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Graphene is considered to be a two dimensional material. Technically, it's one atom thick, but that is as thin as anything can be. There's also carbon nanotubes (CNTs) which are considered to be one dimensional fibers, and fullerenes, which are structurally spherical but considered to be zero dimensional because all three dimensions are less than 1 nm.


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The universe is a four dimensional object i.e. to locate any point within it you need four numbers. Most commonly we use a coordinate system $(t, x, y, z)$ and the four numbers give location of the spacetime point in this coordinate system. You ask: But how can this be, if time is relative and dependent on speed of reference frame? and the answer is ...


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Time is that which the clock shows. Any one clock. Clocks do not all show the same time but their readings are related to each other and that relation is what the theory describes. In non-relativistic theory any two (perfect) clocks can only differ by a constant time difference but they all progress at the same rate. In relativity any two clocks that are in ...


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You're confusing concepts, as far as I can tell. Being a "dimension" doesn't imply all values of that dimension (or any of them) are arbitrarily reachable or even exist physically at a given time. It doesn't mean that the intuitive sense of all the baggage a more usual dimension comes with, are applicable to time. It doesn't imply time travel or multiple ...


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Time is not a combination of a past, present, and future dimensions, but rather a one-dimensional axis, where the past and future are dependent on the present for definition, and the present is a particle's position in time. In the theory of relativity, a particle has position $(x,y,z,t)$, where $(x,y,z)$ is the particle's position in space, and $t$ is the ...


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Itzhak Bars proposes a two-time physics. This means the spacetime(s) metric is of the form $$ ds^2 = dt^2 + du^2 - dx^2 - dy^2 - dz^2. $$ The anti-de Sitter spacetime is a subspace of this type of metric as well, where a constant surface is a hyperboloid. A hyperboloid in 5 dimensional space times is given by $$ t^2 + u^2 - x^2 - y^2 - z^2 = 1. $$ The ...


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Suppose you are standing upright aligned with the $z$ axis and facing along the $y$ axis, then the $x$ axis is to the left of you, at your position and to the right of you. But we don't say there are three $x$ axes. The $x$ axis simply comes in from $-\infty$ from your left, through your position and then off away to $+\infty$ on your right. In exactly the ...


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They are not always "square." Orthogonal bases like you describe are convenient for many reasons, such as the fact that a "length" can be described in easy terms, and that there is only one way to notate any given point. There are others, such as the polar coordinate system which are different. The polar system describes 2 dimensions, one linear and one ...



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