I am a biologist but I’m warning you up front that I’m going off of memory on this one, and animal vision was never my area of specialization (except in evolutionary models, which I can get into but which don’t apply to your specific question).
Cat vision, as I recall, is optimized around two things - seeing in low light conditions and seeing motion. Cats can have a harder time focusing on stationary objects and I don’t believe they have a particularly high level of processing for visual detail.
It’s important to remember - especially when we’re talking about trying to reverse engineer what another species sees - that the phenomenon we refer to generally as “vision” is an incredibly complex process. It involves multiple cell types, chemical and physical processes, and things like memory, taste, and smell. You’ve probably seen comments on nasty rooms where people say “I can smell this picture,” or caught a whiff of a cologne or perfume that evoked powerful memories including being able to visualize the person you associated it with, even though they’re not actually in front of you.
The visual parts of your brain can be activated absent any input from your eyes (something those with PTSD can know all too well), and your eyes take in a huge amount of information that never makes it to the visual processing layers of your brain, because you simply disregard it.
So when we look at the cells in a cat’s eye, we’re only seeing (so to speak) a very tiny part of the story. We learn more when we start to study how cats respond to visual stimuli - how they hunt, how they play, how they explore their worlds - but it’s all a blind men and the elephant kind of thing. Plus, I have to imagine it’s pretty hard to get that kind of research funded.
Anyway, I’d keep that in mind when you do start finding papers on cat vision, and I’d recommend more comprehensive works on cat behavior in general, from which you can infer things about vision but will provide a more full context like I’m talking about.
If you’re thinking about building Rube Goldberg type machines for keeping cats entertained, I think you should just go for it. Experiment. Do note that cats have a huge amount of variability in what they find interesting or fun. Some will watch tv, others will chase a laser pointer or a feather on a string. I had one that would just sit and stare at absolutely nothing all day long and couldn’t be bothered with anything but head scratches and the occasional piece of chicken.
One thing that seems to be pretty popular is having a ball or something that skitters around while under a blanket or towel, but do be aware that you’re basically training them to bite your toes really really hard while you’re trying to fall asleep. I speak from experience on that.
I believe you mean social sciences. They do that by indicating statistical significance or deviation.
Humanities, like philosophy, languages and arts don’t use formulas all that much to describe their work, but it could probably be done using a similar statistical approach for some things.
The placebo effect has been shown to work even when the patient was told about it.
As in, the patient went in being fully informed about the placebo effect and it still worked.
And this weirdness also holds for the nocebo effect, where you get a negative/opposite effect that is out of character or excessive to the degree to which the treatment ought to fail or have negative repercussions.
We (humans) don’t need atmospheric nitrogen to survive, we just need the “other” in the atmosphere to not be toxic. My guess is any element in the same periodic table column as nitrogen that could somehow exist as a gas at STP would be fine (hypothetically).
Don’t they replace nitrogen with like helium for some SCUBA applications?
Other life on Earth obviously does metabolize nitrogen (I think we do a little bit too). So to preserve our biosphere we should not throw off the nitrogen balance. But as others have observed it’s not clear there’s any imbalance coming.
Overall you’re not on a bad track with thinking that other elements in the same column could substitute for nitrogen, often those elements will have similar properties.
However it doesn’t really apply in this particular case, the other elements in its group are all pretty reactive and solid, and include elements like phosphorus and arsenic. Even nitrogen compounds can be pretty damn reactive, it’s just kind of a quirk of chemistry that diatomic hydrogen (N2) which makes up most of our atmosphere is pretty stable and nonreactive under most circumstances.
We need certain nitrogen compounds as part of our biological processes but we don’t get that nitrogen from the air, we get it from food we eat, which ultimately get it from the air mostly from microbes in the soil that are actually able to take nitrogen from the air and turn it into other chemicals.
However since atmospheric nitrogen is, for the purposes of this conversation, inert, you can pretty much replace it with any other nonpoisonous gas, like we often do for deep sea divers, because under high pressure nitrogen will dissolve into our blood and then when we resurface it creates nitrogen bubbles in our blood which is very bad.
I suppose it’s more of a "that’s when they start binding the meat of the lifetime-CO2-stored. Remember, trees also burn quite a bit of their previously fixated CO2 for energy. Perhaps the amount of CO2 fixed in the first 30 years pales in comparison to that of the next 30?
To be overly simple about it, the LLM uses statistics and a bit of controlled RNG to pick its words. Words in the LLM have links to each other with statistical probabilities attached. If you take the sentence “I fed a peanut to an elephant” and “I fed a peanut to a elephant” and then asked 100 people which is more correct, there will be a percentage which favors one over the other. Now with LLMs its not choosing using weighted coin flips, but rather picking the most likely next word (most of the time). So if the 100 people choose “an elephant” over “a elephant” 65% of the time in its training data, then the LLM will be inclined to use “an elephant.” However, Its important to know that the words around “an elephant” will also bias its choice to use the word ‘an’ for the word ‘elephant’.
Really, its largely based on the training data and the contexts to which ‘a’ and ‘an’ are used. Or in other words, the LLM knows because people figured it out for the LLM. People did all the thinking, LLM’s just use statistics on our bottled phrases to know when to use which. Of course, because it got its data from people - it will sometimes get it wrong which is based on how often people got it wrong.
Well, my example of the word ‘elephant’ has the same property as ‘herb’ where the use of ‘a’ or ‘an’ can depend on who you ask. I chose my example trying to anticipate this exact question, and I believe I gave you an answer.
Let me put it this way: it depends… It depends on the data the LLM (Chat GPT for example) has been given to train its output. If we have an LLM dataset which uses only text by people in the United Kingdom, then the data will favor “a herb” as the ‘h’ is pronounced, where data from the United States will favor the other way as the ‘h’ is usually silent when spoken out loud.
As a fairly general rule, people use the article “an” before a vowel sound (like a silent “h”) and “a” before a consonant sound (like a pronounced, or aspirated, “h”). Usually the data gathered is from multiple English speaking countries, so both “an herb” and “a herb” will exist in the training data, and from there the LLM will favor picking the one that is shown more often (as the data will biased.)
Just for fun, I asked the LLM running on my local machine. Prompt: "Fill in the blank: “It is _ herb” Response: “It is an herb.”
This is going to cover the factors that affect the ability of humans to absorb Iron which isnt quite addressing your question directly but I would rather not speculate about things that I have not researched as thoroughly. Iron bioavailability depends on several factors including what you eat along with the Iron. Citric acid and protein significantly increase the bioavailability of Iron. Plant foods rich in phytate (what plants use to store Phosphorus) bind to and render unavailable metals like Iron, Zinc, Calcium etc but these levels vary significantly between plant food sources. Other metals like Zinc can interfere with Iron bioavailability and vice versa. And normally the body’s ability to absorb Iron is regulated such that Iron is absorbed more efficiently if you are deficient and less efficiently if you have an excess. There are a few disorders that cause this Iron regulation to malfunction either resulting in deficiencies or the complete opposite of this, excessive Iron that starts depositing in organs but with a physiologically “normal” person that regulatory system acts to normalize the amount of Iron absorbed to an extent.
Nothing is really definite. The right word to use would be consistent. We dont know the larger or the smaller picture, just that the small pocket of all physics we know is related in a certain way in a comprehensible manner.
No, physics is never vague. Some problems are currently computationally intractable beyond a specific level of accuracy (like predicting the weather more than 2 weeks out), and some questions we do not know answers yet but expect to find answers to in the future (like why did the big bang happen). But there is never an element of the mysterious or spiritual or “man can never know”.
Popular science physics often gets mysterious, but that is a failure of popularization. Like the observer effect in quantum physics, which is often depicted as a literal eyeball watching the photons go through a double slit (?!). This may cause a naive viewer to mistakenly start thinking there is something special or unique about the human eyeball and the human consciousness that physics cannot explain. It gets even worse - one of the most popular double slit videos on youtube for example is “Dr. Quantum explains the double slit experiment” (not even gonna link it) which is not only laughably misleading, but upon closer examination was produced by a literal UFO cult, and they surreptitiously used the video to funnel more members.
Or the “delayed choice quantum eraser experiment” which confounded me for years (“What’s that? I personally can make a choice now that retroactively changes events that have already happened in the past? I have magical time powers?”), until I grew tired of being bamboozled by all its popular science depictions and dug up the actual original research paper on which it is based. Surprise! Having read the paper I have now understood exactly how the experiment works and why the result is sensible and not mysterious at all and that I don’t have magical powers. Sabine Hossenfelder video on youtube debunking the delayed-choice quantum eraser was the first and so far one of only two videos I have seen in the years since that have also used the actual paper. This has immediately made me respect her, regardless of all the controversy she has accumulated before or since.
I believe Heisenberg says there’s vagueness in the amount of things we can know at once. But I agree there’s nothing we shouldn’t be able to know, only things we know that we can’t know simultaneously, which imo is “vagueness”. However the understand principle is something I hope falls some day with better measurement devices than we had a hundred years ago.
Also everyone should listen to Sabine, she’s among the least biased science educators imo. People need to be really careful what they learn from YouTube creators, in fact that was a subject of a recent Sabine video!
The uncertainty principle fundamentally can’t fall. It’s not a limitation of our measurement devices, it’s a fundamental limitation of physics that, as far as we know, can’t be broken.
Also, Sabine Hossenfelder has horrible takes regarding trans people, so I’d take anything from her beyond her immediate field with a giant grain of salt.
On the subject of Heisenberg Uncertainty - even there I blame popular science for having misled me! “You can’t know precise position and momentum at once” - sounds great! So mysterious! If you dig a little deeper, you might even get an explanation like that to measure the position of something you have to bombard it with particles (photons, electrons), and when it’s hit its velocity will change in a way you do not know. The smaller that something is, and the more you bombard it to get more precise position, the more uncertainty you will get.
All misleading! It was not until having taken an actual physics class where I learned how to calculate HU that I realized that not only is HU the result of simple mathematics, but that it also incidentally solves the thousands-years-old Zeno Paradox almost as a side lemma - a really cool fact that I was taught nowhere before!
Basically the wavefunction is the only thing that exists. The function for a single particle is a value assigned to every point in space, the values can be complex numbers, and the Schroedinger equation defines how the values change over time, depending on their nearby values in the now. That function is the particle’s position (or rather its square absolute magnitude) - if it is non-zero at more than one point we say that the particle is present in two places at once. What is the particle’s velocity? In computer games, each object has a value for a position and a value for a velocity. In quantum mechanics, there is no second value for velocity. The wavefunction is all that exists. To get a number that you can interpret as the velocity, you need to take the Fourier transform of the position function. And you don’t get one number out, you get a spectrum.
In one dimension, what is the Fourier transform of the delta function (a particle with exactly one position)? It is a constant function that is non-zero everywhere! (More precisely it is a corkscrew in the complex values, where the angle rotates around but magnitude remains the same). A particle with one position has every possible momentum at once! What is the Fourier transform of a complex-valued corkscrew? A delta function! Only a particle that is present everywhere at once can be said to have a precise momentum! The chirality of the particle’s corkscrew position function determines whether it is moving to the left or to the right. Zeno could not have known! Even if you look at an infinitesmall instant of time, the arrow’s speed and direction is already well-defined, encoded it that arrow’s instantaneous position function!
If you try imagine a function that minimizes uncertainty in both position and momentum at once, you end up with a wavepacket - a normal(?)-distribution-shaped curve peak that is equally minimally wide in both position and momentum space. If it were any narrower in one, it would be way wider in the other. That width squared is precisely the minimum possible value of Heisenberg Uncertainty in that famous Δx*Δp >= ħ/2 equation. It wasn’t ever about bombardment at all! It was just a mathematical consequence of using Fourier transforms.
Even once you understand that the uncertainty principle is not the same as the observer effect, I think it’s still mysterious for the same reason that “the wavefunction is the only thing that exists” is mysterious.
If anything, it’s more mysterious once you understand the difference. People are more willing to accept “Your height cannot be measured with infinite precision” than “Your height fundamentally has no definite value”, but the latter is closer to the truth than the former.
I wouldn’t say that Sabine is among the “least biased”. She strongly advocates for superdeterminism, and her videos on the subject presume it is true even though it is still unproven and currently accepted only by a minority of physicists.
I am generally somewhat skeptical about your comment. Sure, I hadn’t heard about Sabine’s video about the quantum eraser, but I don’t necessarily think that it disproves the idea that physics is never vague or unknown.
Perhaps it is different in physics than my own field, but if you read enough primary papers, enough lit reviews, at least in my field, you’ll see some common themes come up. Things such as “further research is required to determine this mechanism,” “the factors that are involved are unknown,” “it is unclear why this occurs.” Actually, your suggestion that nothing is vague is entirely counter to my entire field of science. When we introduce ourselves in our field, we start off with a sentence about what we do not know. And perhaps it is my bias, having worked in my field, but I cannot see how any scientist could possibly say that nothing is vague.
To me, my interpretation is that “science is not vague” is itself a symptom of popular science. “Science is mystical” is simply a symptom of a slightly different disease - the disease of poor popular science communication. But I think that’s distinctly different from the question, which is asking if anything was vague. I’d love to hear your thoughts on the matter.
Oh yeah for sure, I don’t mean at all to say that all questions have been answered, and even the answers that we do have get more and more vague as you move down the science purity ladder. If all questions were solved, we would be out of a job for one! But I choose to interpret OP’s question as “is there anything unknowable?”. That’s the question relevant to our world right now, and I often disagree with the world view implied by popular science - that the world is full of wonder but also mystery. The mystery is not fundamental, but rather an expression of our individual and collective ignorance. There are even plenty of questions, like the delayed-choice quantum eraser, that have already been solved, and yet they keep popping up as examples of the unknowable, one even sniped me in this very thread (hi there!). Then people say “you do not even know whether eating eggs is good for you” and therefore by implication we shouldn’t listen to scientists at all. In that sense, the proliferation of the idea of mystery has become dangerous. The answer to unanswered questions is not gnosticism, it is as you said “further research” 😄!
Thank you for the thoughtful response. I see that we interpreted the question differently, based on what we thought was the issue of science communication. Which I think is really interesting!
I see what you mean - the people who impose their fantasies onto the science, who seemingly think there is some sort of “science god” who determines what fact is true on which days. Certainly, they are a problem. My experiences with non-scientific folk have actually usually been something of the opposite. They think that science is overly rigid and unchanging. They believe that science is merely a collection of facts to be memorized and models to be applied. Perhaps this is just the flip side of the same problem (maybe these people interpret changes in our knowledge to be evidence that there is no such thing as true facts?)
The difference in interpretation might stem from a difference in our fields. I assume you study physics. And I must assume that scientific rigor in physics depends on being certain about your discoveries. In my field (disease and pathogenesis), the biggest challenge is, surprisingly enough, convincing people that diseases are important things that need to be studied. Or perhaps that’s not a big surprise, given the public’s response to COVID-19. Even grant readers have to be convinced that there is merit in studying your disease of interest.
When I speak of my research to non-scientific people, a lot of the times the response is simply, “why not just use antibiotics? Why do we care about how diseases happen when we can just treat it?” A lot of my field, even in undergraduate programs, is dedicated to breaking down the notion that “we know enough, so don’t bother looking deeper.” I think there’s a very strong mental undercurrent in my field that we know next to nothing, and that we need to very quickly expand our knowledge before conventional medical science, especially our overreliance on antibiotics, gives out and fails. For instance, did you know that one of the most fundamental infection-detecting systems in our bodies (pattern recognition receptors) was discovered in mammals just over 20 years ago? The idea of pattern recognition receptors is literally only college-age.
So I actually find it interesting that you interpret the question so differently. It’s a testament to how anti-science rhetoric manifests in different ways to different fields
There are even plenty of questions, like the delayed-choice quantum eraser, that have already been solved
No, it has not been solved. At least not solved to the satisfaction of many physicists.
In one respect, there is nothing to solve. Everyone agrees on what you would observe in this experiment. The observations agree with what quantum equations predict. So you could stop there, and there would be no problem.
The problem arises when physicists want to assign meaning to quantum equations, to develop a human intuition. But so far every attempt to do so is flawed.
For example, the quantum eraser experiment produces results that are counterintuitive to one interpretation of quantum mechanics. Sabine’s “solution” is to use a different interpretation instead. But her interpretation introduces so many counterintuitive results for other experiments that most physicists still prefer the interpretation that can’t explain the quantum eraser. Which is why they still think about it.
In the end, choosing a particular interpretation amounts to choosing not if, but how QM will violate ordinary intuition. Sabine doesn’t actually solve this fundamental problem in her video. And since QM predictions are the same regardless of the interpretation, there is no correct choice.
Have we watched the same Sabine video? Delayed choice quantum eraser has nothing to do with interpretations of quantum mechanics, at least in so far as every interpretation (Copenhagen, de Broglie-Bohm, Many-Worlds) predicts the same outcome, which is also the one observed. The “solution” to DCQEE is a matter of simple accounting. And every single popular science DCQEE video GETS IT WRONG. The omission is so reckless it borders on malicious IMO.
For example, in that PBS video linked in this very thread, what does the host say at 7:07?
If we only look at photons whose twins end up at detectors C or D, we do see an interference pattern. It looks like the simple act of scrambling the which-way information retroactively [makes the interference pattern appear].
This is NOT WHAT THE PAPER SAYS OR SHOWS! On page 4 it is clear that figure R01 is the joint detection rate between screen and detector C-only! (Screen = D0, C = D1, D = D2, A = D3, B omitted). If you look at photons whose twins end up at detectors C inclusive-OR D, you DO NOT SEE AN INTERFERENCE PATTERN. (The paper doesn’t show that figure, you have to add figures R01 and R02 together yourself, and the peaks of one fill the troughs of the other because they are offset by phase π.) You get only 2 big peaks in total, just like in the standard which-way double slit experiment. The 2 peaks do NOT change retroactively no matter what choices you make! You NEED the information of whether detector C or D got activated to account which group (R01 or R02) to assign your detection event to! Only after you do the accounting can you see the two overlapping interference patterns within the data you already have and which itself does not change. If you consumed your twin photon at detector A or B to record which-way information, you cannot do the accounting! You only get one peak or the other (figure R03).
It’s a very tiny difference between lexical “OR” and inclusive “OR”, but in this case it makes ALL the difference. For years I was mystified by the DCQEE and how it exposes the ability of retrocausality, and turns out every single video simply lied to me.
Right, but in order to get the observed effect at D1 or D2 there must be interaction/interference between a wave from mirror A and a wave from mirror B (because otherwise why would D1 and D2 behave differently from D3 and D4?).
And that’s a problem for some interpretations of QM. Because when one of the entangled photons strikes the screen, its waveform is considered to have “collapsed”. Which means the waveform of the other entangled photon, still in flight, must also instantly “collapse”. Which means the photon still in flight can be reflected from mirror A or mirror B, but not both. Which means no interaction is possible at D1 or D2.
It’s not a problem for Copenhagen if that’s the interpretation you are referring to. Yes, the first photon “collapses” when in strikes the screen, but it still went through both slits. Even in Copenhagen both slit paths are taken at once, the photon doesn’t collapse when it goes through the slit, it collapses later. When the first photon hits the screen and collapses, that doesn’t mean its twin photon collapses too. Where would it even collapse to, one path or the other? Why? The first photon didn’t take only one path! The twin photon is still in flight and still in superposition, taking both paths, and reflecting off both mirrors.
When the first photon hits the screen and collapses, that doesn’t mean its twin photon collapses too.
Yes, it does. By definition, entangled particles are described by a single wave function. If the wave function collapses, it has to collapse for both of them.
So for example, an entangled pair of electrons can have a superposition of up and down spin before either one is measured. But if you detect the spin of one electron as up, then you immediately know that the spin of the second electron must be down. And if the second electron must be down then it is no longer in superposition, i.e. its wave function has also collapsed.
Ok, I thought about it some more, and I want to make a correction to my description! The twin photon does collapse, but it doesn’t collapse to a single point or a single path. It collapses to a different superposition, a subset of its original wavefunction.
I understand it is an option even under Copenhagen. So in your two-electron example, where your have 1/sqrt(2)(|z+z-> + |z-z+>), when you measure your first electron, what if instead of measuring it along z+ you measure it along z+45°? It collapses into up or down along that axis (let’s say up), and the entangled second electron collapses too, but it doesn’t collapse into z-135°! The second electron collapses into a superposition of (I think) 1/2 |z+> + sqrt(3)/2 |z-> . I.e. when you measure the second electron along z+, you get 25% up and 75% down. The second electron is correlated to the first, but it is no longer the exact opposite to the first, because the axis you measured the first at was not z+ but inclined to it. There is exists no axis that you could measure the second electron at and get 100% up because it is not a pure state, it is still in superposition.
So back to the quantum eraser experiment, when the first photon hits the screen D0 and collapses, say at position 1.5, the twin photon collapses to a sub-superposition of its state, something like 80% path A and 20% path B. It still takes both paths, but in such a manner that if you choose to measure which-path information at detector D3 it will be more strongly correlated with path A, and if you choose to measure the self-interference signal from the mirror at D1 or D2, it will still self-interfere and will be more strongly correlated with detector D1. What do you think?
In the electron example, if the two electrons are entangled then the wave functions must be the shared. The new superposition for the second electron would therefore be shared with the first electron. So if you measured the second electron along z+ and got up, then if you measured the first electron again, this time along z+, it would give down.
Likewise if the twin photon is still in superposition, then the first photon is also in superposition. Which is hard to accept in the Copenhagen interpretation, given that the first photon has been absorbed. If absorption doesn’t completely collapse a wave function, then what does?
So if you measured the second electron along z+ and got up, then if you measured the first electron again, this time along z+, it would give down.
Right! So what happens when you have two z+z- entangled electrons, and you measure one along z+45° and then the other along z+0°? What would happen if you measure the second electron along z+45° as well?
Entangled electrons are entangled in all directions. If you measure one along any direction, you can completely predict the measurement of its pair in the same direction.
In other words, measuring one along X and its pair at Y is equivalent to measuring one along X and then measuring the same one again at Y (accounting for the sign shift in the pair, of course).
Hmm interesting. I may have been mistaken about the electrons only being entangled in a single direction. I thought that if you prepared a pair of electrons in state 1/sqrt(2) (|z+z-> + |z-z+>) and then measured it in y there would be no correlation, but based on: …stackexchange.com/…/intuition-for-results-of-a-m… …stackexchange.com/…/what-is-the-quantum-state-of…
if I had done the 90° rotation properly, the math works out such that the electrons would still be entangled in the new y+ basis! There is no way to only entangle them in z alone - if they are entangled in z they are also entangled in x and y. My math skills were 20 years rusty, sorry!
I still think my original proposition, that in the DCQEE under Copenhagen, an observation that collapses one photon, collapses the other photon to a sub-superposition, can be salvaged. In the second stackexchange link we are reminded that for a single electron, the superposition state 1/sqrt(2) (|y+> - |y->) is the same as |z+> state! They describe the same wavefunction psi, expressed in different basis: (y+,y-) vs. (z+,z-). When we take a single electron in superposition 1/sqrt(2) (|z+> + |z->) and measure it in z, and it collapses to, say, z+, we know that it is a pure state in z basis, but expressed in y basis it is now a superposition of 1/sqrt(2) (|y+> - |y->)! Indeed if we measure it now in y, we will get 50% y+ and 50% y-.
So in DCQEE when you collapse the first photon into a single position on the screen, the twin photon does collapse, but its basis is not expressed in terms of single positions! It’s some weird agglomeration of them. If you were to take that “pure” state and express it in terms of position basis, you would get a superposition of, say, 80% path A and 20% path B.
Well, if the second photon is in a new, weird superposition then the first photon must also be in the same new, weird superposition. Again, I don’t that’s compatible with Copenhagen given that the first photon no longer exists.
Note by the way that 50% y+ and 50% y- is how all photons start. So if that’s also the final state then there is no reason for it to prefer any detector over the others.
Yeah, but when you start with a 50% z+ / 50% z- electron, and you measure it and get say z+, it is now 100% z+, right? If you measure it again, you will always get z+. And then you give a bunch of them to your buddy with an identical lab and an identical Stern-Gerlach apparatus and and they say “hey, I measured your electrons that you said were 100% z+, and I’m getting 50% z+ 50% z-”. And you say “dude! your lab is in China! your z+ is my y+! you have to do coordinate rotation and basis substitution! if you look at my pure electron in your sideways basis, it’s in superposition for you”.
When the first photon hits the screen, the basis is the screen basis. Each position on the screen - 1.4, 1.5, 1.6, etc - is an eigenvector and the first photon collapses to one of those eigenvectors. The second photon collapses too, but you are wrongly equating the positions on the screen and positions on paths A/B as if they are in the same basis. They are not! You were just misled to think they are the same basis because they are both named “position”, but they are as different as the z+ axis in America is different from z+ axis in China.
The second photon collapses into the screen basis eigenvector 1.5 but that 1.5 does not correspond to any single location on path A or path B. If you do the basis substitution from screen basis into path basis, you get something like 80% path A and 20% path B (and something weird with the phases too I bet). Does that sound accurate?
I suspect one of them is some people get shockingly little exercise. When I lived in the suburbs, my daily could often be “walk to car, walk from lot to office desk (taking the elevator instead of stairs), walk from there to car (via elevator), walk from car to home”. Total walking time less than five minutes.
When I moved to New York I got at least twenty minutes of walking to and from the subway every day just going into work. Plus now I walk to the grocery and other stuff.
That doesn’t really explain why obesity has increased. If anything, it is often easier to get by without a car today than 20 years ago. For example, my own city is full of bike paths that did not exist then.
They did add a bunch of bike paths in my town too, yet I’m 5 minutes by car from my nearest grocery store, but by bike have to cross a bridge with fenced sidewalks and no shoulder, ride on a 80km/h+ road, and a bunch of other BS just to get there. Bike infrastructure doesn’t mean good bike infrastructure I guess.
Sure, it’s still not good. But that can’t explain why people are more obese now than a couple of decades ago, since bike infrastructure was even worse then.
I wonder if part of it is more likelihood to have multiple cars, less likelihood to have someone prepare meals from scratch … or maybe that’s more than a couple decades.
COViD helped me discover a passion for cooking (baking too, but not just baking) so in the last few years my kids have had more meals prepared from scratch, more balanced and nutritious, and a lot more exposure to meals from other cultures.
One of the new tools I got is an air fryer. It’s a really convenient way to make the equivalent of grilled chicken or other foods …. But all too often I find myself feeding it processed junk like chicken strips and frozen fries
Space elevators on a inhabited world seem like a terrible idea though. One terrorist attack and you have a giant rope that will wrap around the world twice, through lots of heavily populated areas. I can see one going from the moon towards the earth though.
I mean like you could do 10x the damage by just redirecting an asteroid or even just gunning it with a fairly aerodynamic ship, its fantasy
But also the ideal elavator would have to be lightweight anyways so eith gravity it wouldnt work against itself, and therefore pretty easily able to burn up in the atmosphere (maximized surface area with the small size).
Also they wouldn’t have to be that long, a stable orbit isn’t super high up there - more like 100km or so.
And then again all this was about desolate planets in the first place
Space elevators need to have the majority of their mass higher than geostationary orbit to hold it up, which is 22000 miles above the earth. So I suppose it wouldn’t wrap around the planet more than once. And while true you can do more damage with an asteroid, it would be a far easier target for a terrorist group than something that far away.
First, though, your premise is a bit off. Zooming in still wouldn’t change the speed of light or change how fast the photons take to get from point A to your zoom lens. Zooming doesn’t give you a time or distance shortcut - all zooming does is decrease the angle of view of whatever you are pointied at. The only thing that matters in the double slit experiment is whether you observe them enroute or if you observe the screen after impact. If the screen were between you and the photon sources and you zoomed in, the photons would still hit the screen first and the photons you observe through the lens would come after.
The TL/DR of that article I cited earlier is that we still know the field would collapse. The more interesting question (and the one they pose in the article that remains unanswered) is: how fast does the collapse propagate back to the source? Is the propagation delay of the collapse instant/infinite (like what would be described by entanglement) or is the speed of the collapse still subjected to the speed of light (which is the same for the propagation delay of gravitational waves)?
The links to the older articles are dead in that link. Here’s an archive of the 3rd essay (and it links to the second and first). The 3rd essay presents a thought experiment very close to what OP is asking. If we delay the choice of inserting a detector then would we still get an interference pattern when we’re not supposed to? It seems that the question is still unanswered but theoretically, no, because the universe is not locally real and quantum effects seem to happen faster than light in plenty of other experiments.
Naturally this kind of thing happens over tens or hundreds of thousands of years. So, even going back to BC times, we’re still only a small fraction of how far we need to go back to find really major, long-term climatic shifts. These things are supposed to happen sloooowwwwllly, not really discernable as changing over the scale of a single human lifetime, which is just the blink of an eye in planetary time scales.
Can we though? Probably. We can certainly dam rivers and use irrigation to make the land more agriculturally productive. But we should have the technology currently to attempt more dramatic geoengineering projects if we wished.
The problem though, is unintended consequences, where you change one thing over here, and you didn’t realize it was also controlling something else over there, and that thing changes too now, even though you didn’t necessarily want it to.
Like, to make up a fictional example, say we engineered rainfall over the Sahara somehow. But we didn’t know some of this moisture influences air currents, and now southern Europe and the Middle East are changing too somehow, by accident.
It’s like when you’re trying to untie a really tangled knot, and you pull on one part thinking its going to start undoing it, but it just tightens it somewhere else instead.
I know China has done a lot of “regreening” of areas and I’ve read that the Sinai could be a good candidate for the same sort of restoration. It’s not my area of expertise but the best candidates seem to be areas that are deserts because of human activity (like over farming, excessive water use, etc.).
What China did was plant trees, restore nutrients to the soil, add terraces to hills, limit livestock, and other things that slow down water loss. They successfully regreened and area the size of France but I think, crucially, it got enough water naturally. The land was just depleted, which caused the water to wash away topsoil instead of support vegetation.
So, I don’t think we could realistically show up to an arid desert and turn it into much. But there’s places we think of as desert now that would be good candidates for restoration.
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