Why Time Dialation isn't required to solve the twin paradox.

[TakenItSeriously]

The twin paradox is created by both the twin on the ship and the twin on the earth seeing the other persons clock change by the same amount, therefore there doesnt seem to be a way to account for the age difference when they meet up after the voyage.

 

Edit to add: The paradox is not just the fact that the twins are different ages at the end. Its that they have symmetrical observations about each others passage of time and still have a difference in time experienced. Read post # 11 for a better explanation of the specific paradox I'm talking about.

 

First of all, I will use the example from the Wikipedia article about the twin paradox so that I can highlight the facts to make the problem as transparrent as possible without involving too much explanation and you can verify those facts by reading the article.

 

Secondly, I will point out that the destination star system is not moving in reference to the Earth. At least not based on the calculations that were used.

 

Thirdly, I won't mention anything about time dialation because time dialation has nothing to do with the problem. Neither does the relative motion of the destination for that matter, except for easier visualization of the problem.

 

Example:

Consider a space ship traveling from Earth to the nearest star system:

distance d = 4 light years away,

Ships speed v = 0.8c

Assume Acceleration time is negligible.

 

Earths Perspective:

d = 4 light years

t = 2d/v = 8/0.8 = 10 years

 

Travelers Perspective:

Lorentz factor: ε = 0.6

d = 0.6 * 4 = 2.6 light years

t = 0.6 * 2d/v = 0.6 * 10 = 6 years

 

So the solution to the paradox is that traveling 60% of the distance takes 60% of the time. It's that simple.

 

The earth twin observes the ship traveling a total of 8 light years in ten years at 0.8c. The traveling twin thinks he only traveled 5.2 light years in 6 years at 0.8c

 

The illusion of the paradox is created by people assuming that only the length of the ship is contracted which isn't correct. Just as with time dilation working both ways making the problem seem paradoxical, so does length contraction work both ways which resolves the paradox.

 

The length of the ship is contracted only relative to the observers on Earth, not to the traveler on the ship. To the traveler, it is the distance between the Earth and the destination is what is being contracted because they share the same inertial reference frame.

 

If you need to, imagine a very long stick suspended between the two points. Then to the traveler on the ship, the stick, the Earth and the destination star system system are all moving as one system at 80%c therefore the traveler sees that entire system contract by 60%.

 

So what happens if the destination is moving relative to the Earth?

Nothing much exept the math needs to account for the difference just as if you were taking a speed boat from a dock to a moving ship in the distance and back. The distance traveled at 80%c is still going to be 60% of the distance that the observers on the Earth believe was traveled. That's because what ever the point of contact between the ship and the destination, be it 4 light years away or 4 billion light years away one could always imagine that point being a static point relative to the Earth.

 

Think of it like a timing play where the quarter back throws to a spot on the field instead of throwing to a running receiver. The field would be the inertial reference frame.

Edited July 16, 2016 by TakenItSeriously

[ajb]

What is the paradox here?

 

The motion of the two twins is not symmetric in space and the expected time dilation as calculated on Earth agrees with the clock on the twin that made the trip.

[TakenItSeriously]

What is the paradox here?The motion of the two twins is not symmetric in space and the expected time dilation as calculated on Earth agrees with the clock on the twin that made the trip.

There is no paradox, that's only what the problem is known as. Im just showing that the solution has nothing to do with time Dilation. Read the post.

 

I changed the title to "Why time dilation has nothing to do with solving the Twin Paradox" so as to not mislead anyone.

Edited July 16, 2016 by TakenItSeriously

[ajb]

There is no paradox, that's only what the problem is known as. Im just showing that the solution has nothing to do with time Dilation. Read the post.

Well I did ... you seem to have really just shown what the clocks on the traveling twin will read. This can indeed be understood in terms of length contraction.

 

There are other ways to think of this difference in duration. The most basic - and really shows what is going on - is to draw a space-time diagram and look at the space-time interval (and ignore accelerations for ease). The interval is invariant under choices of inertial frame. So we can pick the frame for which the tiwn on Earth is just moving in time. If you sketch the space-time diagram and calculate the space-time intervals for both twins -they are different. You can then relate this to the proper time of each twin and you get the 4 years differnece.

Edited July 16, 2016 by ajb

[TakenItSeriously]

Well I did ... you seem to have really just shown what the clocks on the traveling twin will read. This can indeed be understood in terms of length contraction.There are other ways to think of this difference in duration. The most basic - and really shows what is going on - is to draw a space-time diagram and look at the space-time interval (and ignore accelerations for ease). The interval is invariant under choices of inertial frame. So we can pick the frame for which the tiwn on Earth is just moving in time. If you sketch the space-time diagram and calculate the space-time intervals for both twins -they are different. You can then relate this to the proper time of each twin and you get the 4 years differnece.

I'm not familiar with the method you described but it sounds like it involves a lot of conversions between frames which, I think, is where most people seem to get confused. Ive seen proofs thinking it was due to acceleration, and another proof that seemed to think it was resolved on the return trip, and others that say it has to do with jumping reference frames. The last one is true but not very specific and jumping reference frames makes it sound like it's about acceleration, which it's not.

 

If you simply asked each twin what they thought the distance traveled was, they would give you two different answers that were different by 60%

[ajb]

I'm not familiar with the method you described but it sounds like it involves a lot of conversions between frames which, I think, is where most people seem to get confused.

You can do all this in one chosen inertial frame - the most obvious one is to pick the frame for which the twin on Earth is at rest. You should think about the space-time interval. It also gives you the correst way of dealing with curved paths, so we can include acceleration...

 

Ive seen proofs thinking it was due to acceleration, and another proof that seemed to think it was resolved on the return trip, and others that say it has to do with jumping reference frames. The last one is true but not very specific and jumping reference frames makes it sound like it's about acceleration, which it's not.

Proofs? You mean resolutions of the seeming paradox?

 

Sometimes people talk about acceleration as a means of showing that the motion of the two twins is not symmetric in space. But you don't actually need to think about acceleration carefully to see this. We can assume idealised instantaneous change of direction - more physically this means the period of decceleration and acceleration is small as compared with the duration of the trip as measured by the twin on the round trip.

[TakenItSeriously]

You can do all this in one chosen inertial frame - the most obvious one is to pick the frame for which the twin on Earth is at rest. You should think about the space-time interval. It also gives you the correst way of dealing with curved paths, so we can include acceleration...Proofs? You mean resolutions of the seeming paradox?Sometimes people talk about acceleration as a means of showing that the motion of the two twins is not symmetric in space. But you don't actually need to think about acceleration carefully to see this. We can assume idealised instantaneous change of direction - more physically this means the period of decceleration and acceleration is small as compared with the duration of the trip as measured by the twin on the round trip.

So are you talking about using the Lorentz transform tor time as a kind of scale conversion factor for the earth frame?

 

Example

If the Lorentz factor is 0.6

T = 0.6 * 4/0.8 = 3 years passed on the spaceship to the planet, 6 years round trip

And

T = 4/0.8 = 5 years passed on the earth to get to the planet, 10 years round trip

 

I'm not certain, but that could be seen as circular reasoning if your trying to resolve the paradox. The apparent paradox is that you can run the same exact transform for both twins in both directions and the results appear to be symmetrical.

 

Using the distance they each thought was traveled breaks symmetry because they would be different values.

Edited July 16, 2016 by TakenItSeriously

[ajb]

I am not using a Lorentz transformation explicitly here... just draw the space-time diagram and calculate the space-time intervals. You then use these to compare the proper times that each twin has - this is exactly what time dilation is all about.

[TakenItSeriously]

You mean Minkowski diagrams? Sorry If Im a little slow. Im not a physicist so Im not used to all of the methods and common references.

 

But couldn't you create the same kind of symmetry by redefining which frame is moving?

 

Then it comes down to breaking symmetry by changing the travelers reference frame several times and starting and ending up on the earth frame, but it's leads to a pretty non-specific resolution which seems to be the source for all of the confusion.

 

The distances covered are never the same value regardless of who is moving because the destination always moves with the earth frame and never with the ships frame.

[ajb]

You mean Minkowski diagrams? Sorry If Im a little slow.

Yes, they are also known as Minkowski diagrams.

 

 

 

But couldn't you create the same kind of symmetry by redefining which frame is moving?

I don't think so.

 

 

And why would you want to if you can get the time dilation by using any inertial frame, and in particular the rest frame of the twin on earth?

[TakenItSeriously]

 

You mean Minkowski diagrams? Sorry If Im a little slow. Im not a physicist so Im not used to all of the methods and common references.

Yes, they are also known as Minkowski diagrams.

But couldn't you create the same kind of symmetry by redefining which frame is moving?

I don't think so.

 

And why would you want to if you can get the time dilation by using any inertial frame, and in particular the rest frame of the twin on earth?

It's just how the paradox is constructed. Or at least one version of it, which I'm just now realizing, could be our disconnect in this thread and which I should have made more clear, so I apologize if such is the case.

 

The original and more widely known version only talks about the apparent paradox being that the twins end up being different ages.

 

However there is another version of the paradox that includes symmetrical observations made by the twins and goes something like the following:

 

Assume each twin had a local clock such as a powerful spotlight that would revolve once a second so that the other twin could see it flash on each rotation using a telescope.

 

Both twins would observe their brothers local clock slowing down by the same amount on the trip out and on the return leg they would both observe that the others local clock would speed up by the same amount.

 

So the paradox goes: with symmetrical observations by both twins over their brothers passage of time, how do we explain the 4 year difference in the twins in time experienced.

 

If you look only at the time that has passed by in either twins frame, it's providing self-consistent information and resolves the first version of the paradox, but it's a bit redundant to saying they experienced a different amount of time and doesn't resolve the paradox as it was constructed here.

 

To resolve the second form of the paradox the solution must include the data that isn't symmetrical by virtue of the destination always being stuck to the Earth's inertial frame. And that data which is always different from either of the twins reference frames is the distance they each felt was covered by the rocket.

 

The Earth bound twin would say he saw it cover 8 light years in ten years.

The traveling twin would say he traveled 5.2 light years in six years.

[TakenItSeriously]

I recently discovered a new Twin Paradox video that had been posted on YouTube

 

"The Twin Paradox visualized in Special Relativity"

 

https://youtu.be/ifRuWG98ATY

 

It was posted 6 days after I had posted the OP to this thread which may be an original solution based on what I've been able to Discover. In it he used my solution as one of three solutions claiming that there were several valid solutions that could work. This is simply not true.

 

Why length contraction or it's equivalent is the only valid solution

Nearest star system:

distance: d = 4 light years away

Ships speed v = 0.8c

 

Earths Perspective:

d = 4 light years

t = 2d/v = 8/0.8 = 10 years

 

Travelers Perspective:

Lorentz factor: ε = 0.6

d = 0.6 * 4 = 2.4 light years

t = 2 * 2.4/0.8 = 6 years

 

The unintuitive results are due to the lorentz factor:

γ = 1/sqrt[1-(v²/c²)]

 

The only relavent variables involved in this factor are those that relate to speed which are distance and time. Since time is always symmetrical we are left with only distance as the source of the asymmetrical result. Therefore length contraction must be the source of the time difference experienced by each twin.

 

The Earth bound twin observes the ship travel 8 light years in 10 years.

The ship bound twin only travels 60% of the distance which takes 60% of the time or 6 years.

 

Invalid solutions :

Stepped through the timeline showing all details at each step in order to show the symmetrical observations vs the asymmetrical results. This is only showing that length contraction is the source of the dime deviation. Remove length contraction and time does not deviate.

 

Another solution also goes through all of the details and conclude with the following statement:

 

"The asymmetry in the paradox is that the traveler leaves the earth?s reference frame and comes back, whereas the homebody never leaves the earth"

 

Which says nothing at all but that the traveler left at a relativistic speed and returned at a relativistic speed while the earth twin stayed on earth. Its just a restatement of the problem.

 

Lots of others state its the acceleration, but acceleration doesnt scale. If you traveled 8 ly or 80 lys the acdeleration would be identical at 100days but the delta time is ten x as much.

 

One solution mentioned it had to do with the relatavistic dopler shift + something else. The details were never given for that solution but dopler shift is essentially caused by length contraction.

Edited August 10, 2016 by TakenItSeriously

[disarray]

What is the paradox here?

The motion of the two twins is not symmetric in space and the expected time dilation as calculated on Earth agrees with the clock on the twin that made the trip.

 

As there is no preferred frame, some people might need an explanation as to why it is not symmetric. I have read various explanations....some say that acceleration is key (e.g., leaving earth and turning around), but others say it is only how fast one is going: presumably one could be going from Tokyo to Osaka on a bullet train at a speed of only 320 km/hr and ones watch (if it was super accurate) would be running slower simply because the (EM waves of the) train and everything on it are already moving at the speed of light. Typical explanation would be that a Japanese physics student might have a mirror in each hand facing the other and light could be bouncing back and forth between them: If one added the speed of light between the mirrors and the 320 km/hr of the train, the light between the mirrors would be covering a distance (in the direction that the train was going plus the distance between mirrors) that would imply that it was either going faster than the usual speed of light, or else time slowed down.

 

I rehash this explanation because I wonder whether it matters whether the student left his Aunt on the train platform in Osaka on the train, went to Tokyo, and then returned, finding his watch slower in comparison to his aunts, or whether he just leaves Tokyo where he has lived for 8 years without leaving, and visits his aunt in Osaka (presumably both have atomic watches that keep time with great accuracy).

 

My key point is to suggest that it doesn't matter whether one leaves a particular spot and then returns to it (e.g., in the twin paradox), or whether one just goes fast compared to another spot. For all I know, the student could have synchronized watches and then left his aunt, zig-zagged all over Japan at high speeds (or even near speed of light on some superfast hypothetical bullet train) for a period of time, and then come back to the aunt with his watch a second or two behind his aunts.

 

OR I could suggest that the student synchronized his watch with his aunt. Walked slowly to Osaka (so there is little or no time dilation), stayed a year, then taken a near speed-of-light bullet train back to Osaka to compare watch times. In short....does the alleged time dilation rely upon leaving and coming back to the same inertial frame, or just going really, really, fast?

 

As am aside, the scientific evidence supporting time dilation effects with respect to gravity seems much more substantial than that dealing with traveling at high speeds.

The Earth bound twin observes the ship travel 8 light years in 10 years.
The ship bound twin only travels 60% of the distance which takes 60% of the time or 6 years.

 

I thought it was the length of the moving vehicle (i.e., the ship) that contracted, not the distance between departure and destination.

Edited August 11, 2016 by disarray

[TakenItSeriously]

My key point is to suggest that it doesn't matter whether one leaves a particular spot and then returns to it (e.g., in the twin paradox), or whether one just goes fast compared to another spot. For all I know, the student could have synchronized watches and then left his aunt, zig-zagged all over Japan at high speeds (or even near speed of light on some superfast hypothetical bullet train) for a period of time, and then come back to the aunt with his watch a second or two behind his aunts

.

Understanding the Twin Paradox is only as important as you need it to be. However if you are a theoreticle physicist, then It's probably worth the time to make certain you understand it, because you cannot move forward very easily if one doesn't understand what one thinks they already know. In fact, until any problem suddenly collapses into a very simple solution, you probably don't fully understand the problem. There may be hundreds or even thousands of valid but worthless solutions, because they don't teach you anything about the problem.

 

There is only one other solution that can be found through Relativistic doppler effect which some physicists consider to be the predominant solution. Its a valid solution, but the ultimate source and the most elegant solution is length contraction. I'm pretty sure relativistic doppler effect gets it's information from length contraction.

 

The simplest solutions are only the simplest in hind site, but they are very difficult to find in fore-site. In this case it involved understanding the symmetry of SR being twisted by 90⁰ as a consequence of c being constant.

 

It's like a riddle I posted not long ago based upon a poker home game that you host for many players of different skills while you keep a complete database of every hand ever played.

 

Someone asks you what the average players win rate is. You decided to figure it out and work for hours on finding the answer. But then you still suddenly know the answer, and kick yourself because it's so simple. The thing is, it's not a simple answer to find only simple in hind site. It was only easy to find because you figured out the problem. Finding some good enough solution that doesn't tell you anything won't help either.

 

OR I could suggest that the student synchronized his watch with his aunt. Walked slowly to Osaka (so there is little or no time dilation), stayed a year, then taken a near speed-of-light bullet train back to Osaka to compare watch times. In short....does the alleged time dilation rely upon leaving and coming back to the same inertial frame?

.

Only if length contraction was included as part of your method. Which is very often the case, because its required to work through the entire problem.

 

Or just remove length contracrion from the problem and see if the solution resolves itself down to 0 time difference to prove how many sources there are.

 

I thought it was the length of the moving vehicle (i.e., the ship) that contracted, not the distance between departure and destination.

.

It does but length contraction is symmetrical between frames just like time dilation is.

 

The two frames being the [ship's] frame and the [Earth + spacetime +star system] frame. So the ship contracts from the POV of earth bound twin, and the earth frame contracts from the POV of the traveler.

 

BTW:

There is still a key piece missing from SR symmetries that I'm trying to create a convincing enough argument for because it requires making a minor change to SR, which I doubt will be accepted no matter how convincing or clear I make it. It's a minor issue to SR but in a way it unifies cosmology with SR.

Edited August 11, 2016 by TakenItSeriously

[swansont]

In short....does the alleged time dilation rely upon leaving and coming back to the same inertial frame, or just going really, really, fast?

The change in frequency of a clock depends on the speed. The asymmetry of the effects depends on the presence of an acceleration.

 

I thought it was the length of the moving vehicle (i.e., the ship) that contracted, not the distance between departure and destination.

All lengths are contracted in the moving frame, relative to a stationary observer.

[disarray]

The change in frequency of a clock depends on the speed. The asymmetry of the effects depends on the presence of an acceleration.

 

But wouldn't the change in frequency owing to changes in speed give you effects of time dilation. Elsewhere (clocks and rulers) you seemed to be saying that time dilation has nothing to do with acceleration. Now you seem to be saying that it does.

All lengths are contracted in the moving frame, relative to a stationary observer. Yes, I got it.

Edited August 11, 2016 by disarray

[swansont]

But wouldn't the change in frequency owing to changes in speed give you effects of time dilation. Elsewhere (clocks and rulers) you seemed to be saying that time dilation has nothing to do with acceleration. Now you seem to be saying that it does.

I don't see how you get that from "The change in frequency of a clock depends on the speed." (emphasis added)

[disarray]

I don't see how you get that from "The change in frequency of a clock depends on the speed." (emphasis added)

 

 

It seems that a few things can cause time dilation even though they don't incorporate the comparison of reference fast moving or accelerating frames of reference, e.g. temperature variations and gravitation. What seems to be a common denominator, however, is that the greater the time dilation, the lower the frequency of EM waves. I am not suggesting anything about the frequency of a clock or its internal mechanical mechanisms, but rather to the molecules, and thus EM waves (moving at the SoL) that constitute the clock on the traveling ship. The faster the ship is going (its speed), the longer the wavelength and the lower wave frequency, leading, arguably, to time dilation and lower decomposition (aging) rates:

 

"Hasselkamp, Mondry, and Scharman experiments indicated connection between EM wavelength and frequency variation as the consequence of temperature variation with weak and [strong] time dilation effect [so that] that it affects life span and conception of time in human body and brain....Low body temperature contains high EM frequency and lower wavelength that lead to time dilation, and for high body temperature, the result is inverse "

http://www.isbem.org/conf/2009/7thicbem/IMG/pdf/Poster_Session/39%20Time%20dilation%20and%20EM%20wavelength%20variations%20as%20the%20consequence%20of%20temperature%20changes....pdf

(Note: This is from an Iranian study, and I have noticed the English is a little odd at times)

 

I have not heard of this before, but the authors seem to be saying that lower core body temperature correlates with lower frequency/longer wavelength EM waves leading to time dilation leading to 'improved life signals' and a longer life.

 

If true, this seems to suggest that, whether one is discussing (body) temperature change, or space travel or gravitational effects, increasing the frequency and thus lowering wavelength of EM waves causes, or at least coexists with time dilation and the slowing of metabolism/ aging process,

Edited August 12, 2016 by disarray

[swansont]

It seems that a few things can cause time dilation even though they don't incorporate the comparison of reference fast moving or accelerating frames of reference, e.g. temperature variations and gravitation.

Temperature, as an environmental effect, doesn't cause time dilation. Gravitation and acceleration are indistinguishable.

 

What seems to be a common denominator, however, is that the greater the time dilation, the lower the frequency of EM waves. I am not suggesting anything about the frequency of a clock or its internal mechanical mechanisms, but rather to the molecules, and thus EM waves (moving at the SoL) that constitute the clock on the traveling ship. The faster the ship is going (its speed), the longer the wavelength and the lower wave frequency, leading, arguably, to time dilation and lower decomposition (aging) rates:

 

"Hasselkamp, Mondry, and Scharman experiments indicated connection between EM wavelength and frequency variation as the consequence of temperature variation with weak and [strong] time dilation effect [so that] that it affects life span and conception of time in human body and brain....Low body temperature contains high EM frequency and lower wavelength that lead to time dilation, and for high body temperature, the result is inverse "

http://www.isbem.org/conf/2009/7thicbem/IMG/pdf/Poster_Session/39%20Time%20dilation%20and%20EM%20wavelength%20variations%20as%20the%20consequence%20of%20temperature%20changes....pdf

(Note: This is from an Iranian study, and I have noticed the English is a little odd at times)

I have not heard of this before, but the authors seem to be saying that lower core body temperature correlates with lower frequency/longer wavelength EM waves leading to time dilation leading to 'improved life signals' and a longer life.

 

If true, this seems to suggest that, whether one is discussing (body) temperature change, or space travel or gravitational effects, increasing the frequency and thus lowering wavelength of EM waves causes, or at least coexists with time dilation and the slowing of metabolism/ aging process,

 

I don't think they are discussing relativity. If they are, it's nonsense. But IIRC biology sometimes uses the phrase related to time perception.

[TakenItSeriously]

It seems that a few things can cause time dilation even though they don't incorporate the comparison of reference fast moving or accelerating frames of reference, e.g. temperature variations and gravitation. What seems to be a common denominator, however, is that the greater the time dilation, the lower the frequency of EM waves. I am not suggesting anything about the frequency of a clock or its internal mechanical mechanisms, but rather to the molecules, and thus EM waves (moving at the SoL) that constitute the clock on the traveling ship. The faster the ship is going (its speed), the longer the wavelength and the lower wave frequency, leading, arguably, to time dilation and lower decomposition (aging) rates:

 

 

 

"Hasselkamp, Mondry, and Scharman experiments indicated connection between EM wavelength and frequency variation as the consequence of temperature variation with weak and [strong] time dilation effect [so that] that it affects life span and conception of time in human body and brain....Low body temperature contains high EM frequency and lower wavelength that lead to time dilation, and for high body temperature, the result is inverse "

http://www.isbem.org/conf/2009/7thicbem/IMG/pdf/Poster_Session/39%20Time%20dilation%20and%20EM%20wavelength%20variations%20as%20the%20consequence%20of%20temperature%20changes....pdf

(Note: This is from an Iranian study, and I have noticed the English is a little odd at times)

I have not heard of this before, but the authors seem to be saying that lower core body temperature correlates with lower frequency/longer wavelength EM waves leading to time dilation leading to 'improved life signals' and a longer life.

 

If true, this seems to suggest that, whether one is discussing (body) temperature change, or space travel or gravitational effects, increasing the frequency and thus lowering wavelength of EM waves causes, or at least coexists with time dilation and the slowing of metabolism/ aging process,

This sounds a lot like relativistic dopler shift. When we approach the SOL relative to another inertial frame such as the Earth frame, then earthlings would see light from our ship turn red and due to its frequency slowing down as well as our time slowing down. But light is actually photons carried by EM waves.

 

However, I believe that the redshift is in part an effect of time dilation rather than the other way arround..

[disarray]

 

This sounds a lot like relativistic dopler shift. When we approach the SOL relative to another inertial frame such as the Earth frame, then earthlings would see light from our ship turn red and due to its frequency slowing down as well as our time slowing down. But light is actually photons carried by EM waves.

However, I believe that the redshift is in part an effect of time dilation rather than the other way arround..

 

Well you are far more versed in this subject than I am. But I'm guessing that Relativistic shift is inherent, so that it becomes a chicken and egg question as to whether time dilation causes the shift or the shift causes dilation. Personally, I would prefer the latter, as we can measure the shift, but, we never really measure the abstract notion of time, I suspect, but just measure relative states of motion.

 

As for acceleration, perhaps I am taking it in too commonplace a meaning. The only acceleration I have read about in a discussion of the twin paradox is when the spaceship turns around, which implies a degree of deceleration equal to the acceleration. In any case, when one calculates the ages of each of the twins, one figures in how long the traveling twin has been traveling, so the length of the duration of the trip seems to be the key factor.

 

Reversing directions would take the same amount of energy or frame change or whatever one is measuring in a short trip of 10 years as it would in a longer trip of 50 years:

 

A very thorough examination of all the true effects show that the Time Stretching effects during the acceleration and deceleration EXACTLY CANCEL OUT the Time Dilation effects of the well known Time Dilation during the coasting phase.

http://mb-soft.com/public4/dilation.html

One wonders whether there would be time dilation if the twin does not turn around, but just keeps going. In theory, the traveler could go far enough in one direction that he returns to the twin without turning around, given that space "curves" back on itself.

 

Indeed, there may be a problem of assuming that the earthbound twin is not accelerating:

 

"We on Earth (incorrectly) THINK we are in such a non-accelerating Inertial Rest Frame of Reference! However, we each REVOLVE around the Earth once every day, at nearly 1000 mph in a CURVED circular path, which means we are each CONSTANTLY ACCELERATING (downward) IN A CIRCLE."

Though, I guess the counterargument would be that the twins are co-moving in the same inertial frame of earth before one of them travels off.

 

 

 

 

[swansont]

 

 

 

Well you are far more versed in this subject than I am. But I'm guessing that Relativistic shift is inherent, so that it becomes a chicken and egg question as to whether time dilation causes the shift or the shift causes dilation. Personally, I would prefer the latter, as we can measure the shift, but, we never really measure the abstract notion of time, I suspect, but just measure relative states of motion.

 

As for acceleration, perhaps I am taking it in too commonplace a meaning. The only acceleration I have read about in a discussion of the twin paradox is when the spaceship turns around, which implies a degree of deceleration equal to the acceleration. In any case, when one calculates the ages of each of the twins, one figures in how long the traveling twin has been traveling, so the length of the duration of the trip seems to be the key factor.

 

Reversing directions would take the same amount of energy or frame change or whatever one is measuring in a short trip of 10 years as it would in a longer trip of 50 years:

 

A very thorough examination of all the true effects show that the Time Stretching effects during the acceleration and deceleration EXACTLY CANCEL OUT the Time Dilation effects of the well known Time Dilation during the coasting phase.

http://mb-soft.com/public4/dilation.html

One wonders whether there would be time dilation if the twin does not turn around, but just keeps going. In theory, the traveler could go far enough in one direction that he returns to the twin without turning around, given that space "curves" back on itself.

 

Indeed, there may be a problem of assuming that the earthbound twin is not accelerating:

 

"We on Earth (incorrectly) THINK we are in such a non-accelerating Inertial Rest Frame of Reference! However, we each REVOLVE around the Earth once every day, at nearly 1000 mph in a CURVED circular path, which means we are each CONSTANTLY ACCELERATING (downward) IN A CIRCLE."

Though, I guess the counterargument would be that the twins are co-moving in the same inertial frame of earth before one of them travels off.

 

 

 

 

 

 

 

Deceleration vs acceleration is a meaningless distinction. You can turn around without changing speed.

 

Space curving means you are no longer talking about SR.

 

The earth is assumed to be an inertial frame for the purposes of the twin paradox discussion; the accelerations involved are an irrelevant distraction.

[TakenItSeriously]

Well you are far more versed in this subject than I am. But I'm guessing that Relativistic shift is inherent, so that it becomes a chicken and egg question as to whether time dilation causes the shift or the shift causes dilation. Personally, I would prefer the latter, as we can measure the shift, but, we never really measure the abstract notion of time, I suspect, but just measure relative states of motion.

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You can think of it like this. Imagine the rocketship is moving away from the Earth at 0.8c while transmitting a 100 GHz clock signal, in dilated time. The wave front must still travel back twoards the Earth at c, but time has slowed the transmitting frequency down to 60GHz. On top of this, the regressive speed of the ship may not impact c, but it still enhances the doppler effect, slowing it down to 36 GHz.

 

As for acceleration, perhaps I am taking it in too commonplace a meaning. The only acceleration I have read about in a discussion of the twin paradox is when the spaceship turns around, which implies a degree of deceleration equal to the acceleration. In any case, when one calculates the ages of each of the twins, one figures in how long the traveling twin has been traveling, so the length of the duration of the trip seems to be the key factor.

 

Reversing directions would take the same amount of energy or frame change or whatever one is measuring in a short trip of 10 years as it would in a longer trip of 50 years:

 

 

 

 

 

A very thorough examination of all the true effects show that the Time Stretching effects during the acceleration and deceleration EXACTLY CANCEL OUT the Time Dilation effects of the well known Time Dilation during the coasting phase.

http://mb-soft.com/public4/dilation.html

One wonders whether there would be time dilation if the twin does not turn around, but just keeps going. In theory, the traveler could go far enough in one direction that he returns to the twin without turning around, given that space "curves" back on itself.

 

Indeed, there may be a problem of assuming that the earthbound twin is not accelerating:

 

 

 

"We on Earth (incorrectly) THINK we are in such a non-accelerating Inertial Rest Frame of Reference! However, we each REVOLVE around the Earth once every day, at nearly 1000 mph in a CURVED circular path, which means we are each CONSTANTLY ACCELERATING (downward) IN A CIRCLE."

Though, I guess the counterargument would be that the twins are co-moving in the same inertial frame of earth before one of them travels off.

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The easiest way to visualize that gravity could not be the source of the time deviation is that we know that the deviation changes in direct proportion to the distance. Therefore it's source must be form an inverse Lorentz shift, which is a linear relationship.

 

Gravity or acceleration, on the other hand both operate through exponential curves due to the squared factor, and behave nothing like linear relationships.

 

 

 

[disarray]

 

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You can think of it like this. Imagine the rocketship is moving away from the Earth at 0.8c while transmitting a 100 GHz clock signal, in dilated time. The wave front must still travel back twoards the Earth at c, but time has slowed the transmitting frequency down to 60GHz. On top of this, the regressive speed of the ship may not impact c, but it still enhances the doppler effect, slowing it down to 36 GHz.

The easiest way to visualize that gravity could not be the source of the time deviation is that we know that the deviation changes in direct proportion to the distance. Therefore it's source must be form an inverse Lorentz shift, which is a linear relationship.

Gravity or acceleration, on the other hand both operate through exponential curves due to the squared factor, and behave nothing like linear relationships.

 

If wave speed = frequency (hertz) × wavelength (metre), then lower Ghz suggests slower wave speed....so in effect things are happening more slowly (in comparison with the inertial framework of the earthbound twin) because the EM waves are moving comparatively slower, thereby accounting for the slower metabolism and thus ageing of the traveling twin.....?

 

From whence would Lorentz shift come from if not from gravity?

[swansont]

If wave speed = frequency (hertz) × wavelength (metre), then lower Ghz suggests slower wave speed....so in effect things are happening more slowly (in comparison with the inertial framework of the earthbound twin) because the EM waves are moving comparatively slower, thereby accounting for the slower metabolism and thus ageing of the traveling twin.....?

 

From whence would Lorentz shift come from if not from gravity?

 

Are you suggesting that a formula that doesn't have G in it is related to gravitation?