How can you explain the Time as a Dimension?
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Time is not a spatial dimension. For example, if you have up/down, left/right, forward/back, that’s your three spatial dimensions. Time isn’t one of those.
In modern science you have *spacetime* where space is time.
In the spacetime model, time *is* space. Or in other words, time is equivalent to distance when operating at the speed of light. (It isn’t precisely equivalent, but for ELI5 it’s close enough.) When considered in terms of photons a unit of time and a unit of distance are the same. When involved in relativistic effects light near lightspeed travel, travel near a black hole, and other effects, the same relativistic effects that cause length contraction (the relative increase or decrease in length) also cause time dilation (the relative increase or decrease in time). Effects that distort space have a similar distortion of time.
So if you use certain measurements you have both time and in distance. Three nanolightseconds is about the distance of your arm and about the same time as six CPU clock ticks. Any distance at all is also time. Everything in the universe is in your past relative to your perception, and the distance is the same as the time light would take to reach there.
This ends up working with all manner of spacetime effects, like gravitational lensing, looking at the wells of time being dragged behind neutron stars and black holes and such. Time IS space, distortions in space are also distortions in time. Distances in space are also distances in time.
In math, you can have any number of dimensions you want. In mathematics dimensions are just an element in what is typically a linear algebra equation. You can have an unlimited number of dimensions, each dimension individually indexed. You can also project them onto a display using exactly the same math used in video games to project a 3D world into a 2D display. While it often harder to understand there are systems to project many higher-dimensionality systems into something you can see on a computer screen. Some people struggle to interpret a fourth or fifth dimensionality, but for some systems it’s possible to visualize about ten numeric dimensions before it becomes inscrutable.
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