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Observed vs. Actual Reality

  1. Feb 13, 2014 #1
    Is there an absolute sequence of events in the universe- independent of observation? It seems like so much emphasis is put on our delayed observations rather than what is actually happining in Reality. As I read through the forums, it almost seems as if people do not believe that there is an actual Objective Reality that is occurring in the universe- independent of any observor. Is that a proper ascertation of the state of modern physics?

    I understand that clocks tick slower in certain spaces, but looking at space as a whole, does it not have an absolute topography, independent of the observor?

    Plain language answers please.
  2. jcsd
  3. Feb 13, 2014 #2


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    If there is, we have no way of knowing it.

    How else can we observe what's happening in remote locations except through a delay?

    Modern physics doesn't waste time on meaningless (undefinable) terms such as "actual Objective Reality".

    It's simply a matter of not being able to come up with a consistent, coherent definition of things like "absolute topography" that leaves it out of the realm of physics.

    You're welcome.
  4. Feb 13, 2014 #3


    Staff: Mentor

    It depends on what you mean by "sequence of events". Along a particular worldline (a timelike or null curve in spacetime), yes, the sequence of events is absolute, independent of observation. But that's the only sense in which there is an absolute sequence of events.

    That's because our delayed observations are our data; "what is actually happening in Reality" has to be constructed from the data, and that process introduces uncertainty (over and above the uncertainty in our measurement of the data). So it's good to keep the two separate, conceptually.

    I don't think so. In GR, at any rate, spacetime is perfectly objective and absolute. But how you slice spacetime up into space and time is not. See below.

    No. Spacetime does, but "space" does not, because "space" is observer-dependent; there are different ways to slice up spacetime into space and time, and these different ways lead to different "topographies" of space.
  5. Feb 13, 2014 #4


    Staff: Mentor

    There are many invariants in modern physics, just not as many as in Newtonian physics.
  6. Feb 13, 2014 #5


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    There is an absolute truth about the proper time along any object's path through spacetime, i.e. the time that would be measured by a clock carried along with the object. And a bit more abstractly, there is an absolute truth about the proper length along a "spacelike" path--see here for the distinction between timelike paths (those that could be followed by objects moving slower than light), lightlike paths (those that could be followed by light), and spacelike paths.
  7. Feb 22, 2014 #6


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    There certainly are absolute truths that are independent of the methods and logic that different observers use to explain those truths. The famous paradoxes, the Twins paradox, the Ladder paradox, etc., are only paradoxes because it is hard to see how different observers can see events so differently but still arrive at the same absolute truth.

    But "absolute topography"? -- That is another question.
  8. Feb 23, 2014 #7
    Note the special case of 'causality'. If event A causes event B, there is an absolute sequence between events A and B, which is independent of any observer or observation.
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