pdonis

38 ms·

721.
by pdonis 2y ago
> My point was to illustrate that our physics models don't agree on the nature of this expansion (Hubble tension) The Hubble tension is not an uncertainty about the "nature" of the expansion. No matter how that tension g
722.
by pdonis 2y ago
> I believe we shouldn't ignore it. To be more precisely, you should ignore it if you want to actually understand the science. Pop science presentations will not help you understand the science. That's not what they'r
723.
by pdonis 2y ago
> As a rule of thumb I worry when I hear something described in absolute or moralistic terms: rarely do complicated things happen just out of pure villainy. True, but to paraphrase Arthur C. Clarke, sufficiently advanced ignorance is
724.
by pdonis 2y ago
> a simple hill climbing algorithm Not at all. There is no such thing in a landscape that is changing on time scales that are visible to people, as our societies are. You can't stay stuck on a local maximum if the landscape change
725.
by pdonis 2y ago
> What city was that? Boston, some decades ago. As I noted elsewhere upthread, I understand that the T has deteriorated quite a bit since then. But at the time I lived there, I never felt any need whatsoever for a car and I never had a
726.
by pdonis 2y ago
> The Boston T is not anywhere near as good as the NYC subway My experience of the T is some decades old; I understand it has indeed deteriorated quite a bit since then. But when I used it, I had reasonably contemporary experience of t
727.
by pdonis 2y ago
> the general, informed will of Americans somehow chose cars over public transportation This is a fantasy in any society, not just America. No piece of social infrastructure on the scale of "cars vs. public transportation"
728.
by pdonis 2y ago
> the physical 3d analogous projection would be two slightly overlapping 3d-venn diagram funnels conjoining at an "indefinitely" (asymptotically smaller) small space-time minkowski manifold. I'm not sure what you mean by
729.
by pdonis 2y ago
> we already know that GR isn't the whole story when it comes to BHs. See "soft hair" black holes More precisely, most physicists believe that GR isn't the whole story. But we have no actual evidence for quantum
730.
by pdonis 2y ago
> Does GR predict that there would be any waves confined to the inside of the merged black hole? Yes, but we would of course never observe those, and they would not reduce the externally measured mass of the merged hole.
731.
by pdonis 2y ago
> EM waves can get _transformed_ into mass. In the sense that they can be absorbed by matter and (possibly) increase the invariant mass of the matter, yes.
732.
by pdonis 2y ago
> If the space containing the matter is stretching does that still count as expansion? "Space stretching" is a vague pop science description that doesn't really correspond to anything in the actual physics model. So it d
733.
by pdonis 2y ago
> What if we're expanding because we are in a black hole that is being fed by a collapsing star or other object in a many orders of magnitude larger scale universe? Expanding and collapsing are two different things. So I don'
734.
by pdonis 2y ago
> the Big Bang would be the white hole horizon (i.e. a singularity in out past) The white hole horizon is not the same thing as the white hole singularity. The "Big Bang" as an initial singularity in our universe (which is no
735.
by pdonis 2y ago
> there's only one, maybe two or three cities in the US with good public transportation. NYC's is, as you say, old and decrepit, but its coverage is pretty good. I don't think it's the best system in the US, however
736.
by pdonis 2y ago
> we're all almost certainly inside a black hole No, we're not. The universe is rapidly expanding. Equating the Schwarzschild radius for a given blob of matter with the event horizon of a black hole requires that the matter b
737.
by pdonis 2y ago
> I still do understand what a "gravitational atom" might be. It's a vague gesture in the direction of a speculative theory of quantum gravity. It's not anything we have any actual evidence for.
738.
by pdonis 2y ago
> Gravitational waves carry momentum and energy (and therefore mass), just like electromagnetic waves. No, EM waves do not have mass. They are massless. They carry momentum and energy, yes, but not mass. In GR, the source of gravity is
739.
by pdonis 2y ago
> How do you understand this process of matter escaping a black hole? No matter escapes. Gravitational waves are not matter. They are spacetime curvature. Nor do they "escape" the black hole; they are emitted from outside the
740.
by pdonis 2y ago
> gravitational forces Gravity is not a force in GR. The spacetime curvature in a spacetime with two black holes that merge is not describable in terms of a simple "gravitational field". Spacetime curvature is a fourth rank t
741.
by pdonis 2y ago
> between two singularities merging Two black holes merging does not mean two singularities merging. The singularity (singular, not plural) is a moment of time that is to the future of all other moments inside the hole. If two black ho
742.
by pdonis 2y ago
> living in gated communities where they can keep out the undesirables. Most Americans, including me, who live in areas that aren't large, dense cities with good public transport don't live in gated communities, and our only
743.
by pdonis 2y ago
I've lived in a large, dense city where the public transport was excellent. Having had that experience, and having also had the experience of living in a less dense area where I used a car to get around, I prefer the latter. Have you l
744.
by pdonis 2y ago
> It's a matter of ignorance more than anything else. You have no basis for any such presumption. Plenty of Americans, myself among them, have lived in large, dense cities with good public transit--and we have then chosen to not
745.
by pdonis 2y ago
> There's no public transit in many places because Americans don't want it and don't support it Yes, exactly. This is not a bug, it's a feature.
746.
by pdonis 2y ago
This Wikipedia article has a good timeline showing when the various D&D settings were first released: https://en.wikipedia.org/wiki/Dungeons_%26_Dragons_campaign_... Note that Blackmoor and Greyhawk, at least, were
747.
by pdonis 2y ago
> the original setting Forgotten Realms was not the original setting of D&D. To the extent there was one, it was Gygax's Greyhawk campaign.
748.
by pdonis 2y ago
> I don't buy that the "heart of the game" is at the table. It's at the table where the game is being played, by the rules that the game sets up. In a way that no one had ever really played before, and a way everyone
749.
by pdonis 2y ago
> they presume that the author of the book is the authority of the game, whereas the presumption made by Gygax et al. was that the Dungeon Master was overflowing with ideas, and needed only some reference points to pin them down. Origi
750.
by pdonis 2y ago
> I have a lot less faith in corporations, businesses and entrepreneurs than you do. I didn't say I had lots of faith in those entities. I just have even less faith in governments. Given the respective historical track records, I

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