Gravity and Spin

It seems there are quite a few visitors who have their own ideas about one of the great mysteries of our universe, Gravity. Here's a place where all the budding Einstein's among us can wax eloquent on the subject.

Gravity and Spin

Postby natecull » Thu Apr 10, 2008 5:28 am

I am a bear of very small brain, and it takes me a long time to work some things out, so please forgive me if I ramble.

The idea that 'gravity is rotation' - or at least 'gravity is curvature', which seems the same thing to me - seems to come up a lot, both in conventional Einsteinian Relativity and in various spooky aether systems. But I still can't really get a sensible idea into my head of how this equivalence works.

Take ordinary rotation, for instance. If you spin a 3D object, we notice a few things:

1) We get a force pulling objects attached to the rim of the spinning thing, to the centre (centripetal) through whatever it is that connects us to that centre (the molecular bonds of the material, I guess). The inertia of the orbiting object reacts against this and this 'fictitious' force of inertia (fictitious because it's zero in an inertial frame) pushes outwards. The result is that the orbiting object 'feels' an outward push. This is often called 'artificial gravity', but it's not at all like gravity in many ways.

2) You can only spin or orbit in a two-dimensional plane. Centripetal/centrifugal force is therefore a two-dimensional force. Gravity, however, is three-dimensional. It's like orbiting at the same speed in an infinite number of directions at once - or at least in all three dimensions. And not in a tumble, but a smooth sort of spherical orbit. What's up with that?

3) If you reverse the spin of an object, you do *not* get a reversed centripetal/centrifugal force. But gravity is the opposite - it sucks us in. You can't artificially generate through ordinary 2D spin of a 3D object, a force like gravity that 'sucks things toward the centre' (even though centripetal force 'pushes things toward the centre' but is felt as an outward push). So as well as being 3D, gravity is like a sort of 'anti-spin' - it's like not us but the whole rest of the universe is spinning around us, flinging us inward toward our centre of mass. Does that make sense either?

4) Physicists like to talk about 'inertial frames of reference' versus 'accelerated frames', of which 'rotating frames' are a special case. Rotating frames seem to be considered kind of icky and best avoided - hence that whole business about 'it's not really centrifugal force, it only seems like that from a rotating frame; but the real truth of what's happening is in the inertial frame, where it's clearly centripetal'.

But a) actually there are no inertial frames in nature, *everything* rotates, from atoms to stars - things that seem to be 'moving straight' are just orbiting in a very large circle. So shouldn't we treat rotating frames as more primitive, more 'natural', than inertial ones?

And b) how does the rotating frame 'know' that it's rotating? It's not like it's got anything to compare against, has it?

If you take a piece of rock in space, and give it a push (strap a disposable rocket on the side) in a straight line, it'll accelerate briefly then go back to being (relatively) inertial again. No constant energy expenditure.

But if you take that same rock, strap the same rocket on at an angle so it imparts a spin, and light it up - the same amount of energy gets burned, the same amount of work gets done, but that rock now starts spinning around its own centre of mass - and that means it is now in a permanently accelerated frame of reference.

Same amount of energy, totally different result. What's up with that?

And how does it know it's rotating, anyway? Okay, I can see how rotation could be considered a kind of mechanical stress; we've somehow warped the curvature (spacetime, even) of that rock, such that the atoms on one side want to go left and the atoms on the other want to go right... or whatever. So we've dumped that rocket energy into the chemical bonds, maybe.

But still. That a rock 'knows' that it's rotating around itself, with no external cues, that it even 'feels' a stress at all, means that somehow it must have a connection to an absolute rest point inside it, at its centre of mass. It must have something to compare *against*.

But in physics, even the ordinary Newtonian kind, we don't believe there exists such a thing as a priviledged reference frame, surely. But we do, in rotating frames. Seriously, what's up with that?

Best as I can figure, even Mach's principle doesn't make sense of this; it just shrugs and says 'it's just so, there's a spooky connection, maybe gravity, maybe with all the rest of the mass of the universe'. But that still assumes that gravity travels instantaneously; that my spinning rock can immediately feel a kickback from the Whole Darn Universe.


5) If gravity is not quite the same thing as spin in two dimensions of a 3D object - but if it is somehow a kind of curvature, or spin - is it conceivable that it might be something like a spin in four dimensions?

I have no idea what I mean by that, which is why I apologise. But I'm wondering if it might have something to do with Hamilton's quarternions, which seem to me to be all about the idea of 'extension plus rotation' (from complex numbers, expressed in polar coordinates, which I can almost grok) extended to something like 'an extension in time plus three dimensions of rotation in space'.

More about quaternions if I make any more sense of them, and if anyone is interested.

6) Since spin is a purely mechanical quantity, no electric or magnetic forces needed, is it possible that there might be ways to think of a mechanical coupling between ordinary 2D spin and '4D spin' - as Laithwaite seemed to believe was possible, and as Keely and Carr seem to talk about?
natecull
Senior Cadet
 
Posts: 273
Joined: Sat Mar 22, 2008 10:35 am
Location: New Zealand

Postby Mikado14 » Thu Apr 10, 2008 2:26 pm

nate wrote:If you take a piece of rock in space, and give it a push (strap a disposable rocket on the side) in a straight line, it'll accelerate briefly then go back to being (relatively) inertial again. No constant energy expenditure.

The inertia of the orbiting object reacts against this and this 'fictitious' force of inertia (fictitious because it's zero in an inertial frame) pushes outwards.


First Nate, I love someone who asks a lot of questions. Your thesis here started out with a misunderstanding of inertia. Inertia is not considered a force, it is simply that anything at rest wants to stay at rest or anything in motion wants to stay in motion until acted upon by some outside force. The rock in space is motionless for this particular scenario but in reality it is not, now you strap the rocket to it and ignite. The rock will resist the force applied by the rocket and the rocket has to overcome this force. When the rocket has reached it's final velocity and stops the rock is now moving at that speed. It will continue to travel at that speed until acted upon by another force (of course we are ingnoring friction which is why I suppose you choose the space scenario).

I do not understand why you would call it a "fictitious" force. Since you mentioned the rotating object, you have several forces acting upon it but it still has inertia.

Perhaps I am not being clear enough either but inertia is not fictitious.

Now a question, Is Potential Energy fictitious?

Mikado
There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy
Mikado14
Mr. Nice Guy
 
Posts: 2343
Joined: Thu Aug 10, 2006 1:49 pm
Location: Somewhere in Pennsy

Postby natecull » Thu Apr 10, 2008 8:15 pm

Mikado14 wrote:Your thesis here started out with a misunderstanding of inertia. Inertia is not considered a force, it is simply that anything at rest wants to stay at rest or anything in motion wants to stay in motion until acted upon by some outside force.


Correct. Inertia is quite real. (Though one may ask, *why*? And that's where Mach's Principle comes in. But that is a slightly different question than the one I am asking here, which may be confused in its own way.)

Mikado14 wrote:The rock in space is motionless for this particular scenario but in reality it is not, now you strap the rocket to it and ignite. The rock will resist the force applied by the rocket and the rocket has to overcome this force. When the rocket has reached it's final velocity and stops the rock is now moving at that speed. It will continue to travel at that speed until acted upon by another force (of course we are ingnoring friction which is why I suppose you choose the space scenario).


Also correct - but this is the linear acceleration mode I was referring to earlier, *not* the rotational acceleration mode.

Mikado14 wrote:I do not understand why you would call it a "fictitious" force. Since you mentioned the rotating object, you have several forces acting upon it but it still has inertia.

Perhaps I am not being clear enough either but inertia is not fictitious.


Yes, I think you've misunderstood me. Physics does not call *inertia* a 'fictitious force', it calls 'centrifugal force' that. Centrifugal force, as I understand it, is merely inertia as seen from a rotating frame.

http://en.wikipedia.org/wiki/Fictitious_force

But let me restate the question I am asking:

For an object traveling linearly in space at a constant speed, not accelerating, a reference frame can be found in which this object is at rest.

For an object *rotating* around its own axis at a constant speed relative to a fixed observer, not an accelerating speed, however, even though it's not expending energy to maintain that rotation, we consider this object to be 'accelerating'.

Therefore it seems like, from a first glance, that there's something 'special' about the way we mathematically treat rotation as opposed to linear translation. (At least unless I have misunderstood my basic high school physics, which is quite possible.) Why is one form of relative constant movement considered *acceleration* rather than mere speed, when it's the same amount of movement and kinetic energy in each case? That's like a plus sign on one side of an equation becoming a multiplication sign on the other; an exponential or log transform.

I mean, sure, an object translating linearly through space at a constant speed also possesses an equal amount of kinetic energy as one rotating about its axis. But it seems to me like the rotating one has dumped that energy 'inside' rather than 'outside' its own frame of reference somehow, and that intrigues me.

The other thing is that I believe ultimately there's no such thing as a straight line in a curved universe; therefore 'linear translation' is merely a special case of 'orbiting about a sufficiently distant external axis' rather than 'rotation about an internal axis'. Both forms of rotation could equally be considered 'acceleration', I guess, depending on where you pick your reference point. But it's still curious to me that 'plus' can so easily mean 'multiply' and nobody turns a hair.
natecull
Senior Cadet
 
Posts: 273
Joined: Sat Mar 22, 2008 10:35 am
Location: New Zealand

Postby Mikado14 » Thu Apr 10, 2008 9:44 pm

natecull wrote:Therefore it seems like, from a first glance, that there's something 'special' about the way we mathematically treat rotation as opposed to linear translation. (At least unless I have misunderstood my basic high school physics, which is quite possible.) Why is one form of relative constant movement considered *acceleration* rather than mere speed, when it's the same amount of movement and kinetic energy in each case? That's like a plus sign on one side of an equation becoming a multiplication sign on the other; an exponential or log transform.

I mean, sure, an object translating linearly through space at a constant speed also possesses an equal amount of kinetic energy as one rotating about its axis. But it seems to me like the rotating one has dumped that energy 'inside' rather than 'outside' its own frame of reference somehow, and that intrigues me.

.


The easiest and simplest way is this. In the linear movement, the direction is constant. In a rotational, the direction is constantly changing.

A ball on a string that is rotated is in a constant change of direction acted upon by the force of the string pulling it in. The rock is moving in one direction only.

Too simple and needs more?

Mikado
There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy
Mikado14
Mr. Nice Guy
 
Posts: 2343
Joined: Thu Aug 10, 2006 1:49 pm
Location: Somewhere in Pennsy

Postby natecull » Thu Apr 10, 2008 11:15 pm

Mikado14 wrote:The easiest and simplest way is this. In the linear movement, the direction is constant. In a rotational, the direction is constantly changing.

A ball on a string that is rotated is in a constant change of direction acted upon by the force of the string pulling it in. The rock is moving in one direction only.

Too simple and needs more?


Yes, that's the simplistic high school explanation I've heard many times and which doesn't satisfy, because it's a tautology.

It doesn't explain *why* we should arbitrarily assume that a rotating frame 'is constantly changing direction' when rotational velocity is a constant and no energy is being expended to maintain that velocity. From its own frame of reference, that spinning object is *not* changing its direction. And yet objects inside will be pinned to the rim by inertial forces. They are somehow mysteriously able to sense that they are in an 'accelerating' frame even though in their own coordinate system they are at rest with respect to the axis and no rotation is taking place. The rotational frame has turned a constant rotational *speed* into a linear 'centrifugal' *acceleration*, from its point of view. How?

Saying 'it's easy, a spinning thing is constantly changing direction' overlooks that it's only changing direction from the point of view of rectangular coordinates. But things in this world are not naturally rectangular - circles and spheres are much more natural (for example, complex numbers are best represented geometrically as polar coordinates, not rectangular ones). Why should we privilege that particular coordinate system in our maths?
natecull
Senior Cadet
 
Posts: 273
Joined: Sat Mar 22, 2008 10:35 am
Location: New Zealand

Postby Mikado14 » Fri Apr 11, 2008 12:11 am

natecull wrote:
Yes, that's the simplistic high school explanation I've heard many times and which doesn't satisfy, because it's a tautology.


If you believe it is a tautology, then perhpas so. However, just because it doesn't satisfy you doesn't mean it wouldn't to someone else. Therefore, it don't believe it to be a true tautology but then, that is my opinion.

natecull wrote:It doesn't explain *why* we should arbitrarily assume that a rotating frame 'is constantly changing direction' when rotational velocity is a constant and no energy is being expended to maintain that velocity. From its own frame of reference, that spinning object is *not* changing its direction. And yet objects inside will be pinned to the rim by inertial forces. They are somehow mysteriously able to sense that they are in an 'accelerating' frame even though in their own coordinate system they are at rest with respect to the axis and no rotation is taking place. The rotational frame has turned a constant rotational *speed* into a linear 'centrifugal' *acceleration*, from its point of view. How?

Saying 'it's easy, a spinning thing is constantly changing direction' overlooks that it's only changing direction from the point of view of rectangular coordinates. But things in this world are not naturally rectangular - circles and spheres are much more natural (for example, complex numbers are best represented geometrically as polar coordinates, not rectangular ones). Why should we privilege that particular coordinate system in our maths?


You asked a very simple question that can become very complex in answer. First of all, are we talking in a 2 dimensional reality or a 3 dimensional reality. It is true that both are vectors but in a way they are not calculated the same. In linear velocity, you essentially are using speed and direction. In angular velocity, you are essentially looking at the tangential component.

This probably doesn't help much for you are attempting to look at linear the same as rotational. In linear, you never traverse over the same path but in rotational you are constantly going over where you have been. Therefore, you are making a circle measured in radians since a radius is involved which is part of 360 degrees, in other words, you are constantly changing direction to turn around. Of course this is 2 dimensionally.

I don't understand where you are headed but you implied somewhere else that if you travel in a straight line through the universe you will come back to where you started. Even if that is so, the radian involved would be so small that it would have more decimal places than I would care to consider, the effects wouldn't even be noticeable. However, if you are talking about the rotation of a body around the earth, that is very easily calculated.

I realize this is more than likely not what you are looking for so to go into a 3 dimensional object would not be advantageous.

Mikado
There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy
Mikado14
Mr. Nice Guy
 
Posts: 2343
Joined: Thu Aug 10, 2006 1:49 pm
Location: Somewhere in Pennsy

Postby natecull » Fri Apr 11, 2008 4:07 am

Mikado14 wrote:You asked a very simple question that can become very complex in answer. First of all, are we talking in a 2 dimensional reality or a 3 dimensional reality.


At the moment, I'm talking purely about a two-dimensional rotation on a plane, compared to a two-dimensional translation on a plane. I agree that three dimensions can add more complexity (things like precession and such), but for now let's assume a simple, two-dimensional orbit.


Mikado14 wrote:It is true that both are vectors but in a way they are not calculated the same. In linear velocity, you essentially are using speed and direction. In angular velocity, you are essentially looking at the tangential component.



Again correct, but again you are talking about the mathematics and not the underlying 'why'. This is what interests me.


Mikado14 wrote:This probably doesn't help much for you are attempting to look at linear the same as rotational.


Yes. See, the thing is, it seems that we can exactly substitute linear velocity/momentum for angular velocity/momentum in some cases, but somehow they work differently. It is not clear to me that there has ever been demonstrated an underlying physical reason why this is so - at least, not at the high-school textbook level.

Take this for an example:

1) Take a trip on the next Space Shuttle flight. Bring a golf ball and a smooth (infinitely smooth, frictionless) one-metre-long section of straight pipe wide enough to take the ball. Attach a small firecracker to the golf ball such that it imparts a small momentary thrust. Place the golf ball at one end of the pipe. Light the firecracker.

The golf ball accelerates briefly, then continues in a straight line along the pipe. During its voyage through the pipe, it is in an inertial frame, no?

2) Do the same, but bend the same pipe around so it nwo forms a circle.

This time the golf ball, after being thrusted, will continue to accelerate forever as it orbits around and around the pipe. It is now in a rotating frame, perpetually accelerating, perpetually feeling inertial forces.

Yet it is the same ball, the same pipe, the same firecracker. The same dimensions, the same amount of energy.

What's up with that? Surely, the common-sense way of looking at things is to say that either both balls are accelerating, or neither are? Yet we pick one frame and say 'this is curved therefore accelerating' and another and say 'this is flat therefore inertial' -- and the weird thing is, inertia seems to agree. The curved one feels a centrifugal inertial force, the straight one doesn't.

You could argue that the mathematics says that there are two very distinct kinds of inertia or momentum - linear and rotational, and they must not be confused - but the universe doesn't seem to agree, since they both come from the same firecracker.


Mikado14 wrote:In linear, you never traverse over the same path but in rotational you are constantly going over where you have been. Therefore, you are making a circle measured in radians since a radius is involved which is part of 360 degrees, in other words, you are constantly changing direction to turn around. Of course this is 2 dimensionally.


All this is true, but I'm not sure how it is relevant to the question?
natecull
Senior Cadet
 
Posts: 273
Joined: Sat Mar 22, 2008 10:35 am
Location: New Zealand

Postby natecull » Fri Apr 11, 2008 4:24 am

If you want to know 'where I am headed', the answer is I am trying to understand things like this: http://www.rexresearch.com/laithwat/laithw1.htm

which may or may not have anything to do with the question I ask about 'why does something as simple as ordinary rotation convert constant speed into constant acceleration', but on the other hand, might.

The Laithwaite device however (assuming it is real) functions in three dimensions, so the more complicated aspects of gyroscopic spin and precession presumably come into play.

These may be two separate questions, but both make me think 'there's something we don't understand going on with rotation'.
natecull
Senior Cadet
 
Posts: 273
Joined: Sat Mar 22, 2008 10:35 am
Location: New Zealand

Postby Mikado14 » Fri Apr 11, 2008 2:46 pm

natecull wrote:

Take this for an example:

1) Take a trip on the next Space Shuttle flight. Bring a golf ball and a smooth (infinitely smooth, frictionless) one-metre-long section of straight pipe wide enough to take the ball. Attach a small firecracker to the golf ball such that it imparts a small momentary thrust. Place the golf ball at one end of the pipe. Light the firecracker.

The golf ball accelerates briefly, then continues in a straight line along the pipe. During its voyage through the pipe, it is in an inertial frame, no?

Ok, I see where you at with this example, why are you using the word "frame"? The ball has inertia, it had inertia prior to the firecracker, it wanted to stay at rest, now you impart the force of the explosion, the ball has been acted upon and it is now travelling, it still has inertia and it wants to continue to travel until acted upon by an outside force.

2) Do the same, but bend the same pipe around so it nwo forms a circle.

This time the golf ball, after being thrusted, will continue to accelerate forever as it orbits around and around the pipe. It is now in a rotating frame, perpetually accelerating, perpetually feeling inertial forces.

Yet it is the same ball, the same pipe, the same firecracker. The same dimensions, the same amount of energy.
It is very hard for me to disregard friction for the ball will be in constant contact with the inner wall of the tube, that contact (outside force) is what is causing the ball to change direction inside the tube, how can I disregard friction with this, it is the outside force causing the ball to change direction, if I ignore it, the pipe cannot exist.

What's up with that? Surely, the common-sense way of looking at things is to say that either both balls are accelerating, or neither are? Yet we pick one frame and say 'this is curved therefore accelerating' and another and say 'this is flat therefore inertial' -- and the weird thing is, inertia seems to agree. The curved one feels a centrifugal inertial force, the straight one doesn't.



Mikado14 wrote:In linear, you never traverse over the same path but in rotational you are constantly going over where you have been. Therefore, you are making a circle measured in radians since a radius is involved which is part of 360 degrees, in other words, you are constantly changing direction to turn around. Of course this is 2 dimensionally.


All this is true, but I'm not sure how it is relevant to the question? Extremely relevant.
There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy
Mikado14
Mr. Nice Guy
 
Posts: 2343
Joined: Thu Aug 10, 2006 1:49 pm
Location: Somewhere in Pennsy

Postby kevin.b » Fri Apr 11, 2008 5:52 pm

Hope it's OK to join in here?
I cannot find a circle in nature.
I do find very close to circles, but they are actually spirals.

And it is because of spirals that I consider spin origonates.
If you visualise a ball rolling into a spiral pathway, the spiral decreases in diameter constantly until it reaches a point where the spiral will traverse out in the opposite direction and the ball will be then rolling in the opposite direction.
The ball as it nears the spiral end point must become smaller and more dense, and spin faster and faster, when it reaches the end point it will momenterilly stop and then begin to spin in the opposite direction going out in the reverse way leading to a point where it constantly slows to a stop, and then begins to roll back into the centre point again.

If you think of time this way, it is going faster and faster, always just passing inside of where it was last circulation and is somewhat at a denser state, which relates to a different harmonic frequency rate.
If you push in front of the ball an ever decreasing area, but the same volume , then the pressure will raise as well?
Well well I am back to wells.
Thats because of the spiral pathways that lead to the point where the well is sited, the push up into the point where the well is sited pushes the water level up to the surface in relation to the push downward at that point, in other words the meeting point of the two spirals is closer to the surface at that point, hence gravity is different at that point, because gravity is a consequence of the relationship and position of spiral pathways.
Everything spirals.
Waffling
kevin
fibonacci is king
kevin.b
The Navigator
 
Posts: 1717
Joined: Sun Dec 24, 2006 4:30 pm
Location: oxon, england

Postby natecull » Sat Apr 12, 2008 11:39 am

Mikado14 wrote:Ok, I see where you at with this example, why are you using the word "frame"? The ball has inertia, it had inertia prior to the firecracker, it wanted to stay at rest, now you impart the force of the explosion, the ball has been acted upon and it is now travelling, it still has inertia and it wants to continue to travel until acted upon by an outside force.


Quite so. So we agree that we're talking about the same type of movement, inertia, momentum, etc in both cases - the only difference being that in one case, an object is moving at a constant speed in a straight line with conservation of energy applying, and in the other, it is moving at a constant speed in a curved path with conservation of energy also applying.

Do you see why I find it strange that we should consider the same ball, merely by curving its path, to be considered mathematically 'accelerating' rather than simply 'moving'? From the point of view of an outside observer, that ball is constantly 'changing its velocity vector', yes (although it's not changing the *magnitude* of the forces involved, merely their angle) - but from the point of view of the ball itself, on its rotating path, it's doing no such thing - it's merely maintaining a constant speed and travelling straight ahead on a path that happens to be curved. It's maintaining a balanced, damn-near-'inertial' state. But it's not *quite* 'inertial' because it still feels that centrifugal/centripetal force (the one provided by the curved track). Yet, the centrifugal and centripetal forces balance; we're not getting any energy for 'free'. But we do seem to be getting *acceleration* for free - unlike thrust, which costs us a burnt firecracker and tossing actual particles out the back, this kind of circular 'acceleration' doesn't seem to consume anything physical in order to keep itself going. It seems either to be more like some kind of bookkeeping anomaly than a real force - or there's something deeply weird going on with the fabric of spacetime/ether, and we *are* getting a strange force 'for free' just by curving, that in most sane circumstances we can ignore because it 'goes away' as soon as we let go of the bond pulling us to the centre and fly straight - we're back to straight-line, 'inertial', non-accelerated movement.

You could reply 'but of course in physics we consider being acted on by an outside force to be the same thing as acceleration', and that would be true, because that's what it's defined as. Hence why I call it a tautology - something asserted as true though being self-defining. It's pretty much an axiom of Newtonian physics. My question though, is: looking at the actual physical setup of what's going on, is circular movement, 'velocity change' from an outside (rectangular coordinate) perspective without change of speed *really* 'acceleration'? I know we call it that, we're all trained to call it that, I know that's 'how the math works' - but intuitively, is it quite the same thing as straight-line acceleration or thrust (what we get when we light that firecracker) - or something subtly different?

I admit I could be completely down the wrong rabbit hole here, but it's still something I've never intuitively been able to accept or understand.


Mikado14 wrote:It is very hard for me to disregard friction for the ball will be in constant contact with the inner wall of the tube, that contact (outside force) is what is causing the ball to change direction inside the tube, how can I disregard friction with this, it is the outside force causing the ball to change direction, if I ignore it, the pipe cannot exist.


True, but I was using a pipe merely as an illustration to demonstrate that although the maths for linear and circular momentum/inertia claim they are different things, they seem actually pretty much the same physically.

If you like, you can imagine that the 'pipe' is made of magnetic fields, or that it's a piece of string tied to a centre pole, or that it's a gravity field of a planet that the golf ball is orbiting around.

Certainly in the case of a rock orbiting around a planet in hard vacuum, 'tied' to it merely by gravity, that circular 'acceleration due to gravity' doesn't *seem* to 'consume' any propellants or 'cost' us anything in order to maintain our existence in a non-inertial, 'accelerated' frame. And yet in another manner of speaking, we *are* in an inertial frame, flying straight, just one which happens to be 'curved by spacetime'.

Acceleration which is not really acceleration. Curious, no?

Is it possible that we *do* have in gravity (or magnetism, or any other force which can 'pull us to the centre' of a circle without friction or ongoing expenditure of energy) some kind of infinite cosmic energy being radiated out, which we could tap into through some kind of geometrical loophole, if we only understood how? This seems to be the sort of claim made by people like Aspden, Bearden, Bedini, Laithwaite, when they talk about 'extracting energy from curved spacetime' -- which to normal Newtonian physics and to most of Einsteinian physics sounds like complete bonkers, because 'everyone knows' that forces are always balanced and you get nothing 'for free'.

As I said, I don't quite understand this, but I can see how there seems to be a strange Escher-like, not-quite-fitting quality even to conventional Newtonian mechanics, even in the very simplest, ordinary, cases that we meet all the time.
natecull
Senior Cadet
 
Posts: 273
Joined: Sat Mar 22, 2008 10:35 am
Location: New Zealand

Postby Trickfox » Sat Apr 12, 2008 8:10 pm

Natecull

Your observations are incredibly astute. when dealing with devices using the BB effect we always speak in terms of displacement, rather than thrust.
There is an obvious reason we do so.
Your excellent observations in the last post in this thread do a great job of explaining why we speak the way we do.

Trickfox
The psychopropulsier (as pointed out in the book The Good-bye man by Linda Brown and Jan Lofton) is a Quantum entanglement project under development using Quantum Junctions. Join us at http://www.Peeteelab.com
Trickfox
The Magician
 
Posts: 1462
Joined: Sat Feb 25, 2006 7:06 am
Location: Quebec or Montreal

Re: Gravity and Spin

Postby Bulwark » Fri Apr 18, 2008 3:17 am

natecull wrote:

2) You can only spin or orbit in a two-dimensional plane. Centripetal/centrifugal force is therefore a two-dimensional force. Gravity, however, is three-dimensional. It's like orbiting at the same speed in an infinite number of directions at once - or at least in all three dimensions. And not in a tumble, but a smooth sort of spherical orbit. What's up with that?


Then are you saying that all the satellites, the space station, shuttles, whatever are three dimensional objects orbiting in a two dimensional reference? I was under the impression that the orbits are constantly changing unless of course we are talking geosynchronous. I am not all that knowledgable as you seem so could you clarify this?


How does one have a spherical orbit? A sphere is globular and an orbit would be circular or elipsoid but spherical I just don't see. Could you explain this also?

Thanks,

Bulwark
Bulwark
Space Cadet
 
Posts: 90
Joined: Sun Jan 21, 2007 4:14 pm
Location: Alaska

M. C. Escher

Postby greggvizza » Fri Apr 18, 2008 2:18 pm

Nate,

I see your point. If we were in a space station, of the Ferris wheel variety depicted in the movie 2001 Space Odyssey, then once you gave it it’s initial spin, on its axis, it would continue to spin without the expenditure of energy. As long as it continues to spin the people and contents inside would experience a force pushing them to the outer rim floor, in gravity like fashion. How are we getting that gravity like force for free so to speak?

There is more involved with spin than is commonly thought.

GV
greggvizza
Senior Cadet
 
Posts: 483
Joined: Sat May 06, 2006 3:01 pm

Postby Mikado14 » Fri Apr 18, 2008 10:41 pm

Hello Gregg, nice to hear from you.

I see references to centripetal/centrifugal force referenced in this thread. I have seen the term inertial frame used and a host of others. I have sat here and waited but no one has mentioned it and I thought you would have.

Centrifugal is a non-existant force and is sometimes referenced as a virtual force. The only force Newton expressed in his Principia was centripetal.

Centrifical force is also a non-existant force both it and Centrifugal are non-existant.

Centrifical is used in industry in regards to pumps and clutches etc but that does not mean it is correct. It is improperly named for a fictitious force that in reality is the inertia of the body attempting to stay at rest or in a straight line direction depending upon an inertial reference frame outside of the rotation.

Now, if you wish to reference something else than ok, but when I went to college, quite a few years ago, this is what I remember but then I have died once so they may have changed a few things.....<g>

What do you think Gregg?

Mikado
There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy
Mikado14
Mr. Nice Guy
 
Posts: 2343
Joined: Thu Aug 10, 2006 1:49 pm
Location: Somewhere in Pennsy

Next

Return to Gravity

Who is online

Users browsing this forum: No registered users and 1 guest

cron