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BTBlueSkies
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I have great trouble with the concept of 'local' as it seems very generic in ways. Local can be a plank distance away, or a meter away.. or even a Hubble radius away (if your scale is in Hubble radii (sp) or so).PeterDonis said:So nothing actually moves faster than light in any invariant sense; no object outruns a light beam in its local vicinity.
If distance in the direction of travel approaches zero as velocity approaches the speed of light... how does the concept of 'local' vary in real units? Is 'local' a function of speed? I often hear 'local this' and 'local that'... 'local' is a pain if you ask me... (but no one did so this I suppose is a monoloug) (i'll try to keep it clear and short.. and maybe smily.. spelling will not be checked).
I assert the word 'local' should not be so ambigouous.
I was reading the thread 'The rapidity of the FTL expansion of space' and the word 'local vicinity' showed up in the same paragraph as the word 'Hubble radius'. In another conversation a couple weeks ago, my personal first her on PF btw.. 'local' was expressed to me as 'two points 1mm apart are not 'local''... local is actually closer than 1mm apart.
hmmmmmm...
So... 'Local' is somewhere between less than 1mm and the Hubble radius. ..
It seems to me that the word 'local' needs to be broken down into some formalized vobaculary.
I propose 'local' should be defined as ...
Given a point in space time.. Pn(x,y,z,t), that the idea of 'local' should be absolutely bounded... like |P1-P2| is in some range of local that can be named as like 'Local level 1' or 'Local level 2'
We should not just use the word 'local' and expect the other to 'automatically understand' the bounds of 'local in this situation'.Back to the quote at the top..
If the local area is a 'hubble radius', or even a 1mm radius, ... then light outruns light in the sense that the photon in front of the photon behind it, with both photons going in the same direction, the first photon will be going faster than the photon behind it... and the space between the photons will be ever increasing...
Which makes me ask... how can distance go to zero in the direction of travel when considering two photons going in the same direction... if the distance between the two photons is ever increasing reguardless how close together they originated.
'Photons travel at the speed of the space they occupy?'
I suppose, how we are taught is this... as we approach the speed of light, the distance in the direction of travel goes to zero. I interpret this to mean that all distances in front of me go to zero, meaning I am infinitely in front of myself... simultaneously completely as far as imaginable into the forward distance.
I am thinking, instead, I should interpret that distance goes to zero as meaning I travel zero distance through space... meaning I am at rest in space. I am moving at the same speed as space, but not relative to space. If I am not moving through space, then distance is zero. However, space is itself moving...
Interesting..
I
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