- #1
NoahsArk
Gold Member
- 237
- 22
Hello. Thank you to everyone who helped me with my previous post where I had general questions on special relativity. Several users suggested that I start by trying to understand the relativity of simultaneity which I did. Although I haven't mastered it, I understand it better now. Also, someone on another post recommended the book "Relativity Visualized" by Lewis Epstein which was also very helpful and uses R.O.S. as the foundation.
Regarding this post, I have been stuck on trying to understand the twin paradox. I've been trying to work up to an understanding of it. However, I've watched and read probably over ten different online lessons explaining the twin paradox, but I still don't understand it. Here are a few things that I'm trying to clarify:
1. In Epstein's book and in other lessons that I've seen, he uses a space time diagram to try and illustrate why one twin ages less than the other when they meet again. I'm not sure how to draw a space time diagram in here (I'd appreciate help on that as well), but the diagram is very simple so I'll just describe it: Earth twin has his X and Y coordinate system. He see's space twin get off into a rocket. On Earth twin's diagram, he will see space twin moving at some angle upwards and also to the right. That will be represented by a diagonal line moving in the positive X and Y directions. Then, on the return trip, the Earth twin will see the space twin moving in a diagonal line upwards and to the left. When the space twin returns to earth, the Earth twin will have aged more because he went straight through time up the Y axis, whereas space twin went in a bent line to the right and to the left back to the Y axis.
That all sounds logical, but the question is how would space twin's diagram of Earth twin's "journey" look like (since Earth twin is the one moving from space twin's perspective). It seems to me that it would be a mirror image of Earth twin's diagram. Space twin would see Earth twin first moving up to the left, and then, on the return trip, up and to the right. If that's the case they should be the same age when the meet again. If we drew side by side a space time diagram for each twin, how would those diagrams look compared to one another?
2. Can this all be explained with special relativity? If so, are there explanations that don't involve acceleration and the Doppler effect?
3. As a related question to question 1, I watched the minute physics video on the twin paradox:
Firstly, he says, as an answer to the asymmetry problem, that time rotates. I am very confused by what it means for time to rotate?? When he draws the diagram from the space twin's perspective, the lines are at a different angle then the lines from the Earth twin's perspective. Why is that? Also, he draws the diagram from the perspective of how the Earth twin perceives the time of the space twin, and then compares that to how the space twin views his own journey's time (proper time). Shouldn't we be comparing the Earth twin's perspective of space twin's time with space twin's perspective of Earth twin's time, and not with space twin's perspective of his own time?
Thanks
Regarding this post, I have been stuck on trying to understand the twin paradox. I've been trying to work up to an understanding of it. However, I've watched and read probably over ten different online lessons explaining the twin paradox, but I still don't understand it. Here are a few things that I'm trying to clarify:
1. In Epstein's book and in other lessons that I've seen, he uses a space time diagram to try and illustrate why one twin ages less than the other when they meet again. I'm not sure how to draw a space time diagram in here (I'd appreciate help on that as well), but the diagram is very simple so I'll just describe it: Earth twin has his X and Y coordinate system. He see's space twin get off into a rocket. On Earth twin's diagram, he will see space twin moving at some angle upwards and also to the right. That will be represented by a diagonal line moving in the positive X and Y directions. Then, on the return trip, the Earth twin will see the space twin moving in a diagonal line upwards and to the left. When the space twin returns to earth, the Earth twin will have aged more because he went straight through time up the Y axis, whereas space twin went in a bent line to the right and to the left back to the Y axis.
That all sounds logical, but the question is how would space twin's diagram of Earth twin's "journey" look like (since Earth twin is the one moving from space twin's perspective). It seems to me that it would be a mirror image of Earth twin's diagram. Space twin would see Earth twin first moving up to the left, and then, on the return trip, up and to the right. If that's the case they should be the same age when the meet again. If we drew side by side a space time diagram for each twin, how would those diagrams look compared to one another?
2. Can this all be explained with special relativity? If so, are there explanations that don't involve acceleration and the Doppler effect?
3. As a related question to question 1, I watched the minute physics video on the twin paradox:
Firstly, he says, as an answer to the asymmetry problem, that time rotates. I am very confused by what it means for time to rotate?? When he draws the diagram from the space twin's perspective, the lines are at a different angle then the lines from the Earth twin's perspective. Why is that? Also, he draws the diagram from the perspective of how the Earth twin perceives the time of the space twin, and then compares that to how the space twin views his own journey's time (proper time). Shouldn't we be comparing the Earth twin's perspective of space twin's time with space twin's perspective of Earth twin's time, and not with space twin's perspective of his own time?
Thanks