Explaining Length Contraction with the Light Clock Argument

In summary, the conversation discusses the use of the light clock argument in explaining length contraction in special relativity. One person has a question about the relativity of simultaneity and how it applies to full ticks. The other person clarifies that the half-tick events happen at different locations and are affected by the relativity of simultaneity, while the full-tick events happen at the same location and are agreed upon by all observers. The conversation ends with a thank you for clarification.
  • #1
kehler
104
0
We're just learning special relativity in class and my lecturer uses the light clock argument (two moving clocks - one parallel and one perpendicular) to explain length contraction.

I didn't quite get one thing about it. My notes say the light beam reflects at different times (i.e. they have different half-ticks) when the clocks are moving but reflects at the same time when the clocks are at rest, and this difference is due to the relativity of simultaneity.
But why doesn't this relavity of simultaneity principle also apply to full ticks?? From what I understand, the argument of length contraction is based on the fact that the clocks have to detect the beam at the same time.

I'm sure I must be understanding something wrongly here. Would appreciate if anyone could point it out to me :)
 
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  • #2
Realize that the half-tick events--when the light pulses hit the mirrors--take place at different locations, while the full-tick events happen at the same location. And, due to the relativity of simultaneity, events separated in space (along their direction of motion) that are simultaneous in the rest frame will happen at different times according to a moving observer.

But every observer in every frame agrees that the full-tick events--the two light pulses returning to the source--happen simultaneously.
 
  • #3
Oh right, I see. Thanks Doc Al :)
 

1. What is length contraction?

Length contraction is a theory in physics that explains how an object appears shorter in the direction of its motion when it is moving at high speeds, according to the observer's perspective.

2. How does the light clock argument explain length contraction?

The light clock argument uses the concept of time dilation to explain length contraction. It states that as an object moves at high speeds, time slows down for that object. This means that the number of ticks on a light clock, which measures time using the speed of light, will be fewer for the moving object compared to a stationary object. This leads to the perception that the moving object is shorter in length.

3. What is a light clock?

A light clock is a theoretical device used to measure time based on the speed of light. It consists of two mirrors placed parallel to each other, with a beam of light bouncing back and forth between them. By measuring the time it takes for the light to travel between the mirrors, the clock can accurately measure time.

4. Can length contraction be observed in everyday life?

No, length contraction is only noticeable at extremely high speeds, close to the speed of light. It is not observable in everyday life because the speeds at which we move are significantly slower than the speed of light.

5. Is length contraction a proven theory?

Yes, length contraction is a well-established theory in physics and has been confirmed through numerous experiments, such as the observation of muons in Earth's atmosphere and the use of particle accelerators. It is an important concept in the theory of relativity and has been validated by various experiments and observations.

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