/sci/ - Science & Math

good question. the asymmetry between anon A and anon B really arises from the fact that the anon who stays on earth doesn’t accelerate, whereas spaceship anon at least needs to turn around to come back home. even in a toroidal space time metric where spaceship anon can keep going straight and loop back to earth that way, basically if the anons meeting back up are moving relative to one another, then to compare their ages means they need to come to rest relative to one another, and the one who accelerated more to match the speed of the other will be younger

>>10336231
Saying this in advance: don't listen to anyone who will try to explain this through GR and gravity. The paradox is perfectly explainable solely within SR.

>>10336231
person left on earth will be older
https://www.youtube.com/watch?v=GgvajuvSpF4
>>10336252
acceleration is not important

>>10336261
acceleration IS important though, idiot. why is the earth's frame of reference preferred (i.e. that twin is younger) to the rocket ship's if they're both inertial frames?

>>10336261
acceleration IS important though, idiot. why is the earth's frame of reference preferred (i.e. that twin is older) to the rocket ship's if they're both inertial frames?

Youre right about relativity of frames. Imagine A is smart enough to know B is moving at a relativistic speed and vice versa. There will be a discrepancy in person a's calculation of B's age because of something called the relativistic doppler shift. So the paradox comes down to the fact that theres an asymmetry between frames that occurs before either point returns to a reference frame.

>>10336294
It is completely irrelevant. Sorry to tell you that you are misinformed. Does acceleration need to take place? Yes. Does it matter? No, because it is a thought experiment and calculations for the age of each of the twins does not at any time involve acceleration. Despite this, we have a discrepancy in ages. Is this because the experiment is flawed? Not really. Theres papers out there that use acceleration and GR but it's no longer the twin paradox.

>>10336231
like einstein said. If the twin in the spaceship was looking at a clock on earth, lets say it's 1200. If he was moving at the speed of light then the photons he could see from the clock would show 1200 always, so time on earth would seem to be at a standstill.

>>10336320
first of all, just because there is acceleration doesn't imply this has anything to do with GR. acceleration happens in SR just fine. second of all, you're right that you can ignore the acceleration by approximating the worldline of the spaceship anon as being at constant velocity in the positive direction, and then constant velocity in the negative direction (a > shape on a standard spacetime diagram.) this implies there was an acceleration where the turn was. all the magic happens at that turn

>>10336252
>to compare their ages means they need to come to rest relative to one another
I never thought of that, although I can kind of see how it might make sense.

>>10336339
well simultaneity isn’t frame independent. two observers moving relative to one another see each other’s clocks moving slower than theirs so they have no common way to measure who is older. only in the same frame can they actually compare ages

>>10336323
This has nothing to do with the paradox. Time dilation is neither a paradox in general nor in the twin paradox problem. The paradox is in the seeming symmetry.

>>10336294
>>10336333
watch the video, it's all explained without any acceleration, with 3 observers instead, the pilots still have 2 reference frames compared to the earth, but acceleration is not the fundamental reason why the guy sitting still on earth experiences more time

>>10336374
yes it is. if your video doesn’t point that out, then it’s brainlet tier. i’ve worked the problem and the change of frames that the spaceship amon performs at the turn is where the asymmetry comes from. and physically, a turn is an acceleration

>>10336374
Acceleration is the only thing that distinguishes the stay behind twin from the travelling one, so it must be the fundamental reason for the difference. Your video is mistaken. If you think it's not, explain why here.

>>10336388
>>10336383
the frames of reference are important, not the acceleration, there's also a video without math if high school equations scare you
I'm not going to explain the videos because you're too lazy to watch it, I'm done here

>>10336429
you are so fucking retarded. the spaceship observer changes between two frames when he turns around and starts traveling back. i think you agree with that right? and that's what causes it? now, can we agree that changing between inertial reference frames requires an acceleration?

>>10336252
>doesn’t accelerate
nope, that's a meme
https://www.youtube.com/watch?v=noaGNuQCW8A

>>10336469
no, you're a meme
http://learn.real.physics.edu/from_a_book

>>10336474
ok gramps, pill time, you're getting cranky again

>>10336483
okay zoomer who never cracked a fucking book, look how retarded you are, pic related
sauce: Ohanian

do satellites in orbit have to compensate for differences in time on Earth?

>>10336516
https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Relativity

>>10336501
oooooooh a book, guess if it's printed you can stop thinking then

>>10336464
but information can change between inertial reference frames without any acceleration, do you agree?
what if one pilot, constantly moving at relativistic velocity passes by the Earth and starts a stopwatch at the same time as an Earth observer, then the pilot continues going to a star with no change in velocity; when he reaches the star he coincidentally passes by pilot 2 heading straight back to the Earth at the same speed in the opposite direction, when they pass by one another, pilot 1 tells pilot 2 the stopwatch time with pilot 2 continuing to record the time elapsed
when pilot 2 passes by the Earth and tells the Earth observer the total trip time(pilot 1 trip to star + pilot 2 trip back), the Earth observer's stopwatch will have recorded way more time passing even though there was NO FUCKING ACCELERATION

>>10336560
so what? that replaces a twin paradox with something that doesn’t tell you anything about the twins’ age, so you didn’t answer the question. if you want to have a twin come home he has to accelerate when he turns around; just read the Ohanian pic above

>>10336578
because only human bodies can measure time by aging, right?

>>10336580
you could send twin clocks instead. the clock on the space ship needs to accelerate when it turns around the exact same way.

just read the Ohanian pic asshole; this is completely settled.

>>10336578
watch the video, retard
you're just looking more an idiot every time you reply

>>10336585
it's wrong and you're wrong, read what I wrote again, the same differences in times elapsed is found with just information exchange between inertial reference frames without any acceleration

>>10336593
fuck your video. i hate fucking innumerate zoomer cunts who think youtube is better than textbooks widely used to teach the subject. neck yourself and never attempt physics again

>>10336597
but your scenario doesn’t answer which twin (clock or human) would experience more proper time—you’re making an argument that is irrelevant and you’re confusing yourself. Ohanian is right, and if you argue against a canonical SR textbook you need to realize you’re retarded

>>10336604
it's a thought experiment to show acceleration is not the important part........ you fucking moron

>>10336598
kek
even in the beginning you looked like a village idiot juggling frozen pieces shit,
now you just look like one after the shits have thawed

>>10336598
kek
even in the beginning you looked like a village idiot juggling frozen pieces of shit,
now you just look like one after the shits have thawed

>>10336609
no, the acceleration is important and you’re retarded

>>10336616
too bad you’re wrong and got totally destroyed

>>10336621
oh look Mr. DestroyedZoomer is getting nervous and deleting his posts now and reposting them because he’s shaking in his boots. fuck off back to high school

>>10336628
ooh dirtyhands, so amusing

>>10336633
https://youtu.be/r3qOf0ufxc8

>>10336645
https://www.youtube.com/watch?v=PLmnGjydJyI

if accelerating makes you age slower, will braking turn you old?

>>10336697
>if accelerating makes you age slower
Only in relation to someone in another frame of reference.
To you, personally, your proper time always clicks ahead at the same rate.
From your frame of reference you're not aging slower, everyone else on earth is aging faster.

>>10336697
https://youtu.be/7Ewu03G6krs?t=60

>>10336231
Speed of light is constant no matter how fast you are moving. So if you move at 90% speed of light, your measurement still need to read that light travels at its speed. For that to happen time bends

Why did they start balding?

>>10336762
tougher question is why is there shit all over the millenium falcon

>>10336697
braking is acceleration in the opposite direction of your velocity in all seriousness

>>10336464
>>10336474
>>10336501
>>10336578
>>10336585
>>10336598
>>10336604
>>10336623
pure brainlet

>>10336560
What if some time after pilot one passes the earth, another pilot 3, who is flying even faster, passes earth, records their stopwatch time and starts their own stopwatch similarly? Pilot 3 catches up to pilot 1 conveniently right as pilot 1 reaches the star. Pilot 1 and pilot 3 then compare numbers. And guess what, pilot 1's stopwatch will have recorded way more time passing even though there was "NO FUCKING ACCELERATION".

>>10336231
>Why does the one who leaves the Earth age more?
He doesn't.The ship traveling at relativistic speeds puts the rest of the universe in a hyperbaric time chamber.
Like if goku really needed time to train, he'd punch freeza into space at near the speed of light, and by the time freeza gets back he will have had 20 years to train.

>>10336930
Hyperbolic wasn't it? Hyperbaric could work for faster recovery.

>>10336937
For the purposes of this exercise let Goku = Michael Jackson.

>>10336794
no u

>>10336231
When the travelling twin turns around, his plane of simultaneity jumps over a large period of time (during the turn around his frame is non-inertial).
>>10336261
This video is shit, it shows different experiment and ignores multiple important points that confuse people such as how A, B and C got there and what it means for them to do something "at the same time".
>>10336794
Your autism is off-spectrum.

>>10337771
>This video is shit
hand wavy, good response

OP here, thanks for the discussion and links. I've just bought a book on special relativity since this seems to be a complex topic that requires background reading.

>>10336294
Not the acceleration in any physical sense, but the fact that one had to transition from one frame of reference to different ones while the other just stayed in the same reference frame all along.

>>10338062
Couldn't you say that the whole universe rotated around the one who "travelled"?

>>10336252
fpbp. What makes the difference is the fact that the first has to turn around.

>>10338323
Why can't the whole universe be considered to be turning around him?

>>10338338
That's not what matters, the important part is that he's producing a force to change his acceleration. The perspective of the movement is not important.
>>10337771
It's exactly as this anon says.

Twin paradox is bullshit
If it was real then why don't rich people pay engineers to build structures that spin really fast and live in them so they can live longer until better life extension methods are invented?

>>10338338
Rotation is verboden in special relativity.

>>10338416

>>10338416
We don't have that level of technology dipshit.

>>10337771
>This video is shit
You don't get to call Dr. Don shit around me!

>>10337771
It doesn't matter how they got there, they're just in constant motion, and there's nothing in it happening "at the same time". Anyway, it's the switch between frames/planes of simultaneity, the acceleration is still not the important part.

>>10338891
You measure the proper time along a spacetime trajectory. Since that trajectory has to turn around, the trajectory has acceleration. The turnaround point where the trajectory has nongeodesic motion is the only thing distinguishing the twins.

>>10338975
not really since there's also length contraction, the stationary twin will just see the spaceship contracted while the moving twin will see the entire universe length contracted in the direction of motion

>>10338987
You clearly haven't studied any of this, just shut up already.

>>10339192
if you're trying to say length contraction doesn't happen, you're wrong, but I'm just guessing since you didn't make any argument

>>10338987
Why should I care about what the rest of the universe is doing?

>>10339226
it means that in your own frame you have less space to travel to reach that star, meanwhile the guy on Earth sees the space you travel normally so from his frame you take longer simply because there's more space

>>10339469
The star is just a framing device for setting up the problem. There doesn't need to be anything except for two observers travelling at close to the speed of light relative to each other. The rest of the universe doesn't matter.

>>10339489
but the distance you have to travel to get there matters, and if you're moving at close to the speed of light then you'll see that space contracted, for each tick of your proper time you travel through contracted space
the guy sitting stationary on Earth will see just your spaceship and the space inside it contracted, but the space you travel he sees normally which makes sense since your clock ticks to him are dilated

>>10339510
The earth's clock ticks are just as dilated from the spaceship's perspective.

>>10339560
yes, but the Earth sees only the spaceship contracted, while the spaceship sees the Earth his destination and all the space he has to travel between them contracted
both see each-others clocks dilated but only one, the spaceship, sees the distance to be traveled length contracted

Never thought I'd be saying this about this, but - leaving this little song here due to relevancy:
https://www.youtube.com/watch?v=kE8kGMfXaFU

>>10339577
There doesn't have to BE a destination. He could just decide to accelerate some day to return.

>>10339577
think about this: what if the destination star is moving away from earth at a velocity v. at time t=0 let's assume the distance to the destination star is measured to be D. now also assume the space ship twin hits velocity v at t=0 as he passes earth moving toward the star. right at that moment he measures the distance from earth to the star in his reference frame. fact: he measures a distance greater than D

>>10339617
wait no i screwed that up. if the twin moves at v then he measures equal to D but if he moves at say v/2 then he'll measure more than D. my bad.

>>10336231
That's because the two twins start from the same reference frame (earth) and only one of them will eventually leave this reference frame, and he'll be the younger one

>>10339585
sure, but anyway that's what shows there isn't any paradox, there's an asymmetry between the traveler and the Earth because the traveler sees the space he's actually moving through contracted while the Earth sees only the spaceship contracted moving through normal space

>>10339637
>there's an asymmetry between the traveler and the Earth because the traveler sees the space he's actually moving through contracted while the Earth sees only the spaceship contracted moving through normal space

This is exactly the wrong message of special relativity. Up until the traveller accelerates to turn around, both of their reference frames were equally valid.

If the earth was moving at 0.9c through the milky way, and our traveller decided to leave earth and put himself at rest with respect to the milky way for a few years before returning, the result would be the same: the traveller comes back younger than his twin.

>>10339637
There's no such thing as normal space, that's one of the fundamental postulates of relativity. How could you know that the Earth or the galaxy as a whole aren't moving through "normal" space and therefore experience contraction?

Both inertial sytems are equivalent, it just happens that in one of them the galaxy is more or less stationary

>>10339655
>>10339663
fuck, you're right, I want to bring back the destination

>>10336231

Easy way to remember:
If you move very fast, time moves very slow..

>>10339967
move relative to what?

>>10339968
>move relative to what?

To what ever you want to be your frame of reference.

There is no ABSOLUTE frame of reference.

This means time moves differently everywhere.

>>10336231
Not my area of expertise, but the way I understand it is that, when traveling close to the speed of light, space starts to elongate (for some reason?). Time effectively moves slower in elongated space because in a sense everything is more spread out. Therefore, the twin traveling near light speed will age at a slower rate relative to the twin traveling at normal speed.

>>10340115
you're way way off bro