Do you believe in gravity?

[Mare Tranquillity]

Only when I'm formally dressed.

Woo,woo! You at least, have a sense of humor, Nums is soooooo grim. :-(

 

[numinus]

Yes, I know, I wrote a term paper on that.

You wrote a term paper? About a book? In grad school? Hmmm.

I'm sorry if I misconstrued you. You have an awkward way of saying things, and it is hard to know what you are thinking.

Which is what often happens when you jump in a conversation without knowing its context -- and with a 'you're wrong', no less.

Oh, and there is nothing awkward with what I said. If anything, I try to use more formal language when I'm explaining things -- especially about math or physics. That way, no one would misconstrue. And if one does misconstrue, then I couldn't be faulted for it, the way you are doing right now.

Again I don't understand what you are getting at. I wish there was a visual way of viewing tensor fields, but the local field at each point is a matrix and not a vector and I don't see how one could represent an area of tensor fields as a picture on a piece of paper.

What are you talking about?

Tensor fields are represented by matrices simply because matrix algebra is the best way to solve a functional relation involving many variables.

So when I say 'flux lines', I don't mean an 'actual' line. It just means a line in space best represents the functional relation of a vector at that particular point.

Tensors and vectors are BOTH mathematical functions describing a physical phenomenon.

Is that clear enough or do you wish to argue some other irrelevant point arising from a particular word in my post.

In the mean time, you are no closer to a definite answer to the thread question.

 

[numinus]

Woo,woo! You at least, have a sense of humor, Nums is soooooo grim. :-(

And what exactly did I say that led you to believe I'm here for your amusement, hmmm?

 

[Mare Tranquillity]

And what exactly did I say that led you to believe I'm here for your amusement, hmmm?

Why, nothing, nothing at all. That was the point of my comment. You post like the last surviving member of the Brothers Grimm.

 

[numinus]

Why, nothing, nothing at all. That was the point of my comment. You post like the last surviving member of the Brothers Grimm.

That's because I'm not trying to amuse you. So why would you expect otherwise, to the point of speculating aloud in this forum, hmmm?

 

[Lagboltz]

You wrote a term paper? About a book? In grad school? Hmmm.

No it was about how the mass of the universe wraps itself into a 5 dimensional sphere. The details don't matter here.

Which is what often happens when you jump in a conversation without knowing its context -- and with a 'you're wrong', no less.

I didn't jump into the middle of a conversation. I know bad physics when I see it in any context at this level.

Oh, and there is nothing awkward with what I said. If anything, I try to use more formal language when I'm explaining things -- especially about math or physics. That way, no one would misconstrue. And if one does misconstrue, then I couldn't be faulted for it, the way you are doing right now.

Believe me it is your formal language that is very very awkward.

Tensor fields are represented by matrices simply because matrix algebra is the best way to solve a functional relation involving many variables.

So when I say 'flux lines', I don't mean an 'actual' line. It just means a line in space best represents the functional relation of a vector at that particular point.

Tensors and vectors are BOTH mathematical functions describing a physical phenomenon.

Is that clear enough or do you wish to argue some other irrelevant point arising from a particular word in my post.

Believe me. Some of what you just said is absolutely obvious and other things are plane wrong. But it doesn't really matter. And I agree, we should get off that topic.

In the mean time, you are no closer to a definite answer to the thread question.

Ah. The thread question. "Do you believe in gravity". The answer is yes.

Speaking of amusement, do you find this limerick amusing or just plain wrong and stupid?

There was a young lady named Bright,
Who could travel much faster than light.
She departed one day,
In a relativistic way,
And returned on the previous night.

 

[numinus]

No it was about how the mass of the universe wraps itself into a 5 dimensional sphere. The details don't matter here.

Hmmm.

You are aware, of course that a spherical space-time geometry is unstable, aren't you? Or the fact that such an idea is not even original, hence quite useless in graduate school?

I didn't jump into the middle of a conversation. I know bad physics when I see it in any context at this level.

You are aware that classical mechanics has immensely more use in the applied sciences today than relativity, aren't you?

Just because there are certain limits to its application doesn't make it bad physics, now, does it?

Believe me it is your formal language that is very very awkward.

Actually, you haven't provided anything that would compel me to believe you. And here Im being very polite.

Believe me. Some of what you just said is absolutely obvious and other things are plane wrong. But it doesn't really matter. And I agree, we should get off that topic.

You mean like newtonian mechanics doesn't assume an infinite speed of gravity?

Or perhaps that a force due to gravity is within the field of classical mechanics?

Or could it be that tensors aren't vectors, but matrices?

Or perhaps, everything you said in this thread fall in undergraduate physics?

Or maybe, there is some graduate school significance to the words 'plane wrong'. I mean, if you are going to criticize someone, don't you need to at least get the spelling right?

Ah. The thread question. "Do you believe in gravity". The answer is yes.

Ah, yes. The thread topic. I've seen you define gravity as a wave and space-time curvature. Which is it?

Speaking of amusement, do you find this limerick amusing or just plain wrong and stupid?

There was a young lady named Bright,
Who could travel much faster than light.
She departed one day,
In a relativistic way,
And returned on the previous night.

Amusing in a geeky sort of way. Reminds me of your infatuation with theoretical physics -- and how you peddle them as fact.

I bet mare doesn't get it, though.

 

[Dr.Who]

Numinus and Lagboltz,

You two are talking above me so would you please explain;

Are either of you saying that the effect of some material particle in one part of the galaxy is not realized instantaneously on some other material particle in another part of the galaxy?

 

[Dr.Who]

Mare and Numinus,

You have both failed to be totally civil to each other so why spend all your time trying to demonstrate that the other is an awful person?

 

[Mare Tranquillity]

Mare and Numinus,

You have both failed to be totally civil to each other so why spend all your time trying to demonstrate that the other is an awful person?

I don't think Nums is an awful person, I rather like him. He's intelligent and reasonably well-spoken, but just too grim. Though I tease him a bit because he lends himself well to it, I read all of his posts and respect what he says even if I disagree. Sorry if it seems that I dislike him. I'll be more concilliatory in the future.

 

[Lagboltz]

Ah, yes. The thread topic. I've seen you define gravity as a wave and space-time curvature. Which is it?

Nums, I am not talking down to you nor pretending you don't know this stuff. I am just putting it at a level that anyone who reads these interminable posts can understand.

In a nutshell. Newton's concept of gravity is a valid approximation for small scale, but begins to be problematic at a larger scale, for example the orbit of mercury has a slight deviation that was explained by general relativity. In this theory we can think of instantaneous action at a distance if people want to, but it is unnecessary.

General relativity, a warp in space-time, so far seems to have a fundamental validity on the large scale. Some factors such as dark matter, early hyper-fast expansion (inflation), and others things are not fully understood, but still seem to be consistent with the theory.

In general relativity things travel by the shortest path in space time, but the warped aspect of space/time is why orbits of planets are curved, etc. You can't think of in terms of space being so warped that the planets are traveling in "ruts". The warp is largely imperceptible, but the gravitational force is so weak that it doesn't take much to show it's effects. The warp can more directly be seen when light is slightly bent around massive bodies.

Gravity waves are just propagating ripples of gravity that can theoretically occur from cataclysms, but haven't been found yet. Satellites and ground experiments are or will be searching for them. They are important phenomena, but not a fundamental part of the theory.

Gravitons, are theoretical particles embodying the gravitational force. Just like particles of light (photons) embody electricity and magnetic forces. Contemporary physicists hope to unite gravity via gravitons in the newer string theory's but have not been successful.

The currently held view is that general relativity is our best model, but a deeper theory has to be found to solve some of the problems.

Current problems: The major problem is that general relativity is disjoint from quantum mechanic theory. They need to be unified because general relativity gets boogered by the highly energetic "vacuum froth" at a small enough scale.

For those not familiar with it, a total vacuum is not nuthin. It is swarming with particles of all sorts. Why? Pairs of particles, one matter and the other antimatter, can pop out of the vacuum by borrowing energy from the future and then annihilate each other and return the energy to the past. When you look at smaller and smaller volumes and time scales, these particles become more and more numerous. That activity is called a froth. The mass of the froth gets increasingly larger at smaller scales and the space warp gets indefinitely complex.

If I remember right, the mathematics of gravity in the vacuum leads to singularities - equations that have infinities, and this is why there is a problem with general relativity and the quantum mechanics of the froth.

Amusing in a geeky sort of way. Reminds me of your infatuation with theoretical physics -- and how you peddle them as fact.

I bet mare doesn't get it, though.

I bet Mare does get it, because it's totally silly. Every one knows that nothing can travel faster than light, however, that could not lead to travel back in time. Two screwy phenomena are put in the same limerick, in a way that seems to make sense, but actually doesn't.

It's a good thing that you think it's amusing because Mare will probably think you are less grim.

 

[Mare Tranquillity]

Current problems: The major problem is that general relativity is disjoint from quantum mechanic theory. They need to be unified because general relativity gets boogered by the highly energetic "vacuum froth" at a small enough scale.

For those not familiar with it, a total vacuum is not nuthin. It is swarming with particles of all sorts. Why? Pairs of particles, one matter and the other antimatter, can pop out of the vacuum by borrowing energy from the future and then annihilate each other and return the energy to the past. When you look at smaller and smaller volumes and time scales, these particles become more and more numerous. That activity is called a froth. The mass of the froth gets increasingly larger at smaller scales and the space warp gets indefinitely complex.

If I remember right, the mathematics of gravity in the vacuum leads to singularities - equations that have infinities, and this is why there is a problem with general relativity and the quantum mechanics of the froth.


I bet Mare does get it, because it's totally silly. Every one knows that nothing can travel faster than light, however, that could not lead to travel back in time. Two screwy phenomena are put in the same limerick, in a way that seems to make sense, but actually doesn't.

It's a good thing that you think it's amusing because Mare will probably think you are less grim.

Nanner, nanner, nanner, Nums, you heard it from me first! I'm glad you find something amusing--even if it is at my expense.

 

[numinus]

Nums, I am not talking down to you nor pretending you don't know this stuff. I am just putting it at a level that anyone who reads these interminable posts can understand.

In a nutshell. Newton's concept of gravity is a valid approximation for small scale, but begins to be problematic at a larger scale, for example the orbit of mercury has a slight deviation that was explained by general relativity. In this theory we can think of instantaneous action at a distance if people want to, but it is unnecessary.

General relativity, a warp in space-time, so far seems to have a fundamental validity on the large scale. Some factors such as dark matter, early hyper-fast expansion (inflation), and others things are not fully understood, but still seem to be consistent with the theory.

In general relativity things travel by the shortest path in space time, but the warped aspect of space/time is why orbits of planets are curved, etc. You can't think of in terms of space being so warped that the planets are traveling in "ruts". The warp is largely imperceptible, but the gravitational force is so weak that it doesn't take much to show it's effects. The warp can more directly be seen when light is slightly bent around massive bodies.

Gravity waves are just propagating ripples of gravity that can theoretically occur from cataclysms, but haven't been found yet. Satellites and ground experiments are or will be searching for them. They are important phenomena, but not a fundamental part of the theory.

Gravitons, are theoretical particles embodying the gravitational force. Just like particles of light (photons) embody electricity and magnetic forces. Contemporary physicists hope to unite gravity via gravitons in the newer string theory's but have not been successful.

The currently held view is that general relativity is our best model, but a deeper theory has to be found to solve some of the problems.

Current problems: The major problem is that general relativity is disjoint from quantum mechanic theory. They need to be unified because general relativity gets boogered by the highly energetic "vacuum froth" at a small enough scale.

For those not familiar with it, a total vacuum is not nuthin. It is swarming with particles of all sorts. Why? Pairs of particles, one matter and the other antimatter, can pop out of the vacuum by borrowing energy from the future and then annihilate each other and return the energy to the past. When you look at smaller and smaller volumes and time scales, these particles become more and more numerous. That activity is called a froth. The mass of the froth gets increasingly larger at smaller scales and the space warp gets indefinitely complex.

If I remember right, the mathematics of gravity in the vacuum leads to singularities - equations that have infinities, and this is why there is a problem with general relativity and the quantum mechanics of the froth.

Two quick points, primarily regarding your comment about engineers incapable of seeing the 'big picture'.

1. You are downplaying the incompatibility of general relativity with the standard model of quantum mechanics. General relativity is a background-independent theory while by your admission, the behavior of gravitons are considerably dependent on existing factors very near planck scales.

This isn't just a 'difficulty' but a major stumbling block which prompted theorizing string and/or loop-quantum gravity in the first place.

Which brings me back to my original question, a question that you DID NOT answer despite your overly long response -- is it space-time curvature or wave/particle gravitons?

And if you cannot answer, then you should admit that you believe in gravity without fully comprehending the full extent of its nature. And I have a feeling that the pretend agnostics in this forum would be indignant to such a response.

2. I noticed that you mention general relativity and hyper-inflation in the same breath without batting an eyelash. You claim that gravitons, if they do exist, cannot possibly travel faster than light. And yet, you can readily accept space expanding at speeds thousands of times faster than that.

And if you still cannot see the 'big picture', two objects whose space between them is expanding faster than light would be 'moving away from each other' faster than the speed of light.

So, which is it?

I bet Mare does get it, because it's totally silly. Every one knows that nothing can travel faster than light, however, that could not lead to travel back in time. Two screwy phenomena are put in the same limerick, in a way that seems to make sense, but actually doesn't.

It is very good that you admit -- it is screwy. Should I take your assertions, then, as having the same intellectual weight as a limerick? After all, you have asserted the exact same assertions.

I doubt if mare understands einstein's postulates in special and general relativity.

It's a good thing that you think it's amusing because Mare will probably think you are less grim.

I would prefer a limerick with an ostensibly toilet humor, in keeping with the nature of limericks.

As for mare, well, it is hard to be less grim -- in view of the absurdities coming from an otherwise intelligent person.

 

[numinus]

Numinus and Lagboltz,

You two are talking above me so would you please explain;

Are either of you saying that the effect of some material particle in one part of the galaxy is not realized instantaneously on some other material particle in another part of the galaxy?

Yes. That appears to be the conclusion -- whether you consider gravity as a function of space-time geometry or gravitons.

 

[Lagboltz]

1. You are downplaying the incompatibility of general relativity with the standard model of quantum mechanics. General relativity is a background-independent theory while by your admission, the behavior of gravitons are considerably dependent on existing factors very near planck scales.

This isn't just a 'difficulty' but a major stumbling block which prompted theorizing string and/or loop-quantum gravity in the first place.

Nums, you seem to be in a bad mood today. My post was largely an overview that non-physicists can also understand as in Dr. Who's request.

My last 3 paragraphs focussed on the difficulty (oops, I mean major stumbling block) of relating general relativity to the smallest dimensions - the froth, the infinities in the equations.

Which brings me back to my original question, a question that you DID NOT answer despite your overly long response -- is it space-time curvature or wave/particle gravitons?

Your eyes must have glazed over when you read the following in my interminably long post,
"The currently held view is that general relativity is our best model, but a deeper theory has to be found to solve some of the problems."
That, of course, is my view.

And if you cannot answer, then you should admit that you believe in gravity without fully comprehending the full extent of its nature. And I have a feeling that the pretend agnostics in this forum would be indignant to such a response.

The fundamental concept of Physics is to build mathematical models and test mathematical predictions derived from those models against reality via experiments. One can say "I believe that model is correct". That is the only way I can make sense of the phrase "believe in gravity".

Otherwise proofs of "I believe in gravity" would have to entail an experiment suggested by one unnamed person here throwing another unnamed person (rather than a lag bolt) out a window.

And if you cannot answer, then you should admit that you believe in gravity without fully comprehending the full extent of its nature. And I have a feeling that the pretend agnostics in this forum would be indignant to such a response.

Oh yes, I don't think any Physicist comprehends the full extent of the nature of gravity, especially at the smallest volumes of space. Who is a pretend agnostic here? Bring him on.

2. I noticed that you mention general relativity and hyper-inflation in the same breath without batting an eyelash. You claim that gravitons, if they do exist, cannot possibly travel faster than light. And yet, you can readily accept space expanding at speeds thousands of times faster than that.

And if you still cannot see the 'big picture', two objects whose space between them is expanding faster than light would be 'moving away from each other' faster than the speed of light.

I can see the big picture! I just saw the Battle Star Galactica series. That was a really big picture. Well at least it was long.

It is the fabric of space-time that expanded faster than the speed of light, not the gravitons. Locally they travel at the speed of light. That also explains why I didn't bat an eyelash.

I would prefer a limerick with an ostensibly toilet humor, in keeping with the nature of limericks.

LOL. There's nothing like toilet humor. But I guess it would have been more off-topic than my limerick.