Relativity along an axis in an inertial frame

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SUMMARY

This discussion focuses on the concepts of proper time and proper distance in the context of special relativity, specifically within an inertial frame. The proper time interval is defined as the time measured in the frame where the events occur at the same location, while the proper distance is the length measured in the frame where the objects are at rest. The participants clarify that for two events separated by Δx and Δt, the proper time is Δt observed in frame S' and the proper length is Δx observed in the same frame. The confusion arises from the application of the Lorentz transformation and the length contraction formula.

PREREQUISITES
  • Understanding of special relativity concepts, including proper time and proper distance.
  • Familiarity with Lorentz transformations and their applications.
  • Knowledge of length contraction and its mathematical representation.
  • Basic algebra skills for solving simultaneous equations.
NEXT STEPS
  • Study the derivation and implications of the Lorentz transformation equations.
  • Learn about the concept of simultaneity in different inertial frames.
  • Explore the implications of length contraction in various scenarios.
  • Practice solving problems involving proper time and proper distance using specific examples.
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This discussion is beneficial for physics students, educators, and anyone interested in understanding the principles of special relativity, particularly those focusing on inertial frames and the relationship between time and space measurements.

ZanyCat
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Suppose that two events occur on the x-axis of an inertial frame, Δx apart with a time interval between the events of Δt.
a) the proper time interval between the events is...?
b) the proper distance between the events is...?


I think I'm just getting confused by the wording. I imagined that I was in the same frame of reference, and therefore the answers are Δt and Δx. But evidently, I'm wrong. Do I need to set the speed of the frame to 'v' and do something with simultaneous equations to remove that variable?

Thanks!
 
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OK, so I defined a stationary reference frame as S, and defined the frame in the question as S'. S' is moving wrt S at a velocity v.
So the proper time is the Δt observed in S', and the proper length is the Δx observed in S'.

I think I've worked out a, but struggling with b. I'm using the length contraction formula as one equation, and the Lorentz coordinate transformation as the second equation, but when I solve them simultaneously I can only achieve v=0.
 
Start with definitions. What are proper time and distance?
 
Proper length is measured distance in the FOR where the objects are at rest, i.e. in frame S'.

I'm using the equations L' = L/gamma and x' = gamma(x-vt) and trying to solve these simultaneously, am I on the right track?
I can't determine whether L' = x' and L = x, or L' = x and L = x', though...
 
What are the "objects" in the case? Are they at rest as stated? In what reference frame are they at rest?
 
The objects are two arbitrary points situated along the x-axis of S', and are at rest in frame S', thus always separated by delta x.
 
If you measure distance between two arbitrary points, you get arbitrary results. I do not think this is what the problem is about. Connect "objects" with the description of the problem.
 
ZanyCat said:
Suppose that two events occur on the x-axis of an inertial frame, Δx apart with a time interval between the events of Δt.
a) the proper time interval between the events is...?
b) the proper distance between the events is...?


I think I'm just getting confused by the wording. I imagined that I was in the same frame of reference, and therefore the answers are Δt and Δx. But evidently, I'm wrong. Do I need to set the speed of the frame to 'v' and do something with simultaneous equations to remove that variable?

Thanks!
Given the information as stated, with everything motionless in an inertial frame, why would the "proper time interval" not be \Delta t and the "proper distance" \Delta x.
 

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