Clear up confusion on Minkowski signature
All given metrics are for orthonormal-basis.
2 dimensional spacetime :
I saw that Minkowski Metric looks like this :
I was wondering why it's not written like identity metric. To define a vector in spacetime it's written like this
4 dimensional spacetime :
The minkowski signature is
I know the question is too confusing and I am confused about time coordinate, it is
I forgot to mention which actually made me curious to write the question, we know that dot product of any basis vector to itself is
1 answer
As you probably know, one of the postulates Einstein's Special Relativity is based on is that all observers see light in vacuum go at the same speed
Now consider a lamp at rest relative to John being switched on. The light is going through vacuum from then on, until after some time it arrives at some object, also at rest relative to John.
Now John observes this, and measures that the time between the lamp being switched on, and the light reaching the object, is
Now John has a coordinate system, and in this coordinate system, since light in vacuum goes in a straight line, the distance
Clara, who moves with considerable speed relative to John, will observe a time difference
Thus we see that the term
Now for the calculation above obviously it isn't relevant whether we multiply the full term with
Now conversely one can ask what exactly are the linear transformations that leave the spacetime interval invariant, and one finds that these are exactly the Lorentz transformations. Thus the spacetime interval, with that relative minus sign between space and time directions, captures the essence of special relativity.
Now if you look at the spacetime interval, you see that it almost looks like an Euclidean metric, except for this relative sign. Now if we choose the global sign of the metric so that spacelike distances (those with
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