jcsd
Science Advisor
Gold Member
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Hurkyl said:You don't need GR to handle curved worldlines...
What is the point of #57? I think you're still trying to describe how to go from 3+1-space to 4+1-space... but I think it's much easier than you're making it.
When we're working in 3+1-space, if we pick any pointed worldline, we already know how to assign a proper-time to any point on that worldline. Then, IMHO it's straightforward to lift that worldline into 4+1-space simply by making the new coordinate to be equal to the proper time at that point.
(If I've misunderstood your intent, let me know)
This is precisely how it seems to be and my beef is that 5 coordinates does not necessarily mean 5 dimensions, 5 independent coordinates mean 5 dimensions.
For example in a Cartesin coordinate system describing a Euclidena plane you could insert an extra axis say 45 degrees to the other two axis and assign every point in the plane 3 coordinates. These 3 coordinates are not indepent though, knowing any two coordinates describing a point will allow you to work out the third one.
(Unless I've too misunderstood the intentions) that is precisely what is being done here. In this case the extra axis is the worldline of the object we're descrbing and knowing any four cooridnates of an event will allow you to calculate the fifth.
It seems to me we don't have a 5 dimensional structure, instead we've got a 4 dimensional structure being described by a quirky coordinate system that uses 5 coordinates.