# Thread: Calculating Changes in Time

1. If person A travels away from earth for an hour at .99C and then turns around and returns to earth at the same speed an hour later, how would you calculate how much time person B on earth experienced from the time that person A left earth to the time that person A returned taking in to consideration all effects including length contraction and time dilation from acceleration?

2. Originally Posted by Scheuerf
If person A travels away from earth for an hour at .99C and then turns around and returns to earth at the same speed an hour later, how would you calculate how much time person B on earth experienced from the time that person A left earth to the time that person A returned taking in to consideration all effects including length contraction and time dilation from acceleration?
What you are asking is a very difficult calculation (I can show it to you later).
It is much easier to do the calculation the other way around, if B experienced an elapsed time , then A experience and elapsed time .

3. The gamma factor is a about 7, so I would say 14 hours. The gamma factor is given by:
1/(1-.99^2)^0.5

How much "time" elapsed for each "frame of reference?" Exactly the same "amount" of time occurred for "A" and "B", regardless of velocity.

Also...Hello and Cheers! (nice questions also)

5. Gerry, are you saying that you have never encountered the twins paradox?

I'm not sure, but I think about half of the topics on any physics site revolve around "twins paradox" in way or another, so yes. I'm aware of it.

Was your reply to the question that was posed incorrect? No...not as far as hypothetical constructs of SR would posit. (you get a cookie!)

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I answered the question in terms of "actual reality", and it terms of "reality" of each frame of "A" and "B" the same amount of time passed. An hour is still an hour, regardless of where or

how you experience it...velocity means nothing w/regard to a "thing of no substance of self" (time).

A speed or "gain" of velocity will dramatically alter the state of matter and mass as it approach relativistic speeds, as per Lorentz and Einstein...but it cannot influence "time" itself.

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If it were true that "relativistic speeds" could influence time...it would then mean "A" would be existing in some new dimension, separate from the continuum of the Universe, and I cannot

see the "how" of such an event. It in essence means the ".99 c has left everything behind" and "time is different in this new continuum of velocity".

I cannot envision this as an "actual, real outcome" of matter "moving faster than the rest of the Universe!"

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The "paradox" is not really a true paradox of itself...when you think about it. It's only a mathematical abstract of a "what if" scenario that will never come to pass.

7. Originally Posted by Jilan
The gamma factor is a about 7, so I would say 14 hours. The gamma factor is given by:
1/(1-.99^2)^0.5
This simplistic approach works only for constant speed, it doesn't work for any realistic case where there is acceleration at start, turnaround and stop.

8. Originally Posted by Gerry Nightingale
I answered the question in terms of "actual reality", and it terms of "reality" of each frame of "A" and "B" the same amount of time passed. An hour is still an hour, regardless of where or how you experience it...velocity means nothing w/regard to a "thing of no substance of self" (time).
In SR, the rate at which time passes by me per me is the same rate at which time passes by you per you. That's called the "proper rate" of time. Yet, twin B ages less than twin A, in the classic twins scenario. Seems like a paradox should exist at first thought. However, folks never take into account "the entire mechanism". Let's assume a cosmos (for simplicity) where everything in it is at rest with each other. For simplicity (again) assume twin B does virtually instant accelerations and decelerations, being inertia for virtually all the round trip. As twin B departs for later turnabout and return, all the separations between cosmic bodies (wrt propagation axis) length-contract (only per B). So just after departure, twin B records the earth-planetX separation much smaller (by light signals). Since "time always passes us by" as usual, at the same proper rate, then a shorter distance (per B) requires a shorter duration to traverse given A & B record the same relative speed over the interval. Hence, B ages less than A over the common spacetime interval, and on return the B clock proves it by being behind A's clock (they were sync'd before departure). That said, one must look at more than only the length contraction, or only the time dilation. They must be considered in unison. However, more importantly, one must recognize that the twins are gauging measurements off of 2 bodies at rest in a single inertial frame, the earth frame, ie earth (twin A) and planet X. The twin B trek-distance is defined by bodies at rest in the earth/twin A frame, and so that frame-A length is the common reference for both the twins' measurement of space and time. That's very important to realize, far as understanding the twin's scenario. There's another matter too, ie the rotation of twin B's sense-of-simultaneity (his sense of NOW across space) relative to all bodies of the earth (twin A) frame, but that's a deeper subject matter that is not important far as the scope of this response goes.

Originally Posted by Gerry Nightingale
A speed or "gain" of velocity will dramatically alter the state of matter and mass as it approach relativistic speeds, as per Lorentz and Einstein...but it cannot influence "time" itself.
It impacts "the relative measure of time", frame to frame ... as opposed to the rate of one's own passage of time per oneself (ie proper time).

Originally Posted by Gerry Nightingale
If it were true that "relativistic speeds" could influence time...it would then mean "A" would be existing in some new dimension, separate from the continuum of the Universe, and I cannot see the "how" of such an event. It in essence means the ".99 c has left everything behind" and "time is different in this new continuum of velocity". I cannot envision this as an "actual, real outcome" of matter "moving faster than the rest of the Universe!"
I couldn't envision either, if I looked at it that way. Again, motion impacts the relative rate of time, not the rate at which time passes oneself per onself (which never changes, even during relativistic acceleration rates).

Originally Posted by Gerry Nightingale
The "paradox" is not really a true paradox of itself...when you think about it. It's only a mathematical abstract of a "what if" scenario that will never come to pass. (Thanks for reading!) Cheerio!
All then relativistic effects exist in unison with v>0, even though they may be negligible at everyday speeds. They are still there. That's why GPS satellites use SR and GR corrections, as over the duration of a full day, the corrections are not longer ignorable in many circumstances. The mathematics describe a metric, which relates inertial euclidean systems in a quasi-euclidean way (ie the Minkowski metric). The predictions of the relativistic effects have been consistently tested, analyzed, and verified as valid. That's empirocal testing. This is why relativity has withstood great scrutiny for 109 years, and modern cosmology built upon it.

Thank You,

I wonder if there will ever come a time<(haha) when I understand the "how" of SR being applied to GPS satellites? Really? Again w/ "this validates SR...!

Okay, then. (I was thinking in terms of transmission signals being "compensated" for Earth's rotation, as well as established "time zones" variations in relation to the satellite's position...but

never mind that) I wrote a response that involves a completely hypothetical scenario involving "A" being static and "B" moving at a relativistic velocity for one hour...and I stand with what

I wrote. There is NO "time" to "influence" for "A" OR "B"...an "hour is just an assigned unit of measure". It is not a "real thing". (I also have serious doubts concerning anything posited as

"moving at .99 of lightspeed" and then being told "well, golly...this is what would happen" and then further told that GR supports SR regarding "How much time varied" regarding "B".

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Okay...since most in physics theory concur "Yes...the Emperor's clothes are magnificent...all the numbers say so!" then that is how it is. I just don't see the "clothes", no matter how

many people insist that the "clothes" are there. ( I wish I had some "magic glasses" to see the "clothes" with...maybe some ECT volts will enable my mind to work right so I can believe)

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Time is a real, actual "thing of self". (why be concerned over explaining "how things work" to me? it's a waste of effort...like teaching a pig to sing)

10. Originally Posted by Gerry Nightingale

I wonder if there will ever come a time<(haha) when I understand the "how" of SR being applied to GPS satellites? Really? Again w/ "this validates SR...!
One need only study it. If GPS time is more accurate each day with relativistic corrections, then that's a validation relativity is correct. If relativity were not correct, then the measure of time by GPS would be worse rather than better, or it would be better only about half the time.

Originally Posted by Gerry Nightingale
Okay, then. (I was thinking in terms of transmission signals being "compensated" for Earth's rotation, as well as established "time zones" variations in relation to the satellite's position...but never mind that).
Sounds a bit more like the Sagnac effect, than the LTs.

Originally Posted by Gerry Nightingale
I wrote a response that involves a completely hypothetical scenario involving "A" being static and "B" moving at a relativistic velocity for one hour...and I stand with what I wrote. There is NO "time" to "influence" for "A" OR "B"...an "hour is just an assigned unit of measure". It is not a "real thing".
Actually, all relativity scenarios assume that all clocks used are perfect clocks, made by the same perfect vendor, and calibrated in the same common inertial frame of reference, based upon a common single standard for the measurement of time. For example, an hour could be 1/24th an earthly rotation, per all clocks. They all record a proper-hour the same, but the comparison of his hour to my hour (ie relative time) differs per v with v>0. If time were not real, nothing would move and nothing would exist. There's the measure of time, and then there is time itself. Granted, our understanding of time is incomplete, and time may well not be precisely what we presently figure it to be, yet we quantify and predict it very well.

Originally Posted by Gerry Nightingale
(I also have serious doubts concerning anything posited as "moving at .99 of lightspeed" and then being told "well, golly...this is what would happen" and then further told that GR supports SR regarding "How much time varied" regarding "B" ......

Okay...since most in physics theory concur "Yes...the Emperor's clothes are magnificent...all the numbers say so!" then that is how it is. I just don't see the "clothes", no matter how many people insist that the "clothes" are there. ( I wish I had some "magic glasses" to see the "clothes" with...maybe some ECT volts will enable my mind to work right so I can believe)......
Well, no one ever said relativity theory was easy. Some have great difficulty with it, others not so much. No one's gonna fly at 0.99c anytime soon with a clock and ruler, so all we have is the predictions of the mathematical model (LTs). Can't go that fast, then we measure over very long periods of time, and see if the accumulation of time matches relativistic prediction. It does. Tests of relativity ...

Tests of SR ... Experimental Basis of Special Relativity

Tests of GR ... Tests of general relativity - Wikipedia, the free encyclopedia

Originally Posted by Gerry Nightingale
Time is a real, actual "thing of self". (why be concerned over explaining "how things work" to me? it's a waste of effort...like teaching a pig to sing. (Thanks for reading!)
I've taught pigs to fly. Invisible pink pigs. So, many things are possible.

People explain things to others when they realize others don't have a complete understanding. In relativity theory, one does not understand SR until they fully understand it. The light bulb lights up when one recognizes that length contraction and time dilation always work in unison, and that all moments in time coexist just as inches on a ruler do. For example, a moving body is length contracted and time desynchronized. Many understand length contraction, and many understand time dilation, but many of those folks never envision how both work in unison as a single mechanism. Therein lies the ticket. Then the pigs become elephants, happier than a pig in sh!t. But then, that's just my opinion

Thank You,

Where did I write that "matter cannot alter in response to velocity?" Of course it responds! My contention is w/ "time as a real thing-of-self", NOT atoms/matter/mass. To me, there is NO

"real time" as far as the existence of the Universe is concerned...there is only an instant of NOW, and that instant is a "constant". There is no past-tense state or future-tense, only NOW, and

thus SR is incompatible w/ reality...a reality that is in a "constant state of transition" w/ regard to matter.

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If the Universe consisted of a single atom...there would still be "matter in a constant state of transition" due to intrinsic and extrinsic causality force of gravity. Electrons would still orbit the

nucleus, and the principles of Relativity would still apply in that the "atom will remain as-is" as long as the Universe it inhabits exists. The atom demonstrates that GR works...the only factor

missing is the manifestation of energy as a "radiant" factor. The atom possesses the "potential" to manifest energy as a "radiant" but cannot do so as a single entity...to radiate would

require more atoms, so there would be eternal darkness for the Universe.

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Think the "single-atom" is an exercise in "imaginary conditions?"...NO, it isn't. The "single atom" IS the "real Universe" right now...and always has been. Of course, there are many "single

atoms" in the Universe, each occupying it's own "sphere of existence". Am I presenting a "false perspective" w/ regard to the "single atom Universe?" If so, I cannot find anything to refute

it! The "single atom" model reduces SR to a "false chain of events" w/regard to time as a "real factor".

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You wrote of experiments that "prove" SR as a true circumstance in regard to the function of a light bulb...and I say the experiment itself is both true and false. The filament of the bulb is

demonstrating a reaction to a stimulus and this is the "true" portion...the rest is observational error, at least w/regard to SR factors!