How can you explain the Time as a Dimension?
In: 3
Think of dimensions as a series of coordinates to identify where someone is in the Universe.
You need 3 coordinates the Length, Width, and Height to identify exactly where there are at any given moment.
And that’s the key point about time, depending on what the time or day is that person can be located somewhere entirely different.
So time is as important to your location as Length, Width, and Height
Basically an object on a shelf can be defined in 3 dimensions as to its size shape and location, but if the object is taken off the shelf and replaced by another one in the same location the two objects may have very similar 3 dimensions however they both can be described by the standard dimensions, but if you add in time you can describe the objects without them appearing to be identical.
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You should put more info in your question so people can address what your actual preconceptions are about dimensions are. People ask questions like this a lot and it’s not always clear where they are coming from.
If you mean as a “spatial” dimension, well, time isn’t a spatial dimension.
When people talk about time as a “dimension”, what they mean is 1 degree of freedom, or rather, how many numbers you need to describe the thing you’re talking about. Time requires a single number in order to describe. One event happens 5 seconds before another, or something occurred over a span of 12 minutes. That single number that describes it means that time has 1 dimension. If we talk about where something is in space, we need 3 numbers: how far is it left/right, how far forward/back, and how high, so space is 3-dimensional (for example, we could say a box is 1 ft x 2 ft x 2.5 ft, that’s 3 numbers).
There’s really no need to overthink it beyond that.
Now if you’re confused because you’ve heard about people talking about 4-dimensional space-time, all they’re doing is combining the 3 dimensions of space and 1 dimension of time and talking about them at the same time. For most purposes this isn’t even necessary, and it only really comes into play if you’re doing stuff with General Relativity. The gist of it is that at some sort of fundamental level, space and time are inextricably linked, and anything that has mass (or energy) will warp both space and time simultaneously, so you have to do the math to work it out for both space and time at the same time.
A dimension is another word for a number line. A number line is “a straight, horizontal line with numbers placed at even increments along the length.” And that’s all there is to it. Pretty simple. Did you want to know anything further?
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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