Gravity

[Freethinker]

Originally posted by: BlameTheEx

Freethinker.

 

I stand by my statement.

 

Quantum Mechanics works. It's just difficult to understand. "counter intuitive" is a valid criticism but "paradoxical" is not.

I applaud your decision to stand by your statement.

 

It's not many people, especially amoung us here, that have a greater level of standing in the Scientific community regarding Quantum Mechnics than on-line ecyclopedias, David Joseph Bohm, Erwin Schrödinger, Baidyanath Misra, E. C. George Sudarshan, ....

 

They ALL and many others specifically use the term "PARADOX" when discussing how QM works.

 

We appreciate your allowing Hypography to become a leading edge peer reviewed journal for re-writing the texts on QM and eliminating the concept of Paradoxes involved with it.

 

Where should we send the Noble Prize?

[Bo]

I think that the point BlametheEx actually makes is that he has a problem with a theory with singularities (correct me if i'm wrong!) but then i must make a few remarks here :

First of all:the black hole horizan singularity is only a mathematiclal singularity, and not a physicical one (the singularity is in the metric; the mathematicla discription of space time. As soon as you calculate physical properties like the equations of motion the singularity dissapears). However at the exact centre of a black hole, or any other massive object, there is a sigularity. These same singularities also occur in quantum mechanics (well more exact: in quantum field theory; the relativistic version of QM). For the electromagnetic, weak and strong forces these singularities (that eventualy -both for QM as GR- have to do with the fact we're dealing with point particles) dissapear, only if QM tries to discribe gravity it goes wrong. As probably known: string theory disgards the use of point particles, and thus there are no singularities left.

The main point is that the singularities occur in each theory that uses point particles. Bo

[TeleMad]

BlameTheEx: The best way to think of gravity is that mass/energy reduces the speed of light.

 

No, that's the WORST way to think about gravity...it contradicts Einstein's special theory of relativity.

 

As has already been pointed out, the BEST way to think of gravity is as the curvature of spacetime, caused by the presence of mass/energy.

[BlameTheEx]

Freethinker

 

" Where should we send the Noble Prize?"

 

Do you think sarcasm really improves a debate?

 

OK You have made your point. Paradox is a term well associated with Quantum mechanics. But guilt by association is not enough. I have given my reasons for holding that the term is not valid. You reply so far is no more than abuse and hiding behind the opinions of others. Do you happen to know why Quantum Mechanics can be justified as a paradox, or are you just good at mud slinging?

 

 

We may be arguing semantics here. I found the following definitions of paradox:

 

Webster's 1913 Dictionary

par´a`dox Pronunciation: par´å`doks

n. 1. A tenet or proposition contrary to received opinion; an assertion or sentiment seemingly contradictory, or opposed to common sense; that which in appearance or terms is absurd, but yet may be true in fact.A gloss there is to color that paradox, and make it appear in show not to be altogether unreasonable.- Hooker.

 

This was sometime a paradox, but now the time gives it proof.- Shak.

 

 

WordNet()WordNet Dictionary

Noun 1. paradox - (logic) a self-contradiction; "`I always lie' is a paradox because if it is true it must be false"

 

Given the Webster's 1913 definition I would have to agree to Quantum Mechanics being Paradoxical. It is in appearance absurd. However, with the more modern Wordnet definition I hold fast. There are no self-contradictions in Quantum mechanics.

 

Bo

 

I have nothing against singularities of zero diameter. They don't have an inside where the (supposed) laws of physics that created them break down.

 

TeleMad

 

Er, yes. I am quite happy to contradict the generally held assumptions about Einstein's theories. If it helps any, Einstein didn't believe in singularities ether.

 

I was making a simple chain of logic.

 

1) It is quite possible to construct simple theories for gravitational fields that do not break conversation of mass/energy.

 

2) An object falling into a gravitational field gains kinetic energy. If there is conversation of mass/energy then this energy gain must be balanced by an identical loss.

 

3) The only other characteristic of gravity that seems to apply here is time dilation, so it's the obvious culprit.

 

There is another point here. When an object is travelling towards the centre of a gravitational field at a relativistic velocity, there are, at least, 2 possible ways of measuring its acceleration: from its own (time dilated by velocity) point of view, or that of an observer standing at zero velocity relative to the centre of the gravitational field. For conversation of mass/energy the former must be true. We have to assume that the energy gain for distance travelled is independent of the velocity. Our observer measures the acceleration as rather lower. This is why none of the more energetic cosmic rays are not accelerated to C by the Sun's gravitational field. A good thing too, as they would achieve infinite mass with disastrous consequences!

 

Once we accept that gravitational acceleration must be measured from the viewpoint of the object being accelerated, we find that any FINITE strength of gravitational field can't accelerate an object to the speed of light this side of eternity. Thus finite gravitational fields can't be black holes. If, as I conjecture, gravitational fields are simply proportional to the mass/energy that creates them, and the mass/energy of the universe is finite then NO BLACK HOLE CAN BE CREATED. However this is only an argument against the creation of black holes. If they already exist they have my permission to remain. The maths may well hold that once created a black hole is valid.

[TeleMad]

BlameTheEx: Er, yes. I am quite happy to contradict the generally held assumptions about Einstein's theories.

 

But you must also realize that by making one of his theories contradict another of his theories, that you’ve given us valid reason to reject your claims, and that you little justification for trying to bring Einstein in on your side.

 

BlameTheEx: If it helps any, Einstein didn't believe in singularities ether.

 

But he DID believe in the absoluteness of the speed of light (in a vacuum)…that principle is at core of special relativity.

 

BlameTheEx: I was making a simple chain of logic.

 

1) It is quite possible to construct simple theories for gravitational fields that do not break conversation of mass/energy.

 

2) An object falling into a gravitational field gains kinetic energy. If there is conversation of mass/energy then this energy gain must be balanced by an identical loss.

 

3) The only other characteristic of gravity that seems to apply here is time dilation, so it's the obvious culprit.

 

There’s the problem. Mass/energy is conserved but not as you contend. Let me try to explain.

 

First, let’s take an everyday example. it takes WORK to separate one body from another body when they gravitationally attract each other – for example, you have to struggle to lift a couch or a desk above your head. Thus, you have to add energy into the system to separate objects: by moving two bodies away from each other, you are storing potential energy in that system. Now run the film in reverse. As the two bodies approach one another due to gravitational attraction, the stored (potential) energy is converted into kinetic energy. There’s no need to monkey around with the speed of light. Now, while it is true that we don’t lift asteroids etc. above Earth and then let them fall, the same general principle applies – once a stray object wondering by becomes “gravitationally bound” to the Earth, the Earth-object system has potential energy that can be converted into kinetic energy as the two objects approach one another. Think about it this way. Assume that the asteroid or whatever was already here on the surface – what would it take to get it out where it started from? A huge amount of energy! So again, one doesn’t have to monkey around with the speed of light – one doesn’t have to violate Einstein’s special relativity. (Another way of explaining this has to do with binding energy).

 

I’ve got to get going to work so don’t have time to go over what else you wrote.

[Freethinker]

Originally posted by: BlameTheEx

Freethinker

 

" Where should we send the Noble Prize?"

 

Do you think sarcasm really improves a debate?

No, but irony makes it interesting.

OK You have made your point. Paradox is a term well associated with Quantum mechanics. But guilt by association is not enough. I have given my reasons for holding that the term is not valid. You reply so far is no more than abuse and hiding behind the opinions of others. Do you happen to know why Quantum Mechanics can be justified as a paradox, or are you just good at mud slinging?

OK, so now using specific written quotes and giving valid verifyable reference sources to validate a scientific claim is:

hiding behind the opinions of others

Yes, I hid behind the skirts of David Joseph Bohm, Erwin Schrödinger, Baidyanath Misra, E. C. George Sudarshan, .... (or perhaps "pants of")

We may be arguing semantics here. I found the following definitions of paradox:

Listen, the issues is really very simple. The specific term "paradox" has been directly associated to QM virtually since QM was first identified. All I did was continue to point this out with a series of varifyable references. If you had acknowledged this obvious end result earlier, we would not ahve had to draw it out this long.

[TeleMad]

BlameTheEx: Once we accept that gravitational acceleration must be measured from the viewpoint of the object being accelerated...

 

I don't accept that: neither would Einstein.

[TeleMad]

Let me explain better my last post.

 

BlameTheEx: Once we accept that gravitational acceleration must be measured from the viewpoint of the object being accelerated...

 

TeleMad: I don't accept that: neither would Einstein.

 

Let’s start by looking at an orbiting laboratory such as the International Space Station. If an astronaut gives something a small push it moves off in a straight line at constant speed obeying Newton’s first law of motion. In fact, it does so much better than here on Earth where friction with a surface or air resistance quickly causes it’s motion to stop. Not only Newton’s first law is perfectly exemplified in on orbiting craft, but also his second and third laws. In fact, all the laws of both classical and modern physics are displayed. An orbiting craft is an ideal reference frame in which to do physics experiments.

 

In fact, we should know this already from Einstein’s equivalence principle: a reference frame undergoing constant acceleration is indistinguishable from one in uniform motion, and therefore, a reference frame in free fall (moving only under the influence of gravity) is equivalent to one in uniform motion.

 

Consequently, the reference frame of an object falling in towards a black hole is a perfectly valid reference frame for measuring the speed of light or any other physical quantity. The results for time and length may differ from those other observers in different reference frames would measure, but that doesn’t make theirs right and the falling observer’s wrong.

[TeleMad]

Just happened to re-read this and I might have taken it the wrong way....

 

BlameTheEx: Once we accept that gravitational acceleration must be measured from the viewpoint of the object being accelerated...

 

I took it mean that we have to accept that the gravitational acceleration must be measured from the perspective of the "stationary" observer since only that observer would view the object as being accelerated (any "observers" in the object underoing free fall would be in uniform motion, according to the equivalence principle, and so would not realize they were accelerating). However, now I see that there is some unintended and subtle ambiguity in the words I quoted and I am not at this time sure what was meant. I may have addressed a position that wasn't being put forward.

 

However, regardless which viewpoint you are claiming we MUST accept, I disagree, if you are asserting that the other viewpoint is invalid.

 

*******************************

Came back after reading this.

 

BlameTheEx: When an object is travelling towards the centre of a gravitational field at a relativistic velocity, there are, at least, 2 possible ways of measuring its acceleration: from its own (time dilated by velocity) point of view, or that of an observer standing at zero velocity relative to the centre of the gravitational field. For conversation of mass/energy the former must be true.

 

This indicates to me that my original interpretation was not correct. However, I see fault with the statements.

 

First, as I pointed out, BOTH reference frames are valid. If you are asserting that one of them is not, which I believe you ware, then I disagree.

 

Second, mass/energy is conserved regardless which reference frame we view it from.

 

How about we start over and this time try to eliminate all ambiguity.

 

 

A spacecraft is free falling (moving under the influence of gravity only) towards a black hole. Reference frame S is that of those in the free falling spacecraft. An "observer" is at rest with respect to the center of the black hole (this alone is going to cause us problems and may need to be modified before any sensical discussion can ensue). Reference frame B is that of the "observer" at the black hole.

 

With this tentative setup in place, please present your argument again.

[Freethinker]

Originally posted by: TeleMad

Let’s start by looking at an orbiting laboratory such as the International Space Station. If an astronaut gives something a small push it moves off in a straight line at constant speed obeying Newton’s first law of motion. In fact, it does so much better than here on Earth where friction with a surface or air resistance quickly causes it’s motion to stop.

IN an effort to assure that ACCURATE information be presented on this site, as we have been told is one person's ultimate goal, let us correct this blatant error.

 

The ISS has an atmosphere somewhat similar to Earth's in order for the inhabitants to live without self contained suits. Therefore the "air resistance" in the ISS would be reasonably similar to here on earth and contrary to this post WOULD exhibit a similar effect on the motion of an object in it.

[BlameTheEx]

Freethinker.

 

Well, I don't know exactly the difference between Irony and sarcasm, but right now I don't care. You were abusive, and you have not apologised. Do not expect me to reply to your posts further until you do.

 

 

TeleMad

 

Potential energy has to be stored somehow. Worse our object falling into a gravitational field has GAINED energy. To balance the books you have to consider the storage of negative energy, or to put it another way you have to look for an already existing supply of energy that can be tapped. You can't just assume that it happens. There has to be a mechanism. Right or wrong, I have given a plausible mechanism.

 

I am not convinced I am contradicting Einstein's theories, just generally held assumptions about them. However if i am, is it not possible to claim that the great man might be wrong on one point while right on others? He wasn't God. Still, I too believe in the absoluteness of the speed of light. I just point out that velocity (and acceleration) are dependant on the observers position.

 

I will give you a thought experiment that might make it clearer. Suppose an observer was standing on a planet so massive that it dilated time by a factor of 2. He conducts an experiment to determine mass of a small heavy object. He does this by placing the object on an absolutely level, frictionless surface. He puts a coin on the surface next ot it, and measures its acceleration towards the object.

 

He can now determine the mass of the object by the acceleration of the coin, by using the gravitational constant. There is no particular reason to believe that he won't get the right answer by this, or perhaps more practical methods that we, on earth, have used to determine the mass of objects such as mountains.

 

All well and good. However let us now consider a second observer, standing at a point outside the bulk of the gravity of this planet. Because he is not (significantly) time dilated he observes an acceleration of only half that of our first observer, and concludes that the object has only half the mass. My guess is that they are both right. A kilo of matter is still a kilo when measure locally, but to the external universe, it's mass/energy and thus its gravitational attraction has diminished by half. This is fair as a lump of matter dropped into the planets gravitational field will have double the mass/energy when it hits the surface, as measured locally.

 

Regarding post 96.

 

I was talking about an object travelling at a relativistic velocity, NOT a massive gravitational field. This is an experiment that could be conducted on earth. Take a particle travelling at, say, I mm per second less than the speed of light, and travelling directly towards Earth. given an acceleration of 10 meters per second per second (OK. I know that G is slightly less for the earth). Then it will accelerate up to the speed of light in 0.1 milliseconds, or about 30 kilometres travel distance.

 

But whose 0.1 milliseconds and whose 30 kilometres? If it is to be that of an observer standing on the earth, then he is watching a particle reach the speed of light. This would be most unfortunate as it would now have infinite mass/energy. Not only would his survival be in question, but that of the whole universe.

 

Its much more plausible to take the view point of the particle itself, which is time dilated. In fact we have little choice if we wish to consider gravity as a potential field. The kinetic energy gain of the particle must be proportional to its mass, and independent of its initial velocity. It would take all the energy of the universe to accelerate it that final 1mm per second, but if you take time dilation into account (dilation due to velocity NOT in this instant gravity) all works out well. While both observation points are indeed valid, there IS a difference in measured acceleration. This is defined by the Lorentz-Fitzgerald contraction. If we contend that the acceleration of ANY particle due to gravity is fixed by the stre

[Freethinker]

Originally posted by: BlameTheEx

Freethinker.

 

Well, I don't know exactly the difference between Irony and sarcasm, but right now I don't care. You were abusive, and you have not apologised. Do not expect me to reply to your posts further until you do.

Awe, that's a shame. I did so enjoy watching you try desperately to cling to your claim that, contrary to EVERY authority on the subject, that QM was not based on paradox.

 

I was so hoping you could actually PROVE it as that WOULD set up in line for a possible acknowledgement by the Nobel Prize commitee.

 

I can understand why you can't see the irony in that as you could not see your lack of stance on the QM? Paradox issue either. Had you simply acknowledge originally, rather that stringing it out for so long, none of the further discussion would have been neccesary or ironic.

[IrishEyes]

FreeT,

 

The words you should have used go something like this...

 

"Even though I do NOT agree with your opinion, and I have verifiable facts to prove that your assertions are incorrect, my tone may have indicated an abusive attitude, and that was not my intention. As a moderator in this forum, I do not wish to appear abusive of anyone's feelings. Although I do not feel that I was abusive, please accept my apology."

 

Come on now, I know you can be nice when you want...!! ;~P

[Freethinker]

You say it much better than I Irish, thanks.

 

And yes I can when I want to, thanks.

 

You should see what I WAS going to post! :-)

[IrishEyes]

You say it much better than I Irish, thanks.

 

And yes I can when I want to, thanks.

 

You should see what I WAS going to post! :-)

 

Oh FreeT, I wrote your other reply myself, then remembered that we are both supposed to be setting an example, so i decided to beat you to the punch!

 

As for saying ANYTHING better - HAHAHAHA ! That's just a laugh! You are more eloquent than Henry David, when you want to be. And from me, that's a MAJOR compliment!

[TeleMad]

TeleMad: Let’s start by looking at an orbiting laboratory such as the International Space Station. If an astronaut gives something a small push it moves off in a straight line at constant speed obeying Newton’s first law of motion. In fact, it does so much better than here on Earth where friction with a surface or air resistance quickly causes it’s motion to stop.

 

FreeThinker: The ISS has an atmosphere somewhat similar to Earth's in order for the inhabitants to live without self contained suits. Therefore the "air resistance" in the ISS would be reasonably similar to here on earth and contrary to this post WOULD exhibit a similar effect on the motion of an object in it.

 

Yep, I goofed in the details (but the point I was making is still valid).

 

The real difference is that in the IIS the object would be moving in a straight line at 'constant' speed through "air", while on Earth it couldn't do that. On Earth one would have to slide the object across some surface to make it go in a straight line* at which point friction would prevent the relative motion between the two and bring the object to a quick halt.

 

*Pushing an object horizontally through the air near the surface of the Earth produces semi-parabolic, projectile motion, because of the dowanward accleration gravity produces: so trying such wouldn't produce straight-line motion. One could produce straightline motion in air by just dropping the object, but then its velocity would change, again do to gravity.

[TeleMad]

BlameTheEx: Potential energy has to be stored somehow. Worse our object falling into a gravitational field has GAINED energy. To balance the books you have to consider the storage of negative energy, or to put it another way you have to look for an already existing supply of energy that can be tapped. You can't just assume that it happens. There has to be a mechanism.

 

There is. Again, think about the process in reverse. If the object is already on the surface of the Earth (or other massive object), what must be done to send it out into space? A huge input of energy is needed to overcome gravity. Now if we play that scenario in reverse, where the object is already in space and falls to the surface, then there will be a huge release of energy...there must be. So an object in space gravitationally attracted to the Earth has potential energy: it just needs to fall closer to the Earth in order to convert that potential energy into kinetic energy.

 

I had mentioned that the explanation could also be done using the concept of binding energy. Here’s the definitive definition of gravitational binding energy on the net.

 

Gravitational binding energy

The gravitational binding energy of an object is the amount of energy required to accelerate every component of that object to the escape velocity of every other component. It is also the amount of energy that is liberated (usually in the form of heat) during the accretion of such an object from material falling from infinity.

 

For a spherical mass of uniform density, the gravitational binding energy is

 

U = [(3/5)GM^2]/r

 

Where G is the gravitational constant, M is the mass of the sphere, and r is the radius of the sphere.

 

Assuming that Earth is uniform (which is not correct, but is close enough to get an order-of-magnitude estimate) with M = 5.97×10^24kg and r = 6.37×10^6m, U is 2.24×10^32J. This is roughly equal to one week of the Sun's total energy output.

 

According to the Virial theorem, the gravitational binding energy of a star is -2 times its internal thermal energy.” (http://en.wikipedia.org/wiki/Gravitational_binding_energy)

 

A bound system is at a lower energy level than its constituent parts. It takes an input of energy to unbind the constituents; on the other hand, converting constituents from the free state to the bound state releases energy (note that the quote states that if the Earth’s constituents were all free and then accreted to reform the Earth, the amount of energy that would liberated would be equal to one week of the Sun’s total energy output!)