Time is not a dimension.IronBass
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Quote of 2010?
Some guy named Albert Einstein disagrees.
The term dimension has a specific mathematical meaning: "In mathematics the dimension of a space is roughly defined as the minimum number of coordinates needed to specify every point within it". A minimum of four coordinates are needed to specify every event in spacetime, so spacetime is a four-dimensional space. The fact one coordinate is different from the other three does not make it any less of a coordinate.
Having said that, you are absolutely correct that time is fundamentally different than space as can be seen from the Minkowski metric: ds²=-c²dt²+dx²+dy²+dz². Time is still a dimension, but that minus sign definitely singles it out.
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http://www.jimloy.com/physics/4d.htm
Time, The Fourth Dimension
We live in a world of three dimensions. Well, we only perceive three dimensions. We can hypothesize many more dimensions. But, they are difficult to imagine.
Because of Einstein, we often call time the fourth dimension. Special relativity shows that time behaves surprisingly like the three spatial dimensions. The Lorenz equations show this. Length contracts as speed increases. Time expands as speed increases.
Scientists have been graphing time, as if it were a length, for hundreds of years. To the left is a typical graph, showing two things in motion at the same speed, one to the left and one to the right. Time never behaves exactly like a spatial dimension. You cannot go backward in time. And you normally cannot go forward at different rates. But, there are surprising parallels. For some purposes, it is handy to call time a fourth dimension. For other purposes, it is not.
Pretend, for a moment, that there are more than three spatial dimensions. What is a four or five-dimensional cube like? It is hard to visualize. But, we can make a few deductions about such an object. What if a 5-dimensional cube is 2 centimeters on a side, what is its 5-dimensional volume? Well, we can easily generalize from the first three dimensions. A 2x2 square is 4 (2x2) square centimeters in area. A 2x2x2 cube is 8 (2x2x2) cubic centimeters in volume. A 2x2x2x2x2 5-dimensional cube is 32 centimeters-to-the-5th-power in 5-dimensional volume. None of that can be visualized. But, it makes sense. What is the distance between two points in 5-space? You can easily deduce a 5-dimensional Pythagorean Theorem.
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http://en.wikipedia.org/wiki/Fourth_dimension
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