> The real takeaway is that researchers may have found a potential test for string theory.
Not really. All this paper is really saying is that they have found solutions in classical theories of gravity with extra dimensions that, in four dimensions, can look like standard black holes. So even observing effects predicted by these models would not be evidence for string theory. It would at best be evidence for possible extra dimensions of spacetime at the classical level.
Also, the paper only compares its models with the standard Schwarzschild black hole. But first, most black holes are spinning so the comparison should be with Kerr, not Schwarzschild; and second, as the paper notes early on, there are many other proposed models of compact objects that can look similar to standard black holes. Any given set of observations would have to be tested against all proposed models, not just this one.
(1) The hole's spacetime geometry is axisymmetric but not spherically symmetric;
(2) The hole has a Killing vector field that is timelike at infinity but is not hypersurface orthogonal;
(3) The hole has nonzero angular momentum as viewed in the asymptotically flat region at infinity.
> Can't we just pick as a reference the black hole, and say that the everything else is spinning, just as well?
No. All three of the above conditions are invariant and only depend on the spacetime geometry; they are unaffected by any choice of coordinates or the motion of any outside observers.
No, spinning is an accelerated reference frame. If you spin on a carousel, you won’t feel the same as standing still.
Now what does it mean for a black hole, which we assume to be a singularity occupying no space at all, to be spinning? We don’t know. That’s one of the gaps in our theory. But as the collapsed remnants of an object that was spinning, they should have done residual angular momentum.
Not necessarily. The three definitions for a "spinning" black hole that I gave upthread do not require the presence of any accelerated frames or observers.
> what does it mean for a black hole, which we assume to be a singularity occupying no space at all
This is not correct. A black hole is a finite region of spacetime enclosed by an event horizon. The singularity is inside the hole but is not all of the hole.
> to be spinning? We don’t know.
Yes, we do. We have known since the 1960s that the Kerr solution to the Einstein Field Equation describes a spinning black hole, and all of the geometric properties of that solution have been known for almost as long as that.
> That’s one of the gaps in our theory.
No, it's not. See above.
> as the collapsed remnants of an object that was spinning, they should have done residual angular momentum.
This is correct, but it does not imply or support your other claims.
You're missing the point that, since a black hole is purely made of spacetime geometry, there is no "mechanistic explanation" of its spin in the sense you mean.
An object can spin relative to itself. Particles away from the center are constantly accelerating. Gravity or physical connection are the forces that prevent these particles from flying away.
Thinking about it, I am not even sure an object can spin relative to another object. Orbit sure, but not spin.
> An object can spin relative to itself. Particles away from the center are constantly accelerating. Gravity or physical connection are the forces that prevent these particles from flying away.
This is a reasonable description of spin for an ordinary object, but it can't be used for a black hole, because a black hole is a vacuum solution; it has no "particles". See my other post upthread for better ways to view spin for a black hole.
> I am not even sure an object can spin relative to another object. Orbit sure, but not spin.
The usual definition of "spin" makes use of the object's center of mass frame, yes. Orbital angular momentum is thus separated out.
Note, though, that strictly speaking, in relativity there is no invariant way to make this split. It works very well as an approximation for most objects (like planets and stars), but there are complications when one tries to apply it to things like black holes. That's one reason why physicists prefer other ways of defining "spinning" for black holes that don't involve any split between orbital and spin angular momentum.
I think there are all sorts of other potential tests of string theory. The problem is that for all the actual tests that were ever proposed, it failed (supersymmetry, various proposals for sizes of the extra dimensions).
To be fair, what failed is low-energy Supersymmetry and large extra dimensions, because these things were actually accessible by current gen experiments. But there's a huuuge amount of room left unexplored.
That's my point: what experiments could be performed have been performed, and have failed.
Also, it is a massive weakness of the theory that it can be used to predict such varied values. This is a big part of why it is not exactly a scientific theory: it is not really falsifiable, since you can tweak it to predict any value you want. If we had the kind of particle accelerators needed to test high-energy supersymmetry, and if it failed again, it could be adjusted to predict higher-energy supersymmetry, and since the number line extends towards infinity, this would never stop.
I think you are correct, ST is closer to mathematical abstraction than an actual physical theory. I think that makes it more useful than less useful though.
Not without fine-tuning. The issue is that high-energy supersymmetry no longer removes the "ugly constants" of the standard model -- it just shifts them somewhere else. Disclaimer: not a physicist, but I learned a lot reading "Lost in Math: How Beauty Leads Physics Astray".
I treat her like Jordan Peterson. Obviously smart, but also obviously bitter and if/when they have a valid point I’m sure someone else has said it in a less grating manner.
Sabine argues the data, in good(ish) faith, but she does carry a chip on her shoulder.
Peterson does not argue data - he suggests analogies and then holds those analogies as iron-clad transitive relationships to argue his preconceived position.
I hear this a lot from people. As a non-physicist who enjoys her content, what am I missing? is she wrong on any specific physics? Without specific criticism this comes off as insiders being upset that a fellow insider is critical of the field
Part of the issue for me is that I don't think her research on quantum foundations is viewed very highly. Some would probably consider it completely pointless. In her videos, she claims that the majority of physicists do not understand quantum mechanics and that AI might find patterns in the randomness of quantum mechanics. This doesn't put her tendancy to tell lay people how everyone else's research is a waste of time in a good light. She's just arguing that her research is more deserving of funding.
Plenty of her points aren't without merit but she's frequently disengenious and doesn't give the full argument for what she criticises.
An example is her criticism on "decoherence solves the measurement issue" where she explains the average of multiple particles doesn't tell you what happens to just one of the particles involved. She's not wrong in the example she gives but decoherence actually can be applied to a single particle. Compare with PBS space time, they present both sides and offer an opinion as their opinion not fact.
I recently watched a lecture on issues in particle physics. Naturalness was mentioned due to a need to ensure the theory gave sensible answers, to ensure it was renormalizable, that's far more reasonable to how Sabine presents it.
I'm no insider but I haven't found Hossenfelder's stuff that impressive. Her reasoning tends to take the form "X is true, therefore Y", where "if X then Y" is a valid deduction, and X hasn't been proven false, so we can't say she's wrong on specific physics. But the presumption that X is true is unjustified even if X hasn't been proven false. Example: she likes superdeterminism instead of quantum mechanics with its various weird consequences. Ok, her version of superdeterminism hasn't been proven wrong, but that's a long way off from saying that it is right. It comes down to her saying "I believe X and I haven't been proven wrong, even though most other physicists believe not-X, but I like my theory better, so there". Perfectly fine and legit, but I'll take X seriously when I see more recognition for it from the rest of physics.
The same goes for this stuff about tests of string theory. As far as I can tell, string theory is perfectly good physics whether or not it is experimentally testable. That is, there is a viewpoint called "naive Popperianism" that if something isn't experimentally testable then it it isn't science, but from what I can tell, that viewpoint is not truly decisive (thus "naive"), and its proponents don't have the authority that they wish they did. As a comparable situation, there is not much dispute that general relativity (GR) is perfectly good physics except at the center of a black hole, where it predicts a singularity which people consider non-physical. Particularly, GR makes predictions about the interior of black holes (points inside the event horizon) that are considered perfectly good except at the center. But, since there is no way to observe the inside of a black hole, those predictions of GR are also not verifiable. So I'm not bothered by unverifiability. Theory is good if it has explanatory or interpretive power, not just testable predictive power.
She's not wrong about any of the empirical content of physics (so far as we know), but neither are the people she criticizes. It's a philosophical conflict.
Most physicists are at least weakly inclined towards scientific realism, whereas Hossenfelder is a radical instrumentalist - and doesn't seem to think any other view is even worth engaging with.
Jordan Peterson has had many iterations. The year -5 edition had good psychology lectures and I disagree with the above poster who says he doesn't know what he is talking about. Within his academic realm, I think he did, although there would be points other academics would contest (this is what academics do). He has then gone through at least two transformations.
His position regarding a lot of religious topics seems tainted by his personal beliefs.
He makes frequent reference to judaeo-christian archetypes, which seems to me to grossly overstate the relevance of the belief systems.
The fundamental archetypes represented in the human mind are far older than any current form of religion, to the extent that there's overlap then either the archetypes have been co-opted, or have been overlaid with a culturally mediated avatars.
I don't think that you ever find him framing those underlying structures in a way that does not tie back to Christ.
> which seems to me to grossly overstate the relevance of the belief systems.
It is hardly possible to overstate the relevance of those archetypes and beliefs. Nothing else has been more widespread on earth for as long to have anywhere close to the same influence on humanity.
I'm not familiar enough to know what a "Judeo-Christian archetype" is, but Indian/Chinese origin religions are older, just about as numerous, and not particularly similar.
(Where Buddhism is similar, it's because "religion" as a concept had to be made legible to Westerners when they showed up so they wouldn't colonize you so hard, and they did this by putting Western philosophy in it.)
Things like the virgin mother (bare in mind, much like Peterson, I'm pulling this out of my arse).
My take on that it is a perspective based subset of actuality; in the case of the mother (as opposed) to the wife, 'she' is measured from the perspective of the child, she has her nurturing capabilities but not those of reproduction.
Reproduction is outside of the child's need to understand, and is not a property of the mother as it is seen from the child's perspective.
Bare in mind that the archetype is always perceived by the child, the husband will see something else.
These restrictions are based on perspective and need, and are reflective only of a limited subset of reality.
Christianity has taken that childish abstraction, and declared it to be an actual thing, that actually existed.
It doesn't take much consideration to understand that virgins don't give birth to sons (and if they ever give birth to daughters, they'll be genetic clones of the mother).
> Where Buddhism is similar, it's because "religion" as a concept had to be made legible to Westerners when they showed up so they wouldn't colonize you so hard, and they did this by putting Western philosophy in it.)
Reworded:
Where Buddhism is similar, it's because Westerners showed up and were going to colonize anyone who didn't have something called a "religion", so they had to turn it into a recognizable "religion", which they did by copying a bunch of Western philosophy. So the older forms were even less similar.
I do not mean in terms of pervasiveness - I mean in terms of them innately making up a piece of the underlying structures of human consciousness.
And to the extent that those beliefs are actually archetypal, they are not fundamentally judaeo-christian but predate and have been co-opted by those religions.
"low-energy Supersymmetry" oh, you mean 8 TeV wasn't enough? This kind of reasoning is just like the ether, people keep harping on a god of the gaps explanation for the failure of the search.
Even if it were testable, and the test failed to validate string theory, I don't think that would convince string theorists one way or another. Strings are a de facto religion within physics.
This line of talk is way overplayed. Like people who have an enthusiast amount of knowledge follow a few people who have professional knowledge who are just unreasonably fixated on what other physicists pursue.
Doubt and questioning are a part of science but this "religion" meme about string theory et al is silly. If you're really upset that somebody is pursuing something is a blind alley, go ahead and do some physics that shows results, otherwise I really wish people would tone the unhelpful criticisms down.
I agree. If every physicist quit string theory because we haven’t thought of a way to test it, like what @ravenstein might want, then that would be a sad day.
I don’t see the problem with physicists working on or even promoting string theory.
I am not a physicist, but what I have read from critics (badly paraphrased):
During the hype phase of string theory, every major university wanted to get in on the game, and devoted large amounts of funding towards hiring researchers with a background in string theory. If you weren't one of those people, you were at a severe disadvantage, and might not get hired at all.
String theory hovered up tons of cash in university budgets, and majorly fucked over a lot of careers. The result of all this money has been no actual scientifically proven results despite decades of research.
> devoted large amounts of funding towards hiring researchers with a background in string theory. If you weren't one of those people, you were at a severe disadvantage, and might not get hired at all.
> String theory hovered up tons of cash in university budgets, and majorly fucked over a lot of careers.
This is pretty misleading. An argument could be made - though I'm not necessarily endorsing it - that string theory has crowded out other quantum gravity research programs in the last few decades. But quantum gravity is a small and poorly funded subfield: we're talking about no more than a few hundred people total in the US, fighting over one medium-sized experiment worth of grant money. None of it makes any difference to the overwhelming majority of physicists.
I don't think string theorists are being unreasonable by not having changed their minds yet, given that no evidence has come out one way or the other.
I don't think we can extrapolate from "string theorists didn't update when presented with no evidence" to "string theorists won't update when presented with evidence".
I think it’s a human thing and every generation has to deal with the fanatics or believers or whatever you want to call it of their time.
We’re in a time where a great number of people are extremely religious without having any idea they are. The people that live by what their screen tells them. If you didn’t see some of this in the last three years that there is religion without it being labeled as such, I don’t know I’ll be able to reach you now.
We all live by what our screens tell us. We don't know anything outside of our own direct experience without depending on others. And for the most part we choose to trust others and it usually works out ok. That's not religion - that's an efficient way to intake information about the world, because an individual doesn't have the resources to learn about everything or go every place. If someone abuses our trust, then it's not a problem with the delivery method, it's a problem with them. So the fact that we get a lot of information via a screen is irrelevant.
Though I'm not sure what that has to do with the notion that bad ideas only die when the people who hold them die.
I'm not sure what you're trying to say and I wouldn't go that far. But it's pretty straightforward to say, yes, older people like change less than younger people, even if they aren't fanatics.
>If the researchers can discover an important observational difference between topological solitons and traditional black holes, this might pave the way to finding a way to test string theory itself.
This is a big if. For now they've just shown that once again something in the string theory landscape could look like something in real life.
I know it is the standard nomenclature, but I object to it being called string theory, as it is at best a hypothesis, if not even just philosophical speculation with more math.
It can make no predictions, it is not falsifiable, it meets none of the constraints that allow something to be science.
Speaking of nomenclature, this is not a good characterization of what philosophy is, if your intention is to reduce philosophy to what you seem to have in mind for “philosophical speculation”. Metaphysical theory thoroughly supported by argument (hylomorphic dualism, theory of act and potency) is actually stronger than mere empirical science. Empirically testable predictions do not transcend reasoned argument as observation is interpreted though the body of propositions of prior theory and enters into scientific argument as argument.
String theory is basically just noodles on the wall these days trying to find what sticks. mostly without basis and 99.9% of it falls off eventually as it's not backed by anything of substance.
> Its presumed lack of falsifiability has been one of its drawbacks[..]
Given that the definition of a theory is an hypothesis that can be tested for falsehood, it isn't a theory by definition. It is a hypothesis.. but presumably "string hypothesis" doesn't sound as nice.
You may be surprised to learn that your face is your least identifying trait online. You network of friends/followers/likes identifies you far more readily—even if you use a random username.[1]
Managing your privacy is a lot like CPU side channel attacks. It forces you to re-evaluate your fundamental assumptions about what information can be exploited.
Surprised to see the author suggest that the C64 keyboard did not include the graphics glyphs on the keys.
Both the VIC-20 and the C64 both had them, albeit printed on the front vertical face instead of the horizontal face like the PET.
Moreover, the VIC-20 and the C64 keys include the box glyphs as well so you could see what character you’d get via CTRL and the ‘C=‘ (“Commodore”) key.
The Wikipedia page* states PETSCII includes 192 characters, but the author seems to suggest it’s at most a 7-bit charset. I was a little surprised to find that out after reading the article.
The idea was more about the arrangement of the character set, which isn't always obvious on the VIC-20 or the C64, because of the differences in keyboard layouts as compared to the original PET 2001. (E.g., both the VIC-20 and the C64 are lacking the numeric keypad and what are adjacent blocks on the PET is dispersed over a linear arrangement. So there's no discernible logic in the code, nor in the keyboard. The same is true for several other keys, like those around the space key of the PET.)
Regarding the number of actually assigned codes, mind that the basic code, regarding unique displayed characters, is single case (6 1/2-bit) in two banks (MSB set for shifted characters => 0x60 x 2 = 192). However, the mirrored regions are actually unique codes in BASIC (as far as CHR$() and ASC() are concerned).
Sorry, if I failed in making this clear.
Edit: Arguably, the ortho layout of the PET 2001's chiclet keyboard also helps in identifying logical blocks of graphics characters.
Yup. Early revisions of the 64C had the glyphs on the fronts of the keys, but this was later cost-reduced to having them on the tops.
This is also one of the differences between the "Aldi C64" (breadbin case, but beige keys with front glyphs) and the C64G (beige breadbin case, but beige keys with top glyphs). Commodore loved to mix and match components, too. Some C64Gs have the brown keys of the earlier breadbin C64.
Do you know if Commodore manufactured any two styles of these in parallel intentionally, or if this was a matter of making use of existing housing/keyboard assembly/motherboards?
The corresponding article on C64 Wiki says that side symbol keyboards were used during the first year of production, and also includes a picture of the top glyph version: https://www.c64-wiki.com/wiki/C64C
My understanding is that the "main line" was breadbin, 64C with front glyphs, then 64C with top glyphs. The Aldi 64 was concurrent with the breadbin, but mysteriously used the keys from the early 64C. The 64G was concurrent with the late 64C. The Aldi and 64G were only available in a relatively small area (mostly Germany), rather than internationally.
Commodore was notorious for mixing and matching parts, though. Even the very early breadbin 64s would sometimes ship with VIC-20 function keys (orange instead of dark gray) and vice-versa. I don't know if this was due to poor quality control, or an intentionally sloppy supply chain management. Perhaps a combination of both.
The 64G especially looks like they were scrambling to meet demand any way they could, as the key colors and even the LED colors vary. I'm guessing the beige breadbin was used to increase production speed by taking the old breadbin injection molds out of retirement. They aren't old cases that they had in inventory, because breadbins weren't that color previously.
Given than Mono-the first open source C# implementation-was used to build banshee going back 15+ years, C# on *nix deserves more credit than is given here.
Not sure if STM32L432 is more "open source" than nRF52840 (does latter require blobs for radios?), but I think OpenSK can be ported to STM32 too. It's probably easier to port TockOS-based OpenSK to different MCUs than STM32_hal-based Solo to something other than STM32.
> nRF52840 (does latter require blobs for radios?)
Yes it does ([1]).
But honest question are there any chipsets out there which doesn't? Maybe some open source projects? The radio protocols are incredibly complex so I would be (pleasantly) surprised if there was.
Nordic provides binary blobs for BLE, but also provides full register level documentation for the radio peripheral, so there's nothing in the way of an open source radio solution with the NRF52 family parts.
The Community Edition is open source, though the Enterprise Edition has some proprietary extensions.
It’s admittedly not at all obvious from the repo name, but the following is the top level repo for Couchbase Server (which uses Google’s `repo` tool): https://github.com/couchbase/manifest
My first touchscreen Garmin unit, circa 2007, definitely suffered from reliability issues in FL summer heat. Just keeping it on the dash in direct sunlight while driving was enough to affect its operation.
I’m guessing it didn’t effect their brand much because other companies like Tom Tom were aggressively targeting the entry-level market segment, and then the iPhone came out the same year.
The number people who had these higher-end units in hot southern states was likely just too small to significantly tarnish Garmin’s brand goodwill.
Soon enough most people switched to using their phone once the software was good enough (circa 2009 IIRC).
Xamarin and Microsoft alum Bryan Costanich got some friends together to rescue Netduino and “reboot” it.
They wanted to maintain that same sense of delight for .NET devs, but also modernize the aging hardware platform and replace the restricted .NET Micro Framework with full .NET Standard support on the software side.
Several friends from the old Xamarin docs team worked their magic on the Wilderness docs site—which is why it’s so good.
Its presumed lack of falsifiability has been one of its drawbacks and has been the source of some of the controversy around it.
Finding a potential test that could be conducted with telescopes instead of high energy particle accelerators would be a big moment in modern physics.