Is Time Really the Fourth Dimension?

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Discussion Overview

The discussion revolves around the concept of time as the fourth dimension, exploring its implications in various theoretical frameworks, including relativity and multi-dimensional models. Participants examine how dimensions are defined and quantified in both spatial and temporal contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that the term "the fourth dimension" can have different meanings depending on the context and the theoretical framework being discussed.
  • One participant explains that in relativity, time can be treated as a dimension similar to spatial dimensions, suggesting that describing an object's position in space and time requires four numbers.
  • Another participant introduces the idea that in multi-dimensional models, such as those proposed by Michio Kaku, time might be considered a higher dimension, potentially the 12th dimension in an 11-dimensional multiverse framework.
  • There is a caution expressed about interpreting lay descriptions of complex theories, indicating that such descriptions may lack precision and clarity.
  • A participant provides an example of how dimensions can be quantified in practical terms, using a bicycle as an analogy to illustrate that the number of dimensions can exceed four when considering various degrees of freedom and attributes.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of time as the fourth dimension, with multiple competing views presented regarding its definition and implications in different theoretical contexts.

Contextual Notes

Participants acknowledge that the discussion involves complex theoretical ideas that may not be fully captured in simplified descriptions. There is also an indication that the definitions of dimensions may depend on the specific framework being used.

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How about summarizing the video and relating how you understand what it is saying.
The term "the fourth dimension" has a variety of meaning depending on who you are talking to.

In relativity, time can be treated as a special case of a dimension of space.
There are models which include many more dimensions. Michio Kaku is relating the kinds of ideas that lead to these in this video. Time would certainly be included in any multi-dimensional model ... though, off Kaku's description, time would have to be the 12th dimension since he describes 3D universe-bubbles on the surface of an 11D multiverse which are expanding in time (implying that the 11D mess is evolving in time).

I'm not sure that's the impression he intends - we have to be careful not to read too much into these kinds of lay-descriptions: they are all hopelessly lacking.
In this case Kaku is trying to answer a question - and the questoner appears to have left time off the number of dimensions that our universe has.
 
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Let's put it this way. It takes 3 separate numbers to describe the spatial position of an object relative to a point in space or another object. Since it takes 3 numbers, we refer to each of these as being a "dimension" of space. If we want to describe the position of something in space AND time it takes 4 numbers, with time being the 4th. (It's a little more complicated, but I trust you get the general idea)
 
Yeah - number of dimensions could just be seen as the number of degrees of freedom.
eg. A bicycle can be described by numbers:

x,y,z location (3)
orientation (lean, yaw and pitch) at the location (3)
the relative rotation-angle of each wheel (2)
the relative turn-angle of the handle-bars (1)
the angle of the pedals (1)
time it got there (1)
height and rotation of the seat (2)
... that's 13 dimensions, and I have not gone into it's gears yet.
 

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