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Author Topic: Why is it assumed that gravity is always attractive?  (Read 17764 times)

Offline imatfaal

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Why is it assumed that gravity is always attractive?
« Reply #50 on: 23/06/2011 23:20:24 »
This is a bit beyond the discussion here, but I thought it was interesting:
http://iopscience.iop.org/0295-5075/94/2/20001/

Under CPT symmetry (http://en.wikipedia.org/wiki/CPT_symmetry), general relativity apparently predicts that matter and antimatter gravitationally repel.  I suspect this is highly theoretical at this point, since it's arbitrarily applying a conservation law from quantum mechanics to general relativity, but it's definitely interesting.
Bit beyond me JP - but good stuff nonetheless. 
 

Offline KineticFlow

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Why is it assumed that gravity is always attractive?
« Reply #51 on: 25/06/2011 11:31:31 »
Thanks, appreciate the explanation. 
I didn't know the word gedanken or realise how fun they might be to think about until stumbling upon this thread. 
 

Offline MikeS

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Why is it assumed that gravity is always attractive?
« Reply #52 on: 26/06/2011 06:25:23 »
imatfaal

Sorry about the delay in replying.

In thinking about this problem I have come to realize that the situation is considerably more complicated than I initially believed.  The original gedanken, you and I all assumed that both matter and antimatter particles individually have to conserve energy, surely they don’t.  Energy only has to be conserved within the system.
 
To demonstrate what I mean:-
If a fixed quantity of photons are available to produce matter and antimatter particles then the same quantity are produced regardless of the gravitational field.  However, the higher in the gravitational field this happens then the more photons are required to produce the matter particles (cost of production plus higher PE) and the fewer to produce antimatter particles (cost of production plus lower PE).  The lower in the field this happens then the less photons are required to produce the matter particles and more required to produce antimatter particles.  Although energy is not conserved  particle to particle, it is conserved within the system.

Do you agree?
 

Offline imatfaal

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Why is it assumed that gravity is always attractive?
« Reply #53 on: 27/06/2011 13:12:47 »
imatfaal

Sorry about the delay in replying.

In thinking about this problem I have come to realize that the situation is considerably more complicated than I initially believed.  The original gedanken, you and I all assumed that both matter and antimatter particles individually have to conserve energy, surely they don’t.  Energy only has to be conserved within the system.
It's the system that in a book-keeping exercise conserves energy.  I never thought an other way and sorry if I gave that impression.

Quote
To demonstrate what I mean:-
If a fixed quantity of photons are available to produce matter and antimatter particles then the same quantity are produced regardless of the gravitational field.  However, the higher in the gravitational field this happens then the more photons are required to produce the matter particles (cost of production plus higher PE) and the fewer to produce antimatter particles (cost of production plus lower PE).  The lower in the field this happens then the less photons are required to produce the matter particles and more required to produce antimatter particles.  Although energy is not conserved  particle to particle, it is conserved within the system.

Do you agree?
Not really - it's a clunky way of thinking of a very simple thought experiment.  the xs ke that inital experiment theorised is the neatest way of visualizing it.  You do not need extra energy to create a particle pair at a higher potential!  Please try to work through with the two pairs of invariant potentials and it will become clear
 

Offline MikeS

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Why is it assumed that gravity is always attractive?
« Reply #54 on: 28/06/2011 05:44:55 »
imatfaal

Sorry about the delay in replying.

In thinking about this problem I have come to realize that the situation is considerably more complicated than I initially believed.  The original gedanken, you and I all assumed that both matter and antimatter particles individually have to conserve energy, surely they don’t.  Energy only has to be conserved within the system.
It's the system that in a book-keeping exercise conserves energy.  I never thought an other way and sorry if I gave that impression.

Quote
To demonstrate what I mean:-
If a fixed quantity of photons are available to produce matter and antimatter particles then the same quantity are produced regardless of the gravitational field.  However, the higher in the gravitational field this happens then the more photons are required to produce the matter particles (cost of production plus higher PE) and the fewer to produce antimatter particles (cost of production plus lower PE).  The lower in the field this happens then the less photons are required to produce the matter particles and more required to produce antimatter particles.  Although energy is not conserved  particle to particle, it is conserved within the system.

Do you agree?
Not really - it's a clunky way of thinking of a very simple thought experiment.  the xs ke that inital experiment theorised is the neatest way of visualizing it.  You do not need extra energy to create a particle pair at a higher potential!  Please try to work through with the two pairs of invariant potentials and it will become clear

If we assume that gravity is always attractive and it costs no more to create pair particles at a higher gravitational potential, we can use this to our advantage.
Consider the following experiment.
We use a given amount of energy to create pair particles at a high gravitational potential at the top of a tower and let them fall.  In falling they gain kinetic energy which we use to operate an electric generator at the bottom of the tower.  The electricity generated is used to produce more photons at the top of the tower which are then used to create pair particles which fall gaining kinetic energy and so on.
If this worked it would be perpetual motion but it can't work, so what is wrong with it?
 

Offline MikeS

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Why is it assumed that gravity is always attractive?
« Reply #55 on: 29/06/2011 06:25:35 »
Follow up to my last post.
The problem with the above experiment is it does not take into account the extra energy required to create pair particles at a higher gravitational potential.

If we run the experiment again but this time taking into account the extra energy required to create pair particles at a higher potential.

We use a given amount of energy to create pair particles at a high gravitational potential at the top of a tower and let them fall.  In falling they gain kinetic energy which we use to operate an electric generator at the bottom of the tower.  The electricity generated due to the inefficiently of the generator is less than that required to create pair particles.

In this example the KE gained is the same as the excess energy required to produce the particles at a high gravitational potential.  There is no energy over.  Unlike the first example, energy is conserved.
 

Offline imatfaal

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Why is it assumed that gravity is always attractive?
« Reply #56 on: 29/06/2011 10:39:55 »
Mike - PE is completely relative.  You do not need extra energy to create a particle pair at different places in space. 

In your little experiment in last two posts you can even remove the need to generate paricles - just have a laser light in high orbit connected with a wire to a photovoltaic cell in low orbit.  We can assume very low inefficiency and superconductivity etc - and a huge drop in potential.  I do not know the mechanism - but clearly the transfer of electrical energy thru a wire from low to high grav pot cannot be lossless as this would entail a net energy gain.
 

Offline KineticFlow

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Why is it assumed that gravity is always attractive?
« Reply #57 on: 29/06/2011 10:53:05 »
Oh damn, imatfaal beat me.  But yeah, I understood energy and mass to be proportional (einsteins famous equation), and not related to potential in any way.  The transfer of electricity through the gravitational field looks like the explanation, so this gedanken also beats the dust. 

You know, knocking gedankens out the water seems like fun! 
Must get tedious after a while, but for a newbie like me it's enjoyable for now.   :D
 

Offline KineticFlow

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Why is it assumed that gravity is always attractive?
« Reply #58 on: 29/06/2011 10:55:49 »
Just wondering:  what's a reasonable sort of way to test the behaviour of antimater in real life?  How much of the stuff would you need to see gravitational effects?  Anyone know of any good (scientifically based) reading out there?  (Understandable by someone with interest but not deep knowledge.) 
« Last Edit: 29/06/2011 10:59:05 by KineticFlow »
 

Offline imatfaal

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Why is it assumed that gravity is always attractive?
« Reply #59 on: 29/06/2011 13:31:56 »
KF - we are able to store for decent periods of time now (order of 10^3 seconds) but we need larger amounts.  To measure graviational attraction we are gonna need amounts that if the containment fails is gonna cause a real problem
 

Offline MikeS

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Why is it assumed that gravity is always attractive?
« Reply #60 on: 30/06/2011 07:42:41 »
If we assume that gravity is always attractive and it costs no more to create pair particles at a higher gravitational potential, we can use this to our advantage.
Consider the following experiment.
We use a given amount of energy to create pair particles at a high gravitational potential at the top of a tower and let them fall.  In falling they gain kinetic energy which we use to operate an electric generator at the bottom of the tower.  The electricity generated is used to produce more photons at the top of the tower which are then used to create pair particles which fall gaining kinetic energy and so on.

In your little experiment in last two posts you can even remove the need to generate paricles - just have a laser light in high orbit connected with a wire to a photovoltaic cell in low orbit.  We can assume very low inefficiency and superconductivity etc - and a huge drop in potential.  I do not know the mechanism - but clearly the transfer of electrical energy thru a wire from low to high grav pot cannot be lossless as this would entail a net energy gain.
[/quote]


Both of the above ideas sound like they should work but obviously can't but why not?  Assuming super conductors etc.  Its a two wire circuit, electrons go up one wire presumably slowed by gravity accelerated down the other.  The gravitational effect being cancelled.  So where is the energy going? 

The electricity is being produced in a low gravitational potential where time is dilated relative the high GP where electric is being used.  Due to time dilation at source and contraction at sink the current generated at source is more than at sink.  There is a loss of energy due to gravitational time dilation.
 

Offline MikeS

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Why is it assumed that gravity is always attractive?
« Reply #61 on: 01/07/2011 05:38:26 »
Following on from my last post.

imatfaal

It requires more energy to create pair particles at a high gravitational potential than at a low gravitational potential to compensate for time contraction.
 

Offline MikeS

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« Reply #62 on: 06/07/2011 06:15:18 »
From a previous post
“Consider the following experiment.
We use a given amount of energy to create pair particles at a high gravitational potential at the top of a tower and let them fall.  In falling they gain kinetic energy which we use to operate an electric generator at the bottom of the tower.  The electricity generated is used to produce more photons at the top of the tower which are then used to create pair particles which fall gaining kinetic energy and so on.

In your little experiment in last two posts you can even remove the need to generate paricles - just have a laser light in high orbit connected with a wire to a photovoltaic cell in low orbit.  We can assume very low inefficiency and superconductivity etc - and a huge drop in potential.  I do not know the mechanism - but clearly the transfer of electrical energy thru a wire from low to high grav pot cannot be lossless as this would entail a net energy gain.
[/quote imatfaal]

Both of the above ideas sound like they should work but obviously can't but why not?  Assuming super conductors etc.  Its a two wire circuit, electrons go up one wire presumably slowed by gravity accelerated down the other.  The gravitational effect being cancelled.  So where is the energy going? 

The electricity is being produced in a low gravitational potential where time is dilated relative the high GP where electric is being used.  Due to time dilation at source and contraction at sink the current generated at source is more than at sink.  There is a loss of energy due to gravitational time dilation.”

Gravitational time dilation is the explanation why the above type of perpetual motion cannot work.  Gravitational time dilation is probably the universes main source of entropy.

I believe it follows that:-

(from my last post)
“It requires more energy to create pair particles at a high gravitational potential than at a low gravitational potential to compensate for time contraction.”
In addition to the energy required for the pair production, energy is required to create them with a gravitational potential energy.  It costs energy to increase GPE for any object.  Why should it be any different for pair particle production?

Gravitational potential energy (assuming matter and antimatter to be gravitationally repulsive) is not the same for matter and antimatter.
Consider a matter particle and antimatter particle in free fall in a normal gravitational field.  The matter particle is constantly falling deeper within the gravity well, is constantly accelerating and therefore constantly gaining KE.
This can be represented by PE=MxgxH where PE is potential energy, g is gravity and H is height.

The antimatter particle initially at rest has PE.  In free fall (upwards), all of this PE is quickly converted into KE as the particle accelerates up to its terminal velocity within a constantly decreasing gravitational field.  Thereafter, its velocity remains constant, as does its kinetic energy.
This can be represented as PE=Mxg. As the antimatter particle is moving in a constantly decreasing gravitational field, height has no effect other than to define g.
PE=KE

The original tower experiment to disprove that matter and antimatter are gravitationally repulsive.
The concept of this experiment is flawed.  It was assumed that as the photons fell down the tower they would gain gravitational energy and be blue shifted.  What the logic does not take into account is that, as in the above experiments, the energy gained by falling within a gravitational field is the same as the energy lost due to gravitational time dilation.  Overall, there is no energy gain.  Therefore, the experiment proves nothing.
 

Offline KineticFlow

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Why is it assumed that gravity is always attractive?
« Reply #63 on: 07/07/2011 10:52:41 »
The original tower experiment to disprove that matter and antimatter are gravitationally repulsive.
The concept of this experiment is flawed.  It was assumed that as the photons fell down the tower they would gain gravitational energy and be blue shifted.  What the logic does not take into account is that, as in the above experiments, the energy gained by falling within a gravitational field is the same as the energy lost due to gravitational time dilation.  Overall, there is no energy gain.  Therefore, the experiment proves nothing.
I had thought the first gedanken was invalidated, not from your strange and afaict unproven logic, but this: 
It requires that all the light goes in one direction.  However, in order to conserve momentum, the particle pair will emit two photons, which are traveling in opposite directions.  In the gravity field, one photon would be red-shifted but the other would be blue-shifted. 
There are a few other questions that can also be asked, but this was the main 'deal-breaker' for me. 

I could be wrong, but all this stuff about time dilation and potential energy sounds like BS to me - for a start, you only came up with the idea to support your theory after the previous line of thought was invalidated.  Inventing reality to fit your pre-conceived ideas is not exactly going to give us a model of the real universe imho. 
Still, it is the 'theories' forum, so I guess you're expected to go a bit crazy here?? 


[Edit 12/07/11:  In fact, I don't think my CoM argument works any more.  We could for example anihilate particles at the centre of a large mass, and send the beams out in opposite directions so that they are both red shifted, and do the gedanken in reverse.  Oh well.  ]
« Last Edit: 12/07/2011 15:30:13 by KineticFlow »
 

Offline KineticFlow

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Why is it assumed that gravity is always attractive?
« Reply #64 on: 07/07/2011 11:05:19 »
Something else occurred to me:  what about Hawkin radiation? 

If antimatter graviticly repelled matter, wouldn't we expect black holes to emit more antimatter than matter in the form of Hawkin radiation?  Could this be predicted / observed? 
Eeh, hope I'm not missing something obvious. 
« Last Edit: 07/07/2011 11:12:25 by KineticFlow »
 

Offline MikeS

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« Reply #65 on: 07/07/2011 17:51:25 »
KineticFlow

This is a quote from the original article available here
http://www.desy.de/user/projects/Physics/ParticleAndNuclear/antimatter_fall.html

"Suppose that we now take these photons and send them to someone at the bottom of the tower.  If that person measures the energy of the photons, they will measure a different energy that we did at the top of the tower, because the photons will be blueshifted.  The photons will gain energy as they fall in a gravitational field."

It would seem you misunderstood the original experiment.

Quote kineticflow
"I could be wrong, but all this stuff about time dilation and potential energy sounds like BS to me - for a start, you only came up with the idea to support your theory after the previous line of thought was invalidated."

Time dilation and gravitational potential energy are very real, not my invention.  I seriously thought my previous line of thought was correct but it was not. (Actually upon thinking about it further it probably was correct if you take into account time dilation but more on that in my next post.)  Never the less I remain convinced that matter and antimatter will gravitationally repel each other.  Having explored all of the possibilities that I could think of to prove my point in the above scenario and failing I came to question the validity of the experiment itself.  It is quite obviously flawed for the reasons that I gave.

Quote kineticflow
"Inventing reality to fit your pre-conceived ideas is not exactly going to give us a model of the real universe imho."

I have invented nothing. 
I mentioned the difference between PE for matter and antimatter because imatfaal had previously said they were the same for both particles of the pair and at the time I erronously agreed with him.  They are not the same.

The main point in my last post was this

"The original tower experiment to disprove that matter and antimatter are gravitationally repulsive.
The concept of this experiment is flawed.  It was assumed that as the photons fell down the tower they would gain gravitational energy and be blue shifted.  What the logic does not take into account is that, as in the above experiments, the energy gained by falling within a gravitational field is the same as the energy lost due to gravitational time dilation.  Overall, there is no energy gain.  Therefore, the experiment proves nothing."

This is a known fact, not something I invented.  My point being, in the original experiment, it was overlooked.  This being a main point of the experiment it invalidates the whole experiment. 

I would be happy to debate anything in my last post that you disagree with if you list the points.
« Last Edit: 08/07/2011 10:09:50 by MikeS »
 

Offline MikeS

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« Reply #66 on: 07/07/2011 17:57:33 »
Something else occurred to me:  what about Hawkin radiation? 

If antimatter graviticly repelled matter, wouldn't we expect black holes to emit more antimatter than matter in the form of Hawkin radiation?  Could this be predicted / observed? 
Eeh, hope I'm not missing something obvious. 

Yes, but it would not be Hawkin radiation because he never proposed it.
The most energetic objects in the early universe were quasars. 
I believe quasars were actually white holes in our early universe, left over black holes from the previous universe cycle which was antimatter.  I mention this purely in answer to your question but don't really want to distract from the main point of this thread.
 

Offline MikeS

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« Reply #67 on: 08/07/2011 10:32:18 »
If we go back to the original tower experiment which was flawed for the reason previously mentioned.  It was assumed that was an excess of KE left over if matter and antimatter are gravitationally repulsive.

Let's look at the experiment again.
At the bottom of the tower the photons are re combined to create a matter and an antimatter particle.
The matter particle has been produced deeper within the gravitational well and so contains less PE than the original particle.
The antimatter particle on the other hand was created higher in the gravitational field and hence required more energy for its creation.
Energy has been conserved.
There was no net energy gain from the photons blue shift as it was cancelled by the gravitational time dilation of creating the particles at the bottom of the tower.
Energy has been conserved.
 

Offline KineticFlow

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« Reply #68 on: 12/07/2011 15:19:07 »
I was trying to get my head 'round what you wrote. 

I'm not sure I understood the part about how much energy it takes to create the particles.  However, I see you've started a separate topic for that. 

The bit about time dilation:  can I ask for clarification? 

Are you saying that gravitational time dilation has an effect on the light as it travels 'down'; namely, to blue shift it.  Therefore, we must consider the effect of gravitational time dilation as the re-created particles are moved back 'up'; namely, they 'lose' kinetic energy / slow down.  Is that the idea? 
I know this should be written more formally using frames of reference and such, but I don't have the requisite knowledge/ability! 

The gravitational time dilation was significant enough to cause the blue-shift, and thus should have also been considered on the way back up? 

I know so very little about this; is this the standard interpretation of gravitational time dilation, or is it part of your theory?  Thanks. 
« Last Edit: 12/07/2011 15:33:42 by KineticFlow »
 

Offline MikeS

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« Reply #69 on: 13/07/2011 09:31:04 »
The blue shift of the photons falling down the tower is usually interpreted as the photons gaining energy but what is actually happening, is that from a reference frame deeper within the gravity well (where time is dilated) they just appear to have gained energy.  As there was no energy gain then the experiment is invalidated.

Gravitational time dilation is real but is seldom (I believe) taken into account by physicists.  The tower experiment is an example of that.  I believe my interpretation of it is in accordance with known facts but to most people who have not properly considered it, my ideas may seem non mainstream.
 

Offline MikeS

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« Reply #70 on: 21/07/2011 09:40:19 »
"On the interpretation of the redshift in a static gravitational field
L. B. Okun
a)
and K. G. Selivanov
b)
ITEP, Moscow, 117218, Russia
V. L. Telegdi
c)
EP Division, CERN, CH-1211 Geneva 23, Switzerland
~Received 12 April 1999; accepted 27 July 1999!
The classical phenomenon of the redshift of light in a static gravitational potential, usually called the gravitational redshift, is described in the literature essentially in two ways: On the one hand, the phenomenon is explained through the behavior of clocks which run faster the higher they are located in the potential, whereas the energy and frequency of the propagating photon do not change with height. The light thus appears to be redshifted relative to the frequency of the clock. On the other hand, the phenomenon is alternatively discussed ~even in some authoritative texts! in terms of an energy loss of a photon as it overcomes the gravitational attraction of the massive body. This second
approach operates with notions such as the ‘‘gravitational mass’’ or the ‘‘potential energy’’ of a photon and we assert that it is misleading. We do not claim to present any original ideas or to give a comprehensive review of the subject, our goal being essentially a pedagogical one. © 2000
American Association of Physics Teachers.

Abstract
METHODOLOGICAL NOTES
This paper is concerned with the classical phenomenon of gravitational red shift, the decrease in the measured frequency of a photon moving away from a gravitating body (e.g., the Earth). Of the two current interpretations, one is that at higher altitudes the frequency-measuring clocks (atoms or atomic nuclei) run faster, i.e. their characteristic frequencies are higher, while the photon frequency in a static gravitational field is independent of the altitude and so the photon only reddens relative to the clocks. The other approach is that the photon reddens because it loses the energy when overcoming the attraction of the gravitational field. This view, which is especially widespread in popular science literature, ascribes such notions as a 'gravitational mass' and 'potential energy' to the photon. Unfortunately, also scientific papers and serious books on the general theory of relativity often employ the second interpretation as a 'graphic' illustration of mathematically immaculate results. We show here that this approach is misleading and only serves to create confusion in a simple subject.
http://iopscience.iop.org/1063-7869/42/10/A04

VII. CONCLUSIONS
The present article contains little original material; it is primarily pedagogical. The gravitational redshift being, both theoretically and experimentally, one of the cornerstones of General Relativity, it is very important that it always be taught in a simple but nevertheless correct way. That way centers on the universal modification of the rate of a clock exposed to a gravitational potential. An alternative explanation in   terms of a ~presumed! gravitational mass of a light pulse—and its ~presumed! potential energy—is incorrect and misleading. We exhibit its fallacy, and schematically discuss
redshift experiments in the framework of the correct approach. We want to stress those experiments in which an atomic clock was flown to, and kept at, high altitude and subsequently compared with its twin that never left the ground. The traveller clock was found to run ahead of its earthbound twin. The blueshift of clocks with height has thus been exhibited as an absolute phenomenon. One sees once again that the explanation of the gravitational redshift in terms of a naive ‘‘attraction of the photon by the earth’’ is
wrong.

Page118
 Am. J. Phys., Vol. 68, No. 2, February 2000 Okun, Selivanov, and Telegdi"
Full article here
http://www.itep.ru/theor/persons/lab180/okun/em_13.pdf


Occams Razor.
The gravitational redshift of photons is explainable in two ways
1)The redshift indicates the photons have lost energy.
2)The redshift is caused by gravitational time dilation.

Number 1 is the most generally accepted interpretation of the red shift but I believe it to be wrong, as do the people who wrote the above paper.
To make it work it has to introduce mass and momentum to a massless particle.

Number 2 requires nothing extra and no modifications to existing theories or laws.
Number 2 is a known and experimentally proven fact.

If we apply Occams Razor it favors number 2 gravitational time dilation.




Therefore, it would seem that when considering photons, Newtonian gravity is lacking we should use GR.  In the ongoing debate here
http://www.thenakedscientists.com/forum/index.php?topic=40175.25
is another example of where Newtonian Gravity can not explain (so far) why there is no loss in the electrical circuit that is part of an experiment with gravity, whereas GR time dilation does.
 

Offline MikeS

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« Reply #71 on: 21/07/2011 09:56:52 »
Lets go back and re examine the original tower experiment.
http://www.desy.de/user/projects/Physics/ParticleAndNuclear/antimatter_fall.html
This experiment is important as it is one of the main arguments against matter and antimatter being gravitationally repulsive.

Try as I might I could not make energy be conserved when viewing the experiment from the perspective of the gravitational blue shift being due to photons gaining energy.

However, it looks like the original experiment was flawed, it should have been considered not in terms of photons gaining energy but in terms of time dilation.  If the photons falling down the tower are time dilated not gaining energy then the whole conclusion of the experiment is flawed.  The conclusion is wrong.

Let’s look at the experiment again but this time from time dilation.
A matter and antimatter particle pair are re acted together to produce photons which are sent down the tower.  At the bottom of the tower, the photons have gained no energy but are now in a lower gravitational potential. (relative to matter) The photons have not been affected in any way; they are unaware of the change in gravitational potential.

We collect the photons and react them together to form a matter and antimatter particle pair.  Combined this particle pair has exactly the same total energy as the original pair at the top of the tower.  So far energy has been conserved.  However to complete the experiment we need to return both particles to the top of the tower with no loss or gain of energy.

Let us look at what has happened so far:-
The matter particle at the top of the tower had a high gravitational potential energy (PE) and wanted to fall to the centre of the Earth had it not been physically stopped from so doing.  The antimatter particle on the other hand at the top of the tower has a low PE.  If not constrained would fly off into space.

At the bottom of the tower, the newly created matter particle has less PE than did its counterpart at the top of the tower.  There is a surplus of energy.

At the bottom of the tower, the newly created antimatter particle has more PE than did its counterpart at the top of the tower.  Where has this energy come from?  It’s come from the surplus energy left over from the creation of the matter particle.  Energy, at the bottom of the tower has been conserved.

We still need to get the particles back to the top of the tower, whilst conserving energy.

First, we need to think about gravitational potential energy.  It is not the same for matter and antimatter.

Matter free falling within a normal gravitational field accelerates as its PE is converted to kinetic energy, KE.  It continues to accelerate as the gravitational field is continually strengthening.

(*)  Antimatter, as it accelerates from stationary up to its terminal velocity converts all of its PE into KE in one go.  From its perspective, the gravitational field is continually decreasing so there will be no further acceleration.


The matter particle requires an input of energy to lift it back to the top of the tower.
The antimatter particle has its original energy of creation plus the extra energy needed to create it in a higher gravitational potential.  This extra energy is available to propel the matter particle back to its original position at the top of the tower.  The antimatter particle is left with its original energy.  This is the energy of its creation plus the PE it had at the top of the tower.  This PE has been converted into KE.  It is traveling at constant speed as it rises past the top of the tower.  (Once the antimatter particle at the bottom of the tower has converted its PE into KE, the KE remains the same.)  Energy has been conserved.  The only difference in the experiment from start to finish is the antimatter particle is moving at constant speed out of the gravity field.  Had the original antimatter particle not been constrained it would have done the same.

Although this is in the New Theories section it’s not a new theory.  If you think about it, time dilation fully explains what is happening in this experiment and it shows that energy has been conserved.  This experiment proves energy is conserved if matter and antimatter are gravitationally repulsive.  This is the opposite of what the experiment was designed to prove.

(*)  The part about PE may be new but is simple and logical.
« Last Edit: 21/07/2011 10:00:01 by MikeS »
 

Offline MikeS

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Why is it assumed that gravity is always attractive?
« Reply #72 on: 28/07/2011 09:13:05 »
Here is an interesting paper on whether antimatter and matter are gravitationally attractive or repulsive

CPT symmetry and antimatter gravity in general relativity
http://iopscience.iop.org/0295-5075/94/2/20001/pdf/epl_94_2_20001.pdf
 

Offline granpa

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Why is it assumed that gravity is always attractive?
« Reply #73 on: 28/07/2011 09:39:02 »
the energy stored in an electric field is the integral of the square of the field strenth over all of space.

the potential energy of a gravitational field is calculated in exactly the same way except that it is negative rather than positive.
 

Offline MikeS

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Why is it assumed that gravity is always attractive?
« Reply #74 on: 09/08/2011 09:52:42 »
Here is another link arguing that photons do not gain energy when 'falling' within a gravitational field.
http://www.thenakedscientists.com/forum/index.php?topic=40452.msg363937#msg363937
 

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Why is it assumed that gravity is always attractive?
« Reply #74 on: 09/08/2011 09:52:42 »

 

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