1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Everyday Time Dilation

  1. Sep 15, 2013 #1

    I have some doubts about this problem which I have attached.
    If we assume that both the clocks are started at the time the
    airliner goes for a trip, then for an observer on the airliner,
    when the airliner comes back to the New York, the time interval
    would be a proper time interval since both the time measurements
    are done at the same place on the airliner. But the
    observer in New York is also not moving. So when the airliner
    comes back and the observer in the ground stops his clock, his
    measurement could also be considered proper time interval
    since the measurement is again done at the same place.
    Am I missing something ?



    Attached Files:

    • 1.png
      File size:
      18 KB
    Last edited: Sep 15, 2013
  2. jcsd
  3. Sep 15, 2013 #2
    I'm not sure what you mean by a proper time interval, but both the time intervals seen on the plane and on the ground are correct within their own reference frames. The plane was in a moving reference frame so time will have dilated(1 second on the plane takes more than one second on the ground), relative to the ground. But both clocks are correct, or proper. The velocity of the plane actually meant that the distance it traveled was shorter according to the clock on the ground (length contraction). Try to reconcile this with what the plane sees the clock on the ground doing and check that the clock on the ground still sees 4 hours.
  4. Sep 15, 2013 #3
    Proper time interval is defined as the interval between two events which occur at the same position in a given inertial frame. In this sense, time interval measurements by both these persons seem to be proper time interval.
  5. Sep 15, 2013 #4


    User Avatar
    Gold Member

    Yes, both times are the proper time interval IN THEIR OWN FRAME OF REFERENCE. But since they are not in the same frame of reference, they do not show the same amount of time.
  6. Sep 15, 2013 #5
    Apologies, the last time I studied relativity in any real depth was over a year ago and I forget the terminology for things.......I think my answer is still valid though, despite not using proper properly!
  7. Sep 15, 2013 #6
    I think part which is confusing is that the airliner comes back to New York. If it has landed at some other place like San Francisco, then for clock on the airliner we have proper time interval and for the clock on the ground we don't have a proper time interval.
  8. Sep 15, 2013 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    There's not just one proper time between two events in space-time, if that's what you were thinking. The proper time measured between two events also depends on the motion of the clock.
  9. Sep 15, 2013 #8
    vela, yes that's what I was thinking. But instead of airliner coming back to NY , I can imagine airliner going equal distance forward from the point of return and landing in some location we can all NY2. I think we get the same solution but conceptually its easier. Am I right ?
  10. Sep 15, 2013 #9


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Yeah, if all you're looking to do is calculate the effect of time dilation, that scenario would be easier. But perhaps one of the purposes of the problem was to get you to think about exactly what you did.
  11. Sep 16, 2013 #10


    User Avatar
    Homework Helper

    It's more likely that clocks run a bit faster on the plane, assuming gravitational dilation is greater that velocity dilation.
  12. Sep 16, 2013 #11
    Thanks.. that explains it
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Threads - Everyday Dilation Date
Frame of reference/ time dilation Mar 6, 2018
Physics in everyday life May 19, 2016
Precession and its everyday applications Apr 16, 2012
Simple, everyday problems Oct 20, 2010
Simple, everyday problems Oct 20, 2010