What is time?

Discussion in 'Free Thoughts' started by Michael 345, Nov 14, 2019.

  1. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Go with the definitions
     
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  3. QuarkHead Remedial Math Student Valued Senior Member

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    And the definitions are?
     
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  5. DaveC426913 Valued Senior Member

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    "In classical, non-relativistic physics it is a scalar quantity and, like length, mass, and charge, is usually described as a fundamental quantity."
     
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  7. QuarkHead Remedial Math Student Valued Senior Member

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    Then I don't understand why you started this thread.
     
  8. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    That is for other posters to detail

    Since it was suggested that a thread be made about What is time? here it is

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  9. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    We have one

    Any more?

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  10. DaveC426913 Valued Senior Member

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    Four rabbis had a tradition of spending a day each week golfing and discussing theology between holes. Very often they would argue, with three of them taking one side and eventually arguing the fourth one down.

    One day, though, the fourth rabbi simply would not budge on his point - he swore he was right and that the other three were misguided. Exasperated by the stubbornness of the others, he fell to his knees.

    "Oh, Lord, give me a sign to show that I am right and that these other three are wrong."

    As he was finishing his prayer, a storm cloud blew in and sent a fork of lightning down on four trees standing on a nearby hill.

    "Oh, Lord," he began again before being cut off by a billowing voice from the clouds.

    "HE'S RIGHT!" the voice boomed.

    One of the three rabbis simply shrugged at this. "Alright. So now it's three to two."
     
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  11. kx000 Valued Senior Member

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    All I know is time is kept, not counted. If you start counting from zero one day infinity will incurr and render you useless. The nature of time is singular and has always been a countless number or existence ends. As it once was, so it shall be.
     
  12. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Number 1

    Number 2

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  13. DaveC426913 Valued Senior Member

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    Ah. Well.

    As long we have the kx000 definition.
     
  14. Neddy Bate Valued Senior Member

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    I like to think of time as a coordinate. It is just a number, chosen by convention, like the calendar date & military time on a clock. Then we can easily calculate "duration" by subtracting one time coordinate from the other time coordinate. Just like we do with, for example, the z coordinates on a z-axis, and call it "length" or "distance".
     
  15. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    Number 3

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  16. DaveC426913 Valued Senior Member

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    OK, but that's really about how we count it, not about its fundamental nature.
    Length existed before rulers; so time existed before clocks.
     
  17. DaveC426913 Valued Senior Member

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    Fundamentally, time is a dimension - a degree of freedom of the universe. One degree of the four-dimensional spacetime, in which all events occur.
     
  18. Michael 345 New year. PRESENT is 70 years old Valued Senior Member

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    ?

    Not sure I understand so will leave on shelf uncounted

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  19. Neddy Bate Valued Senior Member

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    Yes, that is a good point, and I agree.

    That is how it looks on a Minkowski diagram, but one is not really free to move through time in any direction one chooses, as one can with the three spacial dimensions. However it is also not so simple as to say that time only moves forward at one rate, and never backwards. Relativity tells us that time can move at different rates, and also that it can move both forward and backward, relatively speaking. But that is getting onto a different topic, and one which was already discussed in a couple of other threads about relativity.
     
  20. DaveC426913 Valued Senior Member

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    Agree. Which is why we refer to them respectively as time-like dimension and space-like dimensions.

    Yes that seems a bit self-referential when put in words, thought not necessarily when put in mathematics.
     
  21. Neddy Bate Valued Senior Member

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    I usually refer to them as simply "spacial" and "temporal".

    In relativity, the terms "space-like," "time like," and "light-like" refer to something totally different. Those terms pertain to intervals between two events, as follows:

    Space-like:
    All inertial frames will agree that the two events occurred at different locations, though they may disagree on the order in which the events occurred.

    Time-like:
    All inertial frames will agree on the order in which the two events occurred, though they may disagree on whether the two events occurred at the same or different locations.

    Light-like:
    All inertial frames will agree on the order in which the two events occurred, and they will also agree that the two events occurred at different locations.
    (Light-like is essentially when a photon could theoretically travel from one event to the other at the speed of light.)
     
  22. Asexperia Valued Senior Member

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    Number ?
    Time is the measure of duration, the (sequential) lentgh of phenomena.
     
    Last edited: Nov 16, 2019
  23. globali Registered Senior Member

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    time is length/speed
     

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