# Can somebody explain time dilation to me please?

Discussion in 'Physics & Math' started by maxjojo, Mar 13, 2017.

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1. ### maxjojoRegistered Member

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Thank you for your considerate reply.

With due respect though , what you said in this post sounds quite contradictory. You describe this now being ''it's “the all points defined as ‘simultaneous’ to ‘now’ in a coordinate system ''.

If all the points are simultaneous in time passing by, then how can there be a variance in the rate of time when time passes by simultaneous and everything is in the present?

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3. ### karenmanskerHSIRIBanned

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Maxjojo: That's OK . . . . seems to be the modus operandi on this forum . . . . but not limited to 'males'. I am reminded of something told to me by a friend (Hatten Yoder, Director, Carnegie Institute): "If a scientist fully understands the research he/she is conducting, they will be able to explain their research understandably to a layman, who knows nothing of his research, in 5 minutes or less."

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5. ### maxjojoRegistered Member

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Thank you, I was hoping for some simple explanation in layman's terms.

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7. ### karenmanskerHSIRIBanned

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BTW: I think the person who can best explain time dilation is RJBeery, a member of this forum - maybe do a search for him or one of his subfora/threads.

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8. ### originTrump is the best argument against a democracy.Valued Senior Member

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Actually, I suspect that you are a troll that is not interested in understanding. I could be wrong, my huge ego not withstanding.

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9. ### Janus58Valued Senior Member

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It is the equivalent of two people walking between two points, one along a straight line and the other along a curved path. They both agree that they left the same point and arrived at the same point, but the one who walked along the curved path will say that he walked a further distance than the other getting there even though both of them started and ended at the same spots.
With you and your daughter there are two events: your daughter leaving for the store and your daughter returning from the store. These two events are fixed in space-time. However, you and your daughter took different routes through space-time to get from one event to the other. Because of this, she would have measured the time passing between the two events as being less than what you measured it as being. You both agree on the same "here and now" both when she leaves and when she returns, You just disagree as to how much time passed between them. When she returns, her clock will have recorded slightly less than 25 min, while yours recorded exactly 25 min. If you compare your clocks when you meet, you both will notice that your clocks do not agree. She will see that your clock reads exactly 25 min and hers reads less, and you will note the same. In other words, what was 25 min for you, was not 25 min for her. That does not mean she did not leave at the same "Then" and return to the same "Now" for both of you , just that the two of you didn't experience the same length of time as passing between "Then and Now".

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10. ### The GodValued Senior Member

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Maxjojo,

1. The highest relative speed between two layman will be around 900 Km per hour, when one is flying and the other one is on ground. Just chill both clocks are not going to differ much even with the longest flight of 17 hrs...

2. The highest altitude difference, and thus differential gravity, is also not going to be more than 40000 ft for two layman, here also you can chill as no appreciable difference will be noticed.

3. Now technically speaking time dilation makes sense if there are more than one clock (both precise). One with you and one with your daughter. Let's say you are stationery with your clock in your pocket and your daughter is running away at some speed with her clock in her pocket. Both the clocks will tick differently due to relative speeds between two. This is the basis of time dilation.

Now the teaser for you as few posters got tired here, do you see a paradox in #3 above? If yes pl revert, if no..just chill.

11. ### RJBeeryNatural PhilosopherValued Senior Member

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If I'm good at layman explanations it's only because I'm a layman myself.

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Hi MaxJojo the shortest explanation I can give you to get started in understanding time dilation is this: the rate of time passage is not the same for everyone. When you get confused because you think this implies that your daughter is behind you in terms of the now it's understandable but only because you aren't used to thinking about it. Imagine staring at your daughter's watch and noticing that it is ticking more slowly than yours. You are both able to communicate normally and both agree that you are in the now together but she sees your watch ticking more quickly. This is what would happen (by an imperceptible amount) if your daughter was standing closer to a massive object than you (for example).

She would not "feel slow" because all of her thought processes are slowed down as well. She would perceive that you are moving more quickly. Likewise, you would not "feel fast" but your daughter's movements would appear to be slower.

It sounds insane but they *must* make this adjustment for time dilation for the GPS satellites to work or else their clocks become unsynced -- the effect has been proven!

Good luck!

12. ### maxjojoRegistered Member

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I am sorry I do not understand, how can the rate of time be different for everyone, what is the rate of time ? A clock is just an equivalent to time to measure time?

13. ### RJBeeryNatural PhilosopherValued Senior Member

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Exactly, a clock represents the local passage rate of time. It is this rate which changes depending on motion and gravity. It's a very foreign concept but it represents reality.

I should also say that this concept only makes sense when our rate differs from someone else's rate, otherwise we would all just say that clocks always measure one second passing per second...which seems nonsensical. It's only useful to say "one second on my clock passes for every .99993 seconds passing on my daughter's clock"...which is why it's called Relativity and not Objectivity

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14. ### gmilamValued Senior Member

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If that was the case, then they would not have thought that your daughter would understand it either. Most of us don't have any idea what the sex of the person on the other end of the internet is. Sounds to me like you have a chip on your shoulder.

15. ### maxjojoRegistered Member

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I find this very strange, do you think a clock, the tool used for an equivalent to measure time has any affect on the time it is measuring equivalent too?

I thought time was a dimension with no future measurement but rather a measurement of time passed?

16. ### RJBeeryNatural PhilosopherValued Senior Member

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If we go deeper you're probably going to get more confused. The clock is just "clocking away" based on local physics. The fact that another clock in another place clocks away at a different rate is just indicative that the rate of time passage for that clock is different. Note that it isn't time passage at that place running differently necessarily, it's time passage in that frame. What I mean is that if you put a clock on a centrifuge and spin it very quickly it will clock more slowly. If your daughter rode this centrifuge she would age more slowly than you even while you were standing right next to her.

The big takeaway is that time isn't some "thing" just marching along at a constant rate but rather a "thing" experienced at different rates depending on where we are and what we're doing. Note that we will always experience time's local rate as a constant because, if you think about it, all clocks are ultimately based on the speed of light (e.g. electromagnetic forces between the teeth of the rotating gears, etc) and, as I mentioned, our thought processes are as well. You are correct that we consider time to be a dimension but what Einstein and others have done is show us the connection between space and time -- when the rate of our movement through space changes, for example, then the rate of our movement through time changes as well.

17. ### maxjojoRegistered Member

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I am finding my questions seem to be ignored and the reply I am getting is rather technical and has nothing to do with the ''points'' I mentioned . Correct me if I am wrong in my thinking, a clock is just a clock , the clock and the rate of the ''clocking'' is independent of time and ''exist'' in time? Time being independent of all matter and existing has an arbitrary entity?

Neither a relativistic time or an absolute time actual having physicality?

18. ### rpennerFully WiredRegistered Senior Member

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Proper time is definitely physical. That is what clocks measure. That's the empirical phenomenon that a good physical theory would describe the behavior of. Relativity is the name of the best physical theory we have to cover this behavior — it is much better at precisely matching the behavior of reality at high speeds and when gravity is important than Newton's concept of universal time.

The first conceptual problem you face is that proper-time is trajectory-dependent and position-dependent in a way that Newton and intuition didn't account for. On Earth, only comparing very precise clocks will allow you to detect this.

The second conceptual problem you face is that Cartesian coordinates and the concept of "at the same time" are so useful, we use them even though the both represent arbitrary choices that don't matter to physics except when "at the same time" and "at the same place" happen together.

Last edited: Mar 14, 2017
19. ### NachoRegistered Senior Member

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Heh! What ever happened to the simple ole' person traveling on the speeding train throwing a baseball of the front of it to STATE (just STATE, not prove/develope) that even though you think velocities simply get added together, that they don't. And then using that to introduce the constant speed of light to show why, and then lastly time dilation???

Last edited: Mar 14, 2017
20. ### maxjojoRegistered Member

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That is interesting, I always presumed that all things with physicality occupied time and space rather than something with physicality being measured and called time. In reflection of your post my question would have to be, if we removed all that has physicality from space leaving an ''empty'' spacial volume, are you saying/suggesting that there is no time in this hypothetical spacial void?

Would Newtons absolute time not apply to this hypothetical spacial void?

21. ### rpennerFully WiredRegistered Senior Member

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The pedagogy of such an approach eludes me. At a minimum, I would start with the 1859 Fizeau experiment which demonstrates that the velocity of light in moving water is not the velocity of light in still water plus the speed of the water.
https://en.wikipedia.org/wiki/Fizeau_experiment

Then I would demonstrate the vacuum doesn't have a preferred state of motion detectable by the motion of light.
https://en.wikipedia.org/wiki/Michelson–Morley_experiment

Then I would point to the absence of objects carrying momentum and energy moving faster the speed of light in a vacuum.

Then I would point to the relation between the energy of a particle and it's speed not being the same as Newton predicts, as tested by Bertozzi (1964).
http://u00003.masterssystems.com/UG0955PS/18/06/Selected_Files/MQ/bertozzi1964.pdf

So then I would ask, what if light's strange behavior wasn't a property of light but a universal property of a special speed, c?

Then I would introduce the Linear algebra of the Lorentz tranform (det=1, eigenvectors corresponding to motion at speed c parallel and antiparallel to the boost direction), the velocity composition law of such a transform (which explains Fizeau experiment), the invariance of the Invarient interval (which explains the consistency of the speed of light in the vacuum and proper time), and the relations:
$E^2 - (c \vec{p})^2 = (mc^2)^2 \\ E \vec{v} = c^2 \vec{p}$
which hold for both massless and massive phenomena which convey energy and momentum. And so light travels at the speed c because it is massless, not because it is light, per se.

22. ### NachoRegistered Senior Member

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LOL! Sounds like you're having as much fun making these demonstrations as I am having fun reading all of them!

23. ### rpennerFully WiredRegistered Senior Member

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Is there time in the vacuum? According to relativity there is, for proper time is how we would measure the "length" of any trajectory through the vacuum, so proper time is a description of how what Relativity would describe as the geometry of space-time applies to trajectories which themselves are geometric in content. Since theory covers that geometry even in the case when no particles cover a particular trajectory, or in your vacuum case, any trajectory, theory says space-time and therefore time is still there, waiting to be measured.

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