Re: Nothing Can Move in Spacetime

Posted by ReillyAtkinson on April 25, 19101 at 13:17:57:

In Reply to: Re: Nothing Can Move in Spacetime posted by Nemesis on April 21, 19101 at 17:03:32:

Sir -- As I have limited energy and brainpower, I can only respond to a small subset of your comments.

I'm afraid I do not understand why there cannot be a time dimension? As the mathmematicians have shown us, anything represented by real numbers can be mapped onto the real line, a one dimensional object, which, typically, is referred to as having a dimension (the language used is not often as precise as it might be)As far as I know, time is measured in terms of real numbers. (You are, I'm sure, more than aware of all the work done by topologists who study the basic notion of dimension; not to mention the more common garden dimensions of linear vector spaces. ) What am I missing here?

You should be aware that in the 20th century the ideas of mechanics have been considerably generalized, and that the basic concept is often taken to be a displacement, what you call a change, but I'm sure you are familiar with this approach. You, I suppose, are formally correct about the problems with dt/dt when you pose them in a limited context. But do not forget that many physicists are improvisors, can do a bit of shucking and jiving, just like they use approximations -- physics is more practical than logical.The only crime with this is if you do not clearly state what you are doing. So, if you need a time velocity? Why not? And then there is proper time, and .....

However, within the 4-dimensional approach to mechanics (recall, this approach is one of practical convenience, not one of logical necessity) Objects do suffer a displacement in time -- if they do not move in time, how does this displacement happen? Actually, one way around your objection is to recognize that in relativity, time is local -- you and I live by different clocks. Whose do we use? Do they run at the same rate? What is dt1/dt2? There is no such thing, in relativity, as global time -- the practicals of all the necessary calibrations would be a bit much, and would fill all of space with signals, and who knows what all that signal energy might do to motion and time. So maybe nothing can move in your space-time, but I'm perfectly content to do a litle bit of redefinition to allow motion in my space-time, makes my life a lot easier.

You don't much care for infinity, continuity and space and a time dimension? You might read some of L.E.J. Brower's work -- a great mathematician who had trouble with infinity and the like.

And you would do yourself a great service by doing the physics you claim should be done. Belittling today's major physics players with the language you use is strictly low-rent. You want to be a big shot? Do the work to be one & do not waste any energy on feeling sorry for me, and stop screaming about small-time problems.So you get more emails from physicists than I do. Hey, some folks have all the luck. Enough, already.

R. Atkinson

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