Time Distortion Debate: Tom & Jerry's Tennis Ball Experiment

In summary, two individuals named Tom and Jerry devise a time measuring device using tennis balls. However, when Jerry travels in a truck past Tom, both see the other's clock running slower. This leads to a discussion on time distortion and special relativity. A Physics BBS member explains that there is no paradox and both Tom and Jerry would see themselves as moving and the other as at rest, causing the discrepancy in clock readings. The member also warns against trying to disprove special relativity and offers to answer any further questions. Another member points out that when Jerry returns to Tom, they will both agree that Jerry has aged less due to entering Tom's reference frame. The conversation also touches on the importance of using the term "time dilation"
  • #1
RAD4921
347
1
Please be aware that before replying to this message that I will be transferring your replies into another forum (of sorts)

Suppose Tom and Jerry get together. They decide that they will devise a simple time measuring device. Each has a tennis ball and both Tom and Jerry (no pun intended) decide that a second will be defined as throwing the tennis ball 5 feet into the air and then the tennis ball will fall back down 5 feet. Therefore ---- 1 second = 10 feet of vertical movement (we won’t consider velocity of the tennis balls as a factor for simplistic reasons). As both stand there with no relative motion between them they agree that a second = 10 feet of vertical motion. Now Jerry gets into the back of a pickup truck going past Tom at ten feet per (tennis ball) second. All that Jerry sees is vertical movement when looking at his ball and so does Tom, when looking at his own ball. When Tom looks at Jerry’s ball going by at ten feet per second he sees both vertical and horizontal movement. Jerry’s clock as compared to Tom’s shows that Jerry’s tennis ball has traveled 20 feet. 10 feet vertically and ten feet horizontally. Jerry’s clock relative to Tom’s ticks slower.

(at this point shouldn’t the above scenario be viva versa?)

As I was trying to figure out how to explain this I found a problem with time distortion that I once stumbled across. It would seem to me that Jerry would see Tom’s clock slowing down and Tom would see Jerry’s clock is slowing down. So the time distortion would cancel each other out and both Jerry and Tom would march on into the future at the same rate but I know this isn’t the case so we will ask the BBS.


Physics BBS: I know time distortion doesn’t cancel each other but I ran into the above problem can anyone set me straight?
 
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  • #2
It would seem to me that Jerry would see Tom’s clock slowing down and Tom would see Jerry’s clock is slowing down

There is no need to devise a new time measuring device to reach this conclusion. Both Tom and Jerry would consider themselves at rest, and the other one moving hence the other's clock runs slower. The situation is completely symmetrical. Each would also see himself marching into the future at a normal rate as he always sees himself at rest. There is no paradox here, what is your question? If Jerry attempts to communicate his age to Tom, various SR effects would contrive to make Tom receive Jerry's messages in such a way as to be consistent with the age Tom would assign to Jerry anyway.
 
  • #3
To Zeframe

Thanks for the reply. I see what your are saying and that is what I am reading in a book. You lost me at "sr effects" because I don't know what SR means. What about the famous situation of a twin brother taking a speeding trip into space and coming back to meet his twin brother who has aged more? If both see the other's clocks running slower and their own running "normally" how does the accelerating aging come into play or does this have to do with the tansmission of information like I think you said at the end of the reply?

Thank RAD
 
  • #4
Heh. SR = special relativity; we use it a lot around here. By "various SR effects" I mean things like length contraction and/or time dilation, which would be necessary for a complete treatment if one sends light signals to the other.

There has been plenty of discussion about the twin scenario at this forum; there is one particularly concise and well-written post that treats it entirely within an SR framework:

https://www.physicsforums.com/showpost.php?p=241755&postcount=71

A note of warning: there are some people in theory development who have made a huge ruckus in trying to disprove SR. If you are trying to further your own SR knowledge, that is NOT a good place to do so in general. If you're not convinced that SR correctly describes the physical world, refer to the thread "Experimental support for SR" in this section.
 
  • #5
To Zframe C

Oh by the way Z- I like your name, very creative and even applicable as to what we are talking about now. Yesterday I figured out that the acronym "SR" stood for special relativity. I understand about length contraction. It has been about 7 years since I read a fundamental book on how to understand relativity. I will check out the link you provided and I need to read back over some things. It seems at this point that time distortion cannot be because of the symmetry described yesterday. I will probably get back to you on this. I know clocks tick slower in in orbit above the Earth because they need to take time distortion into account when synchronizing atomic clocks between Earth and the satellites
Thanks for your help Z talk to you later
RAD
 
  • #6
Anytime. Send me a message if you'd like me to answer more q's as I also hang in other areas of the forum.
 
  • #7
Zefram c, don't forget that when Jerry bring the truck back to Tom, both will agree that Jerry has aged less than Tom since Jerry is entering Tom's reference frame. Just a little detail I thought needed to be pointed out. And RAD, just so no one in another thread corrects you in less polite way, I just want to mention that "time dilation" is the proper term, not time distortion. And I agree with Z about being careful where you try and find more about SR, the problem with the people making the ruckus is that a lot of them seem to do because they're too close minded to accept a world outside common experience and so any attempts to try and convert them result in them doing the equivalent of plugging their ears and yelling, "I'm not listening"...sorry, it just annoys me a little bit. What was I saying again? Oh yeah, just be careful where you try and get help. Feel free to send my PM too if you have any questions.
 
  • #8
Agreed, I think I missed the part about Jerry bringing the truck back. In that case, it's a fairly classical twin experiment.
 
  • #9
Time dilation

Lastone: Thanks for replying. This is what I want to get at. If both systems are symmetrical than why does one age slower than the other? What is this with entering the others frame of reference? Thanks
RAD
 
  • #10
The classic Twin Paradox. In essence, the symmetry breaks down because SR handles acceleration badly and so in order for Jerry to reach speeds that time dilation becomes apparent at, he has to accelerate and then deccelerate to come to rest with Tom. Using the equations of General Relativity, you can show exactly how the symmetry breaks down and why the equations of SR seem to hold for only one observer. At it's most basic, Jerry returning to Tom's reference frame is what does the trick, since Tom never accelerated relative to spacetime (yes, there is something of an almost absolute nature in relativity). You can still use SR's equations, but with the assumption that Jerry will come to rest relative to Tom you can only use them with respect to Jerry. The same goes for length contraction. I'm sorry I can't give a more complete response, I'm in a bit of hurry...I promise when I can really write the response that such a problem deserves I'll make a second post. Nonetheless, hope that helps.
 
  • #11
Just to clarify - the time dilation experiment doesn't work with tennis balls - the conclusions derived from the light clock experiment depend upon the assumption that the other observer is bound by the constancy of the photon velocity - and therefore he concludes the difference in time passage between himself and the other frame is due to the increased path length of the photon which is hypothesized to travel at c in both frames.

LastOne standing - the acceleration explanation is only one of many different ineffective attempts to avoid the SR twin and triplet paradox - the reason so many words and articles have been written about it is because there are different theories as to the entire subject
 
  • #12
Lastone and Yogi

It is funny that I recognize both of your screen names. I know that I have talked to both of you before (I am new to the forum) I want to thank you both for replying. Yogi your are right. I was using tennis balls in place of a light clock. I figured that the movements were not accurate enough and the speeds are of hardly no fraction of c. I was trying to illustrate to others that when moving in respect to others there is two directions of motion. As I was doing this I came upon the symmetry of the two systems and wonders as to how a photon from the big bang has aged none. I too am in a hurry and have to go. I would like to investigate this symmetry breaking in detail but I must go. If this gets too deeply into mathematics it will lose me but now I can see as to why people would question as to one photon aging less than the other.
 
  • #13
Rad,

I had the same problem as you with the symetry. It was "obvious" to me that because each saw the others clock as slowed down by the same amount, they were "cancelling out".

However, two gentlemen, Chroot and Ambitwistor, spent some time one Saturday evening explaining that the proper way to assess what is going on is through the use of spacetime intervals. The two observers will end up having different, asymetrical, spacetime intervals.

The concept of acceleration wasn't helpful at all to me. It seemed that if one accelerated, he could define himself to be at rest and view the other as accelerating. Chroot and Ambitwistor cut straight through that confusion by getting to the concept of the spacetime interval.

I don't feel qualified to go into it myself and wouldn't be able to handle any questions that might arise, but if you can find someone who can explain the asymetry in terms of the spacetime interval, it will remove the confusion created when you come to the very logical conclusion that the two equal and opposite time dilations seem to "cancel out".

-Zooby
 
  • #14
A point I now wish I had made the time to address. While I'm not particularly adept at explaining the situation myself, an article at http://science.howstuffworks.com/relativity.htm explains it well on a page I believe is titled "Fun with Special Relativity" or something like that. It uses the relativistic doppler effect to explain the relative time intervals zooby mentioned.
 
  • #15
I did a little digging and found the thread where they explained this to me:

variable speed of light - Physics Help and Math Help - Physics Forums
Address:https://www.physicsforums.com/showthread.php?t=8769&page=1&pp=20

I start asking questions about halfway down the first page, and if you follow from there on you can see I ask roughly the same questions as Rad, which Chroot and Ambitwistor handle expertly.

(This thread, incidently, is of some historical signifigance to PF in that it is the very first time LaTeX was used here. Ambitwistor used it to show his equations, and Chroot was so impressed that they began working on making it a permanent feature.)

_Zooby
 
  • #16
Thanks, I've been looking for some more info myself to explain the paradox.
 
  • #17
Thanks

I just dropped in on a busy Saturday to see what you guys had to say. I don't have time to check out the provided links at this moment. I will check all this out later. I want to thank everyone for the help on this subject and will talk to you all later.
RAD
 
  • #18
New update: a few hours ago I started reading Brian Greene's "The Elegant Universe" and he tackles the twin paradox quite nicely. Also a good read if you want to learn about the details of special and general relativity as well as quantum mechanics and superstring theory.
 
  • #19
To Last One

Lastone:

I have read "The Elegant Universe". After finishing the book I donated it to a local library which I now regret. I took out a copy of "The Elegant Universe" from a local library a week ago. I was using this book in reference to what Einstein said about 'every object in the universe is moving at the speed of light'. I think his (Greene) analogy using an auto driving into the glaring sun is what we are talking about here. That when traveling at speeds close to c you take some of the velocity moving in the time dimension and redirect to move through the space dimension. I have the book in hand if you have any details you want to refer to me in the book. I am still going over the information provided in this thread.

Rad
 
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  • #20
While the section with the vehicle on the drag strip does a good job of showing why time slows down as you speed up, the twin paradox comes a little before that (though I don't believe he ever calls it by name). As long as you've got the book handy, p.43 is the section I'm talking about. To summarize what he says, the only way the twin that by common standards we would say is moving, he/she has to change directions, thereby accelerating in order to return to other the twin. Acceleration is also necessary to initiate the relative motion. Since SR doesn't cover non-uniform motion, this puts it into the domain of general relativity. Spacetime itself provides a benchmark for non-uniform motion, so by accelerating one of the twins establishes himself/herself as being the one in motion. Of course there are other explanations that Greene doesn't mention but this one is simple and wide-reaching. The point is paradoxes arise from flawed logic, so no matter which method you use to explain the twin paradox, it's just a case of trying to apply SR where it doesn't belong.
 
  • #21
Let's just clear up a common misconception, SR DOES deal with acceleration and the twin paradox can be resolved (and the exact difffrence in the proper times of the two twins predicted) using SR alone.
 
  • #22
jcsd said:
Let's just clear up a common misconception, SR DOES deal with acceleration and the twin paradox can be resolved (and the exact difffrence in the proper times of the two twins predicted) using SR alone.
I agree, the link I posted in one of my earlier posts treats the twin scenario purely within SR and shows that all frames agree on which twin ends up younger upon the return of the traveling twin.
 
  • #23
Fair enough, however my point was that the twin paradox arises from trying to use uniform motion equations in an accelerated setting. While SR can handle acceleration, and while you can also explain the twin paradox without acceleration using world lines, etc, the whole issue comes from trying to apply the principle of relativity in a situation where it's invalid: a non-inertial reference frame.
 
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  • #24
Lastone

I see how spacetime can be used as a benchmark, that is easy to visualize and I think that is what Greene is talking about. Still, in my mind I have two clocks in synch. In a link provided above the doppler effect is brought into the picture. I must reread the article but I cannot see how the doopler effect relates to time dilation but I have heard it before.

Does a frame of reference that has acceleration/decelleration cause it to have unique properties that causes the time dilation? I wouldn't think so since time dilation would probably happen in uniform motion.
 
  • #25
The doppler effect only serves to illustrate how different observers perceive time intervals. Acceleration (technically deceleration isn't a physics term, it's just negative acceleration) does "cause" time dilation to happen. As you said, uniform motion causes time dilation. Acceleleration breaks the symmetry between the two observers as it establishes that one is moving. Imagine a situation in which two observers came into existence while in a state of constant velocity relative to each other. Each would perceive the other observer as appearing to age more slowly. If they tried to convey their age, maybe sending a signal every hour as in the article, effects like relativistic doppler shifts (different than just a regular doppler shift), would cause the information received by each to conform to their observations, hence each would always say that time is passing more slowly for the other observer. (Just a side note, the howstuffworks article explanation is incomplete as the same effect would be observed if the other observer sent the signals. It does illustrate my point, however, that while maintaining constant velocity two observers will always disagree on who is aging faster.) In example of two observers, brought into existence while in uniform motion relative to each other, only if one observer undergoes acceleration and goes to the other observer will the fact that he is actually the one who aged less come into play. As long as the two observers are in a state of uniform motion, they are each entited to their own observations. However, when they enter the same reference frame, it would be impossible for each to say the other aged less. So, by looking for the event that broke the symmetry between the two thereby causing one set of observations to become invalid once both observers entered the same reference frame, you land on the event of the one observer undergoing acceleration. Acceleration was required for the uniting of the two observers. Since spacetime is the acceleration benchmark, the one observer can't claim that it was really the other who accelerated since he felt. It's the defining event. And since acceleration=motion, it establishes who was "stationary" and therefore determines who's observations will be seen as correct when the two observers are reunited. In the classic rocketship example, the rocket observer also has to accelerate to reach cruising velocity, another flag as to who was moving for when the observers meet again. An important thing is that as long the uniform motion persists, both observers will disagree. You might argue that the Earth moves too meaning the Earth observer was also undergoing time dilation, however this doesn't result in a paradox. Indeed, the Earth observer also undergoes time dilation since it establishes itself as having accelerated too relative to the rocket (it's in a circular orbit), however since it's acceleration will be much less than the rocket's, it just means the slowing of time for the rocket observer will be lessened since a milder time dilation will also be affecting the earth. And while it may seem a trivial fact, it's key to mention that when I speak of acceleration I mean between the two observers (and of course to spacetime as well, but that's a given). If your orbiting the Earth in a satellite, you can't argue that when we reunite I should be younger since I'm accelerating with the earth, as the Earth's acceleration isn't part of our relative motion to each other. Acceleration breaks the symmetry between the two observers. It doesn't cause time dilation (though due to general relativity, it also has a contributing effect to time slowing down). It just acts as reference pointing to spacetime itself as to who's observations will be held as valid once the rocketship returns to the earth, since it's required for this rendezvous to happen.
 

1. What is the "Time Distortion Debate: Tom & Jerry's Tennis Ball Experiment"?

The "Time Distortion Debate: Tom & Jerry's Tennis Ball Experiment" is an experiment designed to test the concept of time dilation, which is a phenomenon predicted by Einstein's theory of relativity. It involves measuring the time it takes for a tennis ball to travel from one point to another in two different scenarios.

2. How does the experiment work?

In the experiment, a tennis ball is thrown between two points at different speeds. One point is at rest, while the other is moving at a high speed. The experiment measures the time it takes for the ball to travel between the two points in both scenarios, and compares the results to determine if there is a difference in the perceived time.

3. What were the results of the experiment?

The results of the experiment showed that there was a difference in the perceived time for the tennis ball to travel between the two points. When the second point was moving at a high speed, the time it took for the ball to travel between the points was slightly longer compared to when the second point was at rest. This supports the concept of time dilation, where time appears to pass slower for objects in motion.

4. What implications does this experiment have?

This experiment has significant implications for our understanding of time and space. It supports the theory of relativity and the concept of time dilation, which has implications for fields such as astrophysics and space travel. It also challenges our perception of time and raises questions about the nature of reality.

5. Are there any limitations to this experiment?

Like any scientific experiment, there are limitations to consider. The experiment was conducted on a small scale and may not accurately represent the effects of time dilation on a larger scale. Additionally, there are other factors that could have influenced the results, such as air resistance and the precision of the measurement tools. More research and experiments are needed to further understand and validate this phenomenon.

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