Length contraction occurs infront of AND behind you?

Click For Summary

Discussion Overview

The discussion revolves around the concept of length contraction in the context of special relativity, specifically whether length contraction occurs for objects both in front of and behind an observer in motion. Participants explore the implications of relative motion on the perception and measurement of length contraction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether length contraction applies to objects behind them as well as in front, suggesting a need for clarification on the phenomenon.
  • Another participant asserts that length contraction is independent of the observer's line of sight and depends solely on the relative motion between the observer and the object.
  • A different viewpoint indicates that while length contraction occurs on both sides, visual perception is affected by light travel time, which may lead to different observations than the theoretical contraction.
  • A participant expresses interest in understanding how moving towards or away from an object influences length contraction, concluding that relative velocity is the key factor, rather than the direction of movement.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between visual perception and length contraction, indicating that while some agree on the mechanics of contraction, there is no consensus on how it relates to what one observes visually.

Contextual Notes

The discussion highlights the complexity of interpreting length contraction in relation to light travel time and relative motion, with some assumptions about the observer's frame of reference remaining implicit.

coktail
Messages
118
Reaction score
1
If I am moving through space, things in front of me contract in the direction parallel to my movement. Does this also occur to objects behind me? For example, I look behind me, would things be contracted?

As always, thanks.
 
Physics news on Phys.org
coktail said:
If I am moving through space, things in front of me contract in the direction parallel to my movement. Does this also occur to objects behind me? For example, I look behind me, would things be contracted?
Length contraction has nothing to do with where you look or where an object is with respect to you. Any object moving with respect to you will be measured by your frame to be contracted along its direction of motion.

This is different from the visual appearance of moving objects, if that's what you are interested in.
 
coktail said:
If I am moving through space, things in front of me contract in the direction parallel to my movement. Does this also occur to objects behind me? For example, if I look behind me, would things be contracted?

Yes, the length contraction happens on both sides. However, that's not necessarily what you will SEE with your eyes if you turn around and look backwards because your eyes are responding to the light that hits them where you are, and that light left the object you're looking some time ago.

The thing to remember here is that length contraction and time dilation are what's left over after you've corrected for light travel time.
 
Thank you. I'm not too interested in the visual appearance (at least in this thread), but more about whether if I am moving towards vs away from an object makes a difference in length contraction. From your post, I gather that wether I am moving towards or away from an object is irrelevant, and what matters is the relative velocity between myself and the object?

Edit: I posted this before I saw Nugatory's reply. Thank you to both of you!
 
Last edited:

Similar threads

High School Why does length contraction occur and how does it relate to time dilation?
  • · Replies 63 ·
3
Replies
63
Views
6K
Undergrad Perceive Length Contraction VS Terrell Penrose
  • · Replies 14 ·
Replies
14
Views
2K
Undergrad What causes time dilation and length contraction
  • · Replies 10 ·
Replies
10
Views
2K
Undergrad An issue with length contraction
  • · Replies 78 ·
3
Replies
78
Views
7K
Undergrad Relativity of Simultaneity and Length Contraction
  • · Replies 54 ·
2
Replies
54
Views
5K
High School Thought Experiment: Behavior of shadow of object moving at speed c
  • · Replies 14 ·
Replies
14
Views
2K
Undergrad Question about length contraction
  • · Replies 45 ·
2
Replies
45
Views
6K
High School Does shortness from length contraction have a real physical effect?
  • · Replies 12 ·
Replies
12
Views
2K
Undergrad Linear Accelerator Length Contraction
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Does SR Length Contraction Halve Space Travel Time?
  • · Replies 17 ·
Replies
17
Views
2K