[time-nuts] Beginner's time reference

GandalfG8 at aol.com GandalfG8 at aol.com
Mon Dec 14 22:45:40 UTC 2009


In a message dated 13/12/2009 18:52:37 GMT Standard Time,  
charles_steinmetz at lavabit.com writes:



Volts and yards, at least, are also not absolute measurements  in the 
same sense that measurements of time are not absolute.  Volts  express 
the difference in electrical potential, and yards the physical  
separation, between two spatial points.  But two points in space just  
define a spatial interval, precisely analogously to two points in 
time  specifying a temporal interval (more  below).

-----------------------

But that is no different than  the other three dimensions of spacetime 
-- measuring intervals is all we  have there, too.  "One kilometer" is 
no different from "one second"  in this regard -- in both cases, it is 
one unit *between* two places (we  usually call places in time 
"events," but it's the same thing).  If  general relativity ("GR") is 
correct (and we have every reason to believe  that it is), time is no 
different than space, although we perceive it  quite differently.  For 
example, in order to move about in the space  dimensions we think we 
need to "do something," while we need to do nothing  to move about in 
the usual way in the time dimension (and, indeed, have  not figured 
out how to move differently in time or to stay in one  place).  But 
note that we are really hurtling through space at a good  clip, 
without it being apparent to our natural senses -- and in comparison  
to this, we really haven't much power to move about in space,  
either.  So, we could say that we have an initial velocity through  
both space and time when we are born, and our initial velocity 
through  time is more apparent to our natural senses than our initial 
velocity  through space -- but in reality, there is no difference 
between  them.

----------------------

In my view, these are all  questions, not about time, but rather about 
our perception of time.   At the end of the day, we have every reason 
to believe that GR is correct  and, consequently, that spacetime is 
the fabric of the universe.   Space and time are both altered, in 
complementary ways, by the great  forces of the universe (gravity and 
acceleration -- time will tell whether  the nuclear forces do so, as 
well, and there is some evidence to date that  they may), implying 
that there is a conservation relationship that applies  to the four 
dimensions collectively.  But there is no difference in  terms of the 
spatial dimensions being "absolute" and the temporal  dimension not 
being "absolute" -- all of our measurements of the four  spacetime 
dimensions are relative and "not absolute" in the sense you mean  
(although, as I've pointed out, by refering both back to the origin 
of  this universe, which we have good reason to believe was a 
mathematical and  physical point where this universe began, we could 
in principle at least  have a master datum for all four dimensions, 
providing a form of  absolutism).

The puzzle is why we perceive the spatial dimensions so  differently 
from the temporal dimension.  It is a fascinating  question, but may 
not be fundamentally a question of the physics of  spacetime.
---------------
Hi Charles
 
Many thanks for your reply, but I'm not so sure anymore that spatial and  
temporal intervals really are quite the same.
It deserves more thought.
 
The spatial intervals have the property of persistence until "time" becomes 
 involved, whereas temporal intervals really have the property of decay  
regardless.
 
Whether or not "we" have an initial velocity in any reference frame is not  
so much the issue as to what was the reference to start with.
 
We are indeed hurtling through space "at a good clip" but where exactly  
does that lead us?
 
Mr Flat_Earth mentioned the "arrow of time", without any due  consideration 
to the fact that one doesn't need to invoke the second law of  
thermodynamics, or anything else for that matter, if time is merely an  artefact of 
universal expansion.
Should the universe eventually begin to contract it's then we should  
consider it, time reversal might just be inevitable after all.
 
The puzzle may be one one of perception, but perhaps  perception should not 
always be ignored.
 
I begin to think that we perceive spatial dimensions  so differently from 
the temporal because there might just be a  difference.
 
Perhaps not, but at least the mind is open and thinking:-)
 
regards
 
Nigel
GM8PZR
 
 
 
 
 



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