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The Hole Argument (stanford.edu)
55 points by infinity on July 31, 2015 | hide | past | web | favorite | 18 comments



I never know: should we just click this link and "wait for it," or, will OP give us a bit of insight into the content's context?


The mathematical models of space and time suggest that there might be a philosophical stance where "spacetime" itself is a physical object. What this means, really, is that one might want to talk about situations where two choices of spacetimes differ in configuration.

The problem with this POV is that "internally" we're only able to perceive certain things and, indeed, these things are ignorant to changes in spacetime configuration. This is exactly the power of this mathematical formulation.

So the Hole is a thought experiment where you construct two differently configured spacetimes, ones you might want to distinguish between, and then show that the perceptions of these two cannot differ in meaningful ways.

And then one should question as to whether or not they want to believe with any fervor that spacetime has a physical sense.


>And then one should question as to whether or not they want to believe with any fervor that spacetime has a physical sense.

As I read that, I felt it was a bit too strong - isn't the issue whether spacetime have an independent physical sense? I went back to the article, and I see that it starts "What is space? What is time? Do they exist independently of the things and processes in them?" As the argument starts with a manifold of events, an answer of 'no' to the third question seems reasonable to me (though I realize, from experience, that that's probably because I haven't fully grasped the argument.)

As far as I can tell, the article doesn't indicate any particular problem with the 'no' answer.

In the argument in section 10.3.3, don't you have to accept the reality of K(t) in order to see a paradox?


Didn't read in enough detail to pick out the use of K.

My understanding is that the separation comes from an internal/external dichotomy. Internally we only have our observations as support for the metric, externally (and for a nicer mathematical construction) we need more structure including explicit construction of the manifold. This feels plausible externally, but involves some amount of arbitrary choice which is what is flexed to introduce the paradox.

To be honest, I'm not much of a physicist, but this idea shows up all over in mathematics.


As a philosophy major I'll try to give the simplest way I know how to explain this. If you are testing a scientific theory, what might be some criteria for evaluating that theory? First you want the theory to be verifiable, probably also falsifiable, you also want it to be able replicate your results, independent observation is another. There are other criteria obviously but I'm not going to be able to explain an entire branch of philosophy in one post, so bear with me. The Hole Argument comes in as a thought experiment where you have testers in different spacetime "holes" who are independent observers, replicating the results of a scientific experiment, the question to be answered is whether or not independent observation is a good enough criteria for evaluating a theory since the testers are epistemically blind to one another or if theories should be held to some higher standard. That's the short of it.


Gauge transformations in physical theories can lead to possibly unpalatable conclusions if you believe a certain way.

It certainly wouldn't be the first time. Mostly, people just get used to it and live with "Nature is a perverse bastard."

I don't know how much I like the tone: I may be reading it with a bias. But hey, who knows where the next insight will come.


>> Gauge transformations in physical theories can lead to possibly unpalatable conclusions if you believe a certain way.

This sounds very interesting. Could you provide some examples?


Check out section 10.3 in posted article.

The short of it is that lots of physical observables in nature are derivatives of things. So if the underlying thing contains a constant term, it goes away. Because it goes away, you are free to choose it however you like and still get the same observable result.

So the question then becomes how real you believe those underlying objects are. The linked article constructs a set up to challenge that.


I think there's an odd sense where people think derivatives arise from "change in things" instead of being principal. It's sensible from our personal mindset to believe this but there's no reason a priori.

So that's kind of the question: can things like derivatives be the structure of space time or must they be arising from some underlying thing? Since the underlying thug involves some arbitrary, unobservable choice... it's a bit challenging.


I've run across stuff in mathematical contexts where they'll throw in a derivative (or other operator) just to get the expression in the form they want.

It struck me as a bit odd, because hey, where's the change happening? But ultimately it was just a convenience, and maybe it had some underlying meaning in the original context, and maybe it didn't.


But then sometimes it might be the case that the truly persistent thing is the derivative and the algebra forced your hand for good reason!


in the OP's defense, it's kinda a dense read


So basically you want to know whether you're interested in something without actually bothering to understand it?

I'm increasingly frustrated with this mindset. Yes, you don't have the time to read everything. The answer to this, in my estimation, is gear your reading toward information sources with higher density of quality. If, instead, you only read things with titles that summarize the content for you, you're limiting yourself to ideas which can be summarized in a 5- to 20-word blurb. These ideas and simple, and consequently, frequently wrong. Reality is often complicated and it's not possible to dumb it down into a "1 weird metaphysical argument that will make your brain grow 10 inches"-style clickbait headline.

I do think it's a courtesy to the reader to provide keywords in a title that make it easy to reference and that create an effective vocabulary for talking about the topic (which this title does). I don't think that authors have any responsibility to dumb down their titles into summaries for those who can't be arsed to hear them out.

As an aside: generally stuff published on Stanford's website is written by top professionals in various fields, which makes it a high-density source of good information.


>So basically you want to know whether you're interested in something without actually bothering to understand it? [...] I don't think that authors have any responsibility to dumb down their titles into summaries for those who can't be arsed to hear them out.

I may have misunderstood voidz's question but I don't think he's asking for a dumbed-down tldr or something to be spoonfed to him.

The keyword I read in his question was "context". In other words, was there another event or news article that prompted the OP to submit "Hole Argument" and for multiple people to vote on it enough to have it show up on the HN front page?

For example, on the front page there's a post "Python is the new BASIC"... it's an old 2008 article... why is it there?!? I think many of us can guess that its submission was possibly triggered by the other article "Guido on Python" from EuroCon 2015". Reverse engineering the context is a little easier in that case.

The "Hole Argument" is interesting, but there are thousands of interesting physics articles... so maybe there's another trigger that prompted its submission. E.g. a recent discovery at Hadron Collider, or one of the authors recently passed away, etc.

Of course, the article's submission may be purely random in which case there is no context. The submitter (infinity) can clarify that for the voidz.


> I may have misunderstood voidz's question but I don't think he's asking for a dumbed-down tldr or something to be spoonfed to him.

Okay, I'll just quote voidz's response to the same post you're responding to:

> Most of all, I wanted to kick off the discussion by asking if we should guess what information the link would give us. From the title alone, I have no idea. It's a play on words ("the hole / whole argument"), but beyond that, i had no clue.

Can you think of a way to get "what information the link would give us" without it being a dumbed-down tldr?


I couldn't have said it better myself. Thanks for taking the effort to explain so eloquently what I meant, when I asked my question. I'm not a native English speaker, but you still got it right. ^ht


You are projecting. I said nothing about having time or not, nor did I share any mindset, nor did I say whether I was bothered. Most of all, I wanted to kick off the discussion by asking if we should guess what information the link would give us. From the title alone, I have no idea. It's a play on words ("the hole / whole argument"), but beyond that, i had no clue.

But, after reading (trying to, rather), I felt that the subject deserved some explaining for people who are unfamiliar with the topic as well. Hence my request for context.

I have never asked for anyone to dumb down anything, that's your frame of mind, please don't put that on me. In general, it seems you just tend to get frustrated by your own frustration. That might be a vicious circle, but I'm no part of it. Should I dumb this down for you? Or do you catch my drift.


Actually some of it on SEP is written by undergrads which is kind of awesome in my opinion but it is certainly vetted before being posted.




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