RE: [Algorithms] rather curious

[Akbar A. <sye...@ea...>]

>Nah, this is NOT true according to Einsteinian General Relativity, and
>no one has ever done an experiment sensitive enough to detect that.
>All bodies, in a vacuum, fall at the same rate--the result of
>Galileo's Tower of Pisa experiment, and a cornerstone of Einstein's
>theory, in which it is called "the Principle of Equivalence".

i'm currently doing some reading on General Relativity, <Physics for
Scientists and Engineers, by Raymond A. Serway, 3rd edition. Copyright is
pretty old>

But,
what i brought up is that if we go by Newton's law of universal gravitation
there is a *difference*

>All bodies, in a vacuum, fall at the same rate-
if we take this formula
F = G ((m1*m2)/r^2)

and we run this for 2 separate objects with *very similar* masses,
F will be different.

F = ma;
a = F/m;

even at a *tiny precision* they still fall at different rates, thus hitting
the surface at a different time.
hence i feel that this should be taught in schools at least for a
"technical" viewpoint cause it's the *right thing* to do.

*before you write anything read below ;)

>But in the several dozen experiments where GR predicts a
>measurable difference from the predictions of Newtonian gravitational
>theory, GR has been confirmed.

with the knowledge from above i see what *you mean*, but i still have to
read those books to *understand* and *see the differences* ;)
as well as to understand the essence and derivation of these theory's.


i have always thought adding any 2 arbitrary numbers will always give the
output of the sum of those 2 numbers.
i guess maybe in this level these "elementary" rules do not apply (note: i'm
a  making parallel here)?




*******
*******
this is "non-technical" and is based entirely on my ways/experience with the
"World(Tm)".
also a reply from Ron about switching career field to physics.
this is very biased :)

please DO NOT send reply's to the list about *this* unless you feel it
pertains to "gaining "technical" knowledge" " ;)
*******
*******


or maybe this is the same case with the definition of "light" (
"it's a wave, wait a sec, in this case it's acting like a particle"
here is a conversation with a truthful researcher and on of the chairs on
the book community.

my question is, why can't they just come up with a "new" definition/name,
which combines both of the properties and merges them into one?


btw, speaking of the universe and all, and somebody mentioned string theory,
faster then light issues, etc..
http://www.superstringtheory.com/basics.html
haven't read through it yet, but it "looks" somewhat legit mate.
we all know that looks can be deceiving though.




>Don't be teed off--change your career and study physics.
;)

a.) academia is not my cup of tea ( i have change my ways ;), i have *no*
idea how some of you manage to stay in school for +6 years. i guess if you
like it...

b.) to get a *decent* (imho gov jobs don't count<pay to low>) job let alone
doing research/getting paid in that field you have to have a highly
appraised *background*, and *just* going to oxford doesn't cut it.

c.) don't get me started on thesis's and some issues with proffeesor/deen
pride...

d.) i like the way carmack summarized this up (full time physics people),
the people in that field have to wait a long time to get there ideas built
up into a reality.
some times they wait years for the "authorization" to happen. then there is
organizing the team, building the facilty if it doesn't exsist, etc..

for us in the cg/real time field, we think of something and do it the next
minute :)


e.) yes, writing missile tracking software is *very* cool, this is physics
and just about every other problem in "real life at work" (Tm)!
but the restraints your stuck with are mind blowing.
imagine waking up every morning to restrains like, ("your code segment is
WAY to big, the MEMORY think of the MEMORY!") and your trying your best...

i wonder what types of hardware(memory,cpu) there running for the new missle
guidance systems.
hehe.

i really admire those guys, as well as console developers who manage to
squeeze technically cool stuff through there hardware limitaions...
a good example would be the software team which was responsible for porting
Resident Evil 2 to Nintendo 64.
see gdmag (www.gdmag.com)  for more details.
there might be an article up about it at www.gamasutra.com ?


peace,
akbar A.

"imho, and i'm sure in yours as well, this entire universe follows out a set
of equations...
the objects of course "

// couldn't fit this anywhere else ;)






-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of Ron
Levine
Sent: Sunday, September 10, 2000 10:51 PM
To: gda...@li...
Subject: Re: [Algorithms] rather curious


Akbar A.  wrote:

>hey,
>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.
>

Of course, this thread is entirely off topic with respect to game
algorithms in the ordinary sense (unless of course you want to make
relativistic physics the object of the game :-)).  But physics is one
of the best subjects to be "rather curious" about, so no one has
objected so far.

In the modern physics paradigm,  gravity is one of the four basic
forces,  and,  by many orders of magnitude,  the weakest of the four.
The other three are called (in order of increasing strength), the weak
force (which, for example,  is responsible for the decay of neutrons
into protons, electrons and neutrinos), the electromagnetic force
(which is responsible for all of chemistry, optics and all other
electromagnetic interactions), and the strong force, (which is
responsible for the binding of quarks into protons and neutrons, and
the binding of protons and neutrons into atomic nuclei.  There has
recently been a buzz about some experimenters claiming to have
discovered a fifth force, but it has not yet entered into the
mainstream physics paradigm.  So, in terms of modern physics it is
perfectly OK to call gravity a force.

But in this paradigm, gravity is indeed also understood as a
phenomenon of the curvature of the space-time "fabric", necessarily
caused by the presence of energy (including mass).  You can completely
understand the orbits of bodies under the gravitational force as
motion along geodesics, i.e. paths of shortest length, in the curved
space-time.

The mathematics that you need to put this all on a sound
logical basis is higher-dimensional differential geometry and tensor
analysis.
This is the framework of Einstein's General Theory of
Relativity.

For the most part, for most ordinary experimental
observations, General Relativity predicts the same behavior as the
classical Newtonian gravitational model, up to the precision of
experiments.

But in the several dozen experiments where GR predicts a
measurable difference from the predictions of Newtonian gravitational
theory, GR has been confirmed.  Read any popular book on modern
physics, such as Stephen Hawking's "A Brief History of Time" for a
non-mathematical review of these ideas, experiments and astronomical
observations.  If you want the real stuff, the best book is
"Gravitation", by Misner, Thorne, and Wheeler, but it is daunting.

>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*>

Nah, this is NOT true according to Einsteinian General Relativity, and
no one has ever done an experiment sensitive enough to detect that.
All bodies, in a vacuum, fall at the same rate--the result of
Galileo's Tower of Pisa experiment, and a cornerstone of Einstein's
theory, in which it is called "the Principle of Equivalence".

However, the main unsolved problem of today's physics is the "Theory
of Everything", which would put all four of the forces together into
one logical framework.  The three strongest forces all coexist nicely
in a theoretical framework called "The Standard Model", whose
framework is essentially quantum mechanical.  No one has yet got a
decent theory of quantum gravity, nor done any experiments that would
expose the quantum mechanical nature of gravity.  But everyone (in
physics) believes there ought to be such a theory that would unify all
the forces.  The present dominant line of theoretical investigation is
called "Superstring Theory", which claims, among other  things, that
the dimension of space-time might be as high as ten.  But superstring
theory has not yet made any predictions that are subject to
experimental verification under present experimental technology.  I
don't know but mabe you or someone has heard that some of the results
of string theory predict a departure from the Principle of
Equivalence, but I haven't heard of it, and certainly no one has
observed it in experiments.  For a good popular review of the present
state of this knowledge see the book "The Elegant Universe" by Brian
Greene.  "A Brief History of Time" was an enormous best seller in the
80's and 90's.  Greene's book was a best seller last year.

>
>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.
>
>i told him what is above is true and André Lamothe writes this in all of
his
>books, and i'm pretty sure he knows more than your professor (the laws make
>sense as well), ...

>i am probably just t-ed of cause i didn't have more proof about the space
>time fabric one :|
>

Don't be teed off--change your career and study physics. The proof is
in the elegance and economy of the theory and the fact that it has
been completely confirmed to within the precision of all experimental
tests so far.

>btw, andre, if your not on the list;
>i highly suggest you join :) i know your busy with volume 2 and all..

This comment reminds me of the sign in the post office:  "No dogs
allowed, except seeing-eye dogs".

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