Didymus

If that's the case, swan, when two objects travel relative to each other, their relative speeds are definitively equal. If A is traveling away from B at a speed, B is moving away from A at an identical speed. Thus, relative speed can not yield assymetrical time dilation.

Can you reference when this technique was used in an experiment testingthe speed of light where the source and receiver or moving relative to each other? Preferably testing both a moving source and stationary receiver vs. A moving receiver and stationary source.

Correct me if I've misread, but that sounds like that only measures the delay based on light transferring through different mediums rather than relative speed. I.e. measuring timing over a fixed distance rather than actually measuring the relative speed of the incoming photons. No? I'm particularly interested in the tests verifying that the speed of light is the same even with a moving source. Once the light bounces off the first mirror in the array, that mirror is the new source of light and the speed of light is still only being measured relative to a stationary source (each mirror it bounces off of).

Giving this another honest shot. It's said that long ago, we proved that a source of light traveling either toward or away from measuring equipment will still emit light that will be measured at C. The only ways I would know to measure the speed of light would involve bouncing that light off of an array of mirrors. My question is: Does anyone know of a an experiment to measure the speed of light from a source moving relative to the measuring equipment that used a method that did not involve reflecting that light through a mirror array? Can anyone describe how it would be measured without a mirror array?

So then if clocks are said to catch up in time based on the difference in symmetry, would the duration of each trip be irrelevant? Since it's been claimed that time will catch back up when two symmetrical objects stop.

So if youre floating in deep space when suddenly a clock flies past. You see whether it's ticking slow from your perspective... Then catch up to it and look at it again. Are you suggesting that you can definitively detect which one accelerated more during their trip by noting which clock jumps forward in time when the inertial frames meet back up? If both clocks experienced equal acceleration, it's been suggested that both clocks would jump forward and synch. It seems that one could compare the ratio of how each object had accelerated during it's trip by noting how much each clock adjusts when they come together. Al goes left at .8c and Bert goes right at .7c, but turns around early so they still meet back at the same time. They still had a relative velocity of nearly the speed of light, so the whole trip, each would see the other's clock run slower. Right before they decelerate, they compare how far behind the other clock is. Even if they don't see the clockove forward during deceleration... Once they stop, they can then compare which clock jumped forward more than the other. Is that a fair interpretation of your suggestion? If not, where do you disagree? New post: md65- that's why I suggested a straight line through curved space to limit the "acceleration" to a change in relative velocity. If it's not a matter of G-forces, the. What function differentiates the two inertial frames? When the ship turns around the star, from its perspective, it's going straight and hasn't accelerated at all.... Instead his home planet rapidly changed from flying away at a certain speed, decelerated, then accelerated flying toward the ship at that speed. If SR is a matter of relative velocity, it can't be asymmetrical.

I'm aware that it will alter the calculations a bit relative to the time spent in the gravity well. But the observer on the home planet will also be experiencing Gr time dilation for the gravity well he's been sitting in the whole trip. Assume the two to be proportional (less gravity, but more time in the field) to cancel out the GR variable. The gravity well is just to provide a situation where a person is inarguably accelerating to leave a planet, then accelerating in the same direction to catch up to the planet again without the planet experiencing any acceleration itself. Just to eliminate variables. If acceleration sets the time dilation, dilation may be asymmetrical, but every acceleration/deceleration would compound the slowing of time. There would be no function for acceleration in one direction to slow time, but equal acceleration in the opposite direction to speed it up again. If acceleration doesn't play a role, and only relative velocity affects time... Then there is no function for asymmetric time dilation. How can they be reconciled?

Curious about how dilation differentiates between "deceleration" and "acceleration" in the opposite direction? See the illustration a couple posts up.

So then the net result of time dilation is a function of acceleration rather than time spent moving at a certain velocity? If so, how do you differentiate between acceleration and deceleration? I.e. for the sake of direction, imagine a 2D map of a planet sitting to the south of a neutron star. You accelerate (say at .5c) toward the north to get a closer look from within the star's gravity well. Once you hit your speed, you just coast the rest of the way on a trajectory that will send you just close enough to curve your path close enough to your planet (since this isn't a gravitational force slingshoting you, but a straight path through curved spacetime, there's no further acceleration). As you get to the neutron star, you maintain your inertial frame... Just rotate your ship to keep the star in your forward window even on your way back. Now, from your inertial frame, you're just floating through space, and you see your planet wizzing by from behind you at a speed of .5c. You have to accelerate to catch up to it. Did your rate of time normalize relative to your planet when you went through curved space to change direction without accelerating? Or did you normalize when you accelerated to catch up to the planet after it wizzed by? Or did time slow relative to your planet both when you left and then again once you caught back up with it? Forever giving you Flash-like super powers since everyone else is so slow?

So if two people are moving relative to eachother, yet watching the other one's clock the whole time, each will see the other's clock moving at a slower rate and get farther and farther behind their own clock. Say they travel like this for a year and one clock is a month behind the other clock. If, when they come to the same inertial frame, their clocks are once again synched... How do you suppose that works? Does do you believe deceleration will make the clock on the opposite ship seem to jump forward however much is needed to catch up to the normal time? How would this change if they each accelerated to .8c for 10 seconds then decelerated vs. Staying at that pace for 10 years... Seeing the other clock fall farther behind the whole time.... And then catching up all at once? Or, are you suggesting that when they stop, the rates will cat hbup to one another, but each pilot will still see the other clock as reading a different time according to how far behind that clock appeared to be from their perspective before they decelerated?

While this tangent is worth discussing, I feel like others may disagree with your assertion. Are you suggesting that if two objects are traveling past eachother at nearly the speed of light, they'll each see the other's clock running more slowly than their own clocks. yet, when they meet up, their clocks will be synched again as long as their accelerations were identical? Do you suggest that neither clock is actually ever running slower, that they just appear to be doing so from the perspective of the other person? Or do you suggest that each is actually running slower than the other, but that they speed back up when the two decelerate? Or am I misunderstanding you?

So, to eliminate variables, assume Al and Bert are in space ships that accelerate and decelerate instantly without killing anyone. Acceleration is another topic... We're going with straight special relativity time dilation based on relative motion at different inertial frames. If it makes you feel better, assume they start accelerating on the other side of the ship and Al and Bert simply begin their journies by passing the space station simultaneously. How will Al and Bert compare their clocks with eachothers and Bobs?

From Bob's perspective, yes. But when as Al travels, it's Bob's clock that runs slower. Bert's clock runs even slower as his speed relative to Al is so much closer to the speed of light. So how do Al and Bert see eachother from their frames of reference? Note, avoid general relativity's affect on time dilation by assuming that they're all on space ships in negligable gravity and Al and Bert's ships have the technology to accelerate/decelerate very quickly without smashing the occupants. After Al and Bert get to speed, they are no longer accelerating, so still count as an inertial frame just like Bob.

(Sorry, I wall o' text. For ease of skipping to the question Blue text is a remedial preface. Orange text is the explanation someone else gave for the problem in the blue text. Black text is my question about the orange explanation of the blue problem.) I saw an explanation of the twin paradox online that tried to explain the twin paradox. I understand the theory that relative motion dilates time. Hense, a twin travels at .8c to an object 5 lightyears away. From their perspective about 15 years has passed, but when they come back to earth, everyone else has experienced closer to 25 years. The problem comes from the notion that all frames of reference are equally valid. As two objects pass each other, each will experience their time as normal and see the other person's clock running slow. Thus, if the twin that leaves could see the clock of the twin on earth the whole time, the twin that left would come back and everyone on earth will have experienced less time, thus would be younger. So, when the two are reunited... how does each see the other as nearly a decade younger than themselves? They offer that time dilation is asymetrical due to the asymetrical nature of the trip. They explain that if each brother sends out pings every second. Since the two are traveling apart, each will experience pings from the other party as coming in slower than once per second. But, when the ship turns around, it will receive pings faster than one per second, while the earth still receives pings at a rate slower than one per second. Thus, time is subjective to the same extent that they each experience different number of pings per second. Now, we'll ignore the G-force dyssemetry for now, since that's a whole different set of problems and this is tangled enough as it is, but... there seems to be a serious flaw in this reasoning in that they changed how they treat those pings half way through the trip. If we assume these pings travel at a constant speed relative to a medium, then yes, the ship will receive pings more slowly as it travels away from the earth to the same exact extent that it will receive pings faster as it travels back toward the earth. The earth will receive pings at a normal rate throughout the journy. They exactly even out. If, instead, we assume the pings travel at a speed constant to their source... we get the same exact result with a different explanation. Pings coming from the earth will put along at normal speed. The ship will receive them red-shifted as it travels away and blue-shifted to the same extent on the way back. Yes, it'll get more pings on the way back because the pings have to catch up to the shift... but that doesn't mean "more time has passed" ... it's just lag. The difference of having pings move common to their source rather than a medium is that the earth will also receive red-shifted pings as the ship travels away and blueshifted pings as the shift travels toward it. Again, evening out exactly. There's only a discrepant number of pings if you change the rules halfway through the trip. Further, if Asymmetry is the problem... remove that variable. Assume they're triplets. One person stays home, the other two take the same journy in opposite directions at a speed of about .8c for 5 lightyears and back. How old does each person see the other ones when they all come back? (For ease of explanation, Say Bob stays home, Al goes to left and Bert goes right). Seems that Bob will see Al and Bert as the same (younger) age. But Al and Bert both see the other one as significantly younger than themselves (and younger than Bob sees either of them).

An important thing to consider is that sound travels at a constant speed relative to the medium regardless of how fast the object creating the sound is going. Light, on the other hand travels at a constant speed relative to it's source and requires no medium. So an object can go faster than sound and nothing will hear that object until the object passes. On the other hand an object traveling at any speed will emit light traveling away from it.