Thread: RE: [Algorithms] rather curious
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From: Robert D. <RD...@ac...> - 2000-09-10 22:23:05
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> 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. What is it then ? I mean being caused by the curvature of space-time doesn't explain what it is. A ball rolls down a hill because of gravity, not because of the curvature of the surface its on. Rob |
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From: Frag_ D. <fra...@ho...> - 2000-09-11 02:24:41
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Don't have much time right now, but has anybody on this list heard of
the string theory? If I recall correctly, it said that there were several
more dimensions (I think we have like eight, but I can only name the three +
time). Anyway, it said something that all matter was created of this
"strings", including quirks, protons, neutrons--everything, and that the
dimensions are so "small" that they hardly effect us. The theory
(theoretically, actually hypothetically--it hasn't been proven yet) explains
the spatial warping through these new "micro dimensions", or whatever you
want to call them, for one because it's easier to do stuff in more
dimensions. Consider the example:
Two objects wish to swap places in a one dimensional environment.
Assuming that they couldn't pass through each other, it would be impossible.
In two dimensions, however, one could go over and the other under. In
three dimensions then, you could just step around. In four I'm sure a good
example could be thought of.
This is a horribly unorganized email, but you should check into it.
Steven Hawking has looked into it a little, but I don't want to say any
incorrect quotes or anything like that. In game programming, this may be
completely unnecessary and even detrimental. Still interesting.
>From: "Akbar A." <sye...@ea...>
>Reply-To: gda...@li...
>To: <gda...@li...>
>Subject: RE: [Algorithms] rather curious
>Date: Sun, 10 Sep 2000 20:48:52 -0500
>
> >The reason people don't know a lot about relativistic physics is they
>have
> >trouble with Galileo let alone Einstein.
>i don't want to sound stupid (being that i have not had *any* experience
>with Einstein's work) but wasn't most of his stuff, derived from material
>which was pretty trivial?
>
>
> >No one believed us that the objects hit at basically the same time
>regardless >of mass. So we all started dropping stuff on the table to
>prove
>it.
> >Pretty funny.
>been there, done that :)
>
>well you can always look at it and explain to other people that' it's a
>formula and you are just putting in data which has a very *large* gap.
>the precision is small but the difference is *still* there, so in all of
>it's actuality they *don't* fall at the same rate :)
>just cause we can't see it, doesn't mean it doesn't exsist ;)
>
>imho, it must of been a pain in the ass to convince people that we/objects
>are "attracted" to each other ;)
>
>
> >The whole what is gravity thing is pretty tough. Claiming to have the
> >"right" answer is probably folly.
>aren't researchers still clamoring about a "true/right way" to describe
>light and all it's properties;
>"wait a second it's a wave, oh No it's a particle!" (i will stop this, i'm
>going on a tangent ;)
><grin>
>
> >Using Newton's equations for the force of gravity and f=ma
>the mind is so weird.
>maybe i saw this in a dream or something but wasn't it first published as
>-f = -ma
>?
>
> >Didn't they do the feather and rock demo on an Apollo mission as a pr
>thing? >I seem to remember seeing a video of it.
>
>do we even have video capture devices that are that accurate to get the
>10^-24 precision, so we could "see" the diff?
>
>
>anyways,
>i think i got some reading to do about this topic so i can argue with a
>better foot hold.
>i hope this book does the trick, just put the order in.
>http://www.amazon.com/exec/obidos/ASIN/0517029618/o/qid=968634459/sr=2-1/102
>-7947677-2983366
>
>
>
>peace,
>akbar A.
>
>being in the game biz, we actually *apply* all these fancy equations most
>people just memorize for the midterm and forget about.
>
>
>
>
>-----Original Message-----
>From: gda...@li...
>[mailto:gda...@li...]On Behalf Of Jeff
>Lander
>Sent: Sunday, September 10, 2000 6:37 PM
>To: gda...@li...
>Subject: Re: [Algorithms] rather curious
>
>
>The reason people don't know a lot about relativistic physics is they have
>trouble with Galileo let alone Einstein.
>
>Funny this should come up today since last night we got into a little
>debate
>about this at dinner with some friends. My friend works at JPL and we were
>talking about skydiving and this came up. No one believed us that the
>objects hit at basically the same time regardless of mass. So we all
>started dropping stuff on the table to prove it. Pretty funny. It is
>always amazing how a simple "try it yourself" can surprise people. In
>general they just believe it should be some way and never check it out. No
>wonder Galileo ended up in jail.
>
>The whole what is gravity thing is pretty tough. Claiming to have the
>"right" answer is probably folly. Clearly Galileo/Newton works fine for
>most applications any human would run into. I am no expert on
>gravitational
>physics but from what I know, common thinking is based on Einstein's
>theory of General relativity. The mass of objects warp spacetime and the
>falling is explained by objects following a straight path in space-time.
>
>Galileo went to great pains to prove that Aristotle and Plato were wrong
>about falling objects. If he wasn't exactly right to the order of 10^-24
>or
>whatever, I am not sure it matters. At JPL, good old Newton does the job
>for most things.
>
>Using Newton's equations for the force of gravity and f=ma you can see how
>the mass of the falling object just drops out. Different masses do cause
>the objects to hit with different forces but that is different from the
>time, eh.
>
>If someone wants to implement actual relativistic physics for simple rigid
>body simulations, I am sure it would be cool, but Newton is good enough for
>me :)
>
>Didn't they do the feather and rock demo on an Apollo mission as a pr
>thing?
>I seem to remember seeing a video of it.
>
>-Jeff
>
>At 04:26 PM 9/10/2000 -0500, you 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.
> >
> >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.
> >
> >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 :|
> >
> >
> >btw, andre, if your not on the list;
> >i highly suggest you join :) i know your busy with volume 2 and all...
> >
> >peace,
> >akbar A.
> >
> >
> >_______________________________________________
> >GDAlgorithms-list mailing list
> >GDA...@li...
> >http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
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>
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From: <SHA...@ao...> - 2000-09-11 17:45:00
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In a message dated 10/09/00 21:44:54 !!!First Boot!!!, sye...@ea... writes: << 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. >> Hi Akbar, Yes, it is suprising how many people still follow Newtonian laws where gravity is a force. Einstein theorised that gravity is a distortion of space-time and that 'matter bends space'. With this hypothesis one can then explain how stars which are behind our own sun can be seen as if they were to one side of it. This is caused by the light from the star following the easiest path around the sun, following the curvature of space-time. This phenomenon can only be seen when there is a total eclipse since the sun's brightness does not allow the other stars to be seen. I think most people still think Newtonian since it is easier to visualise and definitely easier on the maths side! :) John. |
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From: Steve W. <Ste...@im...> - 2000-09-11 19:20:57
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> -----Original Message----- > From: Akbar A. [mailto:sye...@ea...] > > 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. > This is very interesting...for a FPS where the player travels on the surface of a planet then gravity is best applied as a constant force. Algorithms become much more interesting (as does any game) when the player is traveling slowely near many large gravitational masses (like an asteroid belt) or traveling near light speed. I'll present some of my thoughts...please don't think they are facts or that I read them in a book...they are my thoughts and I know they are different from what is taught in schools or has been offered to the public as explanations. When gravity is applied to a mass then it will be a applied as a force and gravity can be thought of as a 3D force field which can be displayed graphically as a curvature in 2D space. In 3D, gravity is more like a spacial density which is disturbed by the presence of mass so it's not really a force or a curvature in the space time fabric, but the effect of the presence of a mass in an area of variant density. For example if there was no mass at all...only space...then there would be no gravity so it really doesn't have anything to do with space itself. Also, time doesn't exist so time isn't even an attribute of space. > 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? > Mass disturbs a gravity field which in turn applies a force proportional to the mass so there would be absolutely no difference in an ideal situation. I'd say 10^-24 in error would be a VERY efficient experiment and the difference is the error from apperatus and calculations, and not an actually proof that two objects fall as different speeds. Also, in an experiment with THAT precision performed on Earth it would require including the gravity fields of the Sun, Moon, and any other significant mass where G ((m1*m2)/r^2)/m2 is in the order of 10^-24. Also, something to think about concerning relativity is when an object passes through a gravity field so fast that the gravity field does not have time to effect the mass that disturbed that space (it takes time for an effect to occur in a cause/effect relationship) and results in gravitational force being applied to a very small or zero mass and of course a nice mushroom cloud. I believe Einsteins theories have been grossly misunderstood...time isn't lost or gained near the speed of light (anyone here belive in time travel?), and mass is not lost or gained (it's just not available for measurement)...just that the effect from the gravitational field depends on whether an object's relative velocity is faster than the effect can be applied. You might also ponder how G and c are constants and that c = 1/50G (ignoring units of course). And, yes I've done some work on created a new constant and an equation that links F = G ((m1*m2)/r^2)/m2 and E = mc^2 that can provide empirical data to substatiate my theories. Actually I think G or the speed of light has been mis-quoted by a factor of 10 and the actual relationship is G=2c where c^2 is a function describing the position of a mass 2c is the function describing the rate at which it changed position after disturbing the gravity field. I wish I had more time for this, but time is money and nobody is paying me for this stuff. Well, none of that ever got me an ear at NASA or Sandia Labs so I never got an offer to allow me to develop an experiment to test my theories using the super colliders or particle plasma tools; so it hasn't done me any good exept to allow me a better understanding of gravity. Rockn-Roll |
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From: Xyrus <sfr...@se...> - 2000-09-11 20:46:51
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Hi All,
All this talk about gravity and space-time ;).
If you want the low-down on it all (general relativity included), try
the book GRAVITATION by Misner, Thorne, and Wheeler. Describes much of the
math (including tensor calculus) and ideas behind it all, and experiments
done to prove it.
This book has two courses in it, one for undergraduate and one for
graduate.
Just Me,
*SF
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From: Frag_ D. <fra...@ho...> - 2000-09-11 20:05:44
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Yeah, I had a great day yesterday, and didn't work at all. A little
splat-ball, 14 hours of sleep, talking to friends, wasting time, etc. Then
again, I never ACTUALLY work.
We really have some big physics people on this list. Well, keep going,
this is very interesting.
>From: ro...@do... (Ron Levine)
>Reply-To: gda...@li...
>To: gda...@li...
>Subject: Re: [Algorithms] rather curious
>Date: Mon, 11 Sep 2000 15:08:17 GMT
>
>Jeff Lander wrote:
>
> >Man, we are all working late tonight. On a sunday, that's kinda sad.
>
>Nah, I spent a pleasurable day listening to a free concert by the San
>Francisco Opera in Golden Gate Park, and am so wiped out by sunburn
>that sitting in front of the tube and pontificating on physics is an
>entirely appropriate activity.
>
> >But to drag this back to algorithms, your use of Newton's gravitation law
>is getting you into trouble.
> >
>
> >Realize that the only thing that effects when two dropped objects hit the
>ground
> > is the acceleration of those objects. Force doesn't enter into it yet.
>
>Actually, in most developments of the logical foundations of physics
>that I've seen I think that "force" isnot well defined. In the way I
>was using it, in terms of the "four forces", it refers to a type of
>"interaction".
>
> >....
> >So you can see that a body of any mass will hit the earth at the same
>time.
> >The difference due to the original gravitation law is that a more massive
>body
> > will hit the earth with more FORCE and make a bigger dent.
> >
>
>Here, I think your use of "FORCE" is not appropriate. The two bodies
>fall under the same acceleration, so fall for the same time duration
>and hit the earth with the same speed, but the more massive body has
>more kinetic energy and more momentum, so makes a bigger dent.
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From: Steve W. <Ste...@im...> - 2000-09-11 23:36:42
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> -----Original Message----- > From: SHA...@ao... [mailto:SHA...@ao...] > > Einstein theorised that gravity is a distortion of space-time and that > 'matter bends space'. > > With this hypothesis one can then explain how stars which are > behind our own > sun can be seen as if they were to one side of it. > Hi Shambler, Ah, yes...one of the "wave" characteristics of EMF's (Electro-Magnetic-Forces). You have brought up an important aspect of EMF's and gravity in that the wave phenomenon is effected by large gravitational forces such as in the case of black holes where the light can not "bend" around matter and which I believe is one of the "particle" characteristics of EMF's. Rockn-Roll |
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From: <ro...@do...> - 2000-09-11 03:45:34
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Robert Dibley 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. > >What is it then ? >I mean being caused by the curvature of space-time doesn't explain what it >is. Wrong, it certainly explains very well what it is. But you need a little higher math to see that. >A ball rolls down a hill because of gravity, not because of the curvature of >the surface its on. Right. It's not the curvature of the surface it's on, rather it's the curvature of the space-time continuum. |
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