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Understanding Time Zones

  1. Jan 4, 2014 #1
    Hello, thanks for checking this out. I've come up with a mind boggling thought experiment (at least for me it is), and any insight is welcome.

    Let's say you own an airplane, and you fly west with the same angular velocity as the earth's rotation. Let's also suppose we have a very special clock which determines the time based on your angular position and the direction to the sun.

    So, having reached the correct speed at exactly noon, your special clock now stays fixed at exactly noon, for as long as you fly at that speed. But at some point in your long flight, the date increases, even though you've been flying at noon for hours.

    What location are you above when the date increases? What location is the 'furthest in time' - as in the first place to change to a new date?
    What sense does this make?

  2. jcsd
  3. Jan 4, 2014 #2


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  4. Jan 4, 2014 #3


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    Time zones are an arbitrary convention.

    It's also not clear how your plane flies west with the same angular velocity as the earth's rotation, since the earth rotates from west to east.
  5. Jan 4, 2014 #4
  6. Jan 4, 2014 #5
    The Earth rotates at about 1,000 miles per hour, so in the 12 hours it takes for noon to become midnight; thus, changing the date, you'd have traveled 12,000 miles, which is halfway around the world. Where you end up depends on where you started. What place is the first to change from, for example, Saturday to Sunday? I think the answer to that is unrelated to the experiment. You can probably Google that and find the answer. From a quick search, I found that the answer to that is the island nation of Kiribati.
  7. Jan 4, 2014 #6
    First of all, you are confusing solar time with clock (local) time. The two are not the same. They are not even close. Solar noon and local noon rarely coincide. Once a day for a split second is the general rule, and not even that for the Polar Areas or many places on Daylight Saving Time.

    Secondly, no special clock is going to give you any special time wherever you happen to be. Your time and date in the aircraft will be exactly the same as at a spot directly below you. That’s the way time zones work.

    Thirdly, in order to maintain consistent solar noon in your aircraft, you would have to be travelling west at the speed of the Earth’s rotation at that latitude.

    Don’t feel badly about being confused about time zones. Most people on this planet share your confusion.

    Edit: I did it myself just now. I hope I corrected my error in time.
    Last edited: Jan 4, 2014
  8. Jan 4, 2014 #7


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    That's why I have this map bookmarked. :approve:

  9. Jan 5, 2014 #8


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    The OP's question was answered in the very first reply, by Drakkith:
    People seem confused by the OPs description of the experiment.
    The OP meant the plane would be stationary in an inertial frame, so that it's angular speed relative to Earth is the same as Earth's angular speed, only in the westward direction. In other words, you could think of the plane as "hovering" while the Earth rotates below it.

    Yes, exactly.
  10. Jan 5, 2014 #9


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    The fictional Phileas Fogg experienced something similar in Jules Verne's Around the World in Eighty Days, although he did his journey in 80 days, not 24 hours, and he traveled eastwards, not westwards, so the land-based date decreased by one day for him.
  11. Jan 5, 2014 #10


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    Not to be too far off topic, but hypothetically, there are some neat things you could do involving the International Date Line.

    If you had two residences, preferably near, and on opposite sides of the International Date Line, and a fast transportation method to get from one to the other (or simply just live on a boat that floats near the International Date Line), you could effectively trade in your Mondays for say, Saturdays, assuming you prefer Saturdays over Mondays. The days of the week could be like, Sunday, Tuesday, Wednesday, Thursday, Friday, Saturday, Saturday.
    Last edited: Jan 5, 2014
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