Freethought & Rationalism Archive

ohwilleke · 08-28-2002, 02:40 PM

Quote:

Originally posted by Jonesy:
The person who fully explains gravity will be a genius, because a full understanding of gravity will open up possibilities such as 'controlling gravity' - meaning that you can control 'the gravity force' locally and thus achieve ' antigravity'. When this happens, oil companies are finished (for example), transport with wheels is finished, etc...

We cannot delude ourselves that we 'know' what gravity is, when we don't.

Any further understanding of the mechanism of gravity could not significantly differ in any conditions we have examined scientifically. Thus, no matter how much we learn about the mechanism of gravity, it will be an attractive force very nearly proportional to the gravity of the pulling object in all but the most extreme and unusual conditions.

Given that the predictions of GR have been studied with a great deal of detail, and that the only time where there have been concerns about a difference between GR and experiment have been at vast distances in the gillions of light years where there is some experimental evidence that gravity may be less than predicted by GR, I don't think that we can expect any terrestrial technologies that arise from greater understanding of gravity.

Benefits from a greater understanding of gravity are more likely, IMHO, to come from a better understanding of quantum behavoir in other circumstances that results from the search, than from the improved understanding of gravity per se. I suspect that the only material improvement we might derive from a better theoretical understanding of gravity is a more exact value for G or its equivalent in the new theory.

Mark_Chid · 08-28-2002, 03:03 PM

Quote:

Originally posted by bd-from-kg:
Actually there's a serious question lurking here. According to GR, gravity isn't really a force, but a curvature in the space-time continuum.

I've never really felt that this explains anything. Why would a mere curvature make things move?

If I push my kid's toy car along his curved Hot Wheels track its not the corvature of the track that moves it, its an external force, the curvature merely defines direction.

What makes objects FOLLOW this curve? Why don't they just stay where they are?

bluefugue · 08-28-2002, 03:23 PM

Hmm. Well from what I remember of those old "billiard ball on rubber surface" demonstrations, the idea is that gravity alters direction rather than causing movement. I.e., a planet orbiting a star is moving in a "straight" line along the curved surface of spacetime.

Not sure how that relates to a guy falling off a cliff, though...

Starboy · 08-28-2002, 04:41 PM

A strait line is defined as: the path of a ray of light. In curved space, for a ray of light, Pythagoras�s theorem no longer applies, x^2 + y^2 + z^2 � (ct)^2 != 0. When it does apply space is flat. Motion in flat space is described by Special Relativity.

Starboy

[ August 28, 2002: Message edited by: Starboy ]

Jonesy · 08-29-2002, 01:47 AM

Quote:

Originally posted by Friar Bellows:


Not at all. To know something fully is not necessarily to have total control over it. A final "theory of everything" will not guarantee a spaceship that gets us to the Andromeda Galaxy in a human lifetime. Sure, science opens up opportunities, but it also sets definite limits.

I disagree totoally. To know something FULLY - DOES imply you can have total control of it - at least conceptually; The only problem/question is: even though you KNOW how to control something fully, do you have the 'physical technology' to do so? And this will be the biggest problem.

It;s time for poeple to realize that since gravity is all about "forces between particles" (to put it VERY simply) - and as such - it will one day be possible to know EXACTLY how particles behave w.r.t. one another and as such control them to our liking. Including creation of fields where particles interact in such ways as to 'eleiminate' the 'force' that we describe as 'gravity'.

Infinity Lover · 08-29-2002, 02:16 AM

Even if you know how a force works, doesn't mean you can eliminate it (make it go away around a subject; create a pocket of of 'weightlessness' in an environment where gravitational pull is active, as opposed to creating an environment of weightlessness where such a pocket would be unnessecary). It would still boil down to creating an opposing force to eliminate the effect of that force.

Isn't that pretty much what we're doing already, by combining airodynamics with propulsionmechanisms?

Answerer · 08-29-2002, 08:05 AM

Gravity is equivalent to the acceleration of a mass or a frame of reference. As for curved manifolds, its just to illusrate how objects move in the presence of gravity, thats all. Of course, its a fact that we can't tell whether our spacetime is curved extrinisic or not at all. Thats the job of a higher dimensional being if there are such an entity in the first place.

Infinity Lover · 09-03-2002, 03:35 PM

Here's another thought.

Could anything exist if there wasn't any gravity in existence whatsoever?

Existence couldn't possibly not-exist in itself.

See where I'm going? Gravity existing, because it couldn't possibly not-exist.
Existence of a natural law through sheer logic.

tronvillain · 09-03-2002, 03:58 PM

Infinity Lover:

Quote:

Could anything exist if there wasn't any gravity in existence whatsoever?

Yes.

Infinity Lover · 09-03-2002, 04:11 PM

Well. I'm convinced.

08-28-2002, 04:41 PM	#14
Starboy Banned Join Date: Jun 2002 Location: Tallahassee, FL Reality Adventurer Posts: 5,276	A strait line is defined as: the path of a ray of light. In curved space, for a ray of light, Pythagoras�s theorem no longer applies, x^2 + y^2 + z^2 � (ct)^2 != 0. When it does apply space is flat. Motion in flat space is described by Special Relativity. Starboy [ August 28, 2002: Message edited by: Starboy ]</p>

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08-28-2002, 03:23 PM	#13
bluefugue Veteran Member Join Date: Aug 2001 Location: Los Angeles Posts: 1,427	Hmm. Well from what I remember of those old "billiard ball on rubber surface" demonstrations, the idea is that gravity alters direction rather than causing movement. I.e., a planet orbiting a star is moving in a "straight" line along the curved surface of spacetime. Not sure how that relates to a guy falling off a cliff, though...

08-29-2002, 02:16 AM	#16
Infinity Lover Veteran Member Join Date: Jan 2002 Location: The Netherlands Posts: 1,047	Even if you know how a force works, doesn't mean you can eliminate it (make it go away around a subject; create a pocket of of 'weightlessness' in an environment where gravitational pull is active, as opposed to creating an environment of weightlessness where such a pocket would be unnessecary). It would still boil down to creating an opposing force to eliminate the effect of that force. Isn't that pretty much what we're doing already, by combining airodynamics with propulsionmechanisms?

08-29-2002, 08:05 AM	#17
Answerer Veteran Member Join Date: Feb 2002 Location: Singapore Posts: 3,956	Gravity is equivalent to the acceleration of a mass or a frame of reference. As for curved manifolds, its just to illusrate how objects move in the presence of gravity, thats all. Of course, its a fact that we can't tell whether our spacetime is curved extrinisic or not at all. Thats the job of a higher dimensional being if there are such an entity in the first place.

09-03-2002, 03:35 PM	#18
Infinity Lover Veteran Member Join Date: Jan 2002 Location: The Netherlands Posts: 1,047	Here's another thought. Could anything exist if there wasn't any gravity in existence whatsoever? Existence couldn't possibly not-exist in itself. See where I'm going? Gravity existing, because it couldn't possibly not-exist. Existence of a natural law through sheer logic.

09-03-2002, 04:11 PM	#20
Infinity Lover Veteran Member Join Date: Jan 2002 Location: The Netherlands Posts: 1,047	Well. I'm convinced.

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