Fe gravity as it relates to the speed of light

• 541 Replies
• 140298 Views
?

Curious

• 413
Fe gravity as it relates to the speed of light
« Reply #60 on: September 25, 2006, 01:06:38 PM »
Quote from: "EnragedPenguin"
Quote from: "Curious"
Theoretically you would reach a point where a person on the earth could not lift anything because you would be so close to C that a couple of fps increase of velocity would require extraordinary energy.

Kinetic energy is relative. From our frame of reference we will never reach a point where a person can't lift an object, because the energy required to lift it will never change.

You keep using that word.  I do not think it means what you think it does.

Consider:  Observer A is "observing" rocket B which is traveling at (C - 1fps).  Remembering that in special relativity, the rules of physics apply equally.

Rocket b flies to a planet that is 1 light year from observer A.
Receives a message, replies and Rocket B turns around and flies back to Observer A.

For simplicities sake let's ignore acceleration. And assume that observer A is relatively motionless to the Target.

Now Observer A wants to send a message to rocket B and have it arrive at the target 5 minutes after the rocket lands.

So he calculates that he must send it 5 minute after take off plus the difference in the ships velocity and the speed of light over the year of travel ( ok in rough math that means he needs to give the rocket a 5554 mile head start (about .03 seconds) plus the 5 minutes).

The time line for observer A is 1 year flight out + about .03 seconds (the difference in time for light to travel 1 light year and the ship to travel the same) + 5 minutes wait + 1 year for the ships reply and .03 second till the ship lands.  From the viewpoint of observer A his expectation is that those onboard the ship have only experienced less than one second of travel time (due to time dilation at near light speed).

On board the ship, they see observer A travel at near light speed relatively, and expect the same.  They also see their target as moving at near light speed, so they can calculate that less than 1 second should pass on the target's time line.

They get their message, send their reply and return home to observer A.

How much time has passed for the timeline on board the spaceship?

If time, mass, velocity and all are all relative, and that means that relativistic affects can be "zeroed out" locally;

Then the ship traveling at zero should experience 2 + years for the entire trip, and that Observer A and the Target experience 5 minutes+.

And Likewise to the Observer 2+ years have passed, and he expects 5 Minutes+ to pass for the travelers.

This should seem to say that your version of Special Relativity is contrary to Special relativity.

When the trip is complete and the travelers and observer are on the same frame of reference, how should their watches compare?  If you are right than both should say 2+ years passed.  If I am, then Observer A's expect ions are what should be resolved.

We know from particle acceleration experiments that A particle with a known half life accelerated to near C has does not decay at the expected rate, and does no "recover" the time difference when it is no longer accelerated.

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #61 on: September 25, 2006, 01:26:50 PM »
Quote from: "Curious"
Consider:  Observer A is "observing" rocket B which is traveling at (C - 1fps).  Remembering that in special relativity, the rules of physics apply equally.

Remember that in special relativity, this is only true for inertial observers.

Quote
For simplicities sake let's ignore acceleration. And assume that observer A is relatively motionless to the Target.

The twin paradox proves that you can't ignore acceleration.  The fact that Observer B changed his direction of travel is enough to invalidate your entire argument.  Observer B's world line is objectively longer than Observer A's.
Why did the chicken cross the Möbius strip?

?

Curious

• 413
Fe gravity as it relates to the speed of light
« Reply #62 on: September 25, 2006, 02:10:45 PM »
Quote from: "Erasmus"
Quote from: "Curious"
Consider:  Observer A is "observing" rocket B which is traveling at (C - 1fps).  Remembering that in special relativity, the rules of physics apply equally.

Remember that in special relativity, this is only true for inertial observers.

Quote
For simplicities sake let's ignore acceleration. And assume that observer A is relatively motionless to the Target.

The twin paradox proves that you can't ignore acceleration.  The fact that Observer B changed his direction of travel is enough to invalidate your entire argument.  Observer B's world line is objectively longer than Observer A's.

What I mean by ingnoring acceleration is that I'm not factoring in the time it takes to reach speed.

Why should direction of travel make any difference.  Since to rocket ship, by your argument, they have no direction of travel relative to themselves.

How is B(the Rocket) 's world line longer? On the spacial dimensions, it has a longer "Line" but in the temporeal dimention the line is much shorter.  The length only appears different if you "Veiw" it in two or three dimentions, since it is a four (at least) dimentional figure.

But in terms of the example, Which part do you disagree with?  The time dialation for observer B?  That Observer B's observation of dialated time due to relativity for Observer "A" collapses upon reentering A's frame of reference?

The "Twin Paradox" is not a paradox in four dimentional space.

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #63 on: September 25, 2006, 11:45:41 PM »
Quote from: "Curious"
What I mean by ingnoring acceleration is that I'm not factoring in the time it takes to reach speed.

What I'm saying is, you do have to factor it in.

Quote
How is B(the Rocket) 's world line longer?

It's longer in the sense that if you draw the spacetime diagram, it's longer:

(thick lines are worldlines of timelike particles; thin lines are light cones)

Quote
But in terms of the example, Which part do you disagree with?

I disagree with your belief that the two frames of reference are equally valid.  One is inertial; the other is not.

Quote
The "Twin Paradox" is not a paradox in four dimentional space.

What?  It certainly is -- at least until you admit that the inertial frame of reference is preferred.  I don't know where you got that idea.  Dimensionality ihas nothing to do with it -- the metric has everything to do with it.
Why did the chicken cross the Möbius strip?

?

Curious

• 413
Fe gravity as it relates to the speed of light
« Reply #64 on: September 26, 2006, 08:47:48 AM »
Quote from: "Erasmus"
Quote from: "Curious"
What I mean by ignoring acceleration is that I'm not factoring in the time it takes to reach speed.

Quote
What I'm saying is, you do have to factor it in.

Exactly!

Quote
But in terms of the example, Which part do you disagree with?

Quote
I disagree with your belief that the two frames of reference are equally valid.  One is inertial; the other is not.

Perfect, now by applying your own argument you will see why you can not ignore the velocity of your flat earth and keep saying it is zero, if you are also claiming to be under acceleration to give you gravity.

Quote
The "Twin Paradox" is not a paradox in four dimensional space.

Quote
How is B(the Rocket) 's world line longer?

Quote
It's longer in the sense that if you draw the spacetime diagram, it's longer:

What?  It certainly is -- at least until you admit that the inertial frame of reference is preferred.  I don't know where you got that idea.  Dimensionality has nothing to do with it -- the metric has everything to do with it.

Yes, and again you show why you can not accept the acceleration and deny the velocity.

The world "line" is a projection of four Dimensional space.

Observer A "travels" almost entirely through time at C, with little X,y, or Z displacement. Observer B is accelerating through space (x,y,z) at nearly C, and therefore has little movement through time.

The two are equivalent, but movement is on different coordinates.  There is no paradox.

What I have attempted to do is reconstruct some of the earlier arguments against special relativity, in part they are the reason Einstein worked on General Relativity.

The problem with your model is that for all frames of reference to be valid, the universe has to be infinite and isotropic.

You are creating a model the is not inertial for the purpose of accumulating velocity, but is inertial for the purpose of acceleration.  Your "universe" is moving with you, so is not isotropic, and since it is all being acted upon by a single energy source causing your "acceleration" it is not infinite.

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #65 on: September 26, 2006, 10:14:03 AM »
Quote from: "Curious"
The world "line" is a projection of four Dimensional space.

What does that mean?

Quote
The two are equivalent, but movement is on different coordinates.  There is no paradox.

The two are not equivalent.  One is accelerating, the other is not.  I'm not gonna say it again.

Quote
You are creating a model the is not inertial for the purpose of accumulating velocity, but is inertial for the purpose of acceleration.

Um, no I'm not?
Why did the chicken cross the Möbius strip?

?

steveo

cause of gravitation
« Reply #66 on: November 13, 2006, 12:29:24 PM »
So let me get this straight.  FE theory purports that the Earth's gravity is due to a 1g acceleration upwards, along with everything else in the universe.  So what causes this acceleration?  I'm fine with your explanation of the relativity aspects of it.  If it pushes on everything in the universe, then it must push on us as well unless you have a force that pushes on everything except what's on the Earth...which would be far more mysterious than anything in modern science.  But if it pushed on us, then the 1g acceleration of the proposed Flat Earth would be exactly matched by the force accelerating us (as with the Sun, Moon, stars, etc...) upwards and we wouldn't perceive the acceleration of the Earth as gravity.

How do you propose that this mystery acceleration apply to everything in the universe and not to objects on the Earth?

Steve-O

?

Erasmus

• The Elder Ones
• 4242
Re: cause of gravitation
« Reply #67 on: November 13, 2006, 12:54:29 PM »
Quote from: "steveo"
How do you propose that this mystery acceleration apply to everything in the universe and not to objects on the Earth?

I don't.  Maybe it's as simple as: the force that's accelerating us is below the Earth, and we're above it.  The stuff in the sky is ridigly attached to the Earth in some way that still allows them to move in set paths, so the Earth pushes up on them just as it pushes up on us.

Anyway, this thread's purpose is to present an argument that assuming that the mechanism for this acceleration exists, it would be indistinguishable from gravity from somebody standing on the surface of the Earth with resources available to the common man, and that there would be no "speed of light violations".
Why did the chicken cross the Möbius strip?

?

Zim Foamy Fan

Fe gravity as it relates to the speed of light
« Reply #68 on: November 13, 2006, 03:52:14 PM »
First of all, I would like to point out something that discredits the balloon theory. The universe is not as massive as the critical mass needed to expand forever, and the actual shape of the universe has been figured out.

Second, if the whole earth were accelerating at 9 m/s^2, then the gas on the earth would surely fall off the earth, as it would experience high pressure and would escape to lower pressure, or as in outer space.

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #69 on: November 14, 2006, 04:04:42 AM »
Quote from: "Zim Foamy Fan"
First of all, I would like to point out something that discredits the balloon theory. The universe is not as massive as the critical mass needed to expand forever, and the actual shape of the universe has been figured out.

This paragraph indicates confusion.  The critical mass is not needed to expand forever, but to be stable.  If the universe is "not as massive" as that, it stands to reason that it will expand forever.

The balloon theory is not really discredited by this point.  Furthermore, the balloon theory does not really apply to the FE model of gravity.

Quote
Second, if the whole earth were accelerating at 9 m/s^2, then the gas on the earth would surely fall off the earth, as it would experience high pressure and would escape to lower pressure, or as in outer space.

The pressure on a given volume of gas is only dependent on the gas above it.  At the boundary between the atmosphere and empty space, if such a boundary exists, there is no air above, so the gas at the boundary itself is not under any pressure.
Why did the chicken cross the Möbius strip?

?

mrscience

• 9
Fe gravity as it relates to the speed of light
« Reply #70 on: November 26, 2006, 09:21:13 PM »
Wow.  I thought that this issue had been resolved, because I couldn't find it.  It just occured to me to search for my own posts.

A couple of points:  Kinetic energy.  As was said, once our hypothetical platform reached near light speeds (wrt some inertial observer), we would have enormous kinetic energy FROM THE PERSPECTIVE of that observer.

It would therefore seem impossible for that observer to see me lift a 20-lb dumbell over my head (around 6') in a split second.  But, he wouldn't see me doing that.  Remember lenght contraction and time dilation?  To him, I wouldn't be 6', I'd be miniscule in height.  From his perspective it would also take an enormous amount of time for the dumbell to reach my head, even if it only took a split second for me.

So, to him, I wouldn't be lifting a 20-lb dumbell 6' in a split second, I'd be lifting it a microscopic height, in a decade's time.

Second, the twin paradox:

Okay, there are two ways of explaining this, the special relativity one and the general relativity one.  First, the special.  The twin who travels to the other planet starts out in his own reference frame, where he will say that his friend on earth is aging slower than he.  Each observer is entitled to say that the other is aging slower from his frame of motion.  Fair enough?

Now, rocket boy makes a stop at the other planet, TURNS AROUND, and starts traveling in the opposite direction.  He's changed his frame of reference.  Then, he stops again, landing on earth, and entering earth's frame of reference.(which we approximate as inertial for simplicity's sake.)

Because he is now in earth's frame of reference, his perception of time must conform to that reference frame, which says that he was moving at near light speed for the last year or so of his trip.  His time will therefore be dilated.

Now, the general relativity explanation.  Rocket boy is entitled to say that he was at rest for the entire time, and that at two points in time (his turning around, and his landing on earth) there was a sudden gravitational field that everyone experienced.  At first, the earth was moving away from him at constant speed.

Now, the earth accelerates from this field, while he is held in place by his rocket engine.  The field ceases to exist, but the earth is now moving toward him, from its brief acceleration.  His friend on earth is still aging slower, at this point.

Now, just as the earth is about to reach him, a second gravitational field comes into existence.  Again, he's held in place by his rocket engine, whild the earth accelerates to a stop.  Once the earth is at rest, the field dissapears, and he is on earth.

So why has his terrestrial friend aged so fast?  Gravitational fields alter the rate of time passage, and earth boy's aging process has been accelerated by the two momentary gravitational fields, giving him a couple of "growth spurts" throughout an otherwise sluggish aging process.

That's all for today.  Hope this clarifies some stuff.
IGNATURE

?

Curious

• 413
Fe gravity as it relates to the speed of light
« Reply #71 on: November 27, 2006, 08:36:06 AM »
Quote from: "mrscience"

So why has his terrestrial friend aged so fast?  Gravitational fields alter the rate of time passage, and earth boy's aging process has been accelerated by the two momentary gravitational fields, giving him a couple of "growth spurts" throughout an otherwise sluggish aging process.

That's all for today.  Hope this clarifies some stuff.

No, if increrased gravity decreases the rate of time passage to an external observer, how can it spped up the passage of time in the way you describe?

And As I've asked in a couple of places, if the energy required for acceleration is internal to the earth and bodies being accelerating, where can it be coming from, since in the FE model presented, the mass and volume of what we perceive is limited.

If it is external, then you have all the problems of relative motion between the accelerating earth and the source and the effects of entropy in the energy transfer to the two.

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #72 on: November 27, 2006, 08:51:07 AM »
Quote from: "Curious"
No, if increrased gravity decreases the rate of time passage to an external observer, how can it spped up the passage of time in the way you describe?

At the point of turnaround, when the travelling twin fires his engines to accelerate himself towards the Earth, he must be allowed to continue to treat himself as stationary.  This is where gravity -- the pretend force -- comes into play: he is allowed to assume that a uniform gravitational field has pervaded the entire universe and is oriented in the direction opposite that of the force applied by his rocket engine.  Thus, the Earth is now "above" him in the gravitational sense.

This puts him at a lower gravitational potential, and clocks at lower gravitational potentials run more slowly.
Why did the chicken cross the Möbius strip?

?

mrscience

• 9
Fe gravity as it relates to the speed of light
« Reply #73 on: November 27, 2006, 07:55:46 PM »
Quote from: "Curious"

And As I've asked in a couple of places, if the energy required for acceleration is internal to the earth and bodies being accelerating, where can it be coming from, since in the FE model presented, the mass and volume of what we perceive is limited.

If it is external, then you have all the problems of relative motion between the accelerating earth and the source and the effects of entropy in the energy transfer to the two.

I don't know how the hypothetical scenario is supposed to explain the source of the acceleration.  A giant rocket engine at the underside of our flat earth?  Maybe it gets its fuel from ambient hydrogen atoms in space.  Not very likely from a logistical standpoint, but it still doesn't contradict relativity.

I'm not really sure what you mean by problems of relative motion between the the source of the force, or where entropy comes into play.

Here's another question.  Why bother with an accelerating platform?  A giant platfom with a uniform density would produce an "ordinary" gravitational field, as long as one did not get close to the edges(which are supposed to be shielded by a wall of ice if I'm right?)
IGNATURE

?

mrscience

• 9
Fe gravity as it relates to the speed of light
« Reply #74 on: November 27, 2006, 08:05:15 PM »
Quote from: "Curious"
No, if increrased gravity decreases the rate of time passage to an external observer, how can it spped up the passage of time in the way you describe?

I'll assume that you were referring to my original example of the inertial observer with the dumbell lifting.  Threre is no gravity from the inertial observer's perspective.  He sees my time as being dilated because of our relative velocities.  He also sees my length as being contracted, which is something that a (uniform) gravitational field cannot do.
IGNATURE

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #75 on: November 27, 2006, 11:49:34 PM »
Quote from: "mrscience"
Here's another question.  Why bother with an accelerating platform?  A giant platfom with a uniform density would produce an "ordinary" gravitational field, as long as one did not get close to the edges(which are supposed to be shielded by a wall of ice if I'm right?)

If the platform is not very very thick (in other words, if it's not a long cylinder), the direction towards the Earth's centre of mass will be very noticeably not straight down.  This can be solved by making the Earth a big cylinder, by making it (or the ocean in which it (maybe) floats) infinitely wide, or making it accelerate upwards.
Why did the chicken cross the Möbius strip?

skeptical scientist

• 1285
• -2 Flamebait
Fe gravity as it relates to the speed of light
« Reply #76 on: November 28, 2006, 12:03:25 AM »
Quote from: "Erasmus"
Quote from: "mrscience"
Here's another question.  Why bother with an accelerating platform?  A giant platfom with a uniform density would produce an "ordinary" gravitational field, as long as one did not get close to the edges(which are supposed to be shielded by a wall of ice if I'm right?)

If the platform is not very very thick (in other words, if it's not a long cylinder), the direction towards the Earth's centre of mass will be very noticeably not straight down.  This can be solved by making the Earth a big cylinder, by making it (or the ocean in which it (maybe) floats) infinitely wide, or making it accelerate upwards.

Two things:
1) The direction gravity pulls you is not necessarily directly toward the center of mass. This is true for spherical objects, but not all objects, and not for cylinders.

2) He was implying a very wide cylinder, with all of the area inside the ice wall near the center. Not quite infinite, but not very easily distinguishable either. Gravity would not pull you straight down, but it would be very difficult to detect the deviation, even if the cylinder were very thin.
-David
E pur si muove!

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #77 on: November 28, 2006, 12:25:28 AM »
Quote from: "skeptical scientist"
Two things:
1) The direction gravity pulls you is not necessarily directly toward the center of mass. This is true for spherical objects, but not all objects, and not for cylinders.

Interesting.  I have never heard this claim and would, of course, like to hear / be referred to some justification.

Quote
2) He was implying a very wide cylinder, with all of the area inside the ice wall near the center. Not quite infinite, but not very easily distinguishable either. Gravity would not pull you straight down, but it would be very difficult to detect the deviation, even if the cylinder were very thin.

Well, if you are on the surface of such a cylinder, you can, to a very good approximation, ignore the gravitational pull from all the material whose distance from the centre of the Earth is greater than your distance from the centre of the Earth.  This is true for the RE as well -- assuming the Earth to be of uniform density, if you're beneath the surface of the Earth, the material in the "shell" outside your position exerts no net gravitational force on you.

I figure I'm telling you stuff you already know here -- but the same effect would occur on a cylinder, except the "outer" material would be an annulus rather than a shell.  Thus, for all intents and purposes, you are always near the rim of the cylinder, no matter where you are -- it's just a smaller cylinder if you're in closer.  Oh, this means the force of gravity should change as well, in a way that's not clear to me put is probably linear with distance from the centre.
Why did the chicken cross the Möbius strip?

skeptical scientist

• 1285
• -2 Flamebait
Fe gravity as it relates to the speed of light
« Reply #78 on: November 28, 2006, 01:12:47 AM »
Quote from: "Erasmus"
Quote from: "skeptical scientist"
Two things:
1) The direction gravity pulls you is not necessarily directly toward the center of mass. This is true for spherical objects, but not all objects, and not for cylinders.

Interesting.  I have never heard this claim and would, of course, like to hear / be referred to some justification.

Quote from: "Wikipedia"
If the bodies in question have spatial extent (rather than being theoretical point masses), then the gravitational force between them is calculated by summing the contributions of the notional point masses which constitute the bodies. In the limit, as the component point masses become "infinitely small", this entails integrating the force (in vector form, see below) over the extents of the two bodies.

In this way it can be shown that an object with a spherically-symmetric distribution of mass exerts the same gravitational attraction on external bodies as if all the object's mass were concentrated at a point at its centre. (This is not generally true for non-spherically-symmetrical bodies.)

(Found at the Wikipedia page for Newton's law of universal gravitation.) I'm not sure what sort of an answer you'd get if you used relativity instead of Newtonian gravity, but it can't be that different. Of course in practical applications when you actually calculate gravitational forces, you are almost always doing so between objects which are spheres, or objects which are very far apart relative to their size, so this almost never comes up.

Quote
Quote
2) He was implying a very wide cylinder, with all of the area inside the ice wall near the center. Not quite infinite, but not very easily distinguishable either. Gravity would not pull you straight down, but it would be very difficult to detect the deviation, even if the cylinder were very thin.

Well, if you are on the surface of such a cylinder, you can, to a very good approximation, ignore the gravitational pull from all the material whose distance from the centre of the Earth is greater than your distance from the centre of the Earth.

This is also false, for a similar reason. If you actually perform the integral in question over the material you say you can ignore, you will get a nonzero result. I'm not sure if you've ever read Larry Niven's novel Ringworld or its sequels, but this is why the Ringworld is unstable.

Quote
This is true for the RE as well -- assuming the Earth to be of uniform density, if you're beneath the surface of the Earth, the material in the "shell" outside your position exerts no net gravitational force on you.

This is true, but it is because of a very special property of spheres, and is not equally true for cylinders or rings.

Quote
I figure I'm telling you stuff you already know here -- but the same effect would occur on a cylinder, except the "outer" material would be an annulus rather than a shell.  Thus, for all intents and purposes, you are always near the rim of the cylinder, no matter where you are -- it's just a smaller cylinder if you're in closer.

No.

Quote
Oh, this means the force of gravity should change as well, in a way that's not clear to me put is probably linear with distance from the centre.

If you were to take a very wide (but not infinite) and thin cylindrical disc of some uniform density and perform the integral to determine the exact force it applies to a person standing near (but not exactly at) the center, you'll get a force which is approximately straight down. If the density and thickness are right, it will impart an acceleration of 9.8 m/s/s. The force will not vary much with distance from the center, assuming the distance from the center is small relative to the radius of the disk (I'm not sure how small 'small' is in this case without actually doing the integral, which I really don't want to do. These integrals get very messy very quickly being done in three dimensions, so mistakes are probable, and locating them is extremely time consuming. Even writing down the integral can take some work.)
-David
E pur si muove!

?

Curious

• 413
Fe gravity as it relates to the speed of light
« Reply #79 on: November 28, 2006, 07:42:38 AM »
Quote from: "mrscience"
I don't know how the hypothetical scenario is supposed to explain the source of the acceleration.  A giant rocket engine at the underside of our flat earth?  Maybe it gets its fuel from ambient hydrogen atoms in space.  Not very likely from a logistical standpoint, but it still doesn't contradict relativity.

I'm not really sure what you mean by problems of relative motion between the the source of the force, or where entropy comes into play.

Here's another question.  Why bother with an accelerating platform?  A giant platfom with a uniform density would produce an "ordinary" gravitational field, as long as one did not get close to the edges(which are supposed to be shielded by a wall of ice if I'm right?)

1) Since all observable space is supposed to be accelerating with us, there would be no new supply of fuel, plus now you have external mass racting with the accelerated mass of the earth, the relative velocities being nearly light speed, even the mass of a hydrogen atom would have significant effect.

2) If the source of the force is not accelerating and the object is, then due to relativist mass, the amount of energy needed to accelerate the object must continually increase at a rate greater than just the newtonian acceleration.

And Entropy can be expressed as
Quote from: "http://www.2ndlaw.com/entropy.html"
All kinds of energy spontaneously spread out from where they are localized to where they are more dispersed, if they're not hindered from doing so

So not only does Relativity increase the energy requirements, but since enery must be lost in any system, Entropy also increases the energy requirements.  And where does this "lost" energy go?  If I push on an object, a small amount of my force is transfered into heat, the greater the push the greater the heat. The earth would burn up from the "lost" energy, as well as from the friction of any non-accelerated matter in it's path.

?

mrscience

• 9
Fe gravity as it relates to the speed of light
« Reply #80 on: December 02, 2006, 08:58:12 PM »
Quote from: Curious
Quote from: "http://www.2ndlaw.com/entropy.html"
erating with us, there would be no new supply of fuel, plus now you have external mass racting with the accelerated mass of the earth, the relative velocities being nearly light speed, even the mass of a hydrogen atom would have significant effect.

2) If the source of the force is not accelerating and the object is, then due to relativist mass, the amount of energy needed to accelerate the object must continually increase at a rate greater than just the newtonian acceleration.

And Entropy can be expressed as
Quote from: "http://www.2ndlaw.com/entropy.html"
All kinds of energy spontaneously spread out from where they are localized to where they are more dispersed, if they're not hindered from doing so

So not only does Relativity increase the energy requirements, but since enery must be lost in any system, Entropy also increases the energy requirements.  And where does this "lost" energy go?  If I push on an object, a small amount of my force is transfered into heat, the greater the push the greater the heat. The earth would burn up from the "lost" energy, as well as from the friction of any non-accelerated matter in it's path.

I don't see how the source of the force affects the argument.  From an inertial perspective, the acceleration is approaching zero.  As far as collisions with captured hydrogen atoms slowing the ship down, I hadn't thought of that.

As far as entropy is concerned, if I'm understanding your argument, the only relevance this has is that not all of the energy is going to be used because some of it will go into heat.  As the ship heats up, the only way for it to cool down would be to come into contact with cooler surroundings, which would further hinder it, (and probably generate more heat from the collisions).  The only way around this that I can think of is heat loss through radiation, which would be pretty insignificant.

While you do bring up some good points, these are basically engineering barriers (probably insurmountable ones.)  The laws of relativity don't strictly rule the scenario out.  True, no one's ever designed a machine that could do such a thing, but if you're willing to believe that the earth's really flat and that we're surrounded by a huge wall of ice....
IGNATURE

?

mrscience

• 9
Fe gravity as it relates to the speed of light
« Reply #81 on: December 02, 2006, 09:10:24 PM »
Quote from: "Erasmus"
Quote from: "mrscience"
Here's another question.  Why bother with an accelerating platform?  A giant platfom with a uniform density would produce an "ordinary" gravitational field, as long as one did not get close to the edges(which are supposed to be shielded by a wall of ice if I'm right?)

If the platform is not very very thick (in other words, if it's not a long cylinder), the direction towards the Earth's centre of mass will be very noticeably not straight down.  This can be solved by making the Earth a big cylinder, by making it (or the ocean in which it (maybe) floats) infinitely wide, or making it accelerate upwards.

If a surface (disk, rectangle, whatever) is exremely large compared to the beings on it, it can be approximated as being infinite, and you're always at the center of an infinite platform.  No, you wouldn't literally be at the center of a huge finite disk, but the edges would be so far off that any distance from the center would be insignificant.

If you use the principle of symmetry, it's easy to see why an infinite sheet of mass would generate a field straight down.  There's an equal amount of mass on the left as there is on the right, and so any forces in either direction would cancel out, and only the downward components of your attraction to all parts of the sheet would be left.
IGNATURE

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #82 on: December 02, 2006, 10:47:10 PM »
Quote from: "mrscience"
If a surface (disk, rectangle, whatever) is exremely large compared to the beings on it, it can be approximated as being infinite, and you're always at the center of an infinite platform.

I'm not sure about this.  My not-sureness relates to the point on which skeptical scientist and I don't exactly agree: can the gravitational attraction from points whose distance from the centre is greater than yours be ignored?  My belief is that it can, and I'm currently in the process of checking up on this.  If it is the case, then only the hubwards material exerts a force on you, so you're always near the "rim", so you always feel a non-downward force.

In any case, even if my belief is wrong, some math needs to be done to show that indeed the angle of the force is indistinguishable from straight down.

Quote
If you use the principle of symmetry, it's easy to see why an infinite sheet of mass would generate a field straight down.

Agreed.
Why did the chicken cross the Möbius strip?

skeptical scientist

• 1285
• -2 Flamebait
Fe gravity as it relates to the speed of light
« Reply #83 on: December 03, 2006, 05:50:24 AM »
Quote from: "Erasmus"

I'm not sure about this.  My not-sureness relates to the point on which skeptical scientist and I don't exactly agree: can the gravitational attraction from points whose distance from the centre is greater than yours be ignored?  My belief is that it can, and I'm currently in the process of checking up on this.  If it is the case, then only the hubwards material exerts a force on you, so you're always near the "rim", so you always feel a non-downward force.

In any case, even if my belief is wrong, some math needs to be done to show that indeed the angle of the force is indistinguishable from straight down.

You are indeed right that some math needs to be done to show this is the case. The best way would be to actually write down the integral and do it. For an observer inside a sphere of radius r, density p (measured in mass/area, not mass/volume so we don't need to consider the sphere's thickness, which we assume to be negligible compared to the distances), and centered at 0, the total force on an object of mass m at point x is the integral of Gmp(x-ru)/|x-ru|^3 dA, where u ranges over all unit vectors in 3-space, and dA is area measure on the unit sphere. (Bold quantities are vectors.) This turns out to be zero, as we already know.

A good way of seeing that this is zero without calculating the integral is the following picture:

To determine that the total force on an observer inside the sphere is zero, we perform the cancellation as follows: compare the forces from opposing cones: the amount of area inside the cone at distance d goes up as the distance squared, and the force is proportional to mass/d^2, so the two opposite sides cancel. Of course this is only approximate, but if you imagine the code infinitely narrow, the material inside the cone is all the same distance away in the same direction, and the cancellation is exact. This is all very hand-wavy, but it agrees with what you get when you look it up in a physics textbook, or with what you get when you integrate.

Now lets look at the force from a ring of uniform density p (now in mass/length along the circle) and radius r centered at 0 on an observer of mass m at point x. Again, the most rigorous and unambiguous way of doing this is performing the integral: Gmp(x-ru)/|x-ru|^3 dL (where u ranges over unit vectors in the plane, and dL is length measure on the unit circle). If we assume x=(x,0) is on the x-axis, this is equal to Gmp/r^2 times the integral from 0 to 2pi of ((x/r,0)-(cos w,sin w))/|(x/r,0)-(cos w,sin w)|^3 dw. Since the picture is vertically symmetric, the net force in the y direction is 0, and the net force in the x direction is:
Gmp/r^2 times the integral from 0 to 2pi of (x/r-cos w)/((x/r-cos w)^2+(sin w)^2)^(3/2) dw. If someone has a good symbolic integrator and wants to figure out what this is, be my guest. For x/r bigger than 0 and smaller than 1, it should give a nonzero force in the positive x direction.

We can also see why the force is nonzero, and what direction it is in a similar manner as for the sphere by looking at the following picture:

We again consider cones from the observer in opposite directions. The distances to the ring in opposite directions are ra and rb, and the masses of the red-colored portions of the ring are proportional to ra and rb, respectively. Again, gravity is a 1/r^2 force, so the forces from the two portions go as 1/ra and 1/rb, so B exerts a greater force on the object than does A. You could do this in any pair of opposite directions, with the resultant force always pointing towards the nearer side of the ring. The end result is that the force on an observer in the middle of a ring is nonzero and points towards the nearest part of the ring.

If you consider an observer standing on a large disk, the disk-shaped portion closer that the center than him pulls him down and towards the center of the disk. The ring-shaped portion further from the center than him pulls him down, and towards the nearest point to him on the ring - i.e. directly away from the center of the disk. Thus the resultant force is down and towards the center of the disk, but the magnitude of the force in the horizontal direction gets smaller as the radius of the disk gets larger, tending towards zero as the size of the disk approaches infinity. So a thin very wide disk with gravity could be a good FE model if the entire habitable surface extending to the ice wall were near the center of the disk.

Hurray for doing a lot of non-trivial physics and then using it to provide a possible model for a flat earth! What the hell was I thinking?
-David
E pur si muove!

?

Erasmus

• The Elder Ones
• 4242
Fe gravity as it relates to the speed of light
« Reply #84 on: December 03, 2006, 12:18:15 PM »
Hm, okay, I believe you.  I had forgotten that the spherical shell scenario was based on the delicate balance between the 1/r^2 force and the r^2 mass.

Anyway, I evaluated your integral in Maple.  The result was given in terms of some annoying special functions, but the plot was what you'd expect:

The horizontal axis is signed normalized distance from the centre; the vertical axis is signed strength of the gravitational force.
Why did the chicken cross the Möbius strip?

?

Curious

• 413
Fe gravity as it relates to the speed of light
« Reply #85 on: December 05, 2006, 07:15:43 AM »
Quote from: "mrscience"

I don't see how the source of the force affects the argument.  From an inertial perspective, the acceleration is approaching zero.

Acceleration approaches Zero, but Mass approaches infinite.

Quote
As far as entropy is concerned, if I'm understanding your argument, the only relevance this has is that not all of the energy is going to be used because some of it will go into heat.

And the greater the energy applies, the greater the lost energy, and therefore the "Waste Heat".  The energy being applied must continue to increase, and appears to only affect the bottom layer of the earth, otherwise a rock, when dropped would not fall, but would continue to be accelerated by this mysterious force.

The force must be applied perfectly evenly, and the increase in energy must perfectly match both the increased energy required for the increase of mass due to relativity, and any external resistance applied to the system, such as friction with interstellar dust, or gravity.

Also, another aspect of entropy is that the further the object is from the energy source the more energy is lost.  If the force causing the acceleration is not moving, even the most conservative estimates say we've been around for more than 6,000 years, and traveling at near light speed ever since the first year or so, meaning that we are at least 6000 light years from the source, and if you are not a creationist, it's more like 4,540,000,000 light years away.  That's a long way to focus this incredible force.  And if it is not focused, that just increases the energy requirements by unbelievable amounts, ever increasing.

?

mrscience

• 9
Fe gravity as it relates to the speed of light
« Reply #86 on: December 13, 2006, 09:51:33 PM »
Yeah, okay, I understand your point.  I never said that it was a realistic possibility.  I initially entered the discussion to show that it didn't strictly violate the laws of relativity (nor does it technically violate any laws.)

As far as the source of the force, a nuclear reaction would be what would seem the most plausible to me.  We'd be losing mass astronomically, but who's to place a limit on how much we start out with?  Matter-antimatter conversion would be the most compact form of energy, if it could be harnessed.

As far as how much we'd need to start out with in order to stay accelerating up until today, 4.5 thousand million years, and compensate for heat loss, drag, and all that, I have no idea.  An increadible amount, to be sure.
IGNATURE

?

Grigori Rasputin

• 76
Re: fe and relativity
« Reply #87 on: February 08, 2007, 04:03:57 AM »
Quote from: "mrscience"

Suppose that I hold a golf ball over the edge of the platform.  While the ball is in my hand, it is not an inertial observer, because it is accelerating up with me and the platform.  Now, if I let it go, my and the platform's acceleration will no longer be transmitted to the golf ball, and hence it will stop accelerating up with me, and become an inertial observer.  I will percieve the ball to begin accelerating downward at 9.8 m/s2, and it will see me as accelerating upward at the same rate.

Yes, this would be the case if everything (universe) around the platform (flat Earth) wasn't accelerating as well. But what if everything around the platform was also accelerating at 9.8m/s2?

Now, related to the above, a question to FE'ers: does the FE theory use a geocentric model, i.e. is the FE surrounded by the universe? Or is the FE at the bottom of the universe pushing everything up as it accelerates?

(mods: feel free to split this question to another thread if you feel that it doesn't belong to this one)
hen one person suffers from a delusion it is called insanity. When many people suffer from a delusion it is called conspiracy.

?

Uzor

• 40
Fe gravity as it relates to the speed of light
« Reply #88 on: February 08, 2007, 05:49:50 AM »
Quote

In other words, from Bob's perspective, the Earth is always stationary (we are Bob), but undergoing constant acceleration. From Alice's perspective, the Earth moves at an ever increasing rate, but the acceleration is not constant -- it decreases over time in such a way that the Earth never surpasses the speed of light.

Care explaining how the earth can undergo constant acceleration, while not being constant, and by constantly decreasing its speed?

Because if its decreasing its speed so that it doesn't surpass the speed of light, that means its decreasing its speed with the same ammount it accelerates in. Which means its not changing its speed at all.

Which means one of 3 things

1) you're wrong
2) we're right
3) the earth's speed it constant, its acceleration is not(read: its acceleration is 0).

case 3 may very  well be the case. If earth had a constant speed, you'd still feel the "gravitational pull" you're exlaining. Sadly, that's not what your theory is about. So you're wrong either way.

I think you have no idea what acceleration really means.

?

Uzor

• 40
Fe gravity as it relates to the speed of light
« Reply #89 on: February 08, 2007, 05:53:59 AM »
Quote

Suppose that I hold a golf ball over the edge of the platform. While the ball is in my hand, it is not an inertial observer, because it is accelerating up with me and the platform. Now, if I let it go, my and the platform's acceleration will no longer be transmitted to the golf ball, and hence it will stop accelerating up with me, and become an inertial observer. I will percieve the ball to begin accelerating downward at 9.8 m/s2, and it will see me as accelerating upward at the same rate.

That's not how acceleration works.

If something accelerates, and then the acceleratino reaches 0, it will continue with the same speed unless something stops it. Thus, if you let go of the ball, it would keep going with the same speed untill somethig stops it.

In space, there is nothing to stop it. Thus, things continue with the same speed untill they hit something.

So for the ball to just suddenly stop dead in its track, it requires a force pushit it the opposite way it was going.