As someone watching from the sidelines, I think this might be easier if you gave us your definitions of time dilation, displacement, phase and anything else that I missed.
I think if you lay out your understanding of some of the terminology being tossed around, it might help others to pinpoint your misunderstanding.
Agree. These one sentence replies are getting us nowhere.
The OP has some very deep-seated misconceptions. Or maybe just one small one, but it’s in a very key spot in his worldview. But whichever, it/they are utterly blocking him from seeing the situation in the correct way.
OP: Please explain using a couple or few paragraphs how you think you and your grand daughter or whoever perceive things occurring here and now. How are they the same and how are they different from each other.
We might be able to moor off that to find the spot to make an adjustment.
Thanks for the patience - I get it!!
The guys in the space ship are stuck with the results of their experience but there is nothing to sustain a residual effect.
You have dispelled ignorance and the answer is - I cannot measure my time dilation.
Thanks again
Crane
You can’t measure it after it’s already happened.
Let’s say you want to know how long you sleep tomorrow night. You can set up a medical device that will determine the exact moment you fall asleep and the exact moment you wake up and tell you down to a fraction of a second how long you will be asleep tomorrow night.
Now let’s say you want to know how long you slept yesterday night. What are you going to do to measure something that’s already happened? At most, you might be able to guess a rough estimate.
As I stated above, once I stepped away from the argument, I understood what Vaughn was patiently trying to get through my head. The important thing being that the reading on the space clock is a record of it’s history not an indication of retention of a property.
Rabbit holes that are dug over a long period of time can be very deep.
I have never understood time dilation better than now after following this thread, so there is that.
Please try taking something to measure with, next time.
ETA perhaps this app: TimeDilationX on the App Store
Me too.
As someone who understands (more or less) time dilation, this thread has been extremely frustrating to read, but the conclusion (and resolution) has been equally satisfying.
Just offering up a couple more thoughts, here, for anybody reading along who’s still not getting it.
If two of us drive separately from the house we share to a restaurant for lunch, and we take different routes, we will have traveled different distances between the same two points. We get curious about this at lunch, and decide we want to know the difference between the two distances. Well, did we write down our odometer readings before we started? If so we can go look at the readings now, and each of us sees our odometer changed by a different amount. If we weren’t measuring, or if we lost the starting measurement (we didn’t write them down), then there’s no way to measure the distance now. And it doesn’t matter if the difference was actually two miles and we think two miles is easy to measure. We’re sitting at the same table in the restaurant now, we aren’t two miles apart.
About the oscilloscope being able to measure two microseconds – what the oscilloscope can do is measure a duration of two microseconds. It can’t measure a difference of two microseconds between two intervals lasting years, as in your flying history. Similarly, it is easy to measure an inch, right? And easy to measure a year? Well, tectonic plate drift is moving Europe and the United States apart at a speed of about an inch per year. Does that make it easy to measure? No! You have to measure the distance between Europe and the United States to an accuracy of better than an inch, which is a lot of work if you can do it at all. And you have to repeat this a year later, and then look at the difference between your two measurements. This is very difficult – or at least it used to be, though maybe with GPS today and surveying quality receivers it’s not so hard, but that’s only because the GPS system is already doing something very difficult.
More on this: a different but similar experiment is to stay at different altitudes for a while, with accurate clocks, and then compare the clocks. Leapsecond.com is a fascinating web site for people interested in timekeeping, and the fellow there did exactly this experiment. With his kids in tow.
He used Hewlett-Packard 5171A cesium clocks. Six of them, no less. He synchronized them, then put three in his car and drove to a mountain top for about a day. When he returned, he compared all the clocks. He found approximately the predicted difference between the clocks kept on the mountaintop and the ones that stayed home.
You can do this, too. These clocks are available used on ebay; I just looked and saw one for $15000 and another for $12000.
Note that the challenge was measuring a longer duration (a couple days) with sufficient accuracy to detect a small difference (about 20 nanoseconds).
Can the smarties in the thread stand one more dummy question? Let me start by saying I am CERTAIN there’s an answer to this, and I don’t mean to imply my pea brain has uncovered a flaw in Einstein’s math. 
Please be kind for errors in concepts and terms.
I’m paraphrasing from memory, so I may be getting either the details or the concept wrong, but I recall Einstein having said that it is just as valid to say the train station is rushing past the train as the reverse. It’s all relative between frames of reference.
So, go back to the example of the traveler to Andromeda returning to Earth to discover everybody he knew is dead and gone for a bazillion years (check my math, I may have forgotten to carry a one).
So, why is the traveler the young, not-dead guy? Per Einstein, isn’t it just as valid to say the space guy stayed stationary and the Earth moved an Andromeda distance away and back again? Why isn’t everyone on Earth spring chickens still, and the guy in the spacecraft dust?
I hope this makes sense. I’ve wondered what I was misunderstanding for a while now.
I think we’ve got a misunderstanding even more fundamental than the physics misunderstanding. We keep telling you that neither an oscilloscope nor any other devices can do this measurement retroactively. You keep saying that they can, and then you keep on asking us how to do it, to which we keep on answering that it cannot be done.
But you’re the one who keeps telling us it can be done. So, tell us, how can it be done? If you know it can be done, then why are you asking us?
This is called the Twin Paradox and is a very common question. The basic answer is, the situation is not symmetric because the traveler does not remain in an inertial reference frame during the whole trip. The traveler has to accelerate when he reaches Andromeda to slow down and return to Earth, while the Earth undergoes no such acceleration. There’s a long discussion of the issue in the Wikipedia article.
Yeah. In a nutshell, it’s the acceleration, not the going fast, that produces the change in time perceptions. If Earth is cruising along and the spaceship zooms off and back, the spaceship passengers stay young while Earthers age “normally”. If instead the Earth had zoomed off and back while the spaceship just cruised, the Earth inhabitants would stay young and the ship people would age “normally”.
As an aside…you can kinda get a sense of this on some trains.
I have been on a Metra train in Chicago and it moved out of the station so smoothly I had no sense I was the one moving. Looking out the window it seemed the outside world was the one moving. Not me.
Kinda cool. It really drove home the notion of relative motion for me.
Thanks, guys. Hard for my non-physicist’s brain to digest, even after (especially after!) reading the linked article. As noted, acceleration seems to be a way of explaining it, though not the only way. When that was introduced, it seemed circular to me, in that, couldn’t the earth be the body said to be accelerating in a relative frame of reference? Of course the answer is no: we know time dilation occurs.
I suspect my understanding of this will click if I can grok proper acceleration versus coordinate acceleration, two terms I was unfamiliar with before reading the article. I’m hoping at some point it will click the way a “physics for dummies” explanation of time dilation finally did:
“Picture a train running past an observer on a hill. One car has a glass side, and inside that car is a man observing a light particle that goes from the floor to a mirror in the ceiling, and back again. Given the uniformity of the speed of light as measured from any inertial reference, what distance did the light travel for the guy inside the car? How about for the guy on the hill? If the SoL doesn’t change, then what explains the difference in distances measured?”
Stratocaster: “Hmm, let me see…Oh!!! Oh!! Now I get it…”
I’ll end by saying that show off Einstein indicating there’s no paradox at all, what’s wrong with you nitwits—that guy can be a real jerk.
The important difference here between velocity and acceleration is acceleration is intrinsically measurable. If you’re accelerating, you feel a force pushing you in the direction opposite to the acceleration. The unaccelerated observer (the one in an inertial reference frame) feels no such force, so we can tell which one is accelerating. This is unlike velocity, which produces no measurable effects, so we can’t tell which one is moving and which is standing still; in fact those terms have no meaning.
It’s starting to sink in. The concept of acceleration versus velocity hadn’t occurred to me, and frankly if it had it wouldn’t have seemed relevant.
This may be a situation where it’s math I just don’t understand. But if I go back to the dumbed-down explanation that finally got me to understand time dilation (in my last post), it doesn’t seem like the moving train needs to be accelerating. If it’s moving, the observer on the hill is going to see a light particle that goes to the ceiling on a slant, and bounces back down on a slant, by virtue of the train speeding by. The guy in the moving train car sees a particle the goes up and down in a straight line.
Again, the “physics for dummies” explanation may have left out some subtleties that are kind of important but that would have just confused those of us in the dummy tribe.
The simplest description that’s still accurate of the Twin Paradox is that you can use any reference frame you want for the calculations, but there are not two relevant reference frames, but three.
Let’s say that, instead of building their own spaceship, Bob hitchhikes, while his twin Alice stays on Earth. Going out, he thumbs a ride with ET, and then when he’s gone far enough, he gets out and ET keeps on going. Then, on the way back, he hails Alf, who’s coming this way anyway, and rides back with him.
You can work the problem in Alice’s reference frame, and in that reference frame, Bob is always moving and Alice is always stationary, so Bob always ages slower.
You can work the problem in ET’s reference frame, and in that reference frame, Alice is always moving, and Bob spends part of his time at rest, and during that period, Alice is actually aging slower. But then for the second leg of the trip, Alice is still moving, but Bob is moving much faster, to catch up to Alice, and so Bob is aging much slower. It’s enough of a difference that, by the time Bob catches up to Alice, he’s still younger than her, by the same amount as when you did the calculation from Alice’s frame.
Or, of course, you can work the problem from Alf’s reference frame. Again, in this reference frame, Alice is always moving, and Bob spends part of the time at rest and part moving very quickly, except now, Bob’s quick-moving part is first and then his at-rest part. Again, you’ll find at the end that the age difference is the same as in the first reference frame.
Or, you can, I dunno, use Zaphod Beeblebrox’s reference frame, who’s going in a completely different direction at a different speed and never gets anywhere near the Earth. I don’t know why you’d use his reference frame, and in that frame, the calculations are all a lot more annoying, but you still get the same final answer once the twins meet up again.
But what you can’t do is use Bob’s reference frame, because Bob doesn’t have a reference frame, he has two reference frames. Sometimes Bob is in ET’s reference frame, and sometimes he’s in Alf’s.
Also of note, by the way: At times before the twins re-unite, different reference frames will disagree about which one is older “right now”. This is fine, because different reference frames will also differ about just what “right now” means.
Thanks for that. I need to let it sink in, but “okay, picture this” explanations are really effective for me, just like the train example was.
And any where Zaphod makes an appearance are especially effective. 