Hoisting 100 tons of stuff high into the air, and then efficiently converting that into the high RPM needed to drive a generator seems like it would take a truly staggering construction effort. Suspending that amount of weight high above your house also has some... interesting potential failure modes.
I don't even think the gravity battery thing is viable for individual residential power storage at all. I was just wondering why you'd assume that the 100 ton weight would be placed directly above your house given the obvious problems with that approach, and the obvious way to avoid those problems.
The comment I was replying to literally said "For home use", and a heavy object 10m in the air does not have to be directly above something to be meaningfully (and dangerously) above something.
It's a silly scenario anyway, but I was doing a bit of guesswork about typical "home" lot sizes.
Yeah I understand it's for home use. I am imagining a tower in the back yard or something. It would be closed so that nobody can walk under the weight. Or it could be internal to the house like an elevator shaft.
Anyway I agree it's silly, definitely not a realistic idea
Right - if a tower in the back yard falls down it can still hit your house, since it isn't guaranteed to neatly collapse straight down. Worst case, it may tip over from the base and directly smash stuff up to its height away (and 10m is pretty far).
I have trees in my back yard I'm kind of worried about, which is why this immediately came to mind.
... yeah? You'd expect the false positive rate to be HIGHER when you're not looking at an enriched patient subset. That's why we're careful about recommending certain kinds of screening. See also: PSA screening.
Well, you missed my point. I'm not talking about "you look at the MRI and see something and say it's a positive", I'm referring to the process of reading MRIs as like a statistical model (even if in practice it exists in the minds of radiologists) which is trained on the corpus of MRI data. That model will depend in some way on the distribution of positive/negative examples in the corpus; if the corpus changes the model has to then be updated to match.
Point is, the false positive concern is only a concern if you use the old model with the new corpus. Don't do that! That's dumb!
The net effect of MRIing everyone on public health would likely be enormously positive as long as you don't do that.
Take PSA, since it's a simpler example. You're right that, if we screen everyone, taking action based on the outcome causes more harm than good. The response is to calibrate... which means we don't learn anything usefully actionable from the test and shouldn't apply it.
With the MRI, you don't get back simple dichotomous things, but you get back potential indications. That can be scary - talk about calibration all you want, but if patients see things and start thinking about the big C word there are likely to be a lot of unnecessary biopsies.
The bottom line is that it's possible to imagine a benefit, but it is not reasonable to pretend it's as simple as "just re-calibrate your interpretation of the results!". There's a reason that a lot of thought goes into when to do screening.
> which means we don't learn anything usefully actionable from the test and shouldn't apply it.
This just isn't true. In practice any such screening model can ALWAYS improve with more data—basically because the statistical power goes up and up—up to an asymptote set by noise in the physical process itself.
> That can be scary
Handling that is the job of professionals, is now and will continue to be.
It is extremely reasonable to imagine a benefit! What is doubtful is imagining there wouldn't be one!
I find the line of reasoning in this whole anti-MRI-everyone argument to be bewildering. I think it is basically an emotional argument, which has set in as "established truth" by repetition; people will trot it out by instinct whenever they encounter any situation that suggests it. It reflects lessons collectively learned from the history of medicine, its over-estimation of its own abilities and its overfitting to data, and its ever-increasing sensitivity to liability.
But it is not inherently true—it is really a statement about poor statistical and policy practices in the field, which could be rectified with concerted effort, with a potential for great public upside.
Not that any of this matters at the current price point. But, on a brief investigation, the amortized cost of a single MRI scan is ~$500-800—perhaps 1/5 what I would have guessed!
> This just isn't true. In practice any such screening model can ALWAYS improve with more data—basically because the statistical power goes up and up—up to an asymptote set by noise in the physical process itself.
That isn't how this works at all.
1. If you assume the test results are iid, sure you can increase your precision (presuming you're talking about repeatedly testing people?), but biology is messy and the tests are correlated. You can get all kinds of individual-specific cross-reactivity on a lab assay, for example. As another example, you can't just keep getting more MRIs to arbitrarily improve your confidence that something is cancer/not cancer/a particular type of cancer etc.
2. Statistical power is not relevant here, but rather different kinds of prediction error. It turns out that in the general population, it is NOT medically relevant that PSA is correlated with the presence of prostate cancer, because it is NOT predictive of mortality, and it IS a cause for unnecessary intervention and thus harm to patients.
I really don't mean to cause offense, but you're talking about this like someone who has no idea how these concepts interact with reality in the biomedical world. Like, you seem to be applying your intuition about how tabular data analysis tends to work in systems you're familiar with, and assuming it generalizes to a context where you don't have experience.
> this whole anti-MRI-everyone argument to be bewildering
It's not about being against MRIs, it's about the idea that (even ignoring costs/cost effectiveness) there are known real-world effects of over-screening people for things.
> But it is not inherently true—it is really a statement about poor statistical and policy practices in the field, which could be rectified with concerted effort, with a potential for great public upside.
This is still not at all a certainty. Let's say you lock this behind a screening system run by data scientists so that there's no patient or provider pressure to act in what you're calling a statistically poor manner. Ok, then what? They have to come up with a decision rule about when to dig deeper and get more data (which again, isn't an MRI, but rather is often an invasive procedure). It is not obvious that there exist any decision rule that could reasonably be arrived at that would be a good trade-off in terms of false positives and the corresponding additional burden.
I am 1000% willing to entertain the idea that new screening can be a net benefit, but we'd need to know what kind of sensitivity/specificity tradeoff would be involved to even start approximating the numbers, and then you'd need to do a trial to demonstrate that it's worthwhile, and even then you'd need to do post-trial monitoring to make sure there aren't unexpected second order effects. People DO, in fact, do this work.
The idea that "more data == better" is just way too simplistic when the data is messy and necessarily inconclusive, the outcomes of interest are rare, and the cost of additional screening can be severe - again also ignoring that all of this is expensive in the first place.
You don't get to just pretend these things aren't created and funded by congress, and that their operation hasn't been solidified and formed over decades and decades through interaction with the judicial branch as well.
The executive branch has an obligation to execute the laws - they don't get to arbitrarily pick and choose how to do that without constraint. Period.
If these were somehow created by executive action, it would be a completely different conversation. Pretending otherwise is disingenuous in the extreme.
Apparently Mayorkas didn't have to execute the laws if he didn't want to and moreover got to decide if he wanted to subvert them as well by granting asylum to whomever asked as well as providing transport, guidance, etc., etc.
Democrats make people upset by not applying laws --all the thievery etc that AGs went light on, etc., and the Republicans make people upset by applying laws to a greater extent (being tougher on crime and deportations --though Obama wasn't a laggard in the latter either)
They're not being dismantled. Funding is being paused while they are audited --and the audits are showing very concerning waste, potential fraud and are being reorganized under a different department.
This is a good thing. They should not get to waste our tax dollars without oversight and fraud detection.
O RLY? You might try reading literally anything the people involved are putting out there. They're open about trying to shut down USAID and the department of Education, and interfering so deeply in places like NIH is beyond the plausible legal limit (which is part of the point during an authoritarian takeover).
I know that HN is supposed to be a place of reasoned discourse, but your takes are so removed from reality I can't take you seriously. I hold your authoritarian apologism in utter contempt and disgust. Be better.
I think everyone should be concerned how the government is spending our money and every government administration should have its spending audited and any graft, fraud and waste eliminated with a waste-0 initiative. This should be transparent to the voters. We should know how they are spending our money and where. The purpose of the government agencies isn't to be a jobs program.
> This should be transparent to the voters. We should know how they are spending our money and where.
The fact that you think this is what's happening right now is fucking hilarious. It's also hilarious that you don't seem to know just how much public information IS available from these institutions.
Some random, ketamine addicted, un-elected oligarch with a cadre of teenage lackeys being let loose with unlimited authority over giant institutions in a process with zero accountability or transparency is your fucking idea of an audit? Like the rest of your arguments here, that's either phenomenally stupid or a mediocre astroturfing job.
So you think voters were aware of how USAID moneys were being spent?
Causing instability overseas, paying Reuters, Catholic charities, BBC, NYT, Politico, etc., for disinformation, people smuggling, etc. It's ridiculous. I'm glad it's happening. The corruption is being exposed. It could be Stalin's great-grandkid doing this and I would welcome the exposure of our waste.
Of course Soros junior so mad his manoeuvering isn't as effective no more.
> So you think voters were aware of how USAID moneys were being spent?
What the fuck? We're talking about the availability of information, not what random idiots have bothered to make themselves aware of.
> Causing instability overseas, paying Reuters, Catholic charities, BBC, NYT, Politico, etc., for disinformation, people smuggling, etc. It's ridiculous. I'm glad it's happening. The corruption is being exposed. It could be Stalin's great-grandkid doing this and I would welcome the exposure of our waste.
Nothing is being exposed. There are legal ways to pursue "audits" and "efficiency", but nobody can seriously believe that's what's happening now. USAID could be evil incarnate, and the current power grab would still be illegal and a threat to the very existence of our country (and we're not ONLY talking about USAID, they just started there).
Just admit it - you're an authoritarian at heart and you're happy daddy is going to decide everything now. Real life is too complex to bother trying to understand.
"I see a clock, but I cannot envision the clockmaker. The human mind is unable to conceive of the four dimensions, so how can it conceive of a God, before whom a thousand years and a thousand dimensions are as one?" -Albert Einstein
It would have revealed a lower layer of higher understanding.
No one has been able to calculate the mass of a quark:
"Nobody has seriously calculated theoretically a quark mass from first principles. So there is no issue of agreement with experiment. They are parameters in experimental fits, but sometimes remarkably consistent across a broad range of experiments-- and the QCD/EW calculations using them as inputs. If someone pretends to know their origin, he/she is bluffing."
> apart from the fact that dark matter predictions have been contradicted by increasingly sensitive experiments over and over and over
My impression is that many physicists would disagree with this characterization entirely, and that they're eagerly working to constrain what it is or isn't. Ruling out big classes of phenomena that could be responsible for the things we observe isn't "contradicting" the predictions in the sense implied.
Particle physicist here. I've worked on direct detection DM experiments in the past, and personally know some folks who work on the LZ experiment. That direct detection experiments, such as LZ, have not detected a signal does not contradict any predictions.
Indeed, relevant to what an experiment like LZ might see, there really isn't much in the way of "predictions" which can be "contradicted." What we have at this point are mechanisms to calculate the interaction rate _given at least one free parameter_. If we were to detect a non-zero rate, then we would "know" the free parameter of a single-parameter theory underlying that calculation. If we were to continue to detect a non-zero rate, then we would try to do so using different materials, and look at the time dependence of the rate (or, really, the dependence of the rate on the Earth's direction of travel in our local galaxy). That would help us choose between different theories, pin down the free parameters, and confirm that what we're seeing is consistent with "heavy stuff just sitting out in the universe."
But, from a particle physics perspective, right now there are no predictions to contradict - just an opportunity to detect something.
I'd normally agree with you, but in the particular case of dark matter particles something still smells fishy. The theories that the predicted cross-sections are based on are just too flexible and numerous. I'm not sure how much we gain from ruling out yet more. What if there are in fact no weakly interacting particles? At what point do we decide that enough has been ruled out to start looking elsewhere? Like plasma dynamics or something (please don't shoot me if this is too silly to even contemplate).
Reprioritization of direct experimental searches for dark matter is already happening. WIMPs are by no means being abandoned, but because we are closing in on the neutrino fog background (which is mentioned in another comment), it's been recognized that to myopically cling to the same kind of experiment which dominated the 2000s and 2010s is not a strategic move (both from the "we expect to see something" and the "responsible use of tax dollars" perspectives).
For example: axions, an alternative DM candidate mentioned in another comment, have seen a significant growth in attention in recent years, and the usual detector technology for axion searches is currently being refined and scaled up, from benchtop-scale, dedicated experiments to lab-scale, wide searches.
At the same time, different groups which have developed past WIMP detectors are merging to collaborate on the larger, next-generation detectors. And there is R&D and prototyping happening to create detectors which, although looking for WIMPs, are sensitive in entirely different mass ranges than those of yesteryear.
That's just how particle physics research works. You build a detector that is designed to detect things with specific properties. You run the detector. Did you find the thing? If so, great, if not, well, that's the way the cookie crumbles. Either way you write a paper and you build the next detector.
The Higgs boson has numerous experiments exclude numerous mass ranges excluded before it was finally found.
> At what point do we decide that enough has been ruled out to start looking elsewhere?
"We" don't make that decision. The various institutions who pay for these things decide, one by one, that they're going to fund some thing that sounds more promising instead.
It does kinda suck that there's something there in the universe that is perniciously difficult to see--in fact, that's how it's defined--but that is so important in the way the universe works that we can't simply ignore it. But this is the universe we're given, so this is the universe we'll run experiments on.
