B Inertial and gravitational mass

[Geo]

Doesn't the postulation of the inertial and gravitational mass equivalence suggest that GR is not a complete theory? (since it also cannot be explained as a neccessity by the anthropic principle)

 

[berkeman]

Doesn't the postulation of the inertial and gravitational mass equivalence suggest that GR is not a complete theory? (since it also cannot be explained as a neccessity by the anthropic principle)

Can you post links to the previous PF threads that you have read through about this, and ask specific questions about that reading that you are having trouble understanding? Thanks.

 

[Geo]

Can you post links to the previous PF threads that you have read through about this, and ask specific questions about that reading that you are having trouble understanding? Thanks.

I should have posted on beyond the standard model or general relativity.

It is just seems to me paradoxical for a theory to postulate an axiom that is subject of the microscopic and at the same time offer no bridge from the microscopic to the larger scale. Also the equivalence of inertial mass and gravitational mass shouldn't suggest that there is a hidden cause for this coincedence or one of the two is emergent?

(I can't point it to something i read it is just a question that popped and i wanted to know if it shouldn't for some reason or if it something that bothers the scientific community. Sorry if i am being silly i am just curious)

Thank you for your reply!

 

[Dale]

suggest that GR is not a complete theory

Why should a physical theory be complete? What scientific problem does it solve or cause? I just don’t see why it matters

 

[Geo]

Why should a physical theory be complete? What scientific problem does it solve or cause? I just don’t see why it matters

It solves the problem of progress i think, if you can see a bigger part of the picture you can make better guesses that will turn out to be confirmed by experiments. And after all as Feynman may have said (or may not actually couldn't find source) "physics is like sex sure it may give some practical result but that's not why we do it"

 

[Geo]

Seeing the bigger picture and searching for it when it is possible isn't enough of a reason to do science?

 

[PeterDonis]

Doesn't the postulation of the inertial and gravitational mass equivalence suggest that GR is not a complete theory?

GR doesn't "postulate" the equivalence of inertial and gravitational mass. That is a prediction of GR, not a postulate of it.

 

[Dale]

It solves the problem of progress i think, if you can see a bigger part of the picture you can make better guesses that will turn out to be confirmed by experiments.

I don’t think there is any reason to believe this claim. Einstein didn’t make good guesses or see the bigger picture because previous theories were complete. Nor did anyone else as far as I can tell.

Seeing the bigger picture and searching for it when it is possible isn't enough of a reason to do science?

Sure, it is a fine reason. It is just not connected to completeness.

 

[Geo]

I don’t think there is any reason to believe this claim. Einstein didn’t make good guesses or see the bigger picture because previous theories were complete. Nor did anyone else as far as I can tell.

Sure, it is a fine reason. It is just not connected to completeness.

My claim wasn't that completion as a state is what matters like a switch, if it was expressed that way my bad. My claim is that the hunt for completion and each step towards it is something that matters. So by saying a theory is incomplete the issue that arises is not why a theory should be complete but that if a theory is incomplete maybe there is more to discover in that direction. A fundamental driving force of science is the path towards completion. So to say that something is incomplete is important because a question is being asked and either is answered in the frame of the theory and move towards completion or the approach changes. Einstein in order to get to his theories he tried to answer the right questions and in order for the right question to exist there must be uneasiness towards incompletion

 

[Dale]

My claim is that the hunt for completion and each step towards it is something that matters. ... A fundamental driving force of science is the path towards completion.

I don’t think that there is any evidence to support any of these claims either. Where are you getting this stuff?

So to say that something is incomplete is important

Any theory that uses basic arithmetic and numbers is inherently incomplete! That is simply not a big concern amongst physicists. Philosophers and mathematicians may worry about it, but physicists just go ahead and use arithmetic anyway.

Einstein in order to get to his theories he tried to answer the right questions and in order for the right question to exist there must be uneasiness towards incompletion

No, his goal was not to solve the incompleteness of Newtonian physics. Relativity is incomplete in the same way as all other physical theories.

You may be confusing unification with completeness. It is a good goal to unify explanations, but completeness is not a desideratum for physical theories.

 

[Geo]

In my view It is. The fact that is unachieavble doesn't matter. Tha fact that you don't get there even with infinite steps doesn't matter. Completion as an impossible state is irrelevant but the steps towards it is partly how science is built within the mathematical framework from axioms to theorems to more theorems (this discovery of the consequances of axiomatization is a path towards completion ) and for the truths that can't be investigated inside the frame you create new frame. Unification in a preexisting framework is path towards completeness. Also physics isn't exactly a formal system to just accept that every completeness is impossible because interpretations assign scientific values to theorems and so does incompleteness. The fact that there is a shut up and calculate subgroup doesn't neccesserily dictate that interpetions are purely phillosophical. Physics after all was about explaining the world the minimal approach is usefull when things get complicated but doesn't strip physics from interpretations just assumes that it can also work without them

 

[Dale]

In my view It is.

So far you haven’t shown any evidence to support your view. Do you have any professional scientific reference that takes this stance, or a historical example that supports it?

Tha fact that you don't get there even with infinite steps doesn't matter. Completion as an impossible state is irrelevant but the steps towards it is partly how science is built

This doesn’t make any sense. You cannot make steps towards completeness. A theory is either complete or it is incomplete. And as Goedel proved any theory using arithmetic is incomplete. Physicists as a whole simply don’t care. I can cite every single theory using arithmetic despite its incompleteness.

Can you cite any professional physicist working on completeness? Again, I think you are confusing completeness with unification or universality.

Completeness is something different. It means that every true statement within a theory can be proven from the axioms of the theory. Read about Goedels incompleteness theorems. Even just basic arithmetic on the natural numbers is incomplete. All physical theories are built on arithmetic and are incomplete. I don’t know of any efforts by physicists to “fix” that.

At this point you have done nothing but speculate. If you wish to continue this discussion then please post a professional scientific reference that explains what you are talking about. I strongly suspect you mean something else than what is meant by “complete” in the sense of Goedels theorem.

 

[Geo]

Yes i am familliar with goedels theorems and that's why i ve stated that completeness is impossible. But that is irrelevant because i didnt meant it in goedels terms. Physics as a whole is not a formal system so the word completion can be used in a way that don't have to meet goedels criteria.
Even in goedel's term my point was that incompletence theorem is irrelevant because if you don't know that the certain truth i pointed out is unprovable within the formal system then proving it is not a task that you should not undertake

I should have used another word to avoid confusion and i am sorry for that, it is just that i didn't consider goedel's theorems relevant that made me continue. My fault

 

[Dale]

But that is irrelevant because i didnt meant it in goedels terms.

Please provide a reference that shows the sense in which you did mean it then. We have now wasted a lot of effort talking past each other.

 

[kimbyd]

Doesn't the postulation of the inertial and gravitational mass equivalence suggest that GR is not a complete theory? (since it also cannot be explained as a neccessity by the anthropic principle)

No. The equivalence of gravitational and inertial mass doesn't necessarily need any explanation.

The real problems with General Relativity are two-fold:
1) General Relativity predicts regions of space-time that it cannot describe. This concept is known as "geodesic incompleteness". For example, General Relativity predicts a singularity at the center of a black hole, but you can't actually use a map that includes the singularity and still provides sensible results (in essence, including the singularity means you end up dividing by zero at some point). But GR definitely shows the paths of objects can intersect with this region it can't describe.
2) General Relativity is incompatible with quantum mechanics. Quantum mechanics allows objects to be in a superposition of states. General Relativity uses a definition of matter that assumes that there's no such thing as a superposition. Mathematical attempts to extend General Relativity to allow for quantum effects have proven to be mathematically challenging (the methods used for the electromagnetic field, for instance, just don't work).

 

[Sorcerer]

Yes i am familliar with goedels theorems and that's why i ve stated that completeness is impossible. But that is irrelevant because i didnt meant it in goedels terms. Physics as a whole is not a formal system so the word completion can be used in a way that don't have to meet goedels criteria.
Even in goedel's term my point was that incompletence theorem is irrelevant because if you don't know that the certain truth i pointed out is unprovable within the formal system then proving it is not a task that you should not undertake

I should have used another word to avoid confusion and i am sorry for that, it is just that i didn't consider goedel's theorems relevant that made me continue. My fault

People on this forum like to be precise about definitions when it comes to science and math, and for good reason. Lay definitions tend to lead to confusion and wasted posts. E.g., my post. :P

 

[TeethWhitener]

What’s missing here is a definition of complete. @Dale is invoking Godel, for which “complete” had a precise technical meaning (a formal system is complete iff all valid statements in that system are provable). @Geo seems to be using complete in a non-technical sense, such that the meaning attached to the word is vague. Maybe if you give us a more precise formulation, we can help you more.

 

[pervect]

Doesn't the postulation of the inertial and gravitational mass equivalence suggest that GR is not a complete theory? (since it also cannot be explained as a neccessity by the anthropic principle)

I don't follow the argument at all. The anthropic principle is a philsophical principle, not a scientific one:

The anthropic principle is a philosophical consideration that observations of the Universe must be compatible with the conscious and sapient life that observes it.

I've seen the argument that Newtonian theory isn't complete, because Newtonian theory puts the equivalence down to "coincidence".

GR, to the extent it defines "mass" at all, doesn't bother to distinguish between the "inertial" and "gravitaitonal" mass. So it doesn't make any sense to me to claim that GR is incomplete on this basis. It makes some sense ot me to say that Newtonian physics isn't complete, on this basis, but that's not the claim.

I also suspect that completeness of a theory is also a philosphical issue. So we have two philosphical issues, one of which I don't see has any relevance at all (the anthropic principle), and the other of which appears to be being applied backwards from the usual statement.

This isn't a good start for a philosophicall discussion, which as I recall aren't supposed to happen on PF anyway - due to their tendency to be of low academic quality. This one seems well on the route to becoming a low-quality philosophical discussion already :(.

 

[Nugatory]

I've seen the argument that Newtonian theory isn't complete, because Newtonian theory puts the equivalence down to "coincidence".

I think you're right that that's the sort of thing people are thinking about when they casually use the word "incomplete". It would be better to call these open questions, and if having them makes a physical theory incomplete, then all theories are incomplete - ask enough "why?" questions and we always end up with "just because that's how the universe we live in works".

 

[Geo]

I don't follow the argument at all. The anthropic principle is a philsophical principle, not a scientific one:
I've seen the argument that Newtonian theory isn't complete, because Newtonian theory puts the equivalence down to "coincidence".

GR, to the extent it defines "mass" at all, doesn't bother to distinguish between the "inertial" and "gravitaitonal" mass. So it doesn't make any sense to me to claim that GR is incomplete on this basis. It makes some sense ot me to say that Newtonian physics isn't complete, on this basis, but that's not the claim.

I also suspect that completeness of a theory is also a philosphical issue. So we have two philosphical issues, one of which I don't see has any relevance at all (the anthropic principle), and the other of which appears to be being applied backwards from the usual statement.

This isn't a good start for a philosophicall discussion, which as I recall aren't supposed to happen on PF anyway - due to their tendency to be of low academic quality. This one seems well on the route to becoming a low-quality philosophical discussion already :(.

Anthropic reasoning is at least relevant as long as cosmology and/or string theory are relevant. Anthropic reasoning is not a metaphysical construct, is logical reasoning and as such is used in scientific papers and theories by scientists.
(Witten and Susskind to mention two who at least have referenced it)
https://arxiv.org/abs/hep-th/0302219

I can understand that it may be debatable in the community. And is a very abused and misused term but what i did is to state that anthropic explanations don't apply, so if you don't agree with it you can just dismiss that part and nothing changes on the initial post

P.s. sorry if my use of english is bad, it's not my native language

Thanks for the answers!

 

[Dale]

Still no reference regarding completeness in the sense you mean it?

 

[Geo]

I misused the word in the way that Nugatory explained. I would rephrase my question to that: Is the equivalence of gravitational and inertial mass something that is bothering the scientific community or explaining it as: "that's the way the universe works" is all we got and there is no evidence or reasoning that suggest otherwise?

 

[Dale]

Is the equivalence of gravitational and inertial mass something that is bothering the scientific community

As @pervect said, it bothered people in Newtonian gravity, but that bother is resolved in GR.

 

[A.T.]

Is the equivalence of gravitational and inertial mass something that is bothering the scientific community...

The scientific community should be bothered that it isn't more complicated?

 

[Nugatory]

I misused the word in the way that Nugatory explained. I would rephrase my question to that: Is the equivalence of gravitational and inertial mass something that is bothering the scientific community or explaining it as: "that's the way the universe works" is all we got and there is no evidence or reasoning that suggest otherwise?

The equivalence of gravitational and inertial mass in Newtonian gravity was something that bothered the scientific community, and even Newton himself. Why should they be the same? The universe works this way, but why? There's no answer in Newtonian gravity.

However, Einstein's general relativity provides a satisfactory explanation, so the question is no longer a major concern.

 

[kimbyd]

I don't follow the argument at all. The anthropic principle is a philsophical principle, not a scientific one:

This is a meaningless statement. You might as well state that equations are mathematical statements, not scientific ones.

There are reasonable reasons to object to some uses of the anthropic principle. This is not one of them.

 

[pervect]

This is a meaningless statement. You might as well state that equations are mathematical statements, not scientific ones.

There are reasonable reasons to object to some uses of the anthropic principle. This is not one of them.

At one time philsophical disucssions were banned on PF. I rechecked this point with the current PF global guidelines, apparently they may be slightly looser than I recall them being in the past.

Philosophical discussions are permitted only at the discretion of the mentors and may be deleted or closed without warning or appeal

I see you are a Science Advisor. Does applying the anthropic principle in this situation make any sense at all to you? Philosophy isn't my field, but this discussion does not seem like the sort of philosophical discussion that we want on PF.

 

[Sorcerer]

This is a meaningless statement. You might as well state that equations are mathematical statements, not scientific ones.

There are reasonable reasons to object to some uses of the anthropic principle. This is not one of them.

What explanatory or predictive power in terms of physics and theories about physics does the anthropic principle bring to the table here?

 

[Dale]

This thread has turned, per the OP, from one about completeness of theories to one about things that bother scientists. The anthropic principle makes some scientists feel less bothered by fine tuning.

I don’t think that it merits an in-depth discussion either way.