Re: [Algorithms] rather curious

[Eric L. <le...@C4...>]

> i am just wondering, but how many people know about *this* "gravity isn't
> really a force" and that it is caused by the curvature in the space time
> fabric.
> 
> And, if you drop two objects in a vacuum they *really* don't fall at the same
> rate (difference is very small, order of 10^-24) <this *makes sense*> why
> don't more people know this?
> 
> even if it's at a difference 10^-24, i assure you, if we had money that was
> this accurate, banks would "require" this much precision in there software :|
> 
> i am just curious what is the *the few on this list*  knowledge about this...
> 
> i recently (3 minutes ago) got in an argument with a friend on this *topic*,
> he told me his professor said that "Gravity is a FORCE" and saying anything
> different from that is pure anarchy.

Due to my degree in astrophysics, I have had some exposure to this kind of
stuff.  The presence of matter or energy in space (which are actually
equivalent -- remember E = mc^2) causes the space surrounding it to become
curved.  The more mass (or energy), the greater the curvature.  Gravity is
the attractive force which arises due to this curvature.

General Relativity is very interesting, but I doubt that many programmers
need it unless they're simulating near-light-speed travel or plan to let
users fly a spaceship near black holes.  Basic Newtonian physics ought to
serve you just fine.  For a character standing on the surface of a planet,
time actually travels faster for his head than it does for his feet, but the
difference is so miniscule that it's difficult to measure with even our best
technology.  Implementing a relativistic effect like this would never
produce any noticeable results.

If you're curious about the subject of General Relativity, I have found the
following book to be very well written:

Foster and Nightingale, "A Short Course in General Relativity",
Springer-Verlag.

http://www.amazon.com/exec/obidos/ASIN/0387942955/

Let me warn you though, unless you have an M.S. or better in physics or
mathematics, this book will scare you.

-- Eric Lengyel