moving clock will run slower than the one at rest. I ask, in terms of physics, which one is moving and which one at rest? You say in uniform motion, each clock can be seen as moving or at rest relative to each other. I ask, if I name the two clocks as a and b, then I can say a > b and at the same time I can also say b > a, then what is it? And since no one can give me the answer, I have only two options either I would call it a nonsense or I would say I don't understand. Can you understand yourself? Why don't you help me, Professor Einstein?"
"You mentioned before the time dilation experiment with four atomic clocks by J.Hafele and R. Keating in 1971. You haven't told me about its result?"
"You're interested in knowing the results?"
"Yes." Einstein said.
"What do you think the results would show?"
"That traveling clocks brought back to the observatory would be slower than the stationary ones."
"If the results are exactly what you expect, would you say your theory is right?"
"The truth will show."
"If the results are not what you expect, would you say your theory is wrong?"
"No."
"Why?"
"The experiment might be not perfect. There are so many things involved like gravitation change, acceleration, etc,... Until I know exactly how the experiment is involved and carried out, I cannot make any judgment about its result. Honestly, I can trust thought experiment more than real ones. Anyway, just tell me what the results are."
"They did two tests. First they flied the clocks to the east. And second to the west. The four clocks on the eastward trip, came back with an average of 59 nanoseconds (billionths of a second) slower than the stationary clocks. On the eastward trip the clocks were averagely 273 nanoseconds faster."
"Faster?"
"Yes, faster. Are you surprised by the result?"
"Yes. But as I said I have to check the test myself. How do you interpret the result?"
"The result shows exactly what we've just said. There could be a hundred ways to make a clock runs slower or faster that humans never know, and uniform motion is a wrong one.
(Fig. 15.9)
.....
That is just a part of the section Interview with Einstein. You will find more interesting arguments I have with Einstein over topics like space curvature, MichelsonMorley experiment, Einstein's second postulate about the absolute speed of light, and his philosophy about fear in scientific confrontation.
But just from that sample, you can see many professors writing books explaining Einstein's relativity cannot give straight answer to whether clocks would show different readings after the trip or not. And the reason is because they don't understand what Einstein means by time dilation, what it means that time can run slower.
Secondly, as I point out in my argument with Einstein, time dilation, even understood in the sense of clocks show different readings, is not caused by v in uniform motion. It might be due to something else, gravity or acceleration maybe, but if so where is the equation? Whether we would find that equation or not, we don't know. And that'll be the next section's topic: "What is time? in which time's definition established and put an end to Einstein's time dilation concept. But in the mean time, the least answer we have here, is Einstein's original time dilation equation T = T_{o} /Ö (1  v^{2}/c^{2}) is wrong.