9 ms·
No, negative masses have not revolutionized cosmology
- benwr 8y agoThis is a critical response to https://news.ycombinator.com/item?id=18609375 https://news.ycombinator.com/item?id=18609375 ; in the comments is a response by Jamie Farnes, the author of the paper, and a rebuttal by the blog's author.
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- excalibur 8y agoTo clarify, the response and rebuttal benwr mentions can be found in the comments on the blog post, not in the HN comments from the previous thread. :)
- jcranberry 8y agoI have absolutely no idea who is right, but I don't see why Dr. Hossenfelder is being so patronizing? In her rebuttal in the comments she says >Trust me, I do not enjoy doing this, but I do not want false claims to spread in the popular science literature. The only way to stop popular science lit from misinterpreting/aggrandizing scientific findings and publishing what eventually amounts to false claims would be to just never publish anything provocative at all...and then they'd still probably find some BS to publish. I don't really see why such reasoning would prompt this response for the paper.
- jessriedel 8y ago> I don't see why Dr. Hossenfelder is being so patronizing This is her personality. I don't think it's productive to resolving scientific disagreements and don't endorse it; she looks obnoxious in contrast to the author's polite reply in the comments. But it's definitely her natural state, and it seems to produce a writing style that readers enjoy. > The only way to stop popular science lit from misinterpreting/aggrandizing scientific findings and publishing what eventually amounts to false claims would be to just never publish anything provocative at all Hossenfelder is claiming much more than that the work is provocative. She's claiming it's highly disfavored for widely known reasons that the authors do not sufficiently address. She's probably also implicitly suggesting the authors are allowing their work to be marketed directly to the lay public, who do not have the expertise to assess the work, for personal gain. Obviously you can always give alternative explanations (the establishment is close-minded, or whatever), but keep in mind that Hossenfelder is waaaay outside the establishment.
- onhn 8y agoIt is fun to read these things, and of course discussion is a good thing, but I do hope that blogs and comment sections do not end up serving any formal role in the scientific literature. There are several reasons for this: a blog's visibility is low compared to a preprint server (in the scientific community at least), the contents of the blog probably won't be as well-preserved, and there is a tendency to be more casual with the arguments.
- daveFNbuck 8y agoWhy is that even a concern for you here? This is clearly written for laypeople.
- onhn 8y agoIt may be just text, but the points being made are technical, and the blog's author is an expert. The author of the paper is now in a position where they feel like they have to defend themselves publicly, and I don't think this is the forum for a scientific defense (for the three reasons I listed above).
- beezle 8y agoIf paper in question becomes fodder for the mainstream media (or at least the mainstream scientific media) then there is no reason why they should not have to defend their theory/arguments/speculations publicly in a less than formal peer reviewed forum, especially one of fairly high regard in that subject area.
- onhn 8y agoThere is a good reason: we should not be passing judgement on the validity of scientific work based on informal discussions.
- beezle 8y agoDisagree. As just one example, the Solvay conferences of the 1910s-20s. Much of QM was developed by informal discussions, both written and verbal. Likewise, most of the initial challenges to scientific papers/theories/experimental results happens informally and only later will there be a peer reviewed counter (if the original has not between withdrawn or modified before). Reference the OPERA ftl neutrinos for a recent example.
- hirundo 8y agoNegative matter is created spontaneously everywhere, according the article in theconversation.com. Why then can't we collect it, isolate it, and poke and prod it? Because the particles are too small and interact too weakly?
- Florin_Andrei 8y ago> the particles are too small That's not a good way to talk about these things. Usually it's the really small stuff that is very strongly interacting - see quarks. > and interact too weakly That's better.
- duality 8y ago"[T]he gravitational interaction is exchanged by a spin-2 field, whereas the electromagnetic force is exchanged by a spin-1 field. Note that for this to be the case, you do not need to speak about the messenger particle that is associated with the force if you quantize it (gravitons or photons). It’s simply a statement about the type of interaction, not about the quantization. Again, you don’t get to choose this behavior. Once you work with General Relativity, you are stuck with the spin-2 field and you conclude: like charges attract and unlike charges repel." There was a bit of discussion about this on https://news.ycombinator.com/item?id=18609375 https://news.ycombinator.com/item?id=18609375 as well. Working through the exercise of how spin-2 mediated forces differ from spin-1 is a worthwhile exercise for those who are so inclined.
- pfdietz 8y agoIf negative mass experiences an attractive force (that is, one that adds momentum toward the source of the force), doesn't that push it away? After all, with negative mass, the momentum vector and the velocity vector point in opposite directions.
- khawkins 8y agoOccam's razor is a heuristic used in the investigative process, not a principle. While it's fair to point out that a theory makes everything more complicated and thus might make it less likely to be sound, it's not fair to push back on the first bit of research into a theory because they haven't had the time to fully develop it. Indeed, a scientific revolution generally starts by treating as false an assumption previously held as true. Not to say that this is a revolution, but if you push back too hard it won't be, whether it's true or not.
- garmaine 8y agoAlso that point seemed odd. Isn't unification of two previously separate phenomenon (dark matter and dark energy) simpler in Occam terms? It's using one thing to explain two, even if the actual mathematics are more complex to state. Also there's other troubling cosmological issues that this would appear to address, such as Hubble's constant having slight variation outside of measurement tolerance, which slightly differing fluid densities would explain (vs the current assumption of unknown sources of error). Sabine's point, if it stands up, is that the author used a different equation of motion in their simulation than they write up in the paper. If true that's sloppy and bad, but it's not a point against the actual theory underlying the simulation, no?
- ajkjk 8y agoWhether it is simpler depends on the details of the unification. Two comparatively simple theories are not made simpler with a very complex unification.
- vanderZwan 8y agoOne could also think of it in terms of the the amount of "magic" required to make the simplification work.
- garmaine 8y agoThe electroweak force is most certainly not easier to describe than electromagnetism and the weak force separately. But we still talk about electroweak interaction as being a simpler theory than two separate fundamental forces, because it reduces the number of things that are needed to describe the universe, even with added computational difficulty.
- mbell 8y agoI'm not a physicist, just an interested bystander but some of these arguments don't seem to hold water to me: > There’s a more general point to be made here. The primary reason that we use dark matter and dark energy to explain cosmological observations is that they are simple. > A creation term is basically a magic fix by which you can explain everything and anything. Dark matter is an unknown 'substance' that interacts only through gravity (weakly) and must have a very specific and complex distribution in the universe to 'work'. That strikes me as neither 'simple' nor much different than tossing a constant into an equation to make it work. Similarly Dark Energy is an unknown form of energy that in uniformly distributed through the universe, which to me is just a fancy way of saying "we added a constant to make it work". In both cases I don't see how either are implicitly better than adding a 'creation term'.
- garmaine 8y agoDark energy is the cosmological constant introduced by Einstein. So that criticism is rather ironic.
- mbell 8y agoMaybe? We don't know, also Einstein wasn't a fan: > Einstein originally introduced the concept in 1917 [2] to counterbalance the effects of gravity and achieve a static universe, a notion which was the accepted view at the time. Einstein abandoned the concept in 1931 after Hubble's discovery of the expanding universe. > Einstein reportedly referred to his failure to accept the validation of his equations—when they had predicted the expansion of the universe in theory, before it was demonstrated in observation of the cosmological red shift—as his "biggest blunder".
- lisper 8y agoIt was actually a double-blunder. Einstein missed the opportunity to predict the expanding universe (and, as a corollary, the big bang). And then, when it turned out the universe was expanding, he retracted the CC despite the fact that it actually turned out that there is a (non-zero) CC, the expanding universe notwithstanding. He got the right answer, but he abandoned it because he got it for the wrong reason.
- eutropia 8y agoTone of this blog post is extremely pedantic and comes across as if the author were personally insulted by the paper. But her argument is basically "You didn't understand the math, and you misunderstood the work that you cited". I feel like the burden is a little higher -- i.e. put in some effort to at least show the readers the math she's talking about and the counterfactual conclusions they arrive it if worked out. I would be much more convinced if she took the original paper's claims at their strongest and most convincing and formulating a simple proof or mathematical argument why the paper is wrong -- instead it feels like she's knocking down a straw man and saying "you're too stupid to be doing this kind of work"...
- ajkjk 8y agoThe argument presupposes that a person either believes (if they're not a physicist) or knows (if they are) that a spin-2 field must obey those rules, and that gravity is a spin-2 field, which makes the conclusion follow naturally. The math for this would not make any sense to a layperson, but is widely accepted. Proposing a new theory of negative mass means proposing much more significant alterations to the underlying theory of gravity; the theoretical machinery supporting this current understanding is huge.
- eutropia 8y agoTrue. I'm not a physicist, so help me understand -- we've only ever observed fermions with spin 1/2 and bosons with spin 1 (and recently, Higgs at 0). We've postulated that gravitons would have to be spin-2 because of how the math works out (I don't understand the math but wikipedia suggests that its because gravity is defined by the use of 2nd order tensors) but we've not confirmed the existence of gravitons. Hopefully I'm not talking past you by speaking of particles, correct me if I'm wrong but particles/fields are interchangeable as a matter of quantization, right? I definitely trust the general relativity math -- gravitational lensing /GPS atomic clock corrections are perhaps the easiest bits to wrap my head around as evidence. Anyways, all that is to ask the question -- Is this negative mass model in conflict with observations or is it in conflict with other models of those observations?
- btilly 8y agoObligatory XKCD: https://xkcd.com/955/ https://xkcd.com/955/ When you read breathless science journalism about the latest revolutionary paper, remember how it usually works out. Enjoy it as entertainment if you wish, but don't get your hopes up.
- vymague 8y agoReminds me of the SUSY bets.
- apo 8y agoCan't help but think of phlogiston: Eventually, quantitative experiments revealed problems, including the fact that some metals gained mass when they burned, even though they were supposed to have lost phlogiston. Some[who?] phlogiston proponents explained this by concluding that phlogiston had negative weight; https://en.wikipedia.org/wiki/Phlogiston_theory https://en.wikipedia.org/wiki/Phlogiston_theory Eventually, the mass paradox was resolved by the realization that combustion is really something else altogether: the combination with a then-unknown element, oxygen: Phlogiston remained the dominant theory until the 1770s when Antoine-Laurent de Lavoisier showed that combustion requires a gas that has mass (specifically, oxygen) and could be measured by means of weighing closed vessels.
- narrator 8y agoThe Egyptians and Babylonians didn't really technologically advance much for 1000 years. They placed the most emphasis in their society on maintaining the social order above all else. Progress can be stopped if you interfere properly with disruptive advances in science. Much of the world is still trying to roll back the development and widespread dissemination of small arms technology because it interferes too much with the maintenance of social order. The last major physics discovery gave us atomic weapons. Who knows what deadly forces future advances in physics would unleash? Heaven forbid they were easy to engineer! Perhaps it's in the interest of national security to direct fundamental physics research into "how many angels can fit on the head of a pin" type discussions via directing grant money such as we see with string theory. These endless manipulations of already existing knowledge and an aversion to more daring experimentalism should keep scientists from developing the successors to atomic weapons.
- simonh 8y agoIt’ll keep scientists in the countries that do this from discovering such weapons. Meanwhile elsewhere in the world...
- narrator 8y agoWhat if they've already developed these weapons, but don't find it useful to let the rest of the world know about them? For example, there's the mystery of the very real, but unexplained brain injuries to diplomats at the U.S embassies in China and Cuba.
- ykonstant 8y agoWell, the negative consensus is disappointing, but the criticisms are absolutely massive.
- diffeomorphism 8y ago> These equations tell you that like masses attract and unlike masses repel. We don’t normally talk about this because for all we know there are no negative gravitational masses, but you can see what happens in the Newtonian limit. I feel like I am misunderstanding what the author wants to say here. It seems to me that this would only be the case if you change the sign of the gravitational mass (F[-m_1,-m_2]=F[m_1,m_2]), but not of the inertial mass? In the Newtonian case you get that the force is proportional to m_1m_2, so ++=+, +-=- and --=+, but then F=ma flips the direction of the acceleration, right? ++ gives F>0 and a>0, so attraction. -- gives F>0, but negative inertial mass yield a<0 and hence repulsion. +*- gives F<0, so the positive inertial mass sees a<0 and is repelled, while the negative inertial mass sees a>0 and is attracted. What am I missing here?
- 8bitsrule 8y ago"highly problematic to introduce negative inertial masses .... This fits badly with our observations." Science news is not scarce. Click-bait titles aren't either. There's no shortage of catchy on-paper theories that 1)are not backed by evidence, 2) make no predictions. Cosmology has a big problem, and thrashing around in desperation is not becoming.