Is Gravity a Force?

[dimreepr]

9 hours ago, Davy_Jones said:

Because whether or not physicists purport to describe reality is relevant to how we should read a statement such as "Gravity is a fundamental force" or "Gravity is the curvature of spacetime".

Should such pronouncements be understood as a mere façon de parler, not to be taken at face value, or are we being told this the way things really are.

 

 

And who has the final word on these things again?

I'm tempted to say God, but I know what a shit-storm that would create here. 😉

[swansont]

10 hours ago, Davy_Jones said:

Because whether or not physicists purport to describe reality is relevant to how we should read a statement such as "Gravity is a fundamental force" or "Gravity is the curvature of spacetime".

Should such pronouncements be understood as a mere façon de parler, not to be taken at face value, or are we being told this the way things really are.

Those statements are descriptions of their respective models. In Newtonian terms, gravity is a fundamental force. In GR, it's the curvature of spacetime.

Such statements should be understood in the context of physics. They are not meant to be taken out of context. One has to be willing to invest in some study of the subject matter to provide that context. If not, too bad. You get what you paid for.

[Davy_Jones]

33 minutes ago, swansont said:

Those statements are descriptions of their respective models. In Newtonian terms, gravity is a fundamental force. In GR, it's the curvature of spacetime.

Such statements should be understood in the context of physics. They are not meant to be taken out of context. One has to be willing to invest in some study of the subject matter to provide that context. If not, too bad. You get what you paid for.

 

The obvious problem with simplistic comments such as these is that scientists themselves disagree over how scientific theories or statements ought to be understood.

Contrast, for example, Duhem and Einstein's radically opposed understanding of scientific theories (near the bottom of page 2).

Indeed, the very same scientist may not be consistent in his interpretation of statements or theories.

If you'd asked the Mach-influenced Einstein circa 1920, perhaps, how his general theory of relativity ought to be understood, you'd likely have been told something like this:

"It's a mathematical instrument, not to be taken at face value, not to be read literally."

Twenty years later, you'd have heard something quite different. Perhaps . . .

"My theory is to be understood as a representation of reality. It should be read literally."

 

Our old pal Arthur Fine again . . .

Quote

In particular, following his conversion [from antirealism to realism], Einstein wanted to claim genuine reality for the central theoretical entities of his general theory, the four-dimensional space-time manifold, and associated tensor fields. This is a serious business for if we grant his claim, then not only do space and time cease to be real, but so do virtually all of the usual dynamical qualities.

 

Edited September 3, 2021 by Davy_Jones

[swansont]

1 hour ago, Davy_Jones said:

 

The obvious problem with simplistic comments such as these is that scientists themselves disagree over how scientific theories or statements ought to be understood.

Contrast, for example, Duhem and Einstein's radically opposed understanding of scientific theories (near the bottom of page 2).

Indeed, the very same scientist may not be consistent in his interpretation of statements or theories.

If you'd asked the Mach-influenced Einstein circa 1920, perhaps, how his general theory of relativity ought to be understood, you'd likely have been told something like this:

"It's a mathematical instrument, not to be taken at face value, not to be read literally."

Twenty years later, you'd have heard something quite different. Perhaps . . .

"My theory is to be understood as a representation of reality. It should be read literally."

 

Our old pal Arthur Fine again . . .

 

"Realism" in physics has to do with whether entities have their properties when they are not being observed. Not whether the theories represent reality.  

 

Also, it might help to note that I never claimed that all of physics makes stuff up. Any science that admits it is making up calculational conveniences — even if that's only part of the science — can't be said to be describing reality. And pointing to elements that are not these conveniences does nothing to rebut that claim. It's a distraction to try. If your goal is to show physics describes reality, don't ignore my examples of calculational conveniences. 

Physics has a lot that can't be directly observed (i.e. by eye) so there's a lot of "what's going on inside this black box" and if the behavior is consistent with there being a stick with a spring attached to it, that's how it's modeled. But since we can't actually know what's inside the box, we don't know if that's the reality. We only know what we get from experiment. We won't know, for example, what color the stick is, or what kind of wood it is, unless that affects an observational outcome. If we don't know the color of the stick, or what kind of wood it is, we haven't described reality.

 

[Davy_Jones]

19 minutes ago, swansont said:

If your goal is to show physics describes reality, don't ignore my examples of calculational conveniences. 

 

No, that's not my goal.

You've been telling us (and I quote) "we know physics isn't trying to describe reality"

What I've been showing is certain of your peers, including some of the finest (Einstein, Weinberg . . ), apparently didn't receive the memo; they don't "know" what you (plural) "know".

[dimreepr]

1 hour ago, Davy_Jones said:

Twenty years later, you'd have heard something quite different. Perhaps . . .

That's the god of the gaps argument in reverse... 

[Davy_Jones]

1 minute ago, dimreepr said:

That's the god of the gaps argument in reverse... 

Einstein's views on these matters are well documented, sir.

Would you like me to recommend some reading?

I'm not being sarcastic. Gripping stuff indeed. Or at least I thought so.

[TheVat]

11 hours ago, MigL said:

'True', and 'truth' are subjective, and R Dawkins would be the first to agree.
( and the reason I use the scare quotation marks you previously asked about )

 

Fair warning - if our sunken locker owner is swimming towards philosophy (which may be where this thread was always headed) then truth is,  in the correspondence theory,  a statement which correctly corresponds to an external state of affairs, i. e. to a fact about reality.   The correspondence theory, at least as Bertie Russell advanced it,  is associated with metaphysical realism.  So,  if a realist utters the phrase "gravity is curved space-time, " and holds that to be true,  she is NOT merely suggesting that gravity is a mathematical model with some curved geometry in it,  or that objects move as if space were curved, or that we're just passing around some handy tools to predict where Mercury will be next Tuesday.   She is saying that space-time is curved,  just like the rail on that rocking chair except much more strangely.   IOW,  a statement is being made that purports to objective truth. 

Just saying,  not all definitions of "true" would presume a subjective stance.   

[swansont]

26 minutes ago, Davy_Jones said:

 

No, that's not my goal.

You've been telling us (and I quote) "we know physics isn't trying to describe reality"

What I've been showing is certain of your peers, including some of the finest (Einstein, Weinberg . . ), apparently didn't receive the memo; they don't "know" what you (plural) "know".

"I think this theory describes reality" is not the same as "the goal of physics is to describe reality"

The latter requires one to cover all the bases. All of physics has to be trying to describe reality. Cherry-picking doesn't count. All it takes to rebut it is a single counterexample, and I have given several.

Also, you would have to give assurances that any person you quote is not invoking philosophy in any way.

[Davy_Jones]

Quite so, Mr Vat,

There are certain statements that scientists make, or theoretical entities posited, which are obviously not meant to be taken literally.

Swansont mentioned red quarks or something (can't remember exactly). Or consider point masses and ideal gases, perhaps.

Anyone who takes these things literally is . . . well, missing the point . . . massively. Duh!

But it's not always so obvious how a statement or a theory is to be interpreted . . .

Edited September 3, 2021 by Davy_Jones

[dimreepr]

10 minutes ago, Davy_Jones said:

Einstein's views on these matters are well documented, sir.

Would you like me to recommend some reading?

I'm not being sarcastic. Gripping stuff indeed. Or at least I thought so.

 

[DrDon]

OK...this is Don Lincoln here.  My name was invoked and a little bird came and suggested I pop in.  I have not read all of the chat above.

Regarding gravity and belief.  First, belief is a non-scientific word....or at least it has lots of really ridiculous connotations.  When a scientist says that they believe in a theory, they're just being sloppy.  (And I include me in that.  But language is language and we do the best we can.)  "Belief" to a scientist simply means in this context, that the theory is consistent with all relevant known data and we can take it as an approximation of the truth.

Now, on gravity.  It's very clear that Einstein's formulation is more accurate than Newton's or, for that matter, any other suggested theory of gravity.  It's also eminently clear that general relativity fails at small sizes and very high gravitational fields.  For that, we will need a theory of quantum gravity.  Some ideas have been put forward, but none have been validated in any way, meaning to all intents and purposes, we have no believable theory of quantum gravity.

However, given the established validity of general relativity, it follows that that when quantum gravity is evaluated for gravitational fields not strong enough to manifest their quantum behavior, that the predictions will be effectively identical to general relativity.  From that, we can infer that the bending of spacetime will be valid in quantum formulations as well, although there may be additional explanatory insights.

Accordingly, I feel quite comfortable in saying that I believe in general relativity in the realm in which it is applicable.  Similarly, I believe in Newtonian gravity in the realm in which it is applicable.  After all, we shot the New Horizon probe to Pluto - traveling billions of miles, passing by several planets, and NASA hit a target 10 km in size.  Newton works.  Einstein works.  Well, until they don't.  That's all of science.  Theories work as long as they work.

One other piddly point.  Our current understanding of gravity is qualitatively different from the other known forces.  Sure.  Some of you have been discussing the meaning of the word force.  Classically, it means something that has the potential to cause an object's velocity to change according to some reference frame.  At the quantum level, it has a somewhat different meaning.  There it means that the phenomenon can effect some sort of change, be it changing velocity or causing particle decay.  The fact that the word has a nuanced meaning depending on the size scale at which it is being evaluated implies that the word is fuzzy and anybody trying to nail it down, will fail.

This brings up a more important point is that the mapping of words onto scientific concepts is a dangerous endeavor.  It is highly unlikely that any word can be mapped into a concept so well that it is impossible to find an exception.  There will aways likely be a qualification of some sort.  Accordingly, don't hold onto words very hard.  They will fail you.  Instead, understand the more nuanced scientific principle for which the word is nothing more than an imperfect and ultimately inaccurate placeholder.

For the person who complained about the videos being at a commercial site.  Well, I've worked for over three decades learning this stuff.  I spent half a year writing the lectures, which comprise 12 hours of clearly-explained advanced science.  I spent a week filming the project and many hours ensuring that the quality of the video and audio product was high.

And someone has the temerity to suggest that I and the production company shouldn't be compensated for that effort?  It's like whining that someone won't come and paint your house.  Go ahead - enroll in the streaming service - you will have access to an astonishing amount of knowledge and expertise, translated in such a way that non-experts can understand a portion of the more complex ideas.

BTW I was a solid presence at SPCF for a long time, but I will not be a regular here.  I have just contracted my 5th or  6th book and that will take enough time that active involvement here is simply not in the cards.

Cheers....

Edited September 3, 2021 by DrDon

[swansont]

Quote

It's also eminently clear that general relativity fails at small sizes and very high gravitational fields.

Which, to one of the points of this thread, would not be the case if it gave us "reality"

 

[TheVat]

Thanks for visiting, @DrDon.  Good luck with your 5th or 6th book (I hope this ordinal number indeterminacy does not reflect some sort of Schrodingeresque uncertainty as to the book's existence).

Regarding

"This brings up a more important point is that the mapping of words onto scientific concepts is a dangerous endeavor.  It is highly unlikely that any word can be mapped into a concept so well that it is impossible to find an exception.  There will aways likely be a qualification of some sort.  Accordingly, don't hold onto words very hard.  They will fail you.  Instead, understand the more nuanced scientific principle for which the word is nothing more than an imperfect and ultimately inaccurate placeholder."

This should induce caution in all armchair philosophers who want to reify certain words.   

Edited September 3, 2021 by TheVat
Fat thumbs?

[joigus]

20 hours ago, Davy_Jones said:

Edit P.S. 

Whoops! I just googled Steven Weinberg. Turns out he's six feet under too, as of a few weeks ago. RIP!

Steven Weinberg was a great physicist. Einstein was too. Both have been highly influencial. But I think it's fair to say neither of them are very good at representing the "standard view" of their respective generations.

17 hours ago, MigL said:

As my opinions and thoughts on the nature of Gravity have been split-off from a thread appropriately entitled "Is Gravity a Force ?", I have to wonder ...
What does the ideology of scientists, and the purpose of Science, which is being discussed at some length, have to do with the nature of Gravity ???

Couldn't agree more. We're asymptotically going into meta-physics and epi-stemology.  

 

[beecee]

6 hours ago, DrDon said:

OK...this is Don Lincoln here.  My name was invoked and a little bird came and suggested I pop in.  I have not read all of the chat above.

Regarding gravity and belief.  First, belief is a non-scientific word....or at least it has lots of really ridiculous connotations.  When a scientist says that they believe in a theory, they're just being sloppy.  (And I include me in that.  But language is language and we do the best we can.)  "Belief" to a scientist simply means in this context, that the theory is consistent with all relevant known data and we can take it as an approximation of the truth.

Now, on gravity.  It's very clear that Einstein's formulation is more accurate than Newton's or, for that matter, any other suggested theory of gravity.  It's also eminently clear that general relativity fails at small sizes and very high gravitational fields.  For that, we will need a theory of quantum gravity.  Some ideas have been put forward, but none have been validated in any way, meaning to all intents and purposes, we have no believable theory of quantum gravity.

However, given the established validity of general relativity, it follows that that when quantum gravity is evaluated for gravitational fields not strong enough to manifest their quantum behavior, that the predictions will be effectively identical to general relativity.  From that, we can infer that the bending of spacetime will be valid in quantum formulations as well, although there may be additional explanatory insights.

Accordingly, I feel quite comfortable in saying that I believe in general relativity in the realm in which it is applicable.  Similarly, I believe in Newtonian gravity in the realm in which it is applicable.  After all, we shot the New Horizon probe to Pluto - traveling billions of miles, passing by several planets, and NASA hit a target 10 km in size.  Newton works.  Einstein works.  Well, until they don't.  That's all of science.  Theories work as long as they work.

One other piddly point.  Our current understanding of gravity is qualitatively different from the other known forces.  Sure.  Some of you have been discussing the meaning of the word force.  Classically, it means something that has the potential to cause an object's velocity to change according to some reference frame.  At the quantum level, it has a somewhat different meaning.  There it means that the phenomenon can effect some sort of change, be it changing velocity or causing particle decay.  The fact that the word has a nuanced meaning depending on the size scale at which it is being evaluated implies that the word is fuzzy and anybody trying to nail it down, will fail.

This brings up a more important point is that the mapping of words onto scientific concepts is a dangerous endeavor.  It is highly unlikely that any word can be mapped into a concept so well that it is impossible to find an exception.  There will aways likely be a qualification of some sort.  Accordingly, don't hold onto words very hard.  They will fail you.  Instead, understand the more nuanced scientific principle for which the word is nothing more than an imperfect and ultimately inaccurate placeholder.

For the person who complained about the videos being at a commercial site.  Well, I've worked for over three decades learning this stuff.  I spent half a year writing the lectures, which comprise 12 hours of clearly-explained advanced science.  I spent a week filming the project and many hours ensuring that the quality of the video and audio product was high.

And someone has the temerity to suggest that I and the production company shouldn't be compensated for that effort?  It's like whining that someone won't come and paint your house.  Go ahead - enroll in the streaming service - you will have access to an astonishing amount of knowledge and expertise, translated in such a way that non-experts can understand a portion of the more complex ideas.

BTW I was a solid presence at SPCF for a long time, but I will not be a regular here.  I have just contracted my 5th or  6th book and that will take enough time that active involvement here is simply not in the cards.

Cheers....

Bloody great post! and welcome! Funnily enough though, that's what most of us have been saying. One part of your post I would like to comment on is...

6 hours ago, DrDon said:

However, given the established validity of general relativity, it follows that that when quantum gravity is evaluated for gravitational fields not strong enough to manifest their quantum behavior, that the predictions will be effectively identical to general relativity.  From that, we can infer that the bending of spacetime will be valid in quantum formulations as well, although there may be additional explanatory insights.

On a now defunct science forum, we once had a renowned astrophysicist. He still presently operates at the Anglo Australian Observatory at Coonabarabran in the Warrumbungles NSW. He in a debate one day, noted that any future validated QGT will most likley also encompass the BB model of universal evolution. That seems to fit in with your own inference that it will also accomadate spacetime geometry as per GR. 

That certainly says a lot about the powerful nature of GR and the BB that we presently accept.

A question if I may...How long would you anticipate we will have a validated QGT? It would seem to me that to do that, we would some how need the technology to observe at the quantum/Planck level. That seems to this lay person, to be still a tall order?

3 hours ago, TheVat said:

Thanks for visiting, @DrDon.  Good luck with your 5th or 6th book (I hope this ordinal number indeterminacy does not reflect some sort of Schrodingeresque uncertainty as to the book's existence).

This should induce caution in all armchair philosophers who want to reify certain words.   

Thank you also for inviting him. I love your last senetnce and find it very relevant.

Edited September 3, 2021 by beecee

[Davy_Jones]

@DrDon

First and foremost, I'm thrilled you're able to join us. Why, I feel a little weak at the knees as I type this LOL.

I've been thoroughly enjoying your Great Courses "The Evidence for Modern Physics" series . . . for the second time! Up to lecture 17 so far, but what the hell, since you're here I'm gonna watch the whole Megillah again and keep notes of stuff I'd like to ask you (er, do you charge?) . . . then mercilessly bleed ya dry!

You have a wonderful delivery, moreover wit and self-effacing humor that is very endearing. It's just that Tom Cruise smile at the end of every lecture that needs a little work. Hahahaha!

I'm in no position to question your expert knowledge in physics; happy enough just to drool in awe as @TheVat probably did over Isaac Asimov (he's such a name-dropper, eh?).

Seriously, though, there are some things you say, e.g. regarding proof, confirmation, evidence, etc. (the bread and butter of the philosophy of science) that I think we might discuss productively.

Alright, that's it for the phatic pleasantries. We'll get our hands dirty starting from next post.

P.S. Any chance of a signed copy of that new book?

 

 

7 hours ago, swansont said:

Which, to one of the points of this thread, would not be the case if it gave us "reality"

 

Well, things are never quite that simple. When data sits uncomfortably with theory, one option is to declare the theory false like a well behaved Popperian and head off to the pub to drown your sorrows.

There are, of course, other options.

1. Do nothing at all. Scratch your head and wonder why data is so recalcitrant.

Or more commonly . . .

2. Declare the theory to be perfectly healthy and try to find some way to reconcile the awkward data/evidence with the theory. The problem does not necessarily lie with the theory; it may lie with the "auxiliary hypotheses", "background knowledge" or whatever you wanna call them.

 

After all, when it was noticed circa 1850 or so that Uranus was not behaving in the manner Newtonian physics predicted (i.e. data/evidence clashed with theory) I doubt it crossed anyone's mind that Newtonian physics might be at fault. What they did instead was say "There must be something wrong with our background assumptions. Hmm, perhaps there's something out there that we're not seeing . . ."

 

Enter Neptune.

 

 

8 hours ago, DrDon said:

Regarding gravity and belief.  First, belief is a non-scientific word....or at least it has lots of really ridiculous connotations.  When a scientist says that they believe in a theory, they're just being sloppy.  (And I include me in that.  But language is language and we do the best we can.)  "Belief" to a scientist simply means in this context, that the theory is consistent with all relevant known data and we can take it as an approximation of the truth.

 

Can't resist getting started right away. This is exciting

Well, first of all, "belief" is a scientific word; it's part of the standard ontology of psychology.

More to the point, though, with regards your comments above, as I've cautioned other members, I'd be a little wary of speaking for all scientists. They're an eclectic mob, ya know.

As for "consistent with all relevant known data" . . . do you know any theories like that?

Steven Weinberg again:

Quote

Any theory like Newton's theory of gravitation that has an enormous scope of application is always plagued by experimental anomalies. There is no theory that is not contradicted by some experiment.

Steven Weinberg, "Dreams of a Final Theory", p93

 

 

Things are about to get a lot heavier . . .

@DrDon, you tell us:

" "Belief" to a scientist simply means in this context, that the theory is consistent with all relevant known data and we can take it as an approximation of the truth."

and

"Accordingly, I feel quite comfortable in saying that I believe in general relativity in the realm in which it is applicable.  Similarly, I believe in Newtonian gravity in the realm in which it is applicable." 

 

Once again the fire-breathing dragon of consistency rears its ugly head. We're all agreed that both theories yield accurate predictions. That said, both theories are conceptually wildly at odds with one another. Both theories make logically incompatible claims.

In other words, if one theory is true, or approximately so, it is not logically possible that the other is, or even approximately so.

For example, if Theory A claims that space and time are absolute and uniform, Theory B claims that they are not, as a matter of simple logic, both cannot be true.

Quote

We can indeed see from Newton's formulation of it that the concept of absolute space, which comprised that of absolute rest, made him feel uncomfortable; he realized that there seemed to be nothing in experience corresponding to this last concept. He was also not quite comfortable about the introduction of forces operating at a distance. But the tremendous practical success of his doctrines may well have prevented him and the physicists of the eighteenth and nineteenth centuries from recognizing the fictitious character of the foundations of his system.

- "On the Methods of Theoretical Physics", Albert Einstein, 

Edited September 4, 2021 by Davy_Jones
My dog has no nose

[beecee]

1 hour ago, Davy_Jones said:

 Both theories make logically incompatible claims.

In other words, if one theory is true, or approximately so, it is not logically possible that the other is, or even approximately so.

For example, if Theory A claims that space and time are absolute and uniform, theory B claims that they are not, as a matter of simple logic, both cannot be true.

Again, any  truth and reality that you are on about, may simply not exist, or even be beyond scientific knowledge.....we really have no idea, as we have no idea about the nature of gravity. Why does mass warp spacetime? Why is GR not applicable with the quantum realm? and the core of BH's? Are gravitons real? Are quarks really coloured?

We have two models that while incomplete and both an approximation, still give us correct answers [as you yourself noted with Uranus and Neptune] We havn't yet got a TOE. 

I would also add that truth and/or reality and reference to them, sometimes have a spiritual undertone.

Edited September 4, 2021 by beecee

[Davy_Jones]

10 minutes ago, beecee said:

Again, any  truth and reality that you are on about, may simply not exist . . .

One can only wonder where you're typing that post from then

And mind your own business. It's the job of philosophers to say things like "reality doesn't exist" LOL

(I'm kidding)

Edited September 4, 2021 by Davy_Jones

[beecee]

13 minutes ago, Davy_Jones said:

One can only wonder where you're typing that post from then

And mind your own business. It's the job of philosophers to say things like "reality doesn't exist" LOL

(I'm kidding)

We also desribe and predict gravity quite well, but still do not know its true nature. How do you know I'm not a robot? And I said nothing about reality not existing, just that it may not exist, and/or maybe beyond science.

12 hours ago, dimreepr said:

I'm tempted to say God, but I know what a shit-storm that would create here. 😉

Probably as the supernatural, paranormal and spirituality are unscientific mythical concepts.

10 hours ago, swansont said:

"Realism" in physics has to do with whether entities have their properties when they are not being observed. Not whether the theories represent reality.  

Physics has a lot that can't be directly observed (i.e. by eye) so there's a lot of "what's going on inside this black box" and if the behavior is consistent with there being a stick with a spring attached to it, that's how it's modeled. But since we can't actually know what's inside the box, we don't know if that's the reality. We only know what we get from experiment. We won't know, for example, what color the stick is, or what kind of wood it is, unless that affects an observational outcome. If we don't know the color of the stick, or what kind of wood it is, we haven't described reality.

That's the beauty of science....and why they remain "scientific theories" always open to modification, change, or scrapping. The scientific methodology and modelling has served us well and continues to serve well, without any need for defined truth and/or realty, although as I previously said, if we should accidently reveal such fundamental truth and reality, all well and good.

Edited September 4, 2021 by beecee

[Davy_Jones]

I'd like to quote once more from Prof. Don Lincoln's marvellous lecture series (see above).

Lecture 16, "The Hunt for Gravitational Waves", 5:50 mins . . .

"Gone are the days of Newton's force of gravity. According to Einstein's equations, gravity is literally the bending of space"

 

Two questions for Don and everyone else:

It has been expressed in this thread that science cannot answer the question "What is gravity?" (on the grounds that it's metaphysical).

Q1: Isn't Einstein doing exactly that? Isn't Einstein saying the answer to the question "What is gravity?" is "the bending of space"?

(Even if the answer is wrong, he is still providing an answer.)

 

It has also been expressed in this thread that no one knows what gravity is.

Q2: If Einstein's theory is correct, is it not the case that lots of people know what gravity is? Namely, all those who believe his theory.
 

[beecee]

1 hour ago, Davy_Jones said:

I'd like to quote once more from Prof. Don Lincoln's marvellous lecture series (see above).

Lecture 16, "The Hunt for Gravitational Waves", 5:50 mins . . .

"Gone are the days of Newton's force of gravity. According to Einstein's equations, gravity is literally the bending of space"

 

Two questions for Don and everyone else:

It has been expressed in this thread that science cannot answer the question "What is gravity?" (on the grounds that it's metaphysical).

Q1: Isn't Einstein doing exactly that? Isn't Einstein saying the answer to the question "What is gravity?" is "the bending of space"?

(Even if the answer is wrong, he is still providing an answer.)

 

It has also been expressed in this thread that no one knows what gravity is.

Q2: If Einstein's theory is correct, is it not the case that lots of people know what gravity is? Namely, all those who believe his theory.
 

Gravity is described as the geometry of spacetime within the model GR. It is our superior model of gravity, but still has limitations and regions of non applicability. 

In many circumstances the fascination with truth and/or reality, has religious  undertones.

Edited September 4, 2021 by beecee

[Davy_Jones]

7 hours ago, joigus said:

 

Couldn't agree more. We're asymptotically going into meta-physics and epi-stemology.  

 

 

To that I can only offer the words of a very wise man . . .

"Science without epistemology is -- insofar as it is thinkable at all -- primitive and muddled" 
-- Albert Einstein

[beecee]

[Davy_Jones]

On 9/2/2021 at 6:47 PM, swansont said:

The professor is confirming the validity of general relativity. Any more is you reading something into it.

 The above was in response to my:

 

QUOTE

Near the end of Lecture 15, "The Awesome Evidence for General Relativity", at the 28:30 mark, Prof. Lincoln perorates:

"I hope I've convinced you that there are very good reasons that general relativity has been very clearly validated. I mean I know that it's very weird to think of gravity as the bending of space and time, but it's just literally impossible to believe otherwise these days."

So, pace other contributors to the thread--perfectly entitled to their opinions--who have told us that no one knows what gravity is, or science cannot answer questions such as what gravity is, clearly, Prof. Lincoln does not share your skepticism.

The good professor is not only telling us what gravity is (It's the bending of space and time), but that to believe that gravity is anything other than the bending of space and time is not possible.

A tad hyperbolic if you ask me, but hey, I toss it out here for consideration.

UNQUOTE

 

 

Since the professor is now with us, perhaps he'd be kind enough to expatiate. Am I reading too much into what you said, sir?

Edited September 4, 2021 by Davy_Jones