Understanding Time as a Dimension: A Detailed Explanation

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Discussion Overview

The discussion centers around the concept of time as a dimension, particularly in the context of relativity. Participants explore various interpretations and implications of time as a dimension, touching on theoretical aspects, definitions, and relationships with other physical concepts such as entropy and spacetime.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that a dimension is a coordinate used to ascertain position, size, and direction, with time representing a position on a different axis than spatial dimensions.
  • One participant argues that time should not be viewed merely as a measurement but as a dimension that is measured.
  • Another participant introduces a mathematical perspective, describing time in special relativity as a zeroth dimension juxtaposed with spatial dimensions, using a Pythagorean theorem framework.
  • Some contributions suggest that time is intricately tied to the fabric of the universe and its behavior is not fully understood, raising questions about whether time is continuous or quantized.
  • There is a claim that time can be defined by entropy, linking it to the second law of thermodynamics, while others question the relevance of entropy to the concept of time.
  • One participant expresses frustration over the capitalization of the term "relativity," indicating a lack of consensus on terminology.
  • Another participant suggests a relationship between the increase of entropy and the progression of time, proposing that as the universe's entropy increases, so does time.
  • A different viewpoint is presented that questions the benefit of defining time through entropy, suggesting that while both may be linear, they may not proceed at the same rate.

Areas of Agreement / Disagreement

Participants express a range of views on the nature of time as a dimension, with no consensus reached on its definition or relationship to other concepts like entropy. The discussion remains unresolved with competing interpretations and questions about terminology.

Contextual Notes

Some statements rely on specific definitions of time and entropy, and the discussion includes unresolved mathematical relationships and assumptions about the nature of time in relation to other dimensions.

quant
Could someone give me a detailed explanation of *what* the Time dimension is? I don't mean for someone to start telling me about a clock, but rather to understand relativity you must understand Time as a dimension. I was wondering if anyone could help me out with that? Thanks! :smile:
 
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Originally posted by quant
Could someone give me a detailed explanation of *what* the Time dimension is? I don't mean for someone to start telling me about a clock, but rather to understand relativity you must understand Time as a dimension. I was wondering if anyone could help me out with that? Thanks! :smile:

This thread should, perhaps, be in the Theoretical Physics Forum.

It is a good question that you ask. First off, a dimension is coordinate, which can be used to ascertain the position, size, and/or direction of movement, of an object. Position doesn't just refer to "where" something is, as many think. "Where" you are, refers to your position relative to the spatial dimensions. "When" you are, refers to your position on the time dimension. So, I can tell you the size of the Great Wall of China (for example), but unless it has also existed for a certain amount of time.

One common mistake is saying that the T dimension is just a measurement - of planets spinning, clocks ticking, atoms decaying, etc. Actually, time is a dimension of it's own, and does not measure, but is measured.

I hope I have been clear, and if you need clarification, or if I didn't adequately answer your question, just say so. But, I am in a hurry now, so I can't do my usual proof-reading, sorry.
 
Sorry about it being in the wrong topic.

Well, everything you just told me, i already knew. But, i guess i just need an image of it. Is there anything further anyone could add to explain it a bit more please?

Thanks.
 
Time in special relativity's spacetime is a zeroth (space being first, second, and third) dimension that juxtaposes spatial dimensions in a four-dimensional (conical) Pythagorean theorem:

x^2+y^2+z^2=(ct)^2 for "lightlike" surfaces,

x^2+y^2+z^2<(ct)^2 for "timelike" regions,

x^2+y^2+z^2>(ct)^2 for "spacelike" regions.

All light comes to observers through their contiguous lightlike surface. Inertial events that can affect them mechanically exist in relative timelike regions, and events out of direct communication exist in spacelike regions.

Physics also allows for time defined by entropy (the second law of thermodynamics), cosmology (the big bang), and radiation (quantum decay).
 
Last edited:
Welcome to Physics Forums, quant! :smile:

Originally posted by quant
Could someone give me a detailed explanation of *what* the Time dimension is? I don't mean for someone to start telling me about a clock, but rather to understand relativity you must understand Time as a dimension. :smile:

To add to what the others said so well...

Time is part of the very fabric of the universe itself. It is an aspect of the universe that has a certain behavior that is directly tied to the other dimensions (3D space). A full understanding of its nature is not available at this time (just like a full understanding of space or gravity is not known). Whe can measure it and see its effects, but is it continuous/quantized? How does it work? Don't know.
 
See sig.
 
Originally posted by quant
Could someone give me a detailed explanation of *what* the Time dimension is? I don't mean for someone to start telling me about a clock, but rather to understand relativity you must understand Time as a dimension. I was wondering if anyone could help me out with that? Thanks! :smile:

quite simply, time is an increase of entropy (and what Mentat said is of great importance, esp. in relativity).

BTW, should relativity be capatilized or not?? I am very frustrated; I see it captilized one day, and the next, lower cased!
 
Huhhh? What has entropy got to do with it?
 
That how time's defined. It never occurred to me that there would be relationship..

Maybe, it has something to do with the expansion of the universe. For example, time-space are one in relativity. So naturally, as the universe's entropy increases, so does time.
 
  • #10
Personally, I don't see the benefit in defining time via entropy. Sure, both are on a continuous one-way line, but I think they proceed at different rates.
 

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