How many forces do we know off in physics?

[arkain101]

I've wondered, what if there was more than 1 type of source for gravity.

 

There is the Relativistic geometry type that agrees accurately with close proximity gravity. Though in large scale galaxy functions it falls short in explanation. Thus the implementation of dark mattter.

 

Though what if there is various versions? As I am sure has been pondered.

 

Using the example mentioned ealier. Orbiting crafts are tend to fall towards the planet even when at optimal orbital velocity. Is there a drag force in a secondary extension of gravity.. something on top of that of the geometrics of time and space.

 

Gravity is not a external force, it is a mass to mass relationship which is why no acceleration forces are detected in the increasing of velocity towards a gravity source.

 

If someone can help me with a question. Lets say I push a rock with my hand into a wall of clay. I push only with a maximum of 50newton force even as the rock hits the clay and continue to push and push untill it eventually stops.

 

Then I take the rock and drop it to match the same velocity as when I pushed it and have it impact clay, will it equall the same work?

 

This is what I wonder in comparing gravity force with external force.

 

 

Question: do most galaxies contain black holes at their center?

[HydrogenBond]

There is only one force, at least that is what everyone seems to be striving toward. The rest are there to help humans to differentiate the various aspects of the unified force. If one considers the implications of a unified force, is a like a camelean that has many flavors. Why can't some of the proposed new forces just be combo's of existing forces. The van der Waals sort of acts like this. A gravity-EM hybrid would be a very interesting flavor of the camelean unified force.

[arkain101]

Would this unified force have an equal and opposite force?

 

I think the unvierse is a 1:1 ratio.

 

For example the light realm, knows not of mass or time.

 

The mass world knows not of infinity or massless action (light)

 

There seems to be different places the 'live'.

 

All actions are that of a relationship. A relationship between a minimum of two reference frames. Without the existence on the other side of the 1: , it appears impossible for anything to be.

 

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

 

I read here that this man found a 1 to 1 relationship in infinite sets.

I dont really understand him. But In a philisophical view 1:1 is the universe at its fundemental set.

[sebbysteiny]

However, the same treatment of other fundamental forces like electromagnetic, weak and strong forces DO NOT give correct answers and cannot be explained by geometry. For a start, the concept of relativity does not hold. So they are forces as perceived by all observers.

 

 

What do you mean, the concept of relativity does not hold? AFAIK the only think violating, for example, relativity's predicted speed limit of c is entanglement, something which is not well understood.

 

Maybe you can elaborate on this point?

 

Firstly, Tormod, I must ask how much you know of General relativity. I want to know so I know how much detail to go into.

 

Secondly, I'm not sure if you are asking for a relativistic treatment of electron entanglement. I assume you are not. So, just for you, I will elaberate on what I mean by the other forces not being explained in a similar way to the way gravity has been :hyper: .

 

Einstein came up with some new assumptions on top of special relativity. His assumption was that the laws of physics must be the same for all reference frames regardless of what gravitational field they are in. From this, he discovered that the geometry of the mass curved universe meant that certain equations of motion must result.

 

The really amazing thing is that this was totally independant of Newton's explanation of gravity or even the concept of a force. In other words, Einsteins equations resulted as a natural consequence of applying his insightful assumption and as they are entirely geometric in origin, they could have given any wierd result at all.

 

However, when analysed, his equations of motion looked very similar but not identical to Newton's equation for gravity which relies on the concept of a force.

 

So when this stab in the dark produced a realistic equation, the obvious thing to do is to test which is right by noticing the differences. If Einstein was right, the perihelion of murcury would be slightly different and light should bend around a star (as space is curved). According to the Newtonian 'gravity is a force' interpretation, this shouldn't happen. Every time such differences have been tested, Einstein's geometric explanation has come out on top. So gravity is not a force. A force is just one way of approximating an effect whose origins are in geometry not physical force laws.

 

However, if you give a similar treatment to the electromagnetic force and you assume that the whole universe is charged and that charge curves the universe (creating a 5 d universe I suspect), it will be the force model that comes out on top. The geometric explanations from relativity can only explain gravity and not any of the other forces. The main reason is that it is only gravity which distorts the laws of physics in different frames of reference.

 

This makes sense as the effects of those forces (when treated relativistically) will be observable and agreed by observers in all frames of reference. The phantom force of gravity however is not.

 

There is *another* force accelarating us upwards. It's the tension force of the floor. That arises because the bonds in atoms are being stretched creating a force in the floor that accellarates us constantly against the geodesic of curved spacetime [ie freefall]. The force from those atomic bonds arise out of electromagnetic interactions so that accelaration is caused by the electromagnetic force.

 

 

So what is holding us from falling up? Or are we in constant freefall? The above statement needs some backing up. I am not aware of such an effect as you describe.

 

That would be constant freefall towards the common center of mass. We can't fall "up". The electromagnetic repulsion of the ground prevents us from sinking into the ground and the space-time geodesic that we follow prevents us from being pushed out into space.

 

KickAssClown is essentially right. QP to him. No bias. Just because I like KickAssClown does not mean I give QP's for no reason. He must still earn them and he has now :hyper:.

 

However, I will expand on this and give a real passionate rant because this is probably one of the most interesting concepts I have ever learnt in physics and I want to share it with you.

 

It will lead to how a gravitation field slows time. It will also I believe prove (yes I know, a very bold claim) that gravity IS NOT a force by using the defining equation of a force.

 

If object A accellarates towards object B, then an observer at object B could say all he sees is his object accelarating towards object A. So when two things accellarate towards each other, it is not always simple to know which is the accelarating object and which is the stationary object.

 

So an object accelarates at 9.81 ms-2 towards the Earth's surface. It is falling.

 

An observer on earth sees the falling object accelarating towards him. However the observer on the object sees the Earth's surface accelarating towards him. Who is right? According to General Relativity, an observer is accellarating if he is not in a Lorenzian frame (ie floating like in space). Since the falling object IS in such a frame, it is not accellarating. As the observer on the Earth's surface is not in such a frame, it is the observer that is accellerating.

 

An object that does not accellerate (and is therefore in a Lorenzian frame)can be said to be following a geodesic in spacetime.

 

So what's happening is that the object was busy minding its own business not accellarating at all and just staying still and suddenly this floor hits it and the electromagnetic force from the floor pushes him and pushes him and he accellarates faster and faster from the path he should be following. This is known as resting on the planets surface. We should all be following a geodesic in space time and falling thus be in a Lorenzian frame. The constant accellerating force of the ground is stopping us from doing this.

 

So the answer to your question is that we should indeed be in constant freefall.

 

So where is the exciting revelation I spoke of?

 

People here all know (I think) of the distortions in space time between objects in two different relativistic Lorenzian frames (special relativity). If An object in frame A accellarates to, say, 0.99c (frame :naughty:, and continues, time in frame B slows down according to the observer in frame A and vice versa. But what if the object now in frame B stops and returns at 0.99c to object A. Again time for both observers slows down from the prospective of the other observer.

 

So when object B has returned to object A again, they should both have aged the same. However, in reality, object B has aged significantly less then object A in that time.

 

The reason for this is that object B accellarated and thus changed lorenzian frames. It's this accellaration that causes the time difference. Thus, from special relativity, a constantly accellarating (non-lorenzian) frame will have a constantly slower time and the observer in that non-lorenzian frame will age less than an observer in a lorenzian frame and the stronger the accelleration, the slower time runs.

 

Merging the two concepts together leaves us with the most counter intuitive conclusion of general relativity. As all people in the (non-lorenzian) frame of the Earth's surface are accellarating away at a constant rate from the path they should be following to stick to their geodesic, time should slow down. So time slows down in a gravitational field and the stronger the gravitational field, the slower time becomes. So if you want to travel forward in time, stand on the surface of a very heavy object.

 

Again this time slowing effect has been measured thus proving it is us on the surface that accellarates and not free falling objects.

 

 

The above aside piece of interest could link us in with the topic covered in this thread. If an object falling in gravity is not accellarating and it is infact the objects NOT falling that are accellerating (by the electromagnetic force from the floor), how can gravity be a force?? F = ma (non relativistically). This is the defining equation of a force. But a falling object supposedly acting under the gravitational force does not accellarate (as it's time does not slow). So if a = 0, so too does F = 0. So the apparent force of gravity is not a force. It's an illusion created by the accelleration caused by the electromagnetic force accellarating us towards non accellerating free-falling objects.

 

So if it's not a force, what is it??

 

As explained many times, it is just geometry.

[sebbysteiny]

On another point, I think there is one more force that we should at least consider. Is it just geometry? Who knows. But it very well might be a totally new type of force.

 

In the past decade, we made a discovery.

 

Before that discovery, us scientists were convinced that 'gravity' (or space time curviture) was the only 'force' that acted at a long distance as the weak and strong force only act at nucleonic distances and the electromagnetic field always cancells out in large clumps of matter made out of neutral atoms. Since 'gravity' is always an attractive 'force', then it stands to reason that the universe's expansion must be slowing down.

 

So one day, scientists decided to try and measure the rate of decellaration in the universe. They did this to find out whether the universe will be constantly expanding, reach a limit at infinity or stop entirely and begin to crash in on itself. In other words, the entire fate of the universe depended on their discovery.

 

And what they found shocked the world. It turns out that far from decellarating, the rate of expansion of the universe IS ACCELLERATING. Assuming this has always been true, objects are moving away from each other faster today than they have ever done even at the big bang.

 

So as gravity should be slowing it down, something is speeding it up. So the scientists rushed back to the drawing board and started rushing out new theories. I believe currently scientists are using a concept of 'dark energy' to explain this accellaration.

 

Whatever explains this, it could very well be a new force not yet discovered that is repulsive in nature and acts at a long distance.

 

So for the purposes of this thread, lets call this force 'the wierd and wonderful Force'. Since the wierd and wonderful force is not sufficiently understood, one can't say it is a consequence of geometry. And if it is, why havn't we already predicted it? Thus it is probably a real force.

 

We now have potentially 5 fundamental forces (ignoring geometrical quirks [gravity]). Strong, Weak, electromagnetic, that crazy force that only acts at mega small distances that has been mentioned by someone and the wierd and wonderful force.

[arkain101]

nifty read.

 

I completely follow the bit about us being under constant acceleration. We are being pushed all the time but we arent apparently moving. If you were a magnet, and placed next to a magentic material would it feel like gravity?

 

You'd stick to it the same but the distances obviously vary.

 

It seems the universe is jam packed with attractive forces. They vary in how they act in strength relative to distance and size.

We see there are replusive forces that exist aswell or configurations of the mentioned forces which can make them act in repulsive manner.

 

How could one unite these attractive forces and what is the possible equal and opposite reaction to all these attractions.

[sebbysteiny]

I completely follow the bit about us being under constant acceleration. We are being pushed all the time but we arent apparently moving. If you were a magnet, and placed next to a magentic material would it feel like gravity?

 

In a quick paragraph, if we were in space (ie a free fall / lorenzian frame) and we attach a very powerful magnet to us and we put a piece of iron near us so that we accellarated towards the iron at 9.81ms-2, but we land on a plastic floor, we would not be accellarating. The electromagnetic force of the magnet would counterbalance the electromagnetic force from the atoms in the floor. The resulting force is 0. With no accellaration, time does not slow down.

 

However, if we fall under gravity and stand on a plastic floor, gravity is not accellerating us as that is the Lorenzian frame. The only force on us is the electromagnetic force from the floor. It is thus an accellerating frame and time slows. Thus gravity acts differently to all other forces.

 

About your 'equal and opposite reaction' stuff.

 

I'm personally not convinced it is accurate.

 

Newton's third law of motion is that for every reaction there is an equal and opposite reaction. There is also other symetry in the universe (matter / antimatter, +ve -ve charges, N or S poles etc).

 

But I see no reason why every fundamental force must have an equal and opposite fundamental force.

 

However, the wierd and wonderful force above may turn out to be the equal and opposite 'force' of gravity, but I doubt it since then the wierd and wonderful force must not be a force but a product of geometry and it should have already been predicted in my view.

[Qfwfq]

Yet on board the station you will not experience any gravity. The force is so weak that it is negligible even at 400 kilometers (which is about where the ISS is). However, at the Earth's surface it is 1 G, which we easily feel.

Uhm, wait a sec...

 

At a radius of 400 + 6300 km the field isn't much less than at sea level, it's hardly 6% less. The reason for the negligible gravity is that things are subject to the same acceleration. It is basically the equivalence principle, which is also what he meant about the floor accelerating upward, although this doesn't mean that it is moving away from the centre of Earth, it's just the comparison between locally inertial coordinates the "ordinary" ones.

 

What he's getting at is the geometric interpretation, which the equivalence principle makes possible but doesn't actually prove. In any case, I agree it doesn't make gravitational interaction any less of a force than the other fundamental ones.

[sebbysteiny]

What he's getting at is the geometric interpretation, which the equivalence principle makes possible but doesn't actually prove. In any case, I agree it doesn't make gravitational interaction any less of a force than the other fundamental ones.

 

You've studied general relativity, which makes this comment surprising.

 

Here is the proof that gravity isn't a force.

 

1) From special relativity, all constantly accellarating frames without exception experience a slowing down of time relative to a Lorenzian frame.

 

2) When accellarating under all forces but gravity, time slows down.

 

3) When apparently accellarating under gravity, time does not slow down. Time only slows down when a force (the planet surface) pushes up on you.

 

4) Therefore, the real accellaration under gravity is 0.

 

5) Therefore, from F=ma (or the relativistic equivilant), force caused by gravity = 0 so gravity is not a force.

 

If, as you say, treating gravity as a force is just an alternative but legitimate explanation rather than a false but more easily understood simplification, there must be a flaw in that 5 step arguement.

 

I completely follow the bit about us being under constant acceleration. We are being pushed all the time but we arent apparently moving. If you were a magnet, and placed next to a magentic material would it feel like gravity?

 

Not convinced I dealt with that fully last time. Firstly, as I don't think you've studied general relativity, I'm impressed that you managed to understand a large part of what I wrote. When I first read something like that, it sounded like gobbldygook to me. So QP for reading my rant and understanding much of it.

 

Secondly, if you were a magnet attracted to a pole, I think it would not feel like being in freefall under gravity because there will be an accellaration which your inner ear would feel. If that inner ear was also magnetic, would it detect the motion? Don't know. Quite possibly.

 

But if every atom was singularly charged, say, and there was a large oppositely charged object, would things behave the same? I don't think so because every atom will have different mass numbers so I think the objects in a space ship all have a different mass / charge ratio meaning it would all be accelarating at different rates. The same applies to magnetic poles (even if monopoles exist).

 

Only gravity has the perculiar property that it attracts to everything in the same way. Which just goes to suggest even further that gravity is not a normal force but rather a property of the Universe's structure ie geometry.

[arkain101]

I've studied relativity a little. It seemed pretty easy to comprehend.

 

However I am not as confident in this theory as you appear to be.

 

I said what you saying makes sense to a degree, but I can not agree that it is fully correct.

 

Secondly, if you were a magnet attracted to a pole, I think it would not feel like being in freefall under gravity because there will be an accellaration which your inner ear would feel. If that inner ear was also magnetic, would it detect the motion? Don't know. Quite possibly.

 

I meant, that if we were 100% magnets and lived on a metal floor, (as a thought experiment), it would feel similar to gravity. In the sense that we wouldnt feel a force as we accelerated towards the floor. But as we stood on the floor we would feel heavy. Obviously magnetics and gravity are different, but do have similarities.

 

Time is said to move more slowly the closer you are to a gravity source. So I want to look at satalite time dialation.

 

Satalites are said to lose time in comparison to us on the surface because of their high rate of velocity. Though I can't calculate it, They should also accelerate an amount of time because they are futher out of the gravity well, though obviously not by alot.

So is it the posistion from the source that makes the difference? or is it the amount of force itself that is applied to a frame in a gravity field that will modify the time rate of a particular reference frame.

 

I understand it is the posistion which should completely relate to a geometric model as you have been describing.

 

------------

 

I have a little theory/idea of my own that tries to explain these things with a different perspective on time.

 

For example, If we think of gravity as you say as a kind of space geometry we can try to presume that as gravity is a stretch of space that appears to increase the distance light needs to travel. Though we cant see this distance change in the way we'd like, are we able to see it in the acts all things make in the proximity of a massive body that is generating the 'gravity'?

 

So for an observer viewing photons coming from inside a gravity well they are seeing events that have came from a stretched place and are working there way out to a less distorted area. This warped pathway then modifies how we measure the time to be from the source it is coming from. (it might make better sense to say the gravity well is not a stretched place, but a compacted space.)

 

And vice versa, a person deep inside this gravity source is in a compact or stretched? version of space and the photons that come from outside merge into a tighter traffic of space thus increase the measurement of the time they contain without modifying the velocity of these photons.

 

Thus to try and explain that time is not a dimension in of itself, but measurment from light and mass that can be seen changed in different geometric settings

[Little Bang]

Imagine a universe with only one proton and one electron in it. The two particles are separated by some great distance. The probability of them coming together to form a hydrogen atom is infinite. The reason is that the attractive force between them can never be zero, it can approach zero but never reach it. Now they have found each other to form a hydrogen atom. Do you think that the force which brought them together has now switch off way out there in space? I don’t think it has and I think that force is what we call gravity. If there were two hydrogen atoms in our playlike universe the same situation would be true because they want to form diatomic hydrogen and there is a force between them to make it happen.

[arkain101]

Yes.

 

Another example given before by actual scientists was that;

 

If the universe was to cool down completely and reach a point of near zero. There would still be an astounding amount of energy and action occuring at the molecular and quantum level. A life force as it were is always powering things onward, even when it appears all energy is lost.

[hallenrm]

Very, very interesting discussion indeed :cup:

 

Permit me to change the course of discussion in a new direction now! Let us now contemplate how many physical forces will be neccessary to describe natural phenomena in future?

 

Will it be one, two, .....or ten?

 

Let me hazard a guess! I think in future all natural phenomena will be described by a single force! :) That may require to increase the number of dimensions of the space.

 

Is it possible that charge can be another dimension of space, as may be the so called colour of fundamental particles?

[Qfwfq]

Here is the proof that gravity isn't a force.

 

1) From special relativity, all constantly accellarating frames without exception experience a slowing down of time relative to a Lorenzian frame.

 

2) When accellarating under all forces but gravity, time slows down.

 

3) When apparently accellarating under gravity, time does not slow down. Time only slows down when a force (the planet surface) pushes up on you.

 

4) Therefore, the real accellaration under gravity is 0.

 

5) Therefore, from F=ma (or the relativistic equivilant), force caused by gravity = 0 so gravity is not a force.

 

If, as you say, treating gravity as a force is just an alternative but legitimate explanation rather than a false but more easily understood simplification, there must be a flaw in that 5 step arguement.

The flaw is in the whole argument, including the notion that "time slows down".

 

Time doesn't "slow down", what happens is that the time coordinates are different according to different observers. It isn't the acceleration that determines this it's the velocity. Point 4) makes no sense according to GR, it goes quite against the very purpose of it (general coordinate transformations rather than only those between inertial frames). According to GR the acceleration is 0 in the locally inertial frame. By the very general principle of relativity, there's no meaning in saying which is the "real" acceleration.

 

What GR boils down to is that, using differential geometry, one may choose a coordinate system such that the effect of mass on the motion of of other bodies can be described as a curvature of the space-time manifold. It is argued on the very fact that one may choose an atlas of maps and that, given any (x, t), there are choices that are locally inertial around it.

[sebbysteiny]

Here is the proof that gravity isn't a force.

 

1) From special relativity, all constantly accellarating frames without exception experience a slowing down of time relative to a Lorenzian frame.

 

2) When accellarating under all forces but gravity, time slows down.

 

3) When apparently accellarating under gravity, time does not slow down. Time only slows down when a force (the planet surface) pushes up on you.

 

4) Therefore, the real accellaration under gravity is 0.

 

5) Therefore, from F=ma (or the relativistic equivilant), force caused by gravity = 0 so gravity is not a force.

 

If, as you say, treating gravity as a force is just an alternative but legitimate explanation rather than a false but more easily understood simplification, there must be a flaw in that 5 step arguement.

The flaw is in the whole argument, including the notion that "time slows down".

 

Time doesn't "slow down", what happens is that the time coordinates are different according to different observers. It isn't the acceleration that determines this it's the velocity. Point 4) makes no sense according to GR, it goes quite against the very purpose of it (general coordinate transformations rather than only those between inertial frames). According to GR the acceleration is 0 in the locally inertial frame. By the very general principle of relativity, there's no meaning in saying which is the "real" acceleration.

 

What GR boils down to is that, using differential geometry, one may choose a coordinate system such that the effect of mass on the motion of of other bodies can be described as a curvature of the space-time manifold. It is argued on the very fact that one may choose an atlas of maps and that, given any (x, t), there are choices that are locally inertial around it.

 

It seems to me that you have misunderstood the arguments I have been making.

 

"Time doesn't "slow down", what happens is that the time coordinates are different according to different observers. It isn't the acceleration that determines this it's the velocity."

 

You need to reread one of my above posts. In it, I said that, according to special relativity, if a twin leaves Earth (where the other twin is) at 0.999c, travells 100m light years and returns back to Earth, according to both observers / twins, the traveling will have aged only a few years or something (maybe less) whilst the Earth would have aged 100m years. Infact, all observers in all innertial and non-innertial frames will make the same ovservation.

 

So why does this happen? Cmon, this is special relativity, you should know this. It's the 'twin paradox' if my memory serves me right. Why has one twin aged much faster than the other? It's because the twin on Earth stayed in the same innertial frame whilst the travelling twin had to stop and reverse his speed ie accellarate from one innertial frame to another. This accellaration is what causes time to slow down ACCORDING TO ALL OBSERVERS making the twin undisputably younger when he returns. Thus, frames accellarating from an innertial frame will always exhibit time slowing down. So yes, time DOES SLOW DOWN.

 

"According to GR the acceleration is 0 in the locally inertial frame. By the very general principle of relativity, there's no meaning in saying which is the "real" acceleration."

 

Great. You are arguing over a definition now and this has no effect on the validity of the argument.

 

I say "real accellaration". You say "acceleration relative to a locally inertial frame". They are the same. If you are in an innertial fame, you are not accellarating. If you are in a non-innertial frame, you are accellarating. Thus time slows down in all non-innertial frame / accellarating frames. Point 4 makes perfect sense when you tackle the substantive issue and not knit pick on definitions. I agree that the point was not made extremely clearly leaving open ambiguity, but a previous post explained with full detail exactly what this point 4 meant.

 

From this I have defined accellaration. If time slows down then it follows you must be accellarating.

 

So following through the rest of my argument, when acting under all forces but gravity, time slows down, you therefore accellerate and F=ma, so it is a force.

 

When acting under the phantom force of gravity, time does not slow down, so you are not accellarating so a = 0 and as F=ma, F=0. Ie there is no force. Therefore, gravity cannot be a force.

[sebbysteiny]

I meant, that if we were 100% magnets and lived on a metal floor, (as a thought experiment), it would feel similar to gravity. In the sense that we wouldnt feel a force as we accelerated towards the floor. But as we stood on the floor we would feel heavy. Obviously magnetics and gravity are different, but do have similarities.

 

I understand your point and, looking back, I didn't really know the answer to yours. I think my first attempts were more stalling for time.

 

But I think I have the answer now.

 

Firstly, I agree, there will be clear similarities.

 

But I think the point is that we cannot have 100% EQUAL magnet. Every atom will have a different mass / magnet strength ratio. Therefore every object will also. Thus, all objects will accellarate at different rates under F=ma. So your thought experiment is impossible even in thought. The reason for this is that the strength of the magnetic force can easily increase or decrease. Ie you can have stronger and weaker poles. The same applies for the electric force and so applies for the whole electromagnetic force. And since this strenght is not connected to mass, it cannot be connected to accellaration.

 

So it is impossible to have the equivilent of an inertial frame using any force other than gravity.

 

This is what makes gravity so bizaar. It's the only force that is entirely dependant on the same factor that relates accellaration and Force: mass. It is the only force capable of having such an innertial frame that attracts everything in the same way. Since all objects act the same way only under gravity, only gravity can and is explained by not actually being a force but by being related to the structure of the universe.

 

And if gravity is related to a force whose strength depends on mass, and not universe structure, massless particles should not exhibit any gravitational effects at all. But they do. Photons bend around heavy objects like stars.

 

So once again, the answer to this point leaves me to conclude gravity cannot possibly be a force.

 

Time is said to move more slowly the closer you are to a gravity source. So I want to look at satalite time dialation.

 

Satalites are said to lose time in comparison to us on the surface because of their high rate of velocity. Though I can't calculate it, They should also accelerate an amount of time because they are futher out of the gravity well, though obviously not by alot.

 

You've misunderstood why time dilation occus I think. time dilation occurs in an accellarating frame. Objects free falling under gravity ARE NOT accellarating. Objects provented from falling under gravity are. Thus us on the planet surface are accellarating as a consequence of the electromagnetic force from the floor. Satallites are not much further out of the 'gravity well'. However, they feel no gravitational effects because they are freefalling so there is no force accellarating them from their innertial free fall frame. So there will be no time dialation on satallites.

 

However, thinking about this more, your satalite idea is not completely wrong. Satalites in their innertial frame will lose time [relative to the observer on the planet] because of their velocity. THEY ALSO GAIN TIME because they are in free fall whilst the observer is on a slower time scale as that observer is accellarating whilst the satallite is not.

 

So one should be able to measure this effect.

 

 

On a completely different point, I would love somebody to talk more about the 'wierd and wonderful force' that I talked about before. What is the latest thinking on this?

[Qfwfq]

So, now I see, you are applying an erroneous conclusion of the twin paradox. Your comparison between an object held up by the surface and the other in free fall is not proved by the TP at all.

 

Acceleration is not the cause of time dilatation, it is simply what discriminates between the younger and the older of the two twins. In the classic illustration, in which for simplicity the accelerations are considered to be during negligibly brief parts of the journey and the rest is at zero acceleration, your interpretaion would imply that the difference in proper time should depend only on those brief intervals. It is instead trivial to show that it accumulates during the two intervals at constant relative velocity. This disproves your conjecture:

Satalites in their innertial frame will lose time [relative to the observer on the planet] because of their velocity. THEY ALSO GAIN TIME because they are in free fall whilst the observer is on a slower time scale as that observer is accellarating whilst the satallite is not.

 

So one should be able to measure this effect.

since there are not both contributions and it not only should be but is possible to measure the effect, just ask those who adjust satellite clocks to allow for their orbital velocity, especially those for very precise purposes such as GPS.

 

Let's show the point by imagining we duplicate the classic gedankenexperiment as follows: In both cases twin B leaves Earth at velocity v, common to both cases, the only difference is the duration (and hence how long and far B travel away before reversing and coming back). In the limit of nstantaneous accelerations it is trivial to calculate the elapsed time for B as being that of a times [math]\norm\sqrt{1-v^2}[/math], a direct proportionality. It clearly cannot and does not depend on the accelerations. It is a simple matter thelength of a path between two points being different from that of the staightest path between the same two points. Acceleration is necessary for the "not straight" but doesn't determine the difference in length.

 

You are arguing over a definition now and this has no effect on the validity of the argument.

No, not a definition but the very fundamentals of GR.

 

The fact that photons are deviated by massive objects is a lot less trivial and certainly the geometric interpretation is the easiest explanation. This doesn't remove the fact that gravitation remains an interaction, geometric interpretation or not. Two bodies can be said to interact, regardless of whether this is mediated by bosons or by space-time itself. The source of difficulty in explaining massless trajectories without it lies in the tricky limits, for zero mass, of the dynamics. One thought to chew on is: Does a body weigh slightly more when hot than when cold? Does it, when projected at great velocity?

 

The fact that electric or other charges are independant of mass is hardly to he point. If they weren't they simply wouldn't be distingushable, it's a basic epistemological matter. There couldn't be more than one charge in exact proportion to mass, if there is one at all it is the only one.