Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Trying to understand time delineation

  1. Sep 30, 2010 #1
    Hi, it is my first time posting on this forum, and you have no doubt seen similar questions.

    I am just an average person trying to understand the concept of time dilation. So I've read through the theory, but my mind goes all fuzzy when I get to this part.
    So I know I'm missing something major, and I might be comparing apples with pears.

    I made this graphical representation (of my thoughts) to try and reason it out. Still no success. Could someone explain in layman's terms, with reference to my pics?

    [PLAIN]http://img718.imageshack.us/img718/8779/timedelineation.jpg [Broken]
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Sep 30, 2010 #2


    Staff: Mentor

    Hi Vivaci, welcome to PF,

    I can't really follow your diagrams. Perhaps you can work in a traditional 1,1 spacetime diagram which is drawn with the time axis vertical and one spatial dimension horizontal with the other two spatial dimensions suppressed to make it easier to draw.

    As far as an easy explanation, I actually prefer to start from the spacetime interval. There is a quantity called the spacetime interval which is the same in all reference frames. It can be written:


    All of the relativistic effects can be derived from this one formula.
  4. Sep 30, 2010 #3


    User Avatar
    Science Advisor

    Welcome to PF, Vivaci!

    I think I understand your first two lines of diagrams. Nothing wrong with them except the "when you will see the object..." part, this point is obviously to the right of "You" in the first diagram.
    However, they have nothing to do with time dilation, the're only concerning the classical doppler effect.
    Time dilation is what is left after you correct for light travel times. You have to draw http://en.wikipedia.org/wiki/Time_d...ce_of_time_dilation_due_to_relative_velocity" to derive it, and you have to use the assumption that the speed of light is the same in all diagrams.

    For your other diagrams: you don't need 3D graphs for this "experiment". Try to plot the relevant events and worldlines in a simple 2D time/distance diagram. You'll need http://en.wikipedia.org/wiki/Spacetime_diagram" [Broken] anyway if you want to learn relativity.
    Last edited by a moderator: May 5, 2017
  5. Sep 30, 2010 #4
    Perhaps it is my account but I do not see any diagrams.
    Oh, never mind, I found out why, here in China not everything is accessible and imageshack is one of the blocked sites.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook