Linked by Thom Holwerda on Sat 7th Apr 2007 20:58 UTC, submitted by rx182
Windows Paul Thurrot writes about Windows XP SP3: "If you were looking for any glimpse into the mind of Microsoft, this is it: the company has completely abandoned Windows XP, and it has absolutely no plans to ever ship an XP SP3. My guess is that Microsoft will do what it did with the final Windows 2000 Service Pack: claim years later that it's no longer needed and just ship a final security patch roll-up. This is the worst kiss-off to any Microsoft product I've ever seen, and you'd think the company would show a little more respect to its best-selling OS of all time."
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RE[8]: so ?
by h times nue equals e on Sun 8th Apr 2007 12:15 UTC in reply to "RE[7]: so ?"
h times nue equals e
Member since:
2006-01-21

It is my task to appologise for the confusion I have caused (Disclaimer: I've not slept much and my memory has failed me.)

Say you want to describe the "free" (no external forces) motion of a particle on the surface of the globe. One can find an adjusted set of coordinates (spherical coordinates r, phi and theta with center R0) where the constraint (e.g. particle can only move on the surface of the globe) is satisfied implicitly. If I derive the equations of motion in this set of prefered coordinates (and forget a moment about the fact, that these are - from our point of view - radial and angular components) then it takes the shape of a "straight line".

(Side remark: Damn, another definition of "free" we have to deal with in this forums. o_O)

When one changes the constraints (e.g. turn on external forces, maybe even non-conservative like friction) and proceeds to proceeds to describe the motion of the (now non-free) particle, one has to either modify the set of coordinates to take this into account implicitly (which would yield again "straight lines" in the new, adapted set of coordinates) or have to leave with a curved projection.

So the particle moving along the surface of the globe can be either viewed in its adapted set of coordinates as a straight line or in a less adapted set (our falt R^3) and an external constraint (like a very rigid central force), resulting in curved trajectories.

Light travels in "straight lines" in the 3+1 dimensional space-time, but the projection onto our familiar R^3 looks curved. If one switches on a force field so that the particle is no longer "free" and the particle would stop traveling along null - lines (lightlike world lines).

I know, that my knowledge about GRT is currently limited (as I'm only a number cruncher who tries to finally finish his thesis in computational physics), so feel free to correct me. (mental Post-It to myself: Less posting on OSNEWS, more learning GRT)

Again, my appologies for the confusion I caused

Reply Parent Score: 3

RE[9]: so ?
by h times nue equals e on Sun 8th Apr 2007 12:50 in reply to "RE[8]: so ?"
h times nue equals e Member since:
2006-01-21

Ok, last addition /correction:

Additional (external) "forces" result in a modified functional (like the length or the Lagrange function) via "potentials" that has to be made extreme (e.g. minimised in the case of the "length").

So the resulting Euler - Lagrange equations change, not necessarily the generalised coordinates (they should be only changed, when other (holonomic) constraints are introduced. Non-holonimic constraints can be treated with Lagrange multipliers, IIRC)

*bangs head on the table*, *twice*

I'm off #-|

Reply Parent Score: 2