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prase comments on Query the LessWrong Hivemind - Less Wrong Discussion
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So you are against induction, in general? Nothing directly unobservable is knowable? Do you really think that the assumption that the physical laws are the same outside Earth's light cone as they are inside is an error?
It's not that I am against induction (in fact, I routinely refer to Popperian Falsificationism as the resolution to Hume's Problem of Induction). Instead, I am acknowledging that induction has limits. What inductive process will allow you to derive the words written on the can in front of me as I type this?
No. All things which are entirely unobservable are unknowable. Indirect observation qualifies as a form of observation. That which is outside of our lightcone is entirely unobservable (as yet.)
We have no basis for the assumption at all. It furthermore rests on the additional assumption *that there is even a "physical" at all there.
Furthermore: there is some disagreement at the "bleeding edge" of physics as to whether gravity is a constant. And that's just what we can observe.
I recall the admonition that "The Universe is Queerer than we can suppose". From it, I have a generalized principle: when I have no information to make assertions with, I acknowledge my ignorance. When, however, I observe that no information is available, I note this fact and move on.
Making 'guesses' as to the 'probability' of assertions when you know your priors are entirely arbitrary is ... counterproductive. It can only serve to prime you.
I used to do the same thing and felt quite satisfied doing so. I thought it was settled. But then I started learning about Solomonoff Induction which I now believe is a better solution. If you are a hardcore Popperian Falsification fan, even after learning about Solomonoff Induction, I would suggest reading David Deutsch's The Beginning of Infinity. It pushes falsification as far as I've ever seen and even when you find yourself disagreeing, it's an interesting read.
We have observed that the universe is regular and that there is nothing special about Earth, as far as we know. That's quite a good basis for the assumptions, in my opinion. Although I am not completely sure what you mean by "physical" here.
I don't understand why, in the title of the linked article, possible information leak from black holes is referred to as "gravity not being constant". Nor I understand what this has to do with induction or falsificationism.
The Copernican Principle has served us well. Ironically, it turns out it was somewhat misguided about the Earth itself. I don't believe that out of the single-digit percentage of planets yet discovered that are categorized as "Earth-like", that any of them fall particularly close on the parameters relevant to "humans would be comfortable living here if they brought the right flora and fauna with them Spore-style"). Certainly none of them have been around yellow stars and all have had rather bizarre irradiation profiles.
As to the regularity of the universe -- well, that's what the notion of a variable constant of gravity was about. I've seen conjecture that 'dark matter'/'dark energy' might be nothing more than our failure to recognize that the gravitational constant changes in some regions of space. The thing about the information leak from black holes has to to with a conjectured way of testing that (even Hawking Radiation doesn't retrieve information from black holes; that according to what we now know is a one-way trip.)
Well, imagine spacetime has a definite, discrete barrier. On our side there's still 'physical' stuff. On the outside of that barrier... there's nothing. No physical anything. Not even space. (This gets headachey when we start realizing that means there's no "outside" outside there...)
Suffice it to say that I was being 'colorful' in saying that we have no way of knowing that the universe doesn't just stop at the edge of the Earth's lightcone. (It's actually a pretty mundane assertion; most discussions on the matter I've ever heard of make this the null hypothesis.)
You have a better epistemology for evaluating beliefs about the observable universe?
By special, when speaking about fundamental physics, I certainly don't mean "is capable of maintaining carbon-based life". Earth may be unique in this respect while the physical laws being the same everywhere.
Even if this were true, so what? Instead of standard Einstein equations one would get a modified set of equations with a new dynamical field instead of constant G. This wouldn't challenge regularity of the universe.
The null hypothesis is what? That the universe stops just there, or that we have no way of knowing?
It seems strange. If you walk along an unknown road and are forced to return at one point, do you (without additional information) suppose that the road ends just beyond the last corner you have seen?
By the way, the relevant Earth's lightcone is precisely your lightcone or mine?
In practice the former.