Post by AuntieSocial on Nov 20, 2003 8:26:43 GMT -5
Taken from the old board ... Science & Philosophy forum ... Any Astronomy Questions? thread
emanym Post – November 12, 2003 – Old Board
I've got a question that's been bugging me since highschool:
A set of twins are on a planet. One twin shoots off in a spaceship at speeds nearing the speed of light. The twin in the spaceship comes back to the planet and has aged 5 years, whereas the twin who stayed on the planet has aged 20 years. Time-dialation and what-not, right?
Well, why does the twin who shoots off into space age slower?
jacopo7531 Post – November 16, 2003 – Old Board
emanym Post – November 20, 2003 – Old Board
emanym Post – November 12, 2003 – Old Board
I've got a question that's been bugging me since highschool:
A set of twins are on a planet. One twin shoots off in a spaceship at speeds nearing the speed of light. The twin in the spaceship comes back to the planet and has aged 5 years, whereas the twin who stayed on the planet has aged 20 years. Time-dialation and what-not, right?
Well, why does the twin who shoots off into space age slower?
jacopo7531 Post – November 16, 2003 – Old Board
I think I'll try to field this one. You are correct emanym, it does have something to do with time dialation. For those who don't know, several weird ideas come out of the theory of special relativity. One of this is that observers in reference frames that are moving relative to each other measure length, simultanaity and time differently.
To clarify this a bit, I'll define two people (person A and person B). A and B are moving with respect to each other at a constant velocity. As a result of the postulates of special relativity, B's watch as observed by A will be running more slowly than A's watch as observed by A. This statement is also true for B. This is the idea of time dilation. If you observe a a clock that is moving relative to you, you would note that such clocks run slower than clocks which are not moving with respect to you.
Now, what emanym was referring to is typically called the Twin Paradox. The idea is that we have two identical twins Bob and John. John boards a rocket ship and blasts off. He flies to alpha centauri. Bob stays on Earth. Along the way, he monitors Bob's watch and notes that Bob's watch is running slow compared to his. Bob notes that John's watch is running slow.
When John returns to earth, he leaves his rocket and finds that his twin is an old man, but he has aged only a little. How is this possible if both twins observed that the other twin's watch was running slow?
So for now, I'll leave it at this. I'll give a hint. Special relativity deals only with inertial frames of reference. These are frames which are moving at constant velocity relative to each other and in which no external forces are acting. If either of these conditions are violated, general relativity must be used to obtain an accurate picture of the physics involved.
So can anybody see where the symmetry in the 'Twin Paradox' breaks down?
To clarify this a bit, I'll define two people (person A and person B). A and B are moving with respect to each other at a constant velocity. As a result of the postulates of special relativity, B's watch as observed by A will be running more slowly than A's watch as observed by A. This statement is also true for B. This is the idea of time dilation. If you observe a a clock that is moving relative to you, you would note that such clocks run slower than clocks which are not moving with respect to you.
Now, what emanym was referring to is typically called the Twin Paradox. The idea is that we have two identical twins Bob and John. John boards a rocket ship and blasts off. He flies to alpha centauri. Bob stays on Earth. Along the way, he monitors Bob's watch and notes that Bob's watch is running slow compared to his. Bob notes that John's watch is running slow.
When John returns to earth, he leaves his rocket and finds that his twin is an old man, but he has aged only a little. How is this possible if both twins observed that the other twin's watch was running slow?
So for now, I'll leave it at this. I'll give a hint. Special relativity deals only with inertial frames of reference. These are frames which are moving at constant velocity relative to each other and in which no external forces are acting. If either of these conditions are violated, general relativity must be used to obtain an accurate picture of the physics involved.
So can anybody see where the symmetry in the 'Twin Paradox' breaks down?
emanym Post – November 20, 2003 – Old Board
Is it because of accelleration? But if it is, then from John's perspective, isn't the entire universe accellerating away from him, and then accellerating back? Or is there some sort of universal frame of "still" reference? I'm confused.
