- #71
Justintruth
- 35
- 1
stevendaryl said:
We make a distinction sometimes in engineering between a counter and a clock. A clock is something that ticks at a regular interval. Its sometimes called an oscillator. A counter is something that counts the ticks. The time values you are using are really counters. You can use counters but you must know that two counters can be counting the ticks of a single clock and reading different values. This is because the counter can be reset at different times. We do it all the time. New York is ahead of California but both New York and California's clocks tick at the same rate. The "paradoxes" you mentioned work because the counters in the moving frame are not set to the same initial values at the same time relative to the rest frame. This has nothing to do with the rate of the clock in the moving frame. That is why I recommended that the number of counts in the reference frame between successive ticks in the moving frame be counted. If the number of counts in the rest frame between two ticks in the moving frame is one there is no dilation or contraction. If it is more than one (even by a fraction), there is time dilation of the moving frames clock as measured by the rest frame clock. If it is less than one there is time contraction. This can be measured and when it is one finds dilation is the factual situation always and from both frames.
I get that.
If you took a moving frame of reference in a Newtonian world, two trains let's say, and miss - set the counters to the same values that you would see had they been synchronized in the relativistic world, you would not produce time dilation. The clocks would read different times but not tick at different rates. The difference is not just that the clocks read different numbers. Its that they actually slow down.
Let me tell you something that actually happened to me. I had a prominent professor of Marxism who in fact was a dialectical materialist and actually a naïve materialist argue that all of the "effects" of relativity were merely observational. Now I know you don't believe that the effects are purely observational. But when you suggest that the relativity of time comes down to how time is measured it can imply - or rather obscure - the fact that the effect is real. It can seem that relativity is just a different way of measuring the same situation as we thought existed at the time of Newton.The person trying to understand the theory then goes down the path of trying to construct an image of how things "really are". That is a big mistake when you are trying to understand this theory. This is literally a picture in his head of how reality is at some moment and unfortunately it constitutes an absolute frame of reference even though the person trying to imagine does not realize it. So he is trying to "imagine" an absolute frame of reference and then see how by measurement he can get the relativity of time. He tries to derive observations from his imagined reality that are consistent with relativity theory. They have a lot of trouble - in fact the theory cannot be understood that way. I know this happens because it happened to me. The relative universe is not imaginable - or better not imaginable as existing some 3d way right now. There is more to it than the measurement process. If by "ontology" I mean what the philosopher Quine thought it meant, namely, "what is". Then there is an ontological difference between the frames of reference. One frame may have one set of things that are, while the other frame's list of what is has some that are not yet, and others that already were. And either list is as right as the other. This is why relativity is so counter intuitive - because we all are programed biologically to believe it must actually be in some imaginable way and so if I can just imagine it and see how it is viewed I will understand the theory. The first step is to give up trying to imagine how things are. Unless you use Minkowski. You see my point? Once you try to imagine how it is and then derive how it will look you are dead. It isn't one way or the other. Nor is it both. It is one for one frame and the other for the other.
There are two types of images. The ones observers actually see - that is the same for any two collocated observers even if they are in different frames but they are very different even within one frame for observers at different places because of the transit times. Then there are ones they calculate. These are the same for all observers in the same frame but different between frames. This second set is the notion of "what is" in one frame vs the other. Then there is Minkowski which is strictly speaking not an image. Perhaps you believe that two images produced by calculations and different between observers should not be called real. But these images are real in the sense that they replace the single real image we used in Newtonian physics as they can then be used to predict what observations will be for different observers in each frame.
There are two takeaways for me: First: the rate of the clocks in a moving frame of reference can be measured by the clock(s) in a stationary frame of reference. When that is done it will be found that the clocks in the moving frame are ticking slower than in the rest frame. And second: That the relativity of time is a natural phenomenon that cannot be transformed away. There is something about nature and not just our way of measurement involved.
To me the best way to motivate mutual time dilation - for you are right that it is a problem - is to take two yard sticks and rotate one relative to the other. Then show how dropping a perpendicular from one yardstick to the other and projecting perpendicular to the ruler being measuring will result in a dilation of length and that that same dilation will occur if the second yardstick measures the first by the same method. Both rulers measure each other as larger using the same procedure. By changing the definition of perpendicular to being perpendicular to the measured ruler instead of the measuring you can see how mutual contraction can also occur and be relative which is another source of confusion. Then you use a Minkowski space to show how a space time interval that is entirely temporal will be rotated so that it is partly in space and partly in time in the other frame. This has the advantage of motivating both time dilation and space contraction in one stroke and does not imply that the relativity of time is just an effect of how time is measured. Good luck explaining however, the negative sign in the metric. The interval between two points on a light cone is zero?! What?! Then what separates them?
Still you can show a light cone in two d and then show the world line of the origin of a moving frame and then draw a diagonal line between the rays of the cone oriented so that the world line of the moving frames origin bisects the diagonal. Then by sliding the line along the world line of the moving frames origin you can show that the intersections of the diagonal line with the light cone are always the same distance along this diagonal from the origin of the moving frame while one side is getting farther away when measured by a horizontal line! Rotating the line that defines the present is the key.
Anyway, if you actually read this my complements. I think I understand your point. I am just trying to keep it straight in my head.
I still think we can measure the time dilation and that it occurs and is real.