Prove me wrong!You are wrong, they don't exist.
Prove me wrong!
Centrifugal force exists. It is the force that counters centripetal force. The misconception commonly related to centrifugal force not existing is simple - it only applies to rotating frames of reference. Therefor, in a non-rotating frame of reference there will be no centrifugal force (as there will be no centripetal force).
Prove me wrong!
Prove me wrong!
Prove me wrong!
Can you prove yourself right?
Acceleration and gravity are indistinguishable from each other.
Centrifugal force exists. It is the force that counters centripetal force. The misconception commonly related to centrifugal force not existing is simple - it only applies to rotating frames of reference. Therefor, in a non-rotating frame of reference there will be no centrifugal force (as there will be no centripetal force).No, centrifugal force does not exist altogether.
Sure they exist. These forces are added to convert a non-inertial reference frame into an inertial one so Newton's laws can be used.
Sure they exist. These forces are added to convert a non-inertial reference frame into an inertial one so Newton's laws can be used.
Ok, ummmm I'm not sure what universe he is from...
Sure they exist. These forces are added to convert a non-inertial reference frame into an inertial one so Newton's laws can be used.Right. So they are pseudo forces. They don't actually exist as forces.
So they are pseudo forces. They don't actually exist as forces.Why don't they exist as forces?
QuoteSo they are pseudo forces. They don't actually exist as forces.Why don't they exist as forces?
QuoteSo they are pseudo forces. They don't actually exist as forces.Why don't they exist as forces?
In physics a force causes an acceleration. Since neither gravity nor centrifugal force cause the accelerations they are associated with, but are rather the results of other factors, they are technically not forces.
Gravitation is caused by the warping of spacetime, and centrifugal force is caused by rotation.
No, it just appears that a force is acting. Hence the common terms for these types of phenomena, "pseudo-force" and "fictitious force".
Let's say I am in a frame of reference. How I am supposed to determine whether it is inertial or noninertial without leaving my frame of reference?Without leaving your frame of reference,
If acceleration is observed in my inertial frame of reference, a force must be acting, regardless of its cause or source.Not at all. Newton's first two laws of motion do not apply to a non inertial frame of reference. This transfers to an inertial frame that was transformed from a non inertial one. Such as with gravity.
My point is that a perfectly acceptable inertial frame of reference can be created from a noninertial one if I assume the presence of certain forces.Right. And those are your pseudo forces. They only seem to exist after you transformed your frame of reference.
Since the laws of physics are the same in all inertial reference frames, Newton's laws are now valid and I can explain all phenomena in my frame.Right.
That being said, what makes this new frame so special from any other inertial reference frame?Nothing.
Furthermore, if I were trapped in my frame of reference, how would I be able to determine if the forces I observed acting on objects were "ficticious" forces or "real" forces?Real forces produce varying accelerations on objects with varying mass. Pseudo forces produce the same acceleration on objects with varying mass. Such as with gravity.
When dealing with a noninertial reference frame, one must find a way to convert it to an inertial reference frame so we can use Newton's laws, because Newton's laws are only valid in an inertial frame. There are two methods of accomplishing this. One is by using pseudoforces. The other is searching for another reference frame for which the motion is inertial.There ya go. You finally explained the centrifugal force and gravity force do not exist.
As we have seen, including the existence of pseudoforces in a noninertial frame can convert it entirely into an inertial one. We are now able to use the laws of physics to make accurate predictions about our formerly noninertial reference frame.Right, since pseudo-forces arise in shifting frames of reference (in order to become valid), they cannot possibly exist as real forces. Anyway, either we agree the forces do not exist or you can answer my questions above, which you still haven't.
The second method, finding another reference frame for which motion is inertial, is the method I believe you are trying to advocate. I think you are aware how it works. For circular motion, you simply shift to a non-rotating frame and you can explain the motions such as a ball flying off in a straight line quite easily. Gravitation is a little more tricky. You shift to a reference frame in non-Euclidian space such that the motion we observe, such as orbits of planets, is inertial. This is just general relativity
Both of these methods of transforming a noninertial frame into an inertial one are equally valid. One method may be simpler and more enlightening than the other, such as the case with gravitation, but both methods are equally capable of accurate predictions. So which method is superior? Which method has more right to "existence"? A pseudoforce no more exists than the space-time manifold of general relativity. They are both just constructs of our minds to explain the motions we observe.
So, what makes you think the forces exist? What causes them? Every force must come from an external agent. So, I would like you to tell me where does the force of gravity and the centrifugal force come from.
Right, since pseudo-forces arise in shifting frames of reference (in order to become valid), they cannot possibly exist as real forces.
You've got a valid question. If a force is acting on object, another object must cause the force, right? With gravity, you can attribute the cause of the force to another mass. Mass attracts mass.What about objects that have no mass? Do objects simply turn off this force if there were no other mass in the universe?
Pseudoforces are different from other forces (electromagnetism, friction and such) since they depend on your frame of reference. But how does that make them not exist?They don't exist as forces. They only arise when you look at yourself in the wrong frame of reference. You must invent a force to resolve your observations. Pseudo forces don't actually exist as forces. They only appear to be forces. There is no force acting on an object experiencing gravity. It just appears to be behaving as though acted on by a force, to us.
You obviously misunderstood what I wrote, but I'll answer your question anyway.You said shifting frames of reference is one of the methods to deal with pseudo-forces. Thus, they cannot exist as real forces.
You've got a valid question. If a force is acting on object, another object must cause the force, right?Right.
With gravity, you can attribute the cause of the force to another mass. Mass attracts mass.No, gravity does not exist. Mass never attracts mass. Inverse square law is no longer valid in modern science.
For centrifugal and coriolis forces, there is some debate as to what causes them, but apparently the rest of the universe does.There's no need of debate, as these forces never exist as real. Take some general relativity and you will know they are inertial-forces proportional to inertial masses, which means they don't exist.
I am merely saying that pseudoforces and changing reference frames are equally valid methods of converting from noninertial frames to inertial frames. Since all inertial reference frames are equivalent, what makes either method superior to the other? A pseudoforce exists no more or less than the other inertial reference frame you switch to when dealing with circular motion and gravity.Right, since you must shift frames of reference to deal with these forces, they are considered pseudo-forces. Since pseudo-forces exist only in inertial frames of reference, when one observer enters a non-inertial frames of reference, they cease to exist. These forces are what the observer feels when accelerating. Relative to a stationary observer, nothing is exerted on the accelerating observer.
Pseudoforces are different from other forces (electromagnetism, friction and such) since they depend on your frame of reference. But how does that make them not exist? They certainly exist in the inertial frame of reference you have chosen for them. That's all that matters.You still don't understand. If pseudo-forces only exist in inertial frames of reference, they cannot possibly exist as real forces.
What about objects that have no mass?
Do objects simply turn off this force if there were no other mass in the universe?
You must invent a force to resolve your observations.
They only arise when you look at yourself in the wrong frame of reference.
Like light? Light has energy, so by mass-energy equivalence there is a mass you can associate with it called its relativistic mass. Thus, light can be acted upon by a force even though its component photons have no rest mass.Why do you leave them out of the whole gravity equation, then? Are they not special enough to cause gravity too? Or do you only apply physics to certain things?
Do objects simply turn off this force if there were no other mass in the universe?Mach's principle does not.
Mach's principle seems to imply that the answer is yes.
Do you also not have to "invent" another reference frame such that the observed motion is inertial? That's what Einstein spent a decade doing with general relativity.Inventing inertial frames from non inertial ones is what causes the problem.
How do you know what the "right" reference frame is?It's the one without the pseudo forces.
Adding pseudoforces and transforming to other reference frames are equally valid methods of arriving at inertial reference frames. Since all inertial frames are equivalent, which method is more right?Adding pseudo forces to a transformed frame of reference is quite valid. That does not in any way turn pseudo forces into real ones.
Quote from: epsilon on Today at 02:46:03 PM
Like light? Light has energy, so by mass-energy equivalence there is a mass you can associate with it called its relativistic mass. Thus, light can be acted upon by a force even though its component photons have no rest mass.
Why do you leave them out of the whole gravity equation, then? Are they not special enough to cause gravity too? Or do you only apply physics to certain things?
Quote
How do you know what the "right" reference frame is?
It's the one without the pseudo forces.
Inventing inertial frames from non inertial ones is what causes the problem.
Adding pseudo forces to a transformed frame of reference is quite valid. That does not in any way turn pseudo forces into real ones.
Yup. It's perfectly legitimate to use pseudoforces as if they were real forces in the reference fame you are working in....Which is why they are not considered real...
I am trying to argue that this is just as legitimate as shifting to another frame. Just because pseudoforces don't act like other forces in that they depend on one's frame of reference, how does that make them not exist?No, pseudo-forces work exactly the same as real forces. The only reason why they don't exist is that they are only valid in inertial frames of reference.
No, pseudo-forces work exactly the same as real forces.
The only reason why they don't exist is that they are only valid in inertial frames of reference.
When did I say you say they didn't work the same as real forces?QuoteNo, pseudo-forces work exactly the same as real forces.
When did I say they didn't work the same as real forces?
So, in what frames of reference do Newton's gravity and his laws of motion become valid again?QuoteThe only reason why they don't exist is that they are only valid in inertial frames of reference.
What?
So, in what frames of reference do Newton's gravity and his laws of motion become valid again?
...that they are only valid in inertial frames of reference... Hence, they are considered fictitious.QuoteSo, in what frames of reference do Newton's gravity and his laws of motion become valid again?
Inertial ones. What's your point?
What gravity equation? Newton's law of universal gravitation? We both know that it is incorrect. Are you trying to ask whether light can cause gravity or not? Why not? It has relativistic mass.What would happen if you slowed down light?
Taking a non inertial frame of reference and making it inertial is what gives us our fictitious forces. Such as with gravity. We are undergoing a constant acceleration, but we perceive ourselves to be at rest. Thereby, changing our non inertial FoR into an inertial one. In doing this transformation, we see that objects appear to accelerate towards the ground. Since we are in an inertial FoR, we assume Newton's first two laws of inertia apply, so we assume there must be a force acting on the object, making it accelerate. However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.QuoteInventing inertial frames from non inertial ones is what causes the problem.
Can you explain please?
Just because pseudoforces don't act like other forces in that they depend on one's frame of reference, how does that make them not exist?How does a fictitious force become a real force?
What would happen if you slowed down light?
Taking a non inertial frame of reference and making it inertial is what gives us our fictitious forces. Such as with gravity. We are undergoing a constant acceleration, but we perceive ourselves to be at rest. Thereby, changing our non inertial FoR into an inertial one. In doing this transformation, we see that objects appear to accelerate towards the ground. Since we are in an inertial FoR, we assume Newton's first two laws of inertia apply, so we assume there must be a force acting on the object, making it accelerate. However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.
How does a fictitious force become a real force?
A ficticious force is a real force in the reference frame you have chosen for it. If it acts like a force why can't it be considered a force?
Light is peculiar. It always travels at c.Ok, so what would happen if you slowed it down? What would happen to its relativistic mass? What equations even use relativistic mass in determining 'gravity'?
Yeah, that's right, but why is dealing with pseudoforces problematic? Why should it matter whether I choose a reference frame with pseudoforces or not?I did not say that having pseudo forces was problematic, I said the transformation of FoRs is what was causing our problem, as in, our debate.
A ficticious force is a real force in the reference frame you have chosen for it. If it acts like a force why can't it be considered a force?I'll ask again: How can a fictitious force become a real force?
I'll ask again: How can a fictitious force become a real force?Pinocchio.
I'll ask again: How can a fictitious force become a real force?Pinocchio.
Ok, so what would happen if you slowed it down?
I did not say that having pseudo forces was problematic, I said the transformation of FoRs is what was causing our problem, as in, our debate.
How can a fictitious force become a real force?
My entire point is that 'fictitious' forces are real forces.
My entire point is that 'fictitious' forces are real forces.
But I want to go along the tangent of the circle, and not along its radius. And another thing, what do you mean by a non-inerital reference frame?
But I want to go along the tangent of the circle, and not along its radius. And another thing, what do you mean by a non-inerital reference frame?
An accelerating frame of reference.
But I want to go along the tangent of the circle, and not along its radius. And another thing, what do you mean by a non-inerital reference frame?
An accelerating frame of reference.
Acceleration is a relative term. It has no meaning unless you define the body with respect to which you are considering this acceleration.
But I want to go along the tangent of the circle, and not along its radius. And another thing, what do you mean by a non-inerital reference frame?
An accelerating frame of reference.
Acceleration is a relative term. It has no meaning unless you define the body with respect to which you are considering this acceleration.
The point is, you feel a gravitational force when you are accelerated.
In RE, this is still a fictitious force explained by the bending of space-time.
But I want to go along the tangent of the circle, and not along its radius. And another thing, what do you mean by a non-inerital reference frame?
An accelerating frame of reference.
Acceleration is a relative term. It has no meaning unless you define the body with respect to which you are considering this acceleration.
The point is, you feel a gravitational force when you are accelerated.
In RE, this is still a fictitious force explained by the bending of space-time.
Well, if I am falling freely relative to the Earth, I am accelerated, but I feel weightless, don't I?
But I want to go along the tangent of the circle, and not along its radius. And another thing, what do you mean by a non-inerital reference frame?
An accelerating frame of reference.
Acceleration is a relative term. It has no meaning unless you define the body with respect to which you are considering this acceleration.
The point is, you feel a gravitational force when you are accelerated.
In RE, this is still a fictitious force explained by the bending of space-time.
Well, if I am falling freely relative to the Earth, I am accelerated, but I feel weightless, don't I?
When in free fall, you are traveling at a constant velocity. When you first jump out of a plane, you feel it. It isn't until you reach terminal velocity that you feel weightless.
When you are in freefall, you are actually traveling inertially along a geodesic. Therefore, you feel no force. When you are standing on the earth, you are constantly being accelerated. However, you sense yourself to be at rest, so in your mind, you create a fake force to describe what you are feeling.
If you have mass, it means there is a force acting on you.Not true. Imagine you're in a sealed elevator. The cable is cut and the elevator, along with you, free-falls. Objects floats around you as you are free-falling to the ground. However, you can not tell whether you're in deep space with no gravity or on Earth with gravity. Hence, because it is shown that the effects of acceleration are equal to the effects of gravity, the force of gravity is considered fictitious. Fictitious forces arise in a non-inertial (in this case, free-falling) frame of reference for they are used to explain accelerating objects. In such frame, objects actually move at changing speed with no apparent forces needed, which violates Newton's law because the only way an object can move and accelerate is if a force is applied to it. In other words, these forces do not exist due to that they are only valid in an inertial frame of reference. Now imagine yourself in an accelerating car (non-inertial frame of reference). The car accelerates and stops, thereby forcing you to move towards the dashboard. When viewed relative to the ground (stationary), we can conclude that no force is acted upon you.
You are undergoing inertial motion when you travel along a geodesic. You need to get out of Euclidean geometry.
General relativity is distinguished from other metric theories of gravitation by its use of the Einstein field equations to relate spacetime content and spacetime curvature.[2][3] The field equations are a system of partial differential equations whose solution gives the metric tensor of spacetime, describing its "shape". In the resulting geometry, an object moving inertially in a gravitational field is viewed as following a geodesic path that may be found using the Christoffel symbols of the metric. Solutions of the Einstein field equations model gravitating systems, especially important ones exhibiting spherical symmetry, notable examples being the Schwarzschild solution, the Reissner-Nordström solution and the Kerr metric.
I really wish you people would look stuff up for yourselves.Quote from: WikiGeneral relativity is distinguished from other metric theories of gravitation by its use of the Einstein field equations to relate spacetime content and spacetime curvature.[2][3] The field equations are a system of partial differential equations whose solution gives the metric tensor of spacetime, describing its "shape". In the resulting geometry, an object moving inertially in a gravitational field is viewed as following a geodesic path that may be found using the Christoffel symbols of the metric. Solutions of the Einstein field equations model gravitating systems, especially important ones exhibiting spherical symmetry, notable examples being the Schwarzschild solution, the Reissner-Nordström solution and the Kerr metric.
Stuff contained in spacetime...?
1)Energy, mass or momentum.
2)No.
Well, you said the only reason we say a force of gravity is acting on objects near Earth's surface is because we think we are in an inertial reference frame in which there exists a gravitational field, while, actually, our FoR is a non inertial one.Right.
Then, you also said that freely falling bodies exhibit inertial motion along curved geodesics.Right.
But, from your previous reasoning, it is clear that the curvature of space time is simply because we are in a non inertial FoR and not because of the mass of the Earth.No.
QuoteBut, from your previous reasoning, it is clear that the curvature of space time is simply because we are in a non inertial FoR and not because of the mass of the Earth.No.
But, from your previous reasoning, it is clear that the curvature of space time is simply because we are in a non inertial FoR and not because of the mass of the Earth.How is this clear, again?
QuoteTaking a non inertial frame of reference and making it inertial is what gives us our fictitious forces. Such as with gravity. We are undergoing a constant acceleration, but we perceive ourselves to be at rest. Thereby, changing our non inertial FoR into an inertial one. In doing this transformation, we see that objects appear to accelerate towards the ground. Since we are in an inertial FoR, we assume Newton's first two laws of inertia apply, so we assume there must be a force acting on the object, making it accelerate. However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.QuoteInventing inertial frames from non inertial ones is what causes the problem.
Can you explain please?
Ok, let me make this absolutely clear:
1) Do you agree that a motion along a curved geodesic is perceived as an accelerated motion?
Isn't that what I said in that quote?
However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.
However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.
By simply realizing you are not inertial.
By looking at the evidence...? Thinking logically...?
By looking at the evidence...? Thinking logically...?
Well, I will be contented with your ambiguous answer when you present what you mean by an inertial reference frame.
Inertial - moving inertially.
Non inertial - accelerating.
Inertial frame of reference - one that is moving inertially
Non inertial frame of reference - one that is accelerating
Sorry that was too complicated for you.
Inertial frame of reference - one that is moving inertially
Non inertial frame of reference - one that is accelerating
Sorry that was too complicated for you.
Moving with respect to what?
Space..?
Taking a non inertial frame of reference and making it inertial is what gives us our fictitious forces. Such as with gravity. We are undergoing a constant acceleration, but we perceive ourselves to be at rest. Thereby, changing our non inertial FoR into an inertial one. In doing this transformation, we see that objects appear to accelerate towards the ground. Since we are in an inertial FoR, we assume Newton's first two laws of inertia apply, so we assume there must be a force acting on the object, making it accelerate. However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.
This means that the geodesics in S are straight lines (in 4 dimensional space - time). This, in turn, means that the 4 dimensional space - time for S is flat and described by a Galillean metric tensor (diagonal tensor with values {1,-1,-1,-1}).
There is a simple theorem stating that if some FoR S* is moving with constant velocity w.r.t. an inertial FoR S, then and only then is S* an inertial FoR, meaning that property 2) is also valid for it.
Wait, who was talking about the FE?
Wait, who was talking about the FE?
Taking a non inertial frame of reference and making it inertial is what gives us our fictitious forces. Such as with gravity. We are undergoing a constant acceleration, but we perceive ourselves to be at rest. Thereby, changing our non inertial FoR into an inertial one. In doing this transformation, we see that objects appear to accelerate towards the ground. Since we are in an inertial FoR, we assume Newton's first two laws of inertia apply, so we assume there must be a force acting on the object, making it accelerate. However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.
Taking a non inertial frame of reference and making it inertial is what gives us our fictitious forces. Such as with gravity. We are undergoing a constant acceleration, but we perceive ourselves to be at rest. Thereby, changing our non inertial FoR into an inertial one. In doing this transformation, we see that objects appear to accelerate towards the ground. Since we are in an inertial FoR, we assume Newton's first two laws of inertia apply, so we assume there must be a force acting on the object, making it accelerate. However, if we look at it outside of our inertial FoR, we would see that the object is the inertial one and we are non inertial.
We were discussing this, not the FE, remember.
What about bodies without mass? Why do you leave them out of having gravity?
What about bodies without mass? Why do you leave them out of having gravity?
What bodies would those be?
inertial FoR even mean.You are the one that asked what it was. If you care to show me wrong, please do. I would also like to see more sources to back your claim. I would also like to know why you leave light out of having gravity. I would also like to know how you can't understand my quote, yet are so educated in the mathematical workings of GR.
Is the mass of the Earth the reason that bodies fall towards it?
No. It's because of geodesics.
I have the greatest: Einstein. He says you are an idiot.
In general relativity, light follows a special variety of straightest-possible world-line, so-called light-like or null geodesics – a generalization of the straight lines along which light travels in classical physics, and the invariance of lightspeed in special relativity.[21] As one examines suitable model spacetimes (either the exterior Schwarzschild solution or, for more than a single mass, the Post-Newtonian expansion),[22] several effects of gravity on light propagation emerge.
The best-known is the bending of light in a gravitational field: light passing a massive body is deflected towards that body. While such an effect can also be derived by extending the universality of free fall to light,[23] the maximal angle of deflection resulting from such heuristic calculations is only half the value given by general relativity; from the standpoint of Einstein's theory they take into account the effect of gravity on time, but not its consequences for the warping of space.[24] An important example of this is starlight being deflected as it passes the Sun; in consequence, the positions of stars observed in the Sun's vicinity during a solar eclipse appear shifted by up to 1.75 arc seconds. This effect was first measured by a British expedition directed by Arthur Eddington, and confirmed with significantly higher accuracy by subsequent measurements.[25]
I have the greatest: Einstein. He says you are an idiot.Quote from: WikiIn general relativity, light follows a special variety of straightest-possible world-line, so-called light-like or null geodesics – a generalization of the straight lines along which light travels in classical physics, and the invariance of lightspeed in special relativity.[21] As one examines suitable model spacetimes (either the exterior Schwarzschild solution or, for more than a single mass, the Post-Newtonian expansion),[22] several effects of gravity on light propagation emerge.
The best-known is the bending of light in a gravitational field: light passing a massive body is deflected towards that body. While such an effect can also be derived by extending the universality of free fall to light,[23] the maximal angle of deflection resulting from such heuristic calculations is only half the value given by general relativity; from the standpoint of Einstein's theory they take into account the effect of gravity on time, but not its consequences for the warping of space.[24] An important example of this is starlight being deflected as it passes the Sun; in consequence, the positions of stars observed in the Sun's vicinity during a solar eclipse appear shifted by up to 1.75 arc seconds. This effect was first measured by a British expedition directed by Arthur Eddington, and confirmed with significantly higher accuracy by subsequent measurements.[25]
Please, please, continue. Your ignorance is amusing.
http://astro.berkeley.edu/~jcohn/lens.html
http://imagine.gsfc.nasa.gov/docs/features/news/grav_lens.html
http://csep10.phys.utk.edu/astr162/lect/galaxies/lensing.html
http://cfa-www.harvard.edu/castles/
http://hubblesite.org/newscenter/archive/releases/1996/10
http://www.space.com/scienceastronomy/050503_grav_lensing.html
http://casswww.ucsd.edu/public/tutorial/GLens.html
How about those? Oh, and how about all those pictures? Seems to be a lot of pictures of something that you claim can't happen. Strange...
But you said that light does not follow geodesics..
So, then how does light bend around a massive body?
So, then how does light bend around a massive body?
Principle of Ferma.
What about bodies without mass? Why do you leave them out of having gravity?
What bodies would those be?
Photons and gluons.
What is incorrect about that?
What is the mass of a gluon?
What is the mass of a gluon?
Just as I thought. You think you are clever, but you are just ignorant. You have no idea what you are talking about but you keep on. That's fine. You are not the first to take this approach, and you will definitely not be the last.