Nick
I invite you to entertain a change in Einstein's Equivalence Principle. Einstein equated accelerated motion with gravity. How can something that is not moving be equated to something that is? What is moving will have a rate. A blasting rocket has weight that depends on its rate of acceleration. But that same rocket sitting on the launch pad how can it have a rate of change? It's not moving. The equivalence principle is two parted. Each part is not the same. Weight in the blasting rocket is not calculated exactly the same as weight in gravity.

Take the time rate out of calculating weight in gravity and you have it. Free fall will always have a rate IE it has a motion. It has a rate of change. The equivalence is not what Einstein thought. They are equivalent but not mathematically identical. One has a rate the other doesn't. Only acceleration is equivalent to a rate of change of velocity. Gravity isn't. It is equivalent to change of velocity alone. This means that there is a limit to gravitational force. But none for accelerated motion.
Nick
Hello I have just recently joined the forum.
I think you have made a very clear point.
I am not in a position to speak with authority on the
Topic of Albert Einsteins picture of gravity, but I find
myself struck with wonder when I think that this idea
has been accepted for so long.
It is not a good comparison of real physics.
It seems we had a longing for someone to say something that
sounded profound back then.
No one know what he was saying and so everyone simply quoted others as time passed.
I think we need to start with real basic thought now, and make sure it make sense.
Nick
Right BH. Einstein was the first of his kind. So his physics blancketed everything under one umbrella. Now we know he simply went too far. But what can you expect in being the first?

Science is young.
Confused2
This isn't a trivial question .. hopefully this will help..

When talking about relativity we often refer to an inertial frame. What is an inertial frame you ask? The answer is it's the location of something with no forces acting on it. The alternative to an inertial frame is an accelerated frame.

If we look at a rocket on a launch pad is it in an inertial frame or an accelerating frame? We look at all the supports bearing the weight of the rocket and say "it sure isn't inertial .. the forces on it are preventing it from falling down towards the centre of the Earth. If it has forces acting on it then it is (by definition) NOT inertial. If you boosted the rocket up to a mile above your head and turned the engines off THEN it would be an inertial frame .. anyone inside the rocket would be weightless .. until it hit the ground.

Rocket motors firing OR the supports that stop the rocket falling into the centre of the Earth are the same thing in relativity.

Anything not clear so far?

-C2.
Nick
The roket sitting on the launch pad is equivalent to an accelerating frame. That is what Einstein said. But I am pointing out that there is a mathematical difference between a blasting rocket's weight and one that is sitting still in gravity.

One moves the other doesn't. The one that moves has a rate of movement. The one that doesn't move can have no rate at all. And once you take the rate out you are left with a limited force of gravitation.
Confused2
If the rocket has any force on it then it is in an accelerated frame .. that is the definition of an accelerated frame. Even if it does not seem to be accelerating by the Nick definition of an accelerating frame .. that isn't the point .. as far as relativity is concerned .. it has a force on it and that means it's an accelerated frame. There is no mistake within the formal rules of relativity .. it is consistent .. if your only problem is that you don't like the definition .. please be prepared to accept the definition used by Einstein .. too many people are already using his definition for any other to gain acceptance.

It is not unreasonable .. if you started the rocket motors and kept the power just right .. you could remove the supports and the rocket would stay in the same place. If you fired the rockets with the same power in interstellar space .. nobody inside the rocket could tell the difference.

-C2.
Nick
I believe in the equivalence of acceleration for the rocket on the launch pad but it can have no rate of change. It is not moving so how could it?

I call it timeless or instantaneous acceleration.
AlphaNumeric
QUOTE (boneheaded+Jun 29 2006, 04:11 AM)
It is not a good comparison of real physics.

So why did Einstein manage to predict the results of the Pound-Rebka experiment more than 50 years before it was carried out to exceptional accuracy?
QUOTE
It seems we had a longing for someone to say something that
sounded profound back then.
No one know what he was saying and so everyone simply quoted others as time passed.
BS. What is it with people who don't understand things like relativity or quantum mechanics saying "It's hard to understand, therefore wrong and everyone for the last 7~10 decades just hasn't bothered to do anything new". There are hundreds, if not thousands of people in the physics community right now who understand relativity as good as, if not better than, Einstein did. They've spent their lives working on it and developing it further. I can name more than half a dozen in my uni department alone, say people like Hawking!
QUOTE (->
 QUOTE It seems we had a longing for someone to say something that sounded profound back then. No one know what he was saying and so everyone simply quoted others as time passed.
BS. What is it with people who don't understand things like relativity or quantum mechanics saying "It's hard to understand, therefore wrong and everyone for the last 7~10 decades just hasn't bothered to do anything new". There are hundreds, if not thousands of people in the physics community right now who understand relativity as good as, if not better than, Einstein did. They've spent their lives working on it and developing it further. I can name more than half a dozen in my uni department alone, say people like Hawking!
Science is young.
Sure, a theory will come along one day to superseed relativity, but that doesn't detract from the fact that it's fantastically good at modelling gravitational interactions of non-quantum mechanical objects.

Do a Google or look up on Wikipedia the Pound Rebka experiment, which discusses interial and accelerated frames. It essentially comes down to being able to say the local interial frames of Newtonian theory and SR coincide and that 'normal coordinates' exist, being that you can boost into a frame where gravity doesn't exist, if only locally.
Confused2
Maybe Nick's problem is that he saying there is no rate of change while the rocket is on the launch pad from a frame which is also an accelerated frame .. in all probability the same accelerated frame as he is claiming the rocket is not accelerating in. Nick and the rocket are both in accelerated frames .. otherwise Nick or the rocket would be heading for the centre of the Earth.

-C2.
Ron
Hey Nick, Alpha, C2,
This looks like a good thread to get some thoughts from my intelectual superiors!
C2, Well stated that any object under the influence of a force is in an accelerated reference frame. Hard to grasp but, I believe accurate. This is how I come to grips with the equivilence principle.
When looking at how warped space becomes the easiest path for an object in the vicinity of a gravitational 'field', I sometimes think that the object is accellerating towards the center of mass, only stopped by that mass. If a mass (or other space-time distorter could be permeable, we could accellerate through that 'mass' to it's center. This center, to me, would be a well, and, depending on the mass-density (ie Swartchild radius), I, as light, may not be able to escape.
In this situation, I don't see how the laws of physics are any different from the rest of the universe (from my perspective), I just can no longer communicate with the outside world. (and I probably weigh more than my girlfriend would like!)
Alpha, set me straight if you could!
Thanks All,
Ron
Nick
QUOTE (AlphaNumeric+Jun 29 2006, 09:02 PM)
So why did Einstein manage to predict the results of the Pound-Rebka experiment more than 50 years before it was carried out to exceptional accuracy?
BS.

His equivelnce principle applies so well because gravity is so damn weak. You wouldn't expect to see the kind of effect I am describing but in fairly strong gravity. The original principle is a limiting case. That's all there is to it!

Einstein just carried it to far. What do you expect being one of the first? There is just more to it.
Nick
Einstein's equivalence principle needs modifying. There is no rate in gravitational weight. This means that there is a limit to it.
rpenner
Does anyone know what Nick is saying, it doesn't look like English to my semantic processor.
Nick
The mathematical change to the principle is as follows:
Original Equivalence Principle is gravity is equivalent to:the rate of change of velocity
The new version for gravity's weight alone is simply: change in velocity.

One is limited to less than light speed the other has no such limit. In other words you can reach near light speed in ever smaller intervals. Without an interval weight is limited. Time doesn't apply to gravity's weight. Not so for an accelerating rocket. It has a rate of change. But when sitting still you don't.

AlphaNumeric
But without taking the rate into account, it's meaningless.

Suppose you go from (relative) rest to 99% the speed of light. What's the acceleration on you? What might the gravity being applied to you be?

Without giving a time, you don't know, it could have been a billion g's or it could have been a billionth of a g, but over a long period of time.

Besides, the equivalence principle is about freefalling frames. If you read up about the Pound-Rebka experiment you'd realise this. The experiment involved considering a large, stationary (with respect to the Earth) tower which fired photons from it's base to it's top.

Now obviously the tower isn't moving with respect to the Earth, but you consider a freefalling frame which initially is in the same position as the tower but begins to accelerate downwards under gravity. By then doing a change of reference frame, it can be seen this is the same as taking your stationary frame as the freefalling one and having the tower itself accelerate upwards with normal gravitational acceleration. This then allows for some computation involving photon travel times, giving a prediction about time interval changes.

From another point of view, the tower remains stationary and the photons are fired upwards with a relativistic effect occuring due to redshifting.

The prediction of Einstein was that the first point of view, which is Newtonian viewpoint, will give the same result as the relativistic, second, viewpoint. Hence, Newtonian and relativistic local interial frames coincide, or put another way, geodesics and freefalling particle trajectories are locally the same.

It's all made clearer by sketching space-time diagrams, as found in 'Misner, Wheeler and Thorne - Gravitation'.

The time part of all that is vital, you must consider rates of things otherwise concepts like acceleration are meaningless and how can you describe gravity if you've just made the concept of acceleration meaningless?
Zephir
QUOTE (Nick+Jul 5 2006, 02:26 AM)
Original Equivalence Principle is gravity is equivalent to the rate of change of velocity... The new version for gravity's weight alone is simply: change in velocity.

By the general relativity theory postulate (equivalence principle), the acceleration force is equivalent to the gravity force. But acceleration isn't "rate of change of velocity ", i.e. the "rate of rate of rate" (3rd derivation of distance in time), but just "rate of rate", i.e. the "change in velocity", supposed by you.

Briefly speaking - despite of inspiring insights & questions in other posts of yours - you're just trying to reinvent a wheel by now...
gonegahgah
Sorry to interrupt this thread.

Zephir, could you please help me with some questions I have at Spiral Theory of Energy & Matter.
Nick
Still there is no motion zeph. So no rate no rate no rate. But it is an equivalent to an instantaneous change in velocity. It is a timeless acceleration. It is an equivalence which is not exactly the same. How could it be?

Take time out and you get a limit.

I think for the stationary rocket to be under a rate of change, the base holding the rocket would have to be adding a rate of upward force (sort of growing).

The base is not changing up or down.
The argument of the whole rocket and base is falling to the center of earth, is good.
However this is a question that could consider time.
If we can not find the center point of change of gravity, (gravity from one side of earth to the other) we can not find a place where the time can be considered.

Anyone have a thought about the exact point of gravity change at the center of earth?

Nick
Rate of change only applies to gravity in freefall.

The center of the earth is going around the sun and moving toward the moon a little as it goes around.
Pupamancur
QUOTE (AlphaNumeric+Jul 5 2006, 09:28 AM)
But without taking the rate into account, it's meaningless.

Suppose you go from (relative) rest to 99% the speed of light. What's the acceleration on you? What might the gravity being applied to you be?

Without giving a time, you don't know, it could have been a billion g's or it could have been a billionth of a g, but over a long period of time.

Besides, the equivalence principle is about freefalling frames. If you read up about the Pound-Rebka experiment you'd realise this. The experiment involved considering a large, stationary (with respect to the Earth) tower which fired photons from it's base to it's top.

Now obviously the tower isn't moving with respect to the Earth, but you consider a freefalling frame which initially is in the same position as the tower but begins to accelerate downwards under gravity. By then doing a change of reference frame, it can be seen this is the same as taking your stationary frame as the freefalling one and having the tower itself accelerate upwards with normal gravitational acceleration. This then allows for some computation involving photon travel times, giving a prediction about time interval changes.

From another point of view, the tower remains stationary and the photons are fired upwards with a relativistic effect occuring due to redshifting.

The prediction of Einstein was that the first point of view, which is Newtonian viewpoint, will give the same result as the relativistic, second, viewpoint. Hence, Newtonian and relativistic local interial frames coincide, or put another way, geodesics and freefalling particle trajectories are locally the same.

It's all made clearer by sketching space-time diagrams, as found in 'Misner, Wheeler and Thorne - Gravitation'.

The time part of all that is vital, you must consider rates of things otherwise concepts like acceleration are meaningless and how can you describe gravity if you've just made the concept of acceleration meaningless?

Nick doesn't go to school. Nick doesn't read guys like Thorne and such since they might pollute his thinking.
Nick manufactures theories and "corrects" mainstream physics and physicists.
Pupamancur
QUOTE (Nick+Jul 8 2006, 02:00 AM)
Rate of change only applies to gravity in freefall.

You wouldn't have happened to have run an experiment that proves such a grounbreaking statement?
Pupamancur
QUOTE (Nick+Jun 29 2006, 02:38 AM)

I invite you to entertain a change in Einstein's Equivalence Principle. Einstein equated accelerated motion with gravity. How can something that is not moving be equated to something that is?

Stop right here. How can you tell that something is not moving? There is no such thing as absolute motion or absolute rest.
I snipped the rest of your post as irrelevant.
Before you criticise Einstein, why don't you try understanding him first?
Nick
QUOTE (Pupamancur+Jul 8 2006, 05:50 AM)

Stop right here. How can you tell that something is not moving? There is no such thing as absolute motion or absolute rest.
I snipped the rest of your post as irrelevant.
Before you criticise Einstein, why don't you try understanding him first?

Your telling me that nothing can sit still in gravity?

Ridiculous.

I am not criticising Albert Einstein.

Do you really think that GR needs no correction? Do yo really think that Einstein completed physics?

Go back to school.
Pupamancur
QUOTE (Nick+Jul 8 2006, 04:44 PM)
Your telling me that nothing can sit still in gravity?

Ridiculous.

Nothing ever sits still. Anywhere in the universe. Everything is in relative motion. So I agree, your statements are ridiculous.

QUOTE

I am not criticising Albert Einstein.

Aren't you the one that claims that relativity "needs a tweak" (see below)

QUOTE (->
 QUOTE I am not criticising Albert Einstein.

Aren't you the one that claims that relativity "needs a tweak" (see below)

Do you really think that GR needs no correction? Do yo really think that Einstein completed physics?

Relativity certainly does not need any "corrections" from pseud-didacts that :

-do not understand it
-cannot write an equation
-since they cannot produce valid equations they replace them with "word salads"

You do not even begin to understand what is being told to you, not only by me but by many others
Why would you go back to school and learn when you can make up all the BS you wish?
Ignorance + arrogance = bliss.

What I told you is that your statement assumes ABSOLUTE rest. ABSOLUTE, capisci?
This is what makes your whole followup statement in your OP irrelevant and un(anti?) sciencific.
Nick
You can be still in a gravity field since space-time curvature moves with you. It is a relative stillness but a stillness nonetheless.

Einstein simply went to far. He was one of the first. What do you expect?

This is only the beginning. Everything is going to be transformed. Its bound to happen.

So you believe I am against Einstein for pointing this out do you pupamancur?
AlphaNumeric
QUOTE (Nick+Jul 8 2006, 10:53 PM)
Einstein simply went to far. He was one of the first. What do you expect?

I don't think any of us expected him to be perfect (he did spend decades searching for a theory of everything unsuccessfully afterall) but we don't expect someone who displays clear lacking of knowledge in a subject, who ignores corrections and explainations and who refuses to learn the subject to come along and point out, due to their misconceptions, MASSIVE errors in a theory which some of the cleverest people of the last 90 years have each spent decades working on.

It's like me walking into Bill Gates' office and saying "You don't know how to make computer programs. I do, because I know how to program my microwave!". You'd naturally expect him to be unimpressed and consider my reasons for my point of view highly dubious.
Nick
I've seen your corrections before. I don't buy it.

Why does what I say bother you?

If my reasoning is worth nothing then why do you even respond?

I know what I am talking about. Give it a chance.

You're defending the failing end of a theory. Just because it is Einstein's doesn't mean it can't be corrected.
Pupamancur
QUOTE (Nick+Jul 8 2006, 09:53 PM)
You can be still in a gravity field since space-time curvature moves with you. It is a relative stillness but a stillness nonetheless.

"Relative stillness"? This does not exist in mainstream relativity. Are you making up things again?

QUOTE
Einstein simply went to far. He was one of the first. What do you expect?

The above is a non(anti)scientific statement with no ground whatsoever.

QUOTE (->
 QUOTE Einstein simply went to far. He was one of the first. What do you expect?

The above is a non(anti)scientific statement with no ground whatsoever.

This is only the beginning. Everything is going to be transformed. Its bound to happen.

Not going to be transformed or started by your posts, this is for sure.

QUOTE

So you believe I am against Einstein for pointing this out do you pupamancur?

Yes, it is an obvious form of crackpotism, oft seen in forums: "Einstein was wrong because I think so".
AlphaNumeric
QUOTE (Nick+Jul 8 2006, 11:25 PM)
I've seen your corrections before. I don't buy it.

Why don't you buy it? Because you don't understand the maths? Because you're not done much (if any) non-Euclidean geometry? Tensor mathematics? Differential geometry? Linear algebra?

If you understood the maths, you'd 'buy it' but you don't.
QUOTE
Why does what I say bother you?

If my reasoning is worth nothing then why do you even respond?
You seem to completely ignore what anyone says if they don't agree with you. That's annoying.

The reason I respond is, initially, I wanted you to see where your errors were. Now, due to your prolific posting here about supposed errors in relativity which aren't, I'm replying to your threads so that people who aren't sure or don't know about relativity don't end up thinking your BS views are true, when they clearly aren't to anyone whose done GR.
QUOTE (->
 QUOTE Why does what I say bother you?If my reasoning is worth nothing then why do you even respond?
You seem to completely ignore what anyone says if they don't agree with you. That's annoying.

The reason I respond is, initially, I wanted you to see where your errors were. Now, due to your prolific posting here about supposed errors in relativity which aren't, I'm replying to your threads so that people who aren't sure or don't know about relativity don't end up thinking your BS views are true, when they clearly aren't to anyone whose done GR.
I know what I am talking about. Give it a chance
It's painfully obvious you don't.

I'll give corrections to GR or new theories a chance WHEN I see reason to. Derivation of a result which predicts something relativity doesn't, resolving the problem of melding QM with GR, that sort of thing. When all I see if "Because I say so" and "I know what I'm talking about and...." (and then a statement which is utterly wrong, demonstrating you don't know what you're talking about) then I tend not to believe them.

I mean, I can say "I know what I'm talking about" because of the amount of time I've spent learning GR. Why can you say that? Because you thought about it for 30 seconds and came to the wrong conclusion? Hawking knows what he's talking about and he adamently believes event horizons exist, even if GR isn't perfect. How good has someone got to be before you'll listen to what they're talking about instead of you, or are you given divine knowledge?
Guest_amrit
acceleration without movement
guys here someone is out of the "good sense"
nick maybe you take a brake
a warm tee and relax for a few days
Zephir
QUOTE (Guest_amrit+Jul 9 2006, 11:38 AM)
acceleration without movement, guys here someone is out of the "good sense"

well, the acceleration without time doesn't sound too much better....
Frankly, I don't think, you're the right person for commenting or even criticizing Nick at the point of acceleration concept...

Despite the fact, Nick never said something like this.
Guest_amrit
zephir bodies accelerate into a-temporal space
acceleration we measure with clock that run into a-temporal space too

yes im the write person
to say nick that its speculation on acceleration without movement is a bul****t
old man
Just to add some food for thought - a quote from Einstein

...what characterizes the existence of a gravitational field from the empirical standpoint is the non-vanishing of the G lik, not the non-vanishing of the Riklm. If one does not think intuitively in such a way, one cannot grasp why something like a curvature should have anything at all to do with gravitation. In any case, no reasonable person would have hit upon such a thing. The key for the understanding of the equality of inertial and gravitational mass is missing.

amrit
when a inertial system move fast the "curvature-density" of physical space through it the system moves is increasing
this is the why both masses are equal
CactusCritter
It has been about 55 years since I graduated from Ohio State University with a B.Sc. in Physics. Therefore, it has become difficult at times for me to remember what I was taught in college and what I have gained by self-study.

My remembrance is not that Einstein equated accelerated motion with gravity.

Rather, he stated that one cannot tell the difference between acceleration due to gravity and acceleration due to being accelerated, say in an enclosed elevator.

To me, that doesn't open a discussion of things exotic or mystical.

It's a simple statement of fact and Einstein was right.
Pupamancur
QUOTE (CactusCritter+Jul 21 2006, 07:16 AM)
It has been about 55 years since I graduated from Ohio State University with a B.Sc. in Physics. Therefore, it has become difficult at times for me to remember what I was taught in college and what I have gained by self-study.

My remembrance is not that Einstein equated accelerated motion with gravity.

Rather, he stated that one cannot tell the difference between acceleration due to gravity and acceleration due to being accelerated, say in an enclosed elevator.

To me, that doesn't open a discussion of things exotic or mystical.

It's a simple statement of fact and Einstein was right.

Your recollection is correct. But some of the posters are not mainstream, actually they are far off in the left field. You will need to learn how to tell them apart.
amrit
Rather, he stated that one cannot tell the difference between acceleration due to gravity and acceleration due to being accelerated, say in an enclosed elevator.

yes because in acceleratd elevator density of space D is the same as on the surface of the earth
cefarix
Nick, I think you fail to grasp the principles of general relativity and the concepts of a curved space-time and their implications for matter. Within the curved space-time of GR, everything is travelling. Nothing is still. Not the rocket standing on the ground, and neither the rocket in space. Yes, the rocket is still with respect to you, who are standing on the ground, but it is not still in space-time. The path the rocket traces out in space-time is called it's world-line. The world-line is aligned with the time-axis of space-time, since in our case, the rocket is still. The presence of the Earth curves space-time in such a manner as to bend and twist the time-axis towards the center of the Earth. The rocket then follows along this curved geodesic towards the center of the Earth, unless it's stopped by something. In this case, the rocket doesn't move, because the mutual electromagnetic repulsion between it's atoms and the Earth's atoms stops it from following the geodesic precisely. Now, we can answer your question as to how this rocket could be in an accelerated-frame when its rate of change of velocity is zero. This is because acceleration is not defined as the rate of change of velocity in GR. Rather, it's the rate of deviation from the geodesic defined by the geometry of space-time. And the rocket is indeed deviating from geodesic. The geodesic, being curved by the presence of Earth's mass, leads towards the center of the Earth. Therefore, if the rocket were in an inertial frame -- NO acceleration -- then it would follow this geodesic without any deviation, and have zero acceleration. In this case however, the electromagnetic repulsion between the rocket's atoms and Earth's atoms cause the rocket to deviate from the geodesic, and have an acceleration equal to 9.8 m/s^2. If the rocket has an acceleration, then why doesn't it move? you might ask... Well, the answer is that you, standing on the ground, are also being accelerated away from the center of the Earth at 9.8 m/s^2. Therefore, the relative acceleration between you and the rocket is zero. If you were in a free fall frame, say, falling toward the Earth from space, you would be following a geodesic right to the center of the Earth. You're deviation, and acceleration, would be 0 m/s^2. But the rocket, still on the Earth, would still have an acceleration of 9.8 m/s^2, and you'd see it coming up at you at 9.8 m/s^2. Does that clear things up for you?

Also, for Pupamancur: You seem to be someone in mainstream physics who is knowledgeable and speaks good English. What do you make of my unified model? I'll start up a new thread explaining it if you haven't read it previously.

Cheers
Nick
Its a statement of fact that weight in gravity is equivalent to an acceleration. And it is also a fact that there is no motion involved so there can be no time rate.

There is a difference between accelerated motion's weight and gravity's weight. They are two different things yet equivalent for the most part. They are not exactly the same and there is a way to tell them apart. It involves scales.

AlphaNumeric
QUOTE (Nick+Jul 21 2006, 11:03 PM)
Its a statement of fact that weight in gravity is equivalent to an acceleration. And it is also a fact that there is no motion involved so there can be no time rate.

No, it's actually a statement that the local inertial frames of special relativity are equivalent to those local inertial frames of Newtonian theory.

To quote my GR lecture notes
QUOTE
In the presence of an inhomogeneous gravitational field, there exists no exact inertial frames, but only approximate local ones (LIFs) attatched to freely falling particles (FFPs) and these LIFs are accelerated with respect to one another. Thus suggests that including gravity in physics requires a modification of geometry so that the system of timelike straight lines representing FFPs is deformed into a system of relatively curved geodesics.

Special relativity too had a concept of interial frames in which the metric tensor took it's Minkowski value. Are they perhaps related?

My notes go on to describe the Pound-Rebka experiment which experimentally verified to within 1% that LIFs of Newtonian theory and SR coincide.

The Strong principle of equivalence is that in a neighbourhood of any point p in space-time there exist preferred coordinate systems called 'interial'. In every branch of physics except gravity local physics laws can be found, in terms of interial coordinates, which are independent of the gravitational field.

Nick, you claim there's a fault with the statement because you're not even aware of what the actual principle is, you just misquote it and go from there. Not to mention I would hazard you're unaware of all the experimental results predicted using it and how much it's used in relativity.

Have a read of the Wikipedia page on the principle : http://en.wikipedia.org/wiki/Principle_of_...lence_principle You might even learn something
Nick
QUOTE (cefarix+)
Within the curved space-time of GR, everything is travelling. Nothing is still.

Is the space ship on the pad moving through the Earth's gravitational field?

Touche.
That Rascal Poof
Cactus Critter wrote:
"It has been about 55 years since I graduated from Ohio State University with a B.Sc. in Physics. Therefore, it has become difficult at times for me to remember what I was taught in college and what I have gained by self-study.

My remembrance is not that Einstein equated accelerated motion with gravity.

Rather, he stated that one cannot tell the difference between acceleration due to gravity and acceleration due to being accelerated, say in an enclosed elevator.

To me, that doesn't open a discussion of things exotic or mystical.

It's a simple statement of fact and Einstein was right."
______________________________________________________

Can't say it any more clearly and briefly than that.

Had I found this post earlier I would have said the exact equivalent (no puns intended) of what Cactus Critter said, though probably not with the elegant simplicity of Cactus Critter.

The pink snow blowing lengths that some folks are willing to stretch out in order to one-up or otherwise usurp Einstein, when he's not being overtly bashed, remarkably continue keep on snorting and rolling in.

Misner, Thorne and Wheeler's *GRAVITATION has a lot to do with this 'New Age departure', amounting to a political platform from which to misrepresent in order to then 'gainsay' Einstein (did not 'predict the Big Bang' hypothesis, for example. He was back to working on the previously abandoned 'biggest blunder of my life', until his perishment at Princeton, May 1955. Moreover: Observations of an accelerating expansion of the universe have only begun to be reported <and, have any of you whippersnappers ever heard of Carl Sandage? Well yer gonna: get used to it...)

'Limitless are the number of apparently reasonable conclusions that can be based on a completely false premise'. - Anon

Relative to gravitation, the term 'force' (F) has yet to be identified.

The same is true of the causation of the so called (much maligned) 'gravitational curvature of space'. The 4-D space-time continuum seems to have been completely left out of the entire series of protestors on the podium.

The series of posts in this thread deserves - as a collective - to be massively posted, published and distributed as an exemplary case of a series of self deceptions, conformist group aggression and huffy ignorance interspersed with Popular Delusions & The Madness of Crowds - with the exception of those unyielding contributors stoutly aligned with Cactus Critter's First & Last Words, herein.

Of course Einstein's work - like that of Newton - will evolve with improvements, but not by way of the awry avenues demonstrated in this tribute to glorified futility - portions of which resonate with something more like beguiled evangelism than scientific demeanor or method.

Speaking of 'Accleration without moving' - rocket ships and platforms, Guy Murchie's MUSIC OF THE SPHERES features an exquisite ink drawing of a rocket ship hovering just above the launch pad at full throttle, with a huge spiderweb connecting the ship to the ground. For this reason, with regard to all these statements of the obvious about inertial frames of reference and contortions of the interchangeability of reference - and coordinate - systems taking difference with and disembarking from Einstein's SR & especially GR, Cactus Critter or myself might draw you a picture. Whereas, Guy Murchie has already splendidly done just that.

With the self explicit exception of those on this thread who prove not to need to heed this advise, the rest of you baroque dissenters and vacant, sloe eyed, filigreed innovators may as well go back to Physics 101 and do your forsaken homework, for a change.

http://forums.delphiforums.com/EinsteinGroupie
kraziequus@yahoo.com

"If I knew the beginning and the end, I'd put everything else in the middle."
- Ralph Waldo Emerson

Thank you, CactusCritter, Sir. We all needed that (for various reasons?).

AlphaNumeric
QUOTE (Nick+Jul 22 2006, 04:30 AM)
QUOTE (cefarix+)
Within the curved space-time of GR, everything is travelling. Nothing is still.

Is the space ship on the pad moving through the Earth's gravitational field?

Touche.

That's not what he said. He said withing space-time, not space. The ship is moving through time and therefore through space-time. If you draw a diagram of it's trajectory through space-time it would be a line, all objects (which aren't instatons) are constantly moving through space-time.
That Rascal Poof
While you cited highrollers - you know who you are - are at it, pay particular heed to the difference between inert and heavy mass values, until it sinks in that - until further notice - *there isn't any discernible difference (Refer, Roland Von Eotvos, and others beating the same path, since. Not unrelated to the 'curvature of space-time' being a straight line 'geodesic' caused by the unaccounted for, ominidirectional acceleration of 4-D matter - http://forums.delphiforums.com/EinsteinGroupie ).

*Behold the young and vibrantly beating heart of General Relativity, that would be judged as having been a passing vogue, 'because Einstein and his work were such a novelty at the time (paraphrased)'.

Sorta reminiscent of the Big Bangologists pardoning themselves for their inability to find a common center from which the - newly discovered - expanding universe recedes, 'because the universe is so big'. (Big enough to get that lost in , we may only surmise?)

Let's hear-here & now it then, for Newton's antiquity and how high the - 'New Age' - time is to renovate his furniture and flip his - semi impeccable - house. (rotflmao.)
AlphaNumeric
QUOTE (That Rascal Poof+Jul 22 2006, 07:17 PM)
Sorta reminiscent of the Big Bangologists pardoning themselves for their inability to find a common center from which the - newly discovered - expanding universe recedes, 'because the universe is so big'. (Big enough to get that lost in , we may only surmise?)

No, that's not the reason. Suppose you cover an uninflated balloon with a load of evenly spaced dots, then inflated the balloon. To each dot, it sees the other dots moving away from it, yet none of them can say "I'm the centre of expansion" because they exist on a 2d surface while the expansion of the balloon is occuring in 3d, with the centre not on the surface.

The universe we're in is a dimension up from all that. Hence, it can actually be impossible to find the centre of expansion because it doesn't exist in the universe.
Zephir
QUOTE (AlphaNumeric+Jul 23 2006, 12:40 AM)
...Suppose you cover an uninflated balloon with a load of evenly spaced dots, then inflated the balloon. To each dot, it sees the other dots moving away from it, yet none of them can say "I'm the center of expansion" because they exist on a 2d surface while the expansion of the balloon is occurring in 3d, with the center not on the surface....

I know the "ball model" of Universe, the only problem is, this isn't the model of real situation, because our Universe isn't formed by flat surface of some balloon obviously. The Aether Wave theory (AWT) proposes a much better and more natural model of Universe "expansion", which is the result of gravitational collapse of gravastar instead by such a way, no hypothetical "dark energy" is required for explanation of the observed acceleration of Universe "expansion" at all:

AlphaNumeric
QUOTE (Zephir+Jul 22 2006, 10:54 PM)
I know the "ball model" of Universe, the only problem is, this isn't the model of real situation, because our Universe isn't formed by flat surface of some balloon obviously.

It might be a bit more complicated than that, but it could be possible our universe is a surface of a complex 4 dimensional object.
QUOTE
The Aether Wave theory (AWT) proposes a much better and more natural model of Universe "expansion",
Yes, we get it, AWT explains everything much better than everything else. You don't have to link to it 98% of the posts you make and post a bunch of pictures which half the time have no relevence.
Zephir
QUOTE (AlphaNumeric+Jul 23 2006, 01:15 AM)
Yes, we get it, AWT explains everything much better than everything else.

The 4D Universe model is just an approximation of 6D model of vacuum.

Only housewives believe in three-dimensional space. None of the serious scientists supports such a stupid idea. Are you housewife?
AlphaNumeric
When I make reference to '3 dimensional space' I'm more saying "The 3 spacial dimensions which are uncurled" because that's what is mostly important on a cosmic scale. If other, compactified, dimensions exist then their more direct actions will be on subatomic scales.
QUOTE
Are you housewife?

I certainly enterain the ideas of more dimensions quite readily. I know how to derive the 26 dimensions in string theory and I've seen the derivation for the 10 in super string theory and I know how the 11th dimension in M theory plays an important role.

Bear in mind there's no evidence at the moment, so while many interesting ideas are coming out of string theory or LQG, not to mention supersymmetry, about the number of dimensions, it's jumping the gun a bit to be making firm statements.
Zephir
QUOTE (AlphaNumeric+Jul 23 2006, 02:25 AM)
... while many interesting ideas are coming out of string theory or LQG... about the number of dimensions, it's jumping the gun a bit to be making firm statements....

For example the Heim's theory is using a hidden dimensions concept as well and it's able to predict the mass/charge/stability spectrum of most particles with high precision. So that the experimentally determined values can serve as the experimental confirmation of this concept, which is solely independent, and such of this all the more valuable, in fact.
amrit
zephir you make great pictures
could you design density D of the sun and planets ?
would be great
Zephir
QUOTE (amrit+Jul 23 2006, 10:03 AM)
...could you design density D of the sun and planets?...

I don't know... ...gimme equation, how to compute the D....
SomeGuy
Ok, I recently stumbled onto this page and must admit that I have been dissatisfied with the answers already given. They seem to be dodging the original question or saying "You only ask that question because you don't understand, if you understood you wouldn't have to ask the question!" Well gee, that doesn't really do a lot of good. So I will now attempt to answer the ORIGINAL question by using some elementary mathematics from relativity. My answer comes from A Modern Approach to Introductory Physics - Volume 1 by David J. Raymond at the New Mexico Institute of Mining and Technology. The text is freely available at http://physics.nmt.edu/~raymond/classes/ph13xbook/index.html
I will refer to Chapter 6, section 5 (Accelerated Reference Frames). Please note that I do not intend to derive all of Relativity, but rather just answer the question at hand, and assume that Nick is already somewhat familiar with the mathematics of relativity, or is willing enough to read the text which I have linked to learn. So let's look at the original question again:
QUOTE
How can something that is not moving be equated to something that is?
By the way Nick - VERY good question. It really gets at the heart of general relativity and the equivalence principle, and if you don't understand this, then you won't fully understand things you learn later on.

Anyway, let's consider you are in a car. The car starts accelerating forward with respect to the road. As a consequence, experience tells you that you will be pushed back into the seat as by a force. But what is pushing you back into the seat? There is nothing really forcing you. Then you reach a constant speed, and the force goes away. But then you reach a left turn. As the car turns left, you will feel "forced" towards the right. But again, nothing is really forcing you. Instead of "real" forces, these are referred to as "inertial" or "fictitious" forces. Common examples are the Coriolis effect and centripetal force. Now for some math:

(1) F = ma
If x is the your position with respect to the street's origin, X is the position of the origin of the car's reference frame, and x' is YOUR position in the car (I know, it's kinda confusing) then we can say that
(2) x = x' + X
(adding a vector pointing from the street origin to the car origin to a vector pointing from the car origin to you will result in a vector pointing from the street origin to you)
When we take the second derivative we find of course that
(3) a = a' + A
We can substitute this into equation 1 and find that
F = ma' + mA or
(4) F - mA = ma'
Remember that a' is the acceleration you experience in the car, and A is the acceleration OF the car with respect to the street.
So it seems that you cannot just apply F = ma in an acclerated reference frame without taking into account an additional "force" equal to mA. This "force" is the inertial force mentioned above.
You might now say, sure, but the thing accelerating was still moving, so aren't you just dodging the question still. Well, I was just trying to set up SOME useful information in understanding general relativity. Because when you break it down, general relativity basically says that gravity is nothing more than an inertial force - a downward force that we feel because we are accelerating "upward". But CLEARLY we are not, right? I mean, as you said, we are not moving upward, and since acceleration is the rate of change of the rate of change of motion, without motion there is no acceleration. BUT, I intend to show you, using simple mathematics from special relativity, that something CAN be accelerating away from something even though the distance between them is not changing. I will only show this for the simple 1 dimensional case, but it should illustrate the point.
To understand my explanation, you will need some rudamentary understanding of a spacetime diagram. I recommend reading Chapter 4 (Kinematics of Special Relativity) if you are unfamiliar with them (but I will let you do this on your own as I move on).

I will now be referring to the text (Chapter 6 Section 5) extensively.
The velocity of an object undergoing constant intrinsic acceleration in relativity is
(5) v = dx/dt = [at] / [1 + (at/c)^2]^0.5
an x(t) that satisfies this condition is
(6) x(t) = (c^2/a)[1 + (at/c)^2]^0.5 (you can check by finding dx/dt)
The interval OB (figure 6.5 in the text linked above) has length
(7) x(0) = c^2/a (just plug t=0 into (6))
The line passing through OA (again fig 6.5) represents the line of simultaneity at point A. We can verify this by solving for [1 + (at/c)^2]^0.5 = x / (c^2/a) from (6) and plugging into (5) to find
(8) v/c = ct/x
Let us now consider the invariant interval I (again, check ch 4 from the text)
(9) (I^2) = (x^2) - (c^2)(t^2) (also known as the spacetime Pythagorean theorem due to it's resemblance to the famous (a^2) + (b^2) = (c^2), but note the minus instead of plus).
When we plug (6) into (9) we find
(10) I = [(x^2) - (c^2)(t^2)]^0.5 = [(c^4)/(a^2)]^0.5 = c^2/a
Here we reach an increadible result! Even though the object has undergone acceleration away from the origin, and time has transpired, the distance between the object and the origin is still EXACTLY the same! (Compare (10) with (7))

Combining everything we have said here:
-The object is undergoing constant acceleration away from the orign, but is NOT actually moving
-This acceleration will show up as an inertial force pulling the object towards the origin.

So here we have (hopefully rigorously and completely, but most importanly clearly) demonstrated that you CAN in fact have acceleration without actual movement, and it is easy to understand exactly what the equivalence principle is talking about. If anything was unclear, I encourage you to read through the entire text (it's very terse, but an excellent resource) or ask me, and I'll do my best to clarify things (my email is dwooten@nmt.edu). I understand that it is easy to get lost in equations and forget exactly what they mean, so it might take a few times reading through and will certainly require some critical thinking as to why certain steps are being made and what it all means. And if I were you, I'd get out a pencil and paper and transcribe the equations yourself and work through it all. Not only will you understand it better, but it should look more natural than the text on the computer. And if anybody is considering an education in physics, I can highly recomend the New Mexico Institute of Mining and Technology where Professor Raymond teaches the class that goes with this book (that he wrote). This material comes about halfway through your first semester there, so you really get hit with some interesting stuff early on, but Dr. Raymond is a great teacher who really strives to make his students understand. Anyway, I'm done here - just gonna go back and edit this, make sure it looks pretty and submit it! Enjoy!
SameGuyAsBefore
I forgot to mention one more important (VERY important), yet simple thing. I only did the math for point A, and so only demonstrated that the distance was the same at point A. Yet there is absolutely nothing special about point A, so it can be concluded that this method will work for any point.
Nick
Anybody who tells you you are stupid to have to ask a question is the real ignorant one. You can bet my money on it!

Confused2
QUOTE (Nick+)

Anybody who tells you you are stupid to have to ask a question is the real ignorant one. You can bet my money on it!

I suspect many of us are hoping that your next question will be in some way influenced by the many excellent answers given to the question that precedes it.

Can we take it that SomeGuy has succeeded where so many before him have failed?

-C2.
rpenner
Since a space-time interval (which you don't take the square root of in most books) doesn't really correspond to Euclidean distance in space alone, I'm not sure that Some Guy's generous contribution is going to satisfy Nick. Expressed in pop-physics language, if a rocket starts at relative rest a finite distance, x, away from a supernova and starts it's acceleration away from the supernova at a time calculated to be at precisely the time the supernova explodes, what is the minimum constant acceleration the rocket needs to maintain (neglecting gravity) to ensure that the light from the supernova never overtakes the rocket. a = c^2/x -- it's the minimum acceleration to ensure that the space-time interval never changes sign (when the interval = 0 the first light of the supernova will have overtaken the rocket).

As for "How can you accelerate and not move" -- the answer has always depended on recognizing the two halfs of the question are in different conceptual frameworks. "Accelerate" is defined in the GR system of divergence from a geodesic (a trajectory in free-fall). Every one standing on Earth is diverging from a trajectory in free-fall, therefore, they are accelerating. "Not move" is defined as dx/dt = 0 in a a coordinate system which is geocentric and rotating. It's the same coordinate system used by the ancients who believes that the Sun and stars move around the Earth, and the coordinate system of the intuition. GR can work in this coordinate system, although the calculations get really ugly for objects past the orbit of the moon. Even in this geocentric coordinate system, objects which are stationary relative to the surface of the Earth are diverging from their trajectories in free fall and thus accelerating.

A philosophically similar question is "What happens when an immovable object meets an irresistible force." The two, by definition, only exists in philosophical universes which exclude the other.
CactusCritter
rpenner Posted: Today at 5:46 PM made a post which included:

'A philosophically similar question is "What happens when an immovable object meets an irresistible force." The two, by definition, only exists in philosophical universes which exclude the other.'

Such philosophical questions are merely word games. Suc phrases have absolutely no content involving reality. There's a word for such constructions, but it eludes me at the moment.

"The two, by definition, only exists in philosophical universes which exclude the other.". is valid, but somewhat conceals the fact that the statement is nonsense arising from the fact that incongruous satements can be constructed with our languages
amrit
QUOTE (amrit @ Jul 23 2006, 10:03 AM)
...could you design density D of the sun and planets?...

Zephir: I don't know... ...gimme equation, how to compute the D....

Amrit: D density of the space in the centre of sun is D = (m x G) / dP^2
density D is getting smaller with the distance on square from the centre
you could make that at the centre of the sun a space is most black
than black turns to white with the distance on square

same with planets

would be great because we could see that gravity is carried by the "dark area" between the sun and planets
rpenner
QUOTE (CactusCritter+Jul 24 2006, 06:46 PM)
Such philosophical questions are merely word games. Suc phrases have absolutely no content involving reality. There's a word for such constructions, but it eludes me at the moment.

Omnipotence paradox ? http://plato.stanford.edu/entries/omnipotence/

On p. 163-164 of Summa Theologica, Volume I, ques. 25 ans. 3, (Mcgraw Hill, New York, 1963, Aquinas says:
QUOTE (Thomas Aquinas+13th century)
Whatever implies being and nonbeing simultaneously is incompatible with the absolute possibility which falls under divine omnipotence. Such a contradiction is not subject to it, not from any impotence in God, but because it simply does not have the nature of being feasible or possible.

QUOTE (CactusCritter+Jul 24 2006, 06:46 PM)
"The two, by definition, only exists in philosophical universes which exclude the other.". is valid, but somewhat conceals the fact that the statement is nonsense arising from the fact that incongruous satements can be constructed with our languages

Which is how I feel about demands to answer "How can you accelerate and not move?"
That Rascal Poof
Reiterating the redundancies:

Speaking of 'Acceleration without moving' - rocket ships and platforms, Guy Murchie's MUSIC OF THE SPHERES features an exquisite ink drawing of a rocket ship hovering just above the launch pad at full throttle, with a huge spiderweb connecting the ship to the ground. For this reason, with regard to statements of the obvious about inertial frames of reference and the interchangeability of coordinate - systems taking difference with and disembarking from Einstein's SR & especially GR, Cactus Critter or myself might draw you a picture. Whereas, Guy Murchie has already splendidly done just that.

Post Script: The spotted balloon analogy is inapplicable to a 4 dimensionally expanding universe. Dr. H.P. Robertson was probably the first person to publish this error more than thirty years ago. The astrophysical consensus on the dynamics of the spatially expanding universe determines that no matter what location observation and measurement is made from, the observed expansion is in direct line of sight. This is not the signature of an axial explosion. It is the signature of a repelling force acting across space out of individual material systems, such force being proportionate to mass value in the same manner as the Newtonian concept of 'attraction', except, in the opposite direction.

This is an educational thread, I hope it continues, with more resolutions.

Thank you for reading this missive.
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