asprung Posted March 9, 2009 Share Posted March 9, 2009 The space twin after having run at a speed approaching the speed of light has docked in space. The earth twin visits him in his own space having traveled at a slower speed. When they meet in space it is the year 2000 on the space twin’s calendar,and the year 2010 on the earth’s twin’s calendar. When the earth twin steps aboard the space twin’s ship does he experience the calendar year 2000? If so what happens to his history to the year 2010? Link to comment Share on other sites More sharing options...
swansont Posted March 9, 2009 Share Posted March 9, 2009 The space twin after having run at a speed approaching the speed of light has docked in space.The earth twin visits him in his own space having traveled at a slower speed. When they meet in space it is the year 2000 on the space twin’s calendar,and the year 2010 on the earth’s twin’s calendar. When the earth twin steps aboard the space twin’s ship does he experience the calendar year 2000? No. According to his timekeeping it is 2010. If so what happens to his history to the year 2010? There is no such thing. Time is not absolute. There is only history of 2010 from the reckoning of the earth twin. Whatever happens on the first day back happens on January 1, 2000 according to the space twin and on January 1, 2010 according to the earth twin. ——— If for some odd reason a person decided to renumber his calendar and subtract 10 years from the date, he would not all of the sudden re-experience the year 1999. Dates are bookkeeping aids. Link to comment Share on other sites More sharing options...
asprung Posted March 10, 2009 Author Share Posted March 10, 2009 The earth twin experenced events between 2000 and 2010 on his calender. Are you saying that the space could experence such events but think they occured before 2000? Link to comment Share on other sites More sharing options...
iNow Posted March 10, 2009 Share Posted March 10, 2009 Are you saying that the space could experence such events but think they occured before 2000? Before 2000 relative to whom? Implicit in your sentence is your continued belief in some absolute frame of reference, some absolute time. There's not. So, "occurred before 2000" in which reference frame? Link to comment Share on other sites More sharing options...
john5746 Posted March 10, 2009 Share Posted March 10, 2009 The earth twin experienced 10 years of time, the space twin experienced very little. The space twin traveled thru much space, but the earth twin traveled little in comparison. They do not have to experience the same amount of space or the same amount of time. Link to comment Share on other sites More sharing options...
Mr Skeptic Posted March 10, 2009 Share Posted March 10, 2009 Time is not frozen in relativity, but the rate at which time passes depends on velocity (and acceleration). Both twins would experience the same dates as measured by someone on earth, but for one a particular day (as measured by his clock) would last longer than for the other, and may be labeled as a different day by his clock-calendar. When they meet up, their clock-calendars will disagree, but they will be at the same place at the same time. Link to comment Share on other sites More sharing options...
NowThatWeKnow Posted March 10, 2009 Share Posted March 10, 2009 You have to keep in mind that it is not only the space twin's clock that is running slow relative to the Earth twin's clock. The space twin would not have time for as many "events" as the Earth twin. It may take a week (of Earth time) just to brush your teeth at relativistic speeds but would seem like normal time to you. Relative to the space twin, the Earth twin would be like a movie on fast forward. Link to comment Share on other sites More sharing options...
swansont Posted March 10, 2009 Share Posted March 10, 2009 The earth twin experenced events between 2000 and 2010 on his calender. Are you saying that the space could experence such events but think they occured before 2000? For the space twin to arrive back in 2000, he must have left before then. Up until his departure (let's say that happened in 1990) his clock and calendar were synchronized with the earth twin. After that, they was not. Until his return, all that the space twin experienced happened between 1990 and 2000, according to his clock. His clock ran slow compared to the earth twin's clock, who says that the trip lasted from 1990 to 2010. Their clocks disagree on what time it is. ——— Even though time zones are not from a relativistic effect, the concept has some applicability. I can say that something happened at noon, but for someone in Europe that will be at 5 PM. Did it happen at both times? Did it really happen at noon? It depends on whose clock you are using. We often choose UTC as a convention to avoid the confusion, but the choice of UTC is driven by convenience, not physics. The confounding thing about relativity is that it's not just a static offset of times, but that clocks run at different rates. We could agree on a universal time if we chose to, by picking a single reference frame and do the relativistic conversions, but there is no physics reason to prefer one over the other. 1 Link to comment Share on other sites More sharing options...
iNow Posted March 10, 2009 Share Posted March 10, 2009 Even though time zones are not from a relativistic effect, the concept has some applicability. I can say that something happened at noon, but for someone in Europe that will be at 5 PM. Did it happen at both times? Did it really happen at noon? It depends on whose clock you are using. What a very simple and straight forward way to make this concept more accessible. Thank you for sharing that. I'll be storing that one in the back of my mind for future use. Link to comment Share on other sites More sharing options...
swansont Posted March 10, 2009 Share Posted March 10, 2009 What a very simple and straight forward way to make this concept more accessible. Thank you for sharing that. I'll be storing that one in the back of my mind for future use. <cough>Reputation<cough> 1 Link to comment Share on other sites More sharing options...
iNow Posted March 10, 2009 Share Posted March 10, 2009 Sure, I'd love some. Thanks! 1 Link to comment Share on other sites More sharing options...
asprung Posted March 11, 2009 Author Share Posted March 11, 2009 There must something that proceeds uniformly in the universe to allow the twins to view an event as it occurs, and come back on earth together. 1 Link to comment Share on other sites More sharing options...
iNow Posted March 11, 2009 Share Posted March 11, 2009 There is something like that in the universe. It's your imagination. Link to comment Share on other sites More sharing options...
Mr Skeptic Posted March 11, 2009 Share Posted March 11, 2009 There must something that proceeds uniformly in the universe to allow the twins to view an event as it occurs, and come back on earth together. You could call it "earth time". Just keep in mind that if you want your clock to measure earth time it has to be on earth. Otherwise, you have to get a big telescope and see what time it says on earth from your spaceship. Link to comment Share on other sites More sharing options...
cameron marical Posted March 11, 2009 Share Posted March 11, 2009 There must something that proceeds uniformly in the universe to allow the twins to view an event as it occurs, and come back on earth together. There is something like that in the universe. It's your imagination. no, what i think that asprung is saying is lagit. if i understand it right, there should be something{not time}that is universal and absolute. say i dropped a cup. well, someone on the other side of the galaxy wouldnt know about it, but it still happened at the same... i dont want to say time...moment. they wouldnt be aware of it happening of course, and nothing we know of would reach him directly at the time of the event, but it, nevertheless, did happen at the same moment. so thats an example of an absolute... something. also, to add to little understandment of the twins paradox helpers, i can just copy and paste this from another post. it helped me out alot. syadnom posted it. think of it like this. from any one point, the speed of light must always be the speed of light. so if you travel near the speed of light and you turn on your headlights, you must perceive that light as traveling at the speed if light. Your perception of time will then be slowed by the same ratio as the speed of light - your speed = v so v:c is the same ration as (your time):(a viewpoint at rest relative to your speed). Link to comment Share on other sites More sharing options...
Sayonara Posted March 11, 2009 Share Posted March 11, 2009 You could call it "earth time". Just keep in mind that if you want your clock to measure earth time it has to be on earth. Otherwise, you have to get a big telescope and see what time it says on earth from your spaceship. I quite like the idea of a giant LCD clock complete with snooze button orbiting Earth, but viewed from afar it would always give the wrong time. Link to comment Share on other sites More sharing options...
Sisyphus Posted March 11, 2009 Share Posted March 11, 2009 no, what i think that asprung is saying is lagit. if i understand it right, there should be something{not time}that is universal and absolute. say i dropped a cup. well, someone on the other side of the galaxy wouldnt know about it, but it still happened at the same... i dont want to say time...moment. they wouldnt be aware of it happening of course, and nothing we know of would reach him directly at the time of the event, but it, nevertheless, did happen at the same moment. so thats an example of an absolute... something. Two events can happen simultaneously in your reference frame, but in different reference frames they wouldn't be simultaneous. also, to add to little understandment of the twins paradox helpers, i can just copy and paste this from another post. it helped me out alot. syadnom posted it. That's not the whole story, though. It's important to remember that the situation is symmetrical. In other words, time slows down for him from our perspective, but from his perspective, we (the Earth) are the ones moving at nearly the speed of light, and we're the ones whose time has slowed. Link to comment Share on other sites More sharing options...
swansont Posted March 11, 2009 Share Posted March 11, 2009 no, what i think that asprung is saying is lagit. if i understand it right, there should be something{not time}that is universal and absolute. say i dropped a cup. well, someone on the other side of the galaxy wouldnt know about it, but it still happened at the same... i dont want to say time...moment. they wouldnt be aware of it happening of course, and nothing we know of would reach him directly at the time of the event, but it, nevertheless, did happen at the same moment. so thats an example of an absolute... something. No, that doesn't exist. Physics has to be exactly the same for observers in different inertial reference frames. There is no absolute frame. Link to comment Share on other sites More sharing options...
Mr Skeptic Posted March 12, 2009 Share Posted March 12, 2009 I quite like the idea of a giant LCD clock complete with snooze button orbiting Earth, but viewed from afar it would always give the wrong time. I know what you mean, the light will take time to reach you. But that was part of my intention. There should be a zero spacetime interval [math]s = \sqrt{r^2 - c^2t^2} = 0[/math] between earth at that time, and your position at the time you receive the image of the clock showing that time. Maybe I'm mixing up my spacetime though, I never was all that clear on the time portion of spacetime. Link to comment Share on other sites More sharing options...
swansont Posted March 13, 2009 Share Posted March 13, 2009 I've moved some posts that were discussing the concept of "now" over to the thread discussing that subject. Let's keep discussion here on the topic of the OP, which is at least somewhat still connected with relativity Link to comment Share on other sites More sharing options...
asprung Posted March 14, 2009 Author Share Posted March 14, 2009 Relativity seems to accept a concept of "now", as it has the space twins being able to view an event as it occurs, and having the twin return to earth "now". Link to comment Share on other sites More sharing options...
cameron marical Posted March 14, 2009 Share Posted March 14, 2009 I quite like the idea of a giant LCD clock complete with snooze button orbiting Earth, but viewed from afar it would always give the wrong time. I know what you mean, the light will take time to reach you. But that was part of my intention. There should be a zero spacetime interval between earth at that time, and your position at the time you receive the image of the clock showing that time. Maybe I'm mixing up my spacetime though, I never was all that clear on the time portion of spacetime. you could just see what the clock says for you, and add the amount of time it would take the light to reach you from it, judging by yours and its coordinates. get the right time, i think. Link to comment Share on other sites More sharing options...
NowThatWeKnow Posted March 14, 2009 Share Posted March 14, 2009 you could just see what the clock says for you, and add the amount of time it would take the light to reach you from it, judging by yours and its coordinates. get the right time, i think. The right time on Earth but not your right time. I think. Link to comment Share on other sites More sharing options...
swansont Posted March 14, 2009 Share Posted March 14, 2009 Relativity seems to accept a concept of "now", as it has the space twins being able to view an event as it occurs, and having the twin return to earth "now". I think it's more accurate to say that relativity is oblivious to the concept. It's an issue in your mind, apparently, because you have a preconceived notion about how the universe should behave. Relativity discusses time and clock sychronization and simultaneity. You really need to formulate your objections in those terms if you want this to be a discussion of relativity. Link to comment Share on other sites More sharing options...
asprung Posted March 14, 2009 Author Share Posted March 14, 2009 I have no objections, I am just trying to understand how the twin is in the year 2000 in his time frame yet steps into the year 2010 on earth. I can only think that he is really ageing his with his twin and only his clock runs slower. Link to comment Share on other sites More sharing options...
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