From: PointedEars@web.de   
      
   Chris M. Thomasson wrote:   
   > On 1/5/2026 2:49 PM, Thomas 'PointedEars' Lahn wrote:   
   >> Chris M. Thomasson wrote:   
   >>> On 1/5/2026 1:47 AM, Thomas 'PointedEars' Lahn wrote:   
   >>>> You appear to be   
   >>>> referring to a definition of "dimension" that is used in science-fiction   
   >>>> and fantasy instead.   
   >>> [...]   
   >>>   
   >>> Ponder on it:   
   >>>   
   >>> (4th Dimension Explained By A High-School Student)   
   >>> https://youtu.be/eGguwYPC32I   
   >>   
   >> The argument that they are making about time (not being "the 4th dimension")   
   >> is pseudo-scientific and ridiculous, based on their ignorance of what it   
   >> means when we say "4th dimension" in that regard (which I just explained to   
   >> you in detail).  Scientifically it is complete nonsense to say "every   
   >> dimension has time in it" as they do.   
   >>   
   >> *Their* ignorance is excusable, though, because they are just a high school   
   >> kid and are not expected to know about or understand pseudo-Riemannian   
   >> manifolds like spacetime (although they could have certainly have found   
   >> books that explained it at their level of understanding).  Yours is not (as   
   >> I just explained it to you in detail).   
   >   
   > Say to explain a 3d point in time we need (x, y, z, t), t for time.   
      
   First of all, watch this (which was suggested to me by YouTube when I   
   watched the video that you referred to):   
      
   Dylan J. Dance: Physicist Reacts to 4th Dimension Explained By A High-School   
   Student   
      
      
   This should clarify (as I already indicated) where that kid was right and   
   where they confused themselves and thus were confused.   
      
   Then, as to your claim:   
      
   Once you specify a fourth coordinate for a point, it is no longer a point   
   _of_ (NOT: in) a 3-dimensional space, but a point _of_ (NOT: in) a   
   4-dimensional space.  If the extra coordinate is time, then that space is   
   (for obvious reasons) called _spacetime_.  The point has become an *event*.   
      
   In physics we actually prefer to choose the time coordinate as the zeroth   
   coordinate (unless we use Euclidean time, as I explained before), and count   
   the spatial dimensions beginning with 1.  This is more convenient in the   
   mathematical formulation and -- since we assume for various reasons that   
   there is only one (large) temporal dimension -- makes handling additional   
   spatial dimensions -- which according to string theory exist but are "too   
   small" to see as they are compactified -- easier to handle.  So, as I   
   explained before, instead of (x, y, z, t) we write e.g. (x^0, x^1, x^2, x^3)   
   := (c t, x, y, z).   
      
   We are using "c t" instead of "t" so that the temporal dimension(1) has the   
   same dimensions(2) as each spatial dimensions(1); but the "c" is frequently   
   dropped in the theory by setting c = 1 (called "notation in natural units"),   
   and that is equivalent to not doing that if we specify time in seconds, but   
   then lengths in e.g. light-seconds.   
      
   (1) "dimension" as understood in mathematics   
   (2) "dimension" as understood in physics with regard to quantities   
      
   > For a 4d point we need (x, y, z, w, t), t for time.   
      
   Again, this is now a point _of_ (NOT: in) a 5-dimensional space.   
      
   > t is in every dimension?   
      
   No; (different from the sci-fi/fantasy meaning) a dimension is NOT the whole   
   of this construct, but merely a part.  For example, the x-coordinate of that   
   point represents one dimension, the y-coordinate another, and so on.  See   
   also the video referenced above.   
      
   --   
   PointedEars   
      
   Twitter: @PointedEars2   
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