6D as two times 4D

Although the six dimensional space-time invariant interval represents space and time, we do not observe it as 6D. Instead, we observe space and time as 4D in one of two ways.

The full 6D space-time interval expressed in spatial units is:

s² = Δr² – c²Δw² = Δr1² + Δr2² + Δr3² – c²Δw1² – c²Δw2² – c²Δw3²,

which can also be expressed in temporal units as:

t² = s²/c² = Δr²/c² – Δw² = Δr1²/c² + Δr2²/c² + Δr3²/c² – Δw1² – Δw2² – Δw3².

As we’ve noted here, the space and time vectors are the displacement (r) and the dischronment (w).

In practice this interval compresses into either 3D space + 1D time:

s² = Δr² – c²Δt² = Δr1² + Δr2² + Δr3² – c²Δt²,

or 1D space + 3D time:

s² = Δs² – c²Δw² = Δr² – c²Δw1² – c²Δw2² – c²Δw3².

This is the pattern we’ve learned over and over: there are two ways to observe the world.

One remarkable thing about this is that time is a vector, even if only its magnitude is used (which is the effect of squaring it). Thus to be precise we should define velocity in terms of vectors:

dv = dr / dt = dr / |dw|.

Lenticity should be defined similarly:

dudw / ds = dw / |dr|.

Why can’t we observe all 6D of space-time at once? One reason is our need to form ratios of space and time, which requires that we “scalarize” either space or time for the denominator. Another reason is our inability to visualize six dimensions together. Perhaps we could visualize 2D space + 2D time; that would be new.