Is There A Universal Now?

Discussion in 'Physics & Math' started by Cyperium, Jun 14, 2022.

  1. phyti Registered Senior Member

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    Michael345;
    The complexity of human activities has required increasing precision of smaller units of time, like GPS. The benefits and purposes are very diverse, communications, weather, transportation, financial, geology, etc.
    The natural um; day, year, lunar, were adequate when life was much simpler.
     
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  3. Mike_Fontenot Registered Senior Member

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    The quickest answer to Cyperium's (the OP's) question in his title to this thread (which was
    "Is There A Universal Now?") is "No".

    We know that, because that's what special relativity tells us, and special relativity (SR) is known to be very accurate when gravitational fields are not extremely strong ... SR's accuracy is very good even in experiments conducted on the surface of the Earth.

    Special relativity tells us that inertial observers who are moving relatively to each other will DISAGREE about "Now-at-a-distance". I.e., they do NOT agree about the current age of any given distant person.

    One of the simplest results of special relativity is that any given inertial observer (he) will conclude that any person (she) moving with respect to them (in any way whatsoever) will be ageing more slowly than he is ageing, by the factor

    gamma = 1 / sqrt (1 - v^2),

    where the symbol "^2" indicates the square. For example, for v = 0.866 ly/y, gamma = 2.0.

    And if she is also inertial, SHE will say that HE is the one who is ageing more slowly. Clearly, he and she do NOT share the same "NOW-at-a-distance".

     
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  5. Write4U Valued Senior Member

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    Subjectively from inside the Universe, yes. Objectively the Universe as an "object" had a beginning and has an age, which is a chronological account of consecutive Nows.

    OK. allow me;

    Law of conservation of energy
    If all the energy in the universe has remained conserved since the beginning, did universal energy in toto age as a result of a continuous chronology of Nows?
     
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  7. Mike_Fontenot Registered Senior Member

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    In special relativity, there is nothing "outside the universe", and it is not important to distinguish between the terms "subjectively" and "objectively". In special relativity, the entire universe is infinite in space and time.

    In general relativity, it is currently believed that there was a beginning of the universe we are now in, and there may or may not be an end of the current universe, and perhaps even subsequent "big bangs".

    Personally, my interest is almost entirely in special relativity. I know some general relativity, but very little cosmology. I DO know that in general relativity, VAST portions of spacetime are VERY well described by special relativity, and in those portions, NOW-at-a-distance is subjective ... i.e., it is different for different observers. I suspect that implies that NOW-at-a-distance is subjective everywhere.
     
  8. Write4U Valued Senior Member

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    18,777
    As I said, from that perspective I understand the functionality of SR.

    I just disagree that this universe is infinite if it had a beginning and is expanding. Logically if this 3 dimensional "physical something" is infinite then there can be no room for an infinite "nothingness" or total vacuum, no?

    If this universe had a beginning, what was before the beginning? An infinite nothingness?
    What are we going to do about that paradox?

    Is there a limit to how much the universe can expand?
    https://www.livescience.com/33646-universe-edge.html

    So there is no proof that the universe is infinite? Does that warrant a definitive answer?
     
    Last edited: Sep 29, 2022
  9. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Found this on YouTube (was not looking for anything related to time) so I'm guessing YouTube picked this from my long ago history

    Cannot comment much about except it covers some beliefs and non beliefs of physicist

    I really didn't get much from it

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    but here it is



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    Last edited: Sep 29, 2022
  10. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    TIME

    The faster you go time slows down for you

    I read this

    https://www.infoplease.com/math-sci...e speed of an object,time, so time slows down.

    In summary it says
    • more effort is being put into going faster
    • than moving through time
    ie
    • effort is being diverted from moving through time and
    • redirected to moving through space
    Not sure how the diversion occurs since I am unaware of any effort, on my part, being put into moving through time (? another reason to believe time is non existent ?)

    Working on how to describe Universal NOW

    At the moment going with a imaginative description (impossible in real life but not in imagination)

    Statement

    Universal NOW has no permanency even though Universal NOW contains the entire Universe which by default makes it Universal NOW

    Permanency would be a static Universe, no changes. Changes occur (due to the physics of the Universe)

    Changes made are numerous throughout the Universe and with each change requiring energy (and no external energy to the Universe being pumped in) the Universe is cannibalising itself

    • Stuff is only in existence at / in NOW
    • Nothing remains existing in post NOW
    • Nothing begins existing prior to NOW

    NOW can be thought of as being timeless
    Another way of saying time (fundamental version) does not exist

    Talk of going from the past into the future is misguided

    Such talk would give (gives) the impression
    • a past is still in existence and
    • a future is in existence
    • both waiting for travellers and
    • capable of receiving same

    Consider a race where the fastest runner takes a few stumbles at the start of a race. However the remaining runners are not so far ahead and he still has a chance to win

    His speed is such that he begins to overtake those ahead

    Physics dictates because he is travelling faster, time for him is slower than those he passes (at the speeds both are running at a very minute amount - but still there)

    However during the overtaking process BOTH are running in the same NOW

    One is not OUT of the NOW while the other remains IN the NOW at any stage of the overtaking

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  11. James R Just this guy, you know? Staff Member

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    Measuring the age of the universe requires that a frame of reference first be specified. There are no preferred frames. There are, however, some common-sense ways to choose a frame for "cosmological time".
    Energy is just a number. It makes no sense at all to talk about the age of some energy.
    General relativistic theories of the expansion have implications for the boundedness of the universe. Our current best-fit models have a non-zero cosmological constant and suggest that the spacetime curvature of the universe, on average, is close to being "flat". A flat universe is infinite, as is an open universe. Only a closed universe can be finite. However, the best data seems to point to either a flat or open universe.

    This question will not be settled by what people want to believe. It can only be settled by evidence and understanding. We are working, for instance, to understand both dark matter and dark energy.
    An infinite space has infinite room. That's what infinity means.

    As for "nothingness", that can't have any properties or it wouldn't be "nothingness". "Nothingness" doesn't need "room"; it isn't a thing.
    The beginning would be the moment when time started. If that's the case, then talking about a time before time started doesn't make logical sense.

    It's like asking what country lies to the north of the North Pole.
    There's no proof that you exist. Only evidence that suggests it is the case.

    New evidence can possibly prompt us to re-evaluate tentative conclusions. This is how science is done.
     
  12. James R Just this guy, you know? Staff Member

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    No. Somebody watching you go faster will see your time slow down. You won't notice anything odd about your own time. You're always stationary in your own frame of reference.
    In a certain context, that kind of explanation makes some kind of sense, but it really requires a level of understanding of how space and time work together in the theory of relativity. I'm not personally a big fan of that kind of description, especially when it is given without the relevant mathematical context. It just tends to create more confusion.
    A better way to think about it is in terms of energy input. Suppose it takes 10 gallons of fuel to provide the necessary energy to accelerate your car up to speed X, from rest. Then, according to relativity, it will take slightly more than 10 gallons to speed your car up from X to 2X. Each extra increment of X amount of speed will cost more and more fuel. The limit is the speed of light; it would take an infinite amount of fuel to accelerate your car to the speed of light. This is true for every object that has mass. It is why the speed of light is the ultimate speed limit.
     
  13. Write4U Valued Senior Member

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    18,777
    How about beginning with the BB and the chronology of duration?
    Whence did energy come from?
    Who says a flat universe is infinite? A toroid is bounded, yet infinite, has a curved flat expanding and contracting spacetime surface and allows for recycling, i.e. beginnings and endings.
    It meets all requirements for satisfying everything we know about the universe. It meets all questions about relativity, yet has a defined boundary beyond which there is only a timeless , dimensionless permittive condition.

    There, I just described a model that satisfies all questions.....

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    That is why I don't talk about a time before time of this universe began. But the moment time emerged from the appearance of a singularity, a beginning, thence began a chronology of Nows from that beginning forward.

    The singularity did not split apart, it expanded into a curved manifold, but remained a singular object with an age of 13.8 billion years duration from the beginning to Now.

    Even if the universe split apart, the individual parts would maintain synchronicity of Now, even as each part acquires its own individual timeline.
    That the measurement requires accommodation for distance does not negate the synchronicity at a distance.
     
  14. James R Just this guy, you know? Staff Member

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    37,550
    Write4U:

    I was talking about choosing a reference frame.
    One answer would be: humans invented the concept. Another answer would be that nobody knows where the stuff in the universe came from (or the energy associated with that stuff).
    Various standard general relativistic cosmological models.
    "Curved flat" is a contradiction in terms. If the universe is toroidal, then it isn't flat. Isn't that obvious?

    A toroidal universe would be closed and finite.
    Maybe.
    No. A toroidal universe doesn't have a boundary. If you head off in any direction through a toroidal space, you'll eventually end up back where you started after travelling in a "straight line" for long enough. You'll never hit an "edge". Spherical geometries are similar in that regard. Spherical and toroidal universes are closed and finite.
    The word "singularity" just means a condition in which some mathematical theory or other fails. In the case of the big bang, the "singularity" is not a thing so much as a label for "we don't know what happened here - yet".
    I don't know what you mean.
    Similarly, I have no idea what this is supposed to mean.
     
  15. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    https://youtube.com/shorts/xlGuBT5GT10?feature=share

    How bees perceive time

    I am not sure of the time difference between Paris and New York but I would check if the time the bees left the hive in New York (10 am) it was 4 pm in Paris

    Google tells me it would be 4:00 pm in Paris, France

    I would put this down to bees measuring a period of time ie not perceiving TIME but like clock hands being in the same place after a period

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  16. Mike_Fontenot Registered Senior Member

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    I would add:

    "Special Relativity" says spacetime is flat and infinite. Although spacetime in our universe is not flat and infinite, VAST regions of our universe are flat to a very good approximation, so special relativity is a very good approximation there, and its results are very useful and enlightening. I would go so far as to say that the basic results of special relativity are perhaps the most interesting and bazarre results in ALL of relativity theory.
     
  17. James R Just this guy, you know? Staff Member

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    Even humans have an internal body clock. This is why you feel sleepy in the middle of the night. Our internal clock has a natural period a bit longer than 24 hours, but it tends to get reset by light, so we sync to a daily cycle unless we're in a coal mine or something.

    It's the same thing with the bees. If flown from Paris to NY, the bees' internal clocks will take some time to synchronise to the new day/night cycle, just like ours do. That is, the bees suffer similar effects of jet lag that we do.
     
  18. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    You totally missed the point but seeing as you are staying away from my post "sigh"
    it doesn't matter

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  19. James R Just this guy, you know? Staff Member

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    No. I get it. You're trying to make some kind of distinction between "measuring a period of time" and "perceiving time".

    I think that's an artificial and rather dubious distinction. But you already know what I think about your ideas about time. That's why I didn't comment on that. The circadian clocks that bees and people have are interesting, though.
     
  20. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    No. I get it. No you don't

    I think that's an artificial and rather dubious distinction.

    But since I I'm not trying to make it so what?

    Please please you did say

    can you stick to your saying? PLEASE

    Yes yes I can't see the obvious absurdity of my position (clap clap) well spotted

    then I think you're a lost cause. And you are trying to be the knight to the rescue, by missing the point the lost cause is trying to make?

    Again

    can you stick to your saying? PLEASE

    Coffee time

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  21. phyti Registered Senior Member

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    Michael345;

    The graphic is NOT an x,t plot, but an x,p plot, with p being any direction perpendicular to x.
    Nothing is moving through time. Light is moving in 2 dimensions!
    In view a, Ann sees the light clock oscillate vertically between ED and mirror M, in her own ref. frame.
    In view b, Ann sees an identical light clock c2, as it moves to the right at .5c.
    She perceives its rate to be .87 compared to her clock.
    She knows light speed is constant, but it can intercept M if it moves at an angle.
    In a, all the energy is used in the clock function. In b, the light path is resolved into two components, vt which compensates for the motion of the clock, and ut which becomes the active part of the clock. In c, observer Ben moving with clock c2 perceives the clock reading .87. Ben is not aware his clock rate is less than Ann's since his biological clock is also less by the same factor. I.e. the moving observer is not aware of the changes of time dilation and length contraction resulting from motion, since he is affected to the same extent.

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  22. James R Just this guy, you know? Staff Member

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    If what you say is true, wouldn't it be better to spend a post explaining what you mean, rather than writing a rant about how I have sadly misunderstood your meaning?

    Note that what I posted about, that led to this minor explosion from you, was about the circadian rhythms of bees.

    Your ideas about time are nonsensical, for the most part.
     
  23. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    The above is not really a real post (can't be) because the person allegedly posting said they wouldn't post about my post

    So this is not a reply to the fake post, just a heads up of an intruder in the forum

    Just be careful out there

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