clipka wrote:
> Maybe you'd first need to define "point": Are you talking about a point 
> in 3D space which extends along time - i.e. a line in 4D space - or an 
> actual 4D point that only exists at a certain time T?

In all cases I'm referring to a point as a 4D point in spacetime since 
there's no intrinsically unique way to extend a 3D point along time.


> (Note that of course this leaves the definition of distance subject to 
> your frame of reference, as it defines the orientation of the spacelike 
> components of spacetime, but that's a known effect in relativistic 
> physics.)

If you fix a reference frame there's certainly plenty you can do to 
define spacetime distances in a consistent way.  If you want to 
consistently measure distances independent of the reference frame, then 
you're pretty much stuck with what the Minkowski metric tells you.  Of 
course this metric gives you a single value for the distance (not 
independent time and space distances) and thus can't really be used to 
measure pure-spatial distances.

Not that this is necessarily inconsistent with what you said, I just 
thought I'd point out (in case you weren't already fully aware) that if 
you're going to measure spacetime distances independent of the reference 
frame then the way to do it is to use the Minkowski distance and forget 
about trying to determine what the "spatial" distance is at all.

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somebody wrote:
> "Saul Luizaga" <sau### [at] netscapenet> wrote in message
> news:4ae01d8b$1@news.povray.org...
>> somebody wrote:
>>> "Saul Luizaga" <sau### [at] netscapenet> wrote in message
>>> news:4adfcffe@news.povray.org...
>>>> somebody wrote:
>>>>> How do you know that?
>>>> nobody has ever proved it.
>>> How do you know that?
>> Oh you really think that 2D only beings discovery might have gone
>> unnoticed?
> 
> No, but that's not what you said. You said "ANd nobody knows if we were or
> not 2D beings." Well, if lack of disclosure of discovery is proof (faulty
> reasoning),

I deed, because in all fairness we don't know this for sure, I stand 
correct.

> well, everybody knows that we were not 2D beings (probably a
> correct statement, at least more sensible than its negative).

sensible? I don't think so since it has the same exact meaning.

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"Saul Luizaga" <sau### [at] netscapenet> wrote in message
news:4ae0df6a$1@news.povray.org...
> somebody wrote:

> > well, everybody knows that we were not 2D beings (probably a
> > correct statement, at least more sensible than its negative).

> sensible? I don't think so since it has the same exact meaning.

If a statement and its negative have the exact same meaning, they are both
nonsense :P. But, I'll compromise: I'm pretty sure many, many more people
know that we were not 2D beings than those who know that we were (whatever
either statement means).

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somebody wrote:
> If a statement and its negative have the exact same meaning, they are both
> nonsense :P. But, I'll compromise: I'm pretty sure many, many more people
> know that we were not 2D beings than those who know that we were (whatever
> either statement means).

Yeah this is more proper, thanks for understanding, but anyway not 
necessarily true.

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