Calculating Time Dilation w/ Light Clock - Implications & Mistakes?

In summary, the length of the hypotenuse of the right triangle is the distance which the light moves from the floor to the ceiling of the car for people at rest on Earth. Divide it by c and it's time which the clocks at rest on Earth tick for one way, say ##T_E##. Double it for go-return.The height of those triangles, H, is the distance which the light moves from the floor to the ceiling of the car for the passengers. Divide it by c and it's time which the clocks at rest in the car tick for one way, say ##T_C##. Double it for go-return.As for one way tick counts Pyth
  • #1
rgtr
92
8
TL;DR Summary
## T_B = {T_A} {gamma} ##
In this picture it shows a light clock. Let's use the moving light clock example.
Am I essentially calculating the b component of moving clock.
Assume the moving frame is the B frame.
Assume the stationary frame is the A frame
https://simple.wikipedia.org/wiki/Light_clock

Or essentially the b component of the picture below. Am I essentially calculating Light time for the vertical component?
Does this have any more profound implications?
Did I make any mistakes in my thinking ?

triangle image
In post #15 I asked the question but someone recommended I start a new post and link the the original thread. Here it is https://www.physicsforums.com/threa...ing-by-t_stationary-for-light-clocks.1015831/ .
 
Physics news on Phys.org
  • #2
The length of the hypotenuse of the right triangle is the distance which the light moves from the floor to the ceiling of the car for people at rest on the Earth. Divide it by c and it's time which the clocks at rest on the Earth tick for one way, say ##T_E##. Double it for go-return.

The height of those triangles, H, is the distance which the light moves from the floor to the ceiling of the car for the passengers. Divide it by c and it's time which the clocks at rest in the car tick for one way, say ##T_C##. Double it for go-return.

As for one way tick counts Pythagoras theorem says
[tex]H^2+v^2T_E^2=c^2T_E^2[/tex]
where v is speed of the car, and
[tex]H=cT_C[/tex]
Solving the two equations
[tex]T_E=\frac{T_C}{\sqrt{1-\frac{v^2}{c^2}}}[/tex]
 
Last edited:
  • #3
rgtr said:
Am I essentially calculating Light time for the vertical component?
No. You are calculating the time for light to travel along the hypotenuse and expressing this as a ratio to the time taken for light to travel the vertical marked in your triangle diagram.

The reason for the apparent coincidence is fundamentally related to Minkowski geometry, which is the geometry of spacetime. In Euclidean geometry the distance between two points that are separated by ##(\Delta x, \Delta y, \Delta z)## is ##\Delta l##, where $$\Delta l^2=\Delta x^2+\Delta y^2+\Delta z^2$$ This is true in any reference frame - if you have rotated your axes compared to mine you will have different ##\Delta x, \Delta y, \Delta z##, but ##\Delta l## will be the same.

Minkowski geometry doesn't cover space, though. It covers spacetime. The equivalent to the above is that two events separated by ##(\Delta t, \Delta x, \Delta y, \Delta z)## are separated by a "distance" (formally called interval) defined by $$\Delta s^2=c^2\Delta t^2-(\Delta x^2+\Delta y^2+\Delta z^2)$$(NB: some sources define this with the opposite sign - either convention is fine and you just have to get used to checking your signs obsessively.) Again, if you are using a different frame with different coordinates you will have different ##\Delta t, \Delta x, \Delta y, \Delta z## but you will agree with me on ##\Delta s^2##.

So, in the case of the light clock, one frame says that the bottom and top reflection events happened at the same place (so ##\Delta x##, ##\Delta y##, and ##\Delta z## are all zero) and separated by some time ##\Delta t=T_A##. The other frame says that the reflection events were separated by ##\Delta x'=b##, ##\Delta y'=0##, ##\Delta z'=0##, and time ##\Delta t'=T_B##. But the two frames must agree on ##\Delta s^2##, so you can calculate ##\Delta s^2## in both frames and equate them:$$c^2\Delta t^2=c^2\Delta t'^2-\Delta x'^2$$
If you rearrange that you can make it look like Pytharoras' theorem applied to one of the right triangles in your image - that's the coincidence. It follows just from the presence of the minus sign in the Minkowski equivalent of the distance formula. It's pretty specific to the case where events happen at the same location in one frame.
 
  • Like
Likes PeroK
  • #4
I think I meant to say horizontal component. Saying vertical component was just a mistype. Whoops.
 
  • #5
Direction of vertical perpendicular or Horizontal transverse do not matter with the discussion when we disregard usually tiny gravity effect of GR.
 
Last edited:

FAQ: Calculating Time Dilation w/ Light Clock - Implications & Mistakes?

What is time dilation and how does it relate to light clocks?

Time dilation is a phenomenon in which time appears to pass slower for an observer in motion relative to another observer. Light clocks, which use the speed of light to measure time, are often used to explain this concept as they demonstrate how time can be perceived differently depending on the observer's frame of reference.

How is time dilation calculated using a light clock?

The formula for time dilation is t' = t / √(1 - v^2/c^2), where t' is the time measured by the moving observer, t is the time measured by the stationary observer, v is the velocity of the moving observer, and c is the speed of light. In a light clock, the time measured by the moving observer will be longer than the time measured by the stationary observer due to the constant speed of light.

What are the implications of time dilation in physics?

Time dilation has significant implications in physics, particularly in the theory of relativity. It explains how time can be perceived differently depending on the observer's frame of reference and how the laws of physics remain consistent regardless of an observer's relative motion. It also has practical applications in fields such as GPS technology and particle accelerators.

What are some common mistakes made when calculating time dilation with light clocks?

One common mistake is forgetting to convert units of velocity to meters per second, as the speed of light is typically measured in meters per second. Another mistake is using the wrong formula, as there are different formulas for time dilation depending on whether the observer is moving at a constant speed or accelerating. It is also important to consider the direction of motion and the relative velocities of the observers.

How does time dilation with light clocks differ from time dilation in general relativity?

Time dilation with light clocks is a simplified concept used to explain the effects of relative motion on time. In general relativity, time dilation is a more complex phenomenon that takes into account the curvature of spacetime caused by massive objects. In this case, time can appear to pass slower in regions with stronger gravitational fields, such as near a black hole.

Similar threads

Replies
22
Views
2K
Replies
54
Views
2K
Replies
16
Views
1K
Replies
88
Views
5K
Replies
55
Views
3K
Replies
14
Views
516
Replies
36
Views
2K
Replies
58
Views
4K
Back
Top