3 dimensions of space and 1 of time

[dx]

I would continue this conversation with you, but the thread you made your new post in, "why does mass cause gravity", has no relationship with this issue, and we would be hijacking it.

You've also shown some misunderstanding of the role of mathematics in physics etc. in your new post, so if you really want to discuss this deeply, I think it would be more appropriate to make a new thread in the philosophy forum since it is more of an epistemological/metaphysical question.

 

[brainstorm]

Ok, NOW the thread has been hijacked. Did either of you really read my last post? Please let your differences go and move on. Resolution between you is not needed - and apparently not possible. Live and let live or argue it out in the philosophy section. Any further posts along this line will be reported. Let's get this thread back on track, please.

What is the obsession here with controlling the thread? Granted it is annoying when the topic of a thread is diverted in such a way that it becomes difficult to address the original question. Still, there is the possibility of scrolling past uninteresting side-tracks. Of course, the problem then becomes how to quickly find the next interesting thread.

My suggestion would be that if you want to divert back to an earlier issue in a thread, the best strategy would be to say that explicitly in your post and either highlight it, set it away from other paragraphs or both. That way it is easy to scroll through other posts and immediately get that your post is trying to get back to the OP topic or something else.

Bickering about whether or not a thread is hijacked and whether posts belong in a different thread or forum is itself a distraction from substantive discussion. Scrolling and scanning are more convenient than multiplying threads for the sake of controlling content, imo.

 

[brainstorm]

Just to be clear, I was not saying that gravity is not one of the fundamental forces/interactions. I was just saying that the question "is gravity a force or is it curvature of spacetime" is a meaningless question. It is both, and there is no contradiction there.

Maybe I should have phrased it differently. My point was that when an object's inertia is described as its tendency to remain in motion or at rest until acted upon by external force, a satellite in circular orbit at constant velocity could be considered to be unimpinged-upon by external force so long as it is following the path of least resistance through spacetime.

This is fundamental to the issue of dimensionality and spacetime, because theorizing gravity as a force that operates within non-curved space (cartesian space?) is radically different from theorizing gravity as a cause of the shape of spacetime in the first place.

In one theory, forces occur in neutral space while in the other they control and define it.

 

[Hoku]

@ Brainstorm, first of all dx wasn't talking to you. He was referring to a conversation that occurred and ended before you even made yourself known.

Second of all, why don't you use that "critical literature training" that you are so "priviledged" to have received, to read the Physics Forums Global Guidelines. https://www.physicsforums.com/showthread.php?t=5374 I'll pick out some important features to make it easier for you:

"Do not hijack an existing thread with off-topic comments or questions--start a new thread.

Any off-topic posts will be deleted or moved to an appropriate forum per administrator or mentor discretion."

@ dx, I'm sorry that you oppose my position so vehimently. You may be right about me not understanding all of this, but I'm really doing my best to clear it up. I'm not yet convinced that my postion is a philosophical one. Perhaps others who are willing to pursue the discussion in the other thread will help clear that up. So far, the OP has not given the "hijack" sign, so I'm sticking with it. Thanks for your contributions to this thread, dx.

 

[dx]

dx, I'm sorry that you oppose my position so vehimently. You may be right about me not understanding all of this, but I'm really doing my best to clear it up. I'm not yet convinced that my postion is a philosophical one. Perhaps others who are willing to pursue the discussion in the other thread will help clear that up. So far, the OP has not given the "hijack" sign, so I'm sticking with it. Thanks for your contributions to this thread, dx.

I'm not saying your position is a philosophical one. I'm saying the very issue that is being discussed is a philosophical question (which does not mean "things that make no sense" as another member once pointed out . I was merely inviting you to start a thread in the philosophy forum (instead of posting in unrelated threads), and if you do, I would participate in it.

 

[Altabeh]

Apparently, you did, since Hoku concluded that "the argument between dx and Altabeh is more proof that the question about whether gravity is a force or not is more of an issue than people realize."

When I showed that the Lagrangian picture of GR yet allows gravity to expose itself as a force in the Newtonian limit, I was not denying the "curvature-like" nature of gravity in GR but just made you understand that the Newton's laws can be easily extracted from the gravitational Lagrangian, too, meaning that the implication of "force" could be searched in GR as well and this stands for the idea that the "force-like" nature of gravity can still be retained by GR! This is been my idea since I had a conversation with a friend here in some thread (where I insisted the force-like picture in GR only but later I had that idea left behind and took the current path you see) and you can find it throughout these forums!

AB

 

[Frame Dragger]

Really, I think Hoku has the right idea. I know for Altabeh isn't messing about with you dx, and you're (dx) a homework helper and seemingly nice guy. I think this thread is doomed to be a pit of mutual misunderstandings.

Having read both of your posts elsewhere here, I don't believe EITHER of you have a particular misconception about the current understanding of gravity in GR or a la Newton. One person being mistaken about a position (Hoku) doesn't mean you didn't make it clear. Misunderstandings do happen, and this is merely extending the silliness. Come on... let's all have a nice cuppa and relax hmm?

 

[brainstorm]

the implication of "force" could be searched in GR as well and this stands for the idea that the "force-like" nature of gravity can still be retained by GR! This is been my idea since I had a conversation with a friend here in some thread (where I insisted the force-like picture in GR only but later I had that idea left behind and took the current path you see) and you can find it throughout these forums!

You are alluding to some reasons that you have for thinking this way, but you're not stating them. Can you explicate your reasoning so that I can contemplate how gravity can be both an external force on objects and the very contours of spacetime at the same time?

The only way I can at this point see your claim being valid is if spacetime itself were viewed as some sort of substance affected by gravity. Imo, though, such a notion would be silly because spacetime cannot be measured except as relations between things. It is not a substance in and of itself.

All "spacetime curvature" means, imo, is that objects and light trace certain trajectories between points when traveling only by momentum of their own inertia. Am I overlooking something?

 

[Altabeh]

You are alluding to some reasons that you have for thinking this way, but you're not stating them. Can you explicate your reasoning so that I can contemplate how gravity can be both an external force on objects and the very contours of spacetime at the same time?

It has a mathematical approach and you can find it in almost any prestigious book on GR. But in this thread somewhere I said that if you started with the Lagrangian approach, then you would see at some level that gravity can be given a force-like character if the gravitational field is weak. This is the cornerstone of Einstein's field equations and that constant factor beside the energy-momentum tensor i.e. \frac{-8\pi G}{c^4} in

G_{\mu\nu}=- \frac{-8\pi G}{c^4}T_{\mu\nu}.

The Laplace equation

\nabla^2\phi=0,

for some gravitational potential \phi can accept the Newtonian gravitational potential as a solution. Thus \phi=-GMm/r, with m being the mass of a particle around some gravitating body of mass M and by definition one can get the Newoton's gravitation law via the formula

F=-\nabla\phi=GMm/r^2.

On the other hand since the field equation for vacuum can lead to the Laplace equation above, you can see that GR could actually support the idea of "gravity as a force" with some assumptions (partially omitted above) that are required to be taken into account in the beginning! These assumptions are 1- the spacetime must be nearly flat or the metric differs from the Minkowski metric with only some small terms called, up to first order, the "perturbed tensor". 2- The radial velocity of particles falling toward the gravitating body must be so tiny compared to the speed of light (Newtonian limit of velocity or nonrelativistic velocity). 3- The potential (metric) must be time-independent everywhere.

For more details, see A first course in general relativity by Schutz, section 7.2.

The only way I can at this point see your claim being valid is if spacetime itself were viewed as some sort of substance affected by gravity. Imo, though, such a notion would be silly because spacetime cannot be measured except as relations between things. It is not a substance in and of itself.

Spacetime needs not be "some sort of substance" as for gravity to be held responsible for the curvature of it. This is a matter of definition: whatever is curved in GR can also be sensitive to a gravitational force applied to it. But the usual literature of GR does not say the cause of curvature is a force but the presence of matter and gravitational fields. We just claim this cause would be a force due to gravity in the Newtonian limit of GR.

All "spacetime curvature" means, imo, is that objects and light trace certain trajectories between points when traveling only by momentum of their own inertia. Am I overlooking something?

But external fields can also get involved in the geodesic equations and thus they have their own affect on the curvature of spacetime. These external fields, if any, are considered to be within the energy-momentum tensor as in the case where an electromagnetic field is introduced into the field equations through the electromagnetic energy-momentum tensor.

AB

 

[brainstorm]

Well, if your intent was to belittle my level of expertise by using terms and math that elude me, you succeeded. You win. You are a physics expert and I am not. I am just a critical thinker applying reason and logic to these explanations of matter-energy relations vis-a-vis gravitation. I can't do math worth anything and I don't know many of the words you use. Do you think that means I should shut up with anything I have to say or ask and run with tail between legs away from this topic? If you do, you're a bully.

Spacetime needs not be "some sort of substance" as for gravity to be held responsible for the curvature of it. This is a matter of definition: whatever is curved in GR can also be sensitive to a gravitational force applied to it. But the usual literature of GR does not say the cause of curvature is a force but the presence of matter and gravitational fields. We just claim this cause would be a force due to gravity in the Newtonian limit of GR.

How can gravity shape spacetime and at the same time affect objects in spacetime? I think you are right that it is a matter of definition. Spacetime should be defined as a general pattern of relations between matter-energy in the same frame. Too often, imo, is it described as a thing instead of a generalized concept. I think this leads to wrongheaded thinking for many people, even if you are too smart to fall victim to confounding language.

But external fields can also get involved in the geodesic equations and thus they have their own affect on the curvature of spacetime. These external fields, if any, are considered to be within the energy-momentum tensor as in the case where an electromagnetic field is introduced into the field equations through the electromagnetic energy-momentum tensor.

I almost follow what you're saying here, until you seem to be mixing qualitative descriptive language with the math you're using to analyze it. I separate descriptive language from analytical language to avoid confusing analysis with observations, but again maybe this is something you are above.

 

[Frame Dragger]

Well, if your intent was to belittle my level of expertise by using terms and math that elude me, you succeeded. You win. You are a physics expert and I am not. I am just a critical thinker applying reason and logic to these explanations of matter-energy relations vis-a-vis gravitation. I can't do math worth anything and I don't know many of the words you use.

11 out of 10 for honesty brainstorm, but that didn't exactly shock the crowd.

All kidding aside, that's a useful rhetorical flourish, but all it really asks is, "Why are you in the Special Relativity section of the Physics Forum discussing this? Why not learn some of these terms first, or discuss philosophy in a philosophy forum?"

Saying that Altabeh was in some way, trying to belittle you (or rather, that he did so and the reasons don't matter) and your "I'm so helpless" approach is tired. Just because you don't LIKE the fact that some of these concepts are not answerable in the fashion you've become accustomed to, or that people talking about science are not interested in mixing metaphysics with their physics, doesn't mean you should throw a fit.

How can gravity shape spacetime and at the same time affect objects in spacetime? I think you are right that it is a matter of definition. Spacetime should be defined as a general pattern of relations between matter-energy in the same frame. Too often, imo, is it described as a thing instead of a generalized concept. I think this leads to wrongheaded thinking for many people, even if you are too smart to fall victim to confounding language.

Part of the reason that people here are so militant about taking their physics straight is that NO ONE is too smart to be confounded by someone using words that are terms of art in physics, and common usage elsewhere. You're struggling with the most basic concept here, and that is WHAT Relativity is! If you had some concept of the theory beyond parsing the language (which is pointless as you have now discovered) you'd know:

1.) The Stress (or Momentum) Energy Tensor describes the action you're asking about. It doesn't come attatched with a note from god or a pair of dice, so the WHY is still a mystery. If it isn't clear yet from the excitement over the LHC (Large Hadron Collider), there are still some questions to be answered before this one can be turned over to the philosophers.

2.) Being intelligent won't help you if you don't know the basics and the language. Try to read a legal document made for lawyers by lawyers. Are your reading skills failing you, or are they using "Terms of Art" which confuse you? You "almost follow" because we're all using WORDS. You're missing the point, because as you've discovered, these words mean different things in different fields; a concept I really would have expected you to grasp intuitively, if not when beaten over the head with it.

May I suggest that you stay in the rarified atmosphere of your profession as a "Critical Thinker" (which by the way, is a circa 80's teaching buzz-phrase for an old concept called "Thinking") and leave the physics to people who can "...do math worth anything..."? After all, every time you say "IMO" here, people are going to think, "WHAT opinion? You've admitted to total ignorance of the subject!" Maybe this is some new way of handling "critical thinking" I've missed lo these many years.

EDIT: Now that, is how you can tell that someone is taking the piss out of you brainstorm. The fact that none of us have made a nasty rhyme in iambic pentameter about you name being "brainstorm" is proof, if such were needed, that the intentions of Altabeh and others have been good. You on the other hand have been very disingenuous. You speak in a manner which exudes knowledge you simply don't have, and put forth opinions on subjects with which you now admit you have ZERO meaningful knowledge.

 

[Dale]

Well, if your intent was to belittle my level of expertise by using terms and math that elude me, you succeeded. ... If you do, you're a bully.

I just got this vision:

"Hey kid, give me your lunch money or I will pound you with the quadratic equation!"

 

[Frame Dragger]

I just got this vision:

"Hey kid, give me your lunch money or I will pound you with the quadratic equation!"

What, didn't the nerds always bully the jocks in your stereotypical schools? I also love the implication that by expressing a thought in terms of Relativistic Physics, IN the RELATIVITY forum of PF, would EVER be a way to belittle someone. Don't get the symbols? Try google or wikipedia, or maybe... just maybe... you shouldn't be in the RELATIVITY forum!

Sorry... got a bit worked up for a moment. All better now.

EDIT: Btw, am I the only one who almost died laughing at the phrase "...my level of expertise..." followed by the admission that not only is he not an expert, but utterly uninformed? That's not a level of expertise, that's rank ignorance! Get it? Level? Rank? ...wait, am I being an English bully now?! DaleSpam, are we all terrible people (and not because of that dead hobo incident) for having an interest in this subject that doesn't perfectly match Brainstorm's expectations?! AIIIIEEEE!

 

[brainstorm]

What, didn't the nerds always bully the jocks in your stereotypical schools? I also love the implication that by expressing a thought in terms of Relativistic Physics, IN the RELATIVITY forum of PF, would EVER be a way to belittle someone. Don't get the symbols? Try google or wikipedia, or maybe... just maybe... you shouldn't be in the RELATIVITY forum!

Sorry... got a bit worked up for a moment. All better now.

EDIT: Btw, am I the only one who almost died laughing at the phrase "...my level of expertise..." followed by the admission that not only is he not an expert, but utterly uninformed? That's not a level of expertise, that's rank ignorance! Get it? Level? Rank? ...wait, am I being an English bully now?! DaleSpam, are we all terrible people (and not because of that dead hobo incident) for having an interest in this subject that doesn't perfectly match Brainstorm's expectations?! AIIIIEEEE!

Apparently you have some emotional intensity associated with use of the word, "bully."

I don't really care how you rank my level of knowledge, ignorance, or whatever you call it.

I was just making the point that I don't think the poster was as intent on communicating with my post as he was trying to make a show of his breadth of concepts and math skill.

It can be hard for people to distinguish communication from spreading their ego-feathers sometimes. Scientists can be really bad about this because they tend to be completely convinced that everything they say is objective and disinterested.

I don't know for sure if this was the intent behind the post or not. It just came across that way to me so I figured I would mention it.

No reason to push people off threads. I'm not trolling, even if I do understand what I do in layman's terms and communicate as such. These threads are about learning and sharing knowledge, to me, not separating experts from lay people.

 

[Frame Dragger]

Apparently you have some emotional intensity associated with use of the word, "bully."

I don't really care how you rank my level of knowledge, ignorance, or whatever you call it.

I was just making the point that I don't think the poster was as intent on communicating with my post as he was trying to make a show of his breadth of concepts and math skill.

It can be hard for people to distinguish communication from spreading their ego-feathers sometimes. Scientists can be really bad about this because they tend to be completely convinced that everything they say is objective and disinterested.

I don't know for sure if this was the intent behind the post or not. It just came across that way to me so I figured I would mention it.

No reason to push people off threads. I'm not trolling, even if I do understand what I do in layman's terms and communicate as such. These threads are about learning and sharing knowledge, to me, not separating experts from lay people.

First, thank you for the phrase "Spreading ego-feathers" which I may make into a T-Shirt.

Second, give up the attempts at pop-psych... when you follow a truly wild swing about "emotional intensity" by telling the person who's opinion you don't value that you don't value it, they're left with the impression that you are childish. You're anticipating that I'll respond to "rank my level of knowledge" by saying you're not knowledgeable, but ignorant? No brainstorm, I don't care enough, having had fun in the last post with DaleSpam. Frankly, if you'd never responded, I'd never have given you another thought.

I'd respond to more, explain the difference between the product of the scientific method and "disinterested", and why "objective" isn't a dirty word, but frankly this just isn't why I come to PF, and you already seem to know so much about scientists... I'm sure you'll do just fine.

You may think I've been nasty, or brusque, or that others have, but keep in mind that if we were not being moderated by rules we all agreed to, you'd be lucky if people didn't just pass out laughing at you. If this is how your comport yourself in life, be ready for constant rejection by the very people you want to learn from (or teach as the case seems to be lol).

 

[brainstorm]

First, thank you for the phrase "Spreading ego-feathers" which I may make into a T-Shirt.

Second, give up the attempts at pop-psych... when you follow a truly wild swing about "emotional intensity" by telling the person who's opinion you don't value that you don't value it, they're left with the impression that you are childish. You're anticipating that I'll respond to "rank my level of knowledge" by saying you're not knowledgeable, but ignorant? No brainstorm, I don't care enough, having had fun in the last post with DaleSpam. Frankly, if you'd never responded, I'd never have given you another thought.

I'd respond to more, explain the difference between the product of the scientific method and "disinterested", and why "objective" isn't a dirty word, but frankly this just isn't why I come to PF, and you already seem to know so much about scientists... I'm sure you'll do just fine.

You may think I've been nasty, or brusque, or that others have, but keep in mind that if we were not being moderated by rules we all agreed to, you'd be lucky if people didn't just pass out laughing at you. If this is how your comport yourself in life, be ready for constant rejection by the very people you want to learn from (or teach as the case seems to be lol).

This post is so defensive and aggressive at the same time! I really just said what I thought and I wasn't trying to start any fights. I don't even think objective is a dirty word - I was just explaining the reason I thought some scientists might be less mindful of their own ego-trips where their science is concerned.

If you or anyone else is really ego-neutral, why not just discuss where discussion is merited or desired and ignore what's not worth your time and effort? You don't have to define someone else's level of expertise or anything else about them to decide whether there's something in their post worth responding to.

The broader your reading-comprehension abilities, the more you can engage in discussions on a topic with people other than specialists/experts in your particular sub-field. There's nothing degrading about engaging with lay thinkers. Only the most insecure intellectuals bolster their sense of status by limiting their contact with lay people. Of course, everyone gets tired of addressing the same old issues so don't put yourself out to respond to things you've discussed a thousand times before.

 

[Frame Dragger]

This post is so defensive and aggressive at the same time! I really just said what I thought and I wasn't trying to start any fights. I don't even think objective is a dirty word - I was just explaining the reason I thought some scientists might be less mindful of their own ego-trips where their science is concerned.

If you or anyone else is really ego-neutral, why not just discuss where discussion is merited or desired and ignore what's not worth your time and effort? You don't have to define someone else's level of expertise or anything else about them to decide whether there's something in their post worth responding to.

The broader your reading-comprehension abilities, the more you can engage in discussions on a topic with people other than specialists/experts in your particular sub-field. There's nothing degrading about engaging with lay thinkers. Only the most insecure intellectuals bolster their sense of status by limiting their contact with lay people. Of course, everyone gets tired of addressing the same old issues so don't put yourself out to respond to things you've discussed a thousand times before.

Who's claiming to be "ego-neutral"?

 

[Dale]

These threads are about learning and sharing knowledge

I agree completely, which is why your posts in this thread have been such a problem. We were sharing knowledge with Hoku and seemed to be making some good progress helping her understand the basics of some pretty difficult concepts. By hijacking the thread in order to push your uninformed opinion you interfered with the knowledge sharing that was in progress for no benefit to anyone.

 

[brainstorm]

I agree completely, which is why your posts in this thread have been such a problem. We were sharing knowledge with Hoku and seemed to be making some good progress helping her understand the basics of some pretty difficult concepts. By hijacking the thread in order to push your uninformed opinion you interfered with the knowledge sharing that was in progress for no benefit to anyone.

If you want to have a private discussion, why not use PMs?

What gives you the authority to determine what is relevant, irrelevant, or progressive on a given issue?

If you see my posts as "hijacking," shouldn't you provide explicit grounds and reasoning? I see no reason why I shouldn't treat this thread as an open discussion on the issue of dimensionality and spacetime.

If I did, or if I saw the topic as uninteresting I wouldn't have gotten into the discussion.

It seems you're just playing with exclusivity as further ego/power tripping.

 

[Frame Dragger]

If you want to have a private discussion, why not use PMs?

What gives you the authority to determine what is relevant, irrelevant, or progressive on a given issue?

If you see my posts as "hijacking," shouldn't you provide explicit grounds and reasoning? I see no reason why I shouldn't treat this thread as an open discussion on the issue of dimensionality and spacetime.

If I did, or if I saw the topic as uninteresting I wouldn't have gotten into the discussion.

It seems you're just playing with exclusivity as further ego/power tripping.

Oh come on, now you're just lowering the tone. I also notice you keep talking about ego... tell me what do you make of that baby Sigmund? As for exclusivity, read the rules here, which are explicit and not to be played with. If you want to ramble about your apparent disdain for "scientists" and make sweeping (yet meaningless) generalizations, you're going to lose access to this site. You really did derail what had become a very interesting thread with Hoku and DaleSpam, and some of us who are capable of doing so, were enjoying it. Now that is ego-tripping., or "spreading ego feathers"

 

[brainstorm]

Oh come on, now you're just lowering the tone. I also notice you keep talking about ego... tell me what do you make of that baby Sigmund? As for exclusivity, read the rules here, which are explicit and not to be played with. If you want to ramble about your apparent disdain for "scientists" and make sweeping (yet meaningless) generalizations, you're going to lose access to this site. You really did derail what had become a very interesting thread with Hoku and DaleSpam, and some of us who are capable of doing so, were enjoying it. Now that is ego-tripping., or "spreading ego feathers"

I agree with you about not getting into bickering battles. But it's hardly fair for you to tack such jabs onto the end of your posts and then warn that if people respond to them they're hijacking the thread and will be banned.

Again, I don't know what your basis is for claiming that I was derailing a discussion. Can you site the last post that you're referring to so I can go back and look at where I entered the discussion relative to that post so I can get an idea of what you're talking about?

 

[Frame Dragger]

I agree with you about not getting into bickering battles. But it's hardly fair for you to tack such jabs onto the end of your posts and then warn that if people respond to them they're hijacking the thread and will be banned.

Again, I don't know what your basis is for claiming that I was derailing a discussion. Can you site the last post that you're referring to so I can go back and look at where I entered the discussion relative to that post so I can get an idea of what you're talking about?

Well, seeing as this thread will inevitabely be locked, or locked/cleaned why not? You're right, I'm unfair, next you'll be telling me there's no Santy Claws. Speaking of which, and I realize this is glistening with comic irony, the word is "CITE" not "Site". As for how you're derailing the discussing, the last few pages have been revolving around you, have they not? You entered a discussion without the capacity to contribute to it in a meaningful way, and now you insist on dragging this out.

Anyway, with luck, when I wake up tommorrow your name will have a little line through it, and all of this (my own comments included) can be removed so the discussion with Hoku can resume. This is the last response I'll make to you on this thread, because on the off-chance it isn't locked and cleaned, or just locked, I don't want to clutter it anymore. Besides, we both know you need the last word.