Ask MetaFilter questions in the science & nature category

What mathematical techniques came after calculus?

alex1965 — Wed, 21 Apr 2021 12:10:47 -0800

I was reading this article about Nobel prize-winning physicist Richard Feynman, and I came upon an interesting quote. I hope that the quote can be explained to me by someone with a background in math and/or physics. The article was written by Stephen Wolfram, who was a PhD student in the physics department at CalTech, where Feynman was based at the time. Wolfram writes:

It’s kind of interesting to look at [Feynman's handwritten note with calculations related to a Feynman diagram]. His style was always very much the same. He always just used regular calculus and things. Essentially nineteenth-century mathematics. He never trusted much else. But wherever one could go with that, Feynman could go. Like no one else.

So this quote is interesting to me for a couple of reasons. I'm wondering what sorts of more-modern mathematical techniques were available to Feynman to use. What's more advanced than calculus? I'm also curious why Feynman didn't trust the newer techniques. Is there something that's unreliable about those methods? Feynman was a genius, so I think he probably understood the newer techniques very well, but he consciously chose not to use them. He must have had his reasons.

Crepuscular Hallucinations

sjswitzer — Mon, 19 Apr 2021 18:21:41 -0800

Going on 20 years or so I've experienced occasional, for want of a better word, visual hallucinations. I know they're not real (except perhaps in one case) and I'm not worried about them in the least. I just want to know if they're common and if there's a name for them. They typically occur in the complete dark while my eyes are accommodating from light after having got up to go to the bathroom. For instance, in the complete dark, with closed eyes and with a cover over my face I can sometimes "see" my hand very dimly. If I put up two fingers I see two fingers. If I move my hand I can see it move. I know there are many inputs to the visual system, including very detailed information about the body map. What I think is happening is that my visual system is using that information to tell me what it knows in other ways.

Relatedly, perhaps, are visual phenomena that happen in dim light, also usually after having just been exposed to brighter light... and with my eyes closed. In a few cases I seemed to be seeing the red blood cells coursing through my retinal capillaries. I can just believe that my eyes were sensitized so that they were able to see what was going on in the retina directly. So this case is the one that I think might not be a hallucination, as such. But perhaps it was after all.

And sometimes, very rarely, again in crepuscular situations, I can see moving figures along a horizontal line at or below the center. Sometimes they are abstract and sometimes they suggest figures of sorts. I would even say they are similar to the descriptions I've read about the "machine elves" people see when taking DMT (FWIW, I have no direct experience of this). I assume this is a case where my brain's image recognition apparatus is primed to identify figures from noise much as "deep dream" does. To be clear I was not in any kind of partial dream state; I was fully awake.

Again, this isn't something that alarms me and if I weren't such a nerd I'd neither have noticed it or thought much about it. And the images are generally dim, though sometimes distinct. Anyway, I'm wondering if anyone else has noticed/experienced this and, better, if someone can point me for a name for this (these) phenomena and anything written about it; I'm going to tag this as a "science and nature" question.

Which of these trees have pretty flowers in the spring?

geegollygosh — Fri, 16 Apr 2021 19:10:38 -0800

Do you know a lot about flowering trees? Can you tell me which species have traditionally pretty flowers in the spring? Northeastern US (New England). This is for a data project I'm doing as part of a class I'm taking for fun at the library, if you're curious. I found out that my city maps every tree (amazing!), and for my final project I want to map the neighborhoods in my city that will have the most flowering ornamental trees in the spring.

The list of trees is as follows (I converted the most common ones from latin names into common names. I only broke it down to the genus level, because at the species level it was completely unmanageable):
Maple
Aesculus
Ailanthus
Alnus
Amelanchier
Betula
Carpinus
Carya
Catalpa
Cedrus
Hackberry
Cercidiphyllum
Cercis
Chionanthus
Cladrastis
Dogwood
Corylus
Hawthorn
Empty
Eucommia
Fagus
Ash
Ginkgo
Honey Locust
Gymnocladus
Halesia
Hamamelis
Hibiscus
Ilex
Juglans
Juniperus
Koelrenteria
Sweet Gum
Liriodendron
Maacki
Magnolia
Crab Apple
Metasequoia
Morus
Nyssa
Ostrya
Other
Oxydendrum
Parrotia
Paulownia
Picea
Pinus
Plane Tree
Populus
Black Cherry
Callery Pear
White Oak
Robinia
Salix
Sophora
Sorbus
Stewartia
Stump
Lilac
Taxodium
Tilia
Tsuga
Elm
Zelkova

Thank you!

Trail making standards

falsedmitri — Fri, 16 Apr 2021 09:46:22 -0800

Trail making standards, either federal (US) or state (New Mexico)? In particular, I want to know if there is a standard number for an incline to decide whether it can be a trail or it should be steps. Maybe its a hard number, maybe its based on angle of repose?

Is there such a thing as a water draining pump?

fantasticness — Thu, 15 Apr 2021 17:26:57 -0800

Specifically to drain soapy water from a tub? The shower in our RV doesn't work so when we travel for several days in a row, we take simple showers which consist of literally standing in an a plastic kiddie pool while pouring water over our heads and lathering up.

The problem is that the soapy water that ends up in the pool becomes impossible to drain out. Even though there is only about an inch of water it's impossible to pick up the pool and dump the water out. So we just grab a small bucket- gather in water- dump out the water- and keep repeating until it's possible to just pick up the whole pool. Very tedious.

The kiddie pool DOES have a drain that we can open which is on the side of the pool, but since the pool sits on the floor we can't use it. We were thinking of getting a small platform to stand the entire pool on. That way we can just put a bucket underneath the side drain , open the drain and let gravity do the work, but if there's a way to leave the pool on the floor and still have the water drain out that would be ideal. Not sure if the laws of physics allow that though. Which is why I'm asking here.

How make this vase "water safe"

dancing leaves — Wed, 14 Apr 2021 19:02:00 -0800

I bought a metal (aluminum?) vase at a thrift store. It has some kind of coating on the inside that I assumed meant it would be fine to use as a vase for fresh flowers. I didn't notice the sticker says "not water safe" on it until I was at home washing it. Can I make it water safe with some kind of coating? NOTE: I DO NOT WANT TO USE A SEPARATE INNER CONTAINER.

Please help id this moth

bleary — Sat, 10 Apr 2021 09:58:33 -0800

I'm not having luck with insect id sites. jpg

Elephants on a Bridge

Eyebrows McGee — Thu, 08 Apr 2021 19:34:13 -0800

Mini McGee says, "I learned you can ask physics really weird questions! Like, how thick would a cardboard bridge have to be if it was over a 40-foot gap and could support the weight of an elephant?" I said, "I don't know, do I look like an engineer?" and he said, "But you could Ask MetaFilter, I bet they like weird physics questions!"

He said it's corrugated cardboard, and I decided on an adult male Asian elephant weighing 8,000 pounds, which seems to be right in the middle of possible elephant sizes.

I will gratefully take either actual answers to this question that I can show to him how you would figure that out, or pointers to bridge/materials equations that we can work out ourselves (as an 11-year-old and a woman who did pass calculus many years ago but is only reliable up through algebra anymore). This is not homework or anything he's learning in school, this is just him having recently discovered Mythbusters and us all having been trapped in a house together for a solid year. :)

(His follow-up example of "weird questions you can ask physics" was "How thick would walls made of cheese have to be to hold up the water in an above-ground swimming pool?" And that one I knew was, "First you need to specify your cheese and second it probably depends on the size of the pool.")

Why does a moderate amount of vaccination not majorly cut covid rates?

wnissen — Thu, 08 Apr 2021 07:54:54 -0800

If the growth is exponential, isn't even a relatively small amount of vaccination going to cut the exponent? Naively I would think that if the R value is, say, 1.1, then vaccination of 30% of the population would drop it to 0.8, which would extinguish the outbreak (or at least decrease it massively). What's going on? From the slightly increasing U.S. case rates, it's clear that R is greater than 1 in the actual population. So any effect from vaccination is being more than offset by something else. Does anyone have information on what? Is it increased transmissibility, increased risky behavior, are the sub-populations that are unvaccinated that are driving the numbers overall? Happy to read intuitive explanations and scholarly work.

Tea-Light and Tempered Glass - The Safe Distance Factor Question

watercarrier — Thu, 08 Apr 2021 06:15:51 -0800

So, I put together a tea-light tempered glass kettle warmer from 2 elements I had around, one being sterling, the stainless top being the top - they fit together like one unit. The stainless top has holes pre-drilled in circular design. Question - how close can I place the tea-light under the stainless top under the kettle without it cracking? I want the kettle to keep as hot as possible for as long as the tea-light stays lit. I need the distance to be precise and scientifically based, because this is how the production is rolling. Thank you :)

Where do restriction enzymes come from?

wesleyac — Tue, 06 Apr 2021 22:51:32 -0800

When doing DNA recombination, how do people select what restriction enzymes to use? Is there like, a catalog of restriction enzymes I can look at and pick the right ones? I'm trying to understand how insulin is produced via recombinant DNA, but I can't find anything that goes into the level of "here are the actual physical steps that are involved in producing insulin". Particularly mysterious to me is how the restriction enzymes are selected. I'm curious both what restriction enzymes are used to produce insulin (is it the same for all the different types of insulin? is it a trade secret, or something?), how those particular enzymes were decided on, and how those enzymes are actually produced.

What’s inside the magnetic levitator?

varion — Wed, 31 Mar 2021 10:49:05 -0800

What is inside this four kilo magnetic levitation device? https://virtualongroup.com/product/levitation-display-4-kg/

How flexible is an unconscious body

Quillcards — Tue, 30 Mar 2021 02:46:27 -0800

How flexible is an unconscious body under anaesthetic? I watched a video on relaxation, and the person giving the lesson said that people under anaesthetic are very flexible.

She said you can put the legs of even an older person with stiff joints right over their head and that people are so flexible when anaesthetised that doctors and nurses have to be careful when moving them.

I'd like to hear from anyone with substantial direct experience of the truth or otherwise of this statement.

Was it a storm? Was it a swarm?

dreamphone — Sun, 28 Mar 2021 18:06:48 -0800

I’ve never really understood what kind of weather or insect event occurred on a highway between Tucson and Phoenix back in the 90s. Surely, someone here can enlighten me. Many years ago now, I was driving with a passenger in my small car on Rt 17 from Tucson to Phoenix. It was daytime and there were no other cars around us. Seemingly out of nowhere, I had the sensation of my car being buffeted by a sudden and intensely strong wind, such that the car jogged a (tiny) bit to the left. It lasted but a second. My windshield was simultaneously scattered with debris, and when I pulled over to figure out what was up, the windshield was pretty smeary and there were about a dozen or so partial bodies of bees on the windshield. We hadn’t noticed anything out of the ordinary in the moments before this occurred, but we are both, admittedly, rather unobservant.

What happened there? Why were there bees? Why were there bee halves? Were they already halved, or did that occur when they hit my car? I’ve always assumed it was a “dust devil” that picked up some random bees along the way, but I’m thinking that there’s got to be someone out there who might be able to clear up this persistent personal mystery.

The More Things Change, the More They Stay the Same...

AugustWest — Fri, 26 Mar 2021 10:53:27 -0800

Has either (or both) of the Pfizer and Moderna vaccines formula changed over time. That is, if I got the vaccine tomorrow would I be getting the exact same formula as the person who got it first (once available to the public -- I think it was a nurse in NY)? Or, does the formula change slightly to take into account current data or current variants of the virus?

Long Range Weather and Climate Forecasting? Building for distant future

GPF — Tue, 23 Mar 2021 07:48:25 -0800

Is there a source that makes localized forecasts of weather and climate in the far (years to decades) future and presents them in a unified, data driven presentation? There are lots of broad models of global and regional changes presented in narrative form, but is there something that could, say, take an address and present a forecast or prediction of future climate? This is obviously fraught with uncertainty. Even a range might be helpful. Surely there are well-funded civil and infrastructure projects that do this work at least on an ad hoc basis. How does that work? Hire an climate scientist to write a report? If one wants to build a project that will last more than a generation or two (or more) how do we evaluate long rang climate effects? What's the market and technology for a public-oriented or publicly-accessible approach?

How do geneticists try to thwart racists from misusing their research?

theory — Mon, 22 Mar 2021 18:19:49 -0800

An article I read within the past couple years (sorry, can’t remember the source) mentioned a human genetics conference in the US. At this conference there was apparently not enough support for convening a panel to discuss the problem of racists who appropriate and disseminate twisted interpretations of legitimate research. So I have several questions: Why would there have been a reluctance to discuss this problem, which seems like it should encompass not just bad faith readings by racists, but also science journalists misinterpreting and miscommunicating the content of scientific papers? To what extent do scientists in general —and human geneticists in particular— think about ways to thwart bad takes on their findings? And finally, what tactics have actually been tried and seem to be beneficial?

Parks with Magnolias (+ spring flowers) in/near Columbia, MD

needs more cowbell — Sun, 21 Mar 2021 06:41:54 -0800

I am, for various reasons, in Columbia, Maryland in a neighborhood where none of yards or parks have the kind of landscaping I'm used to enjoying in the spring and I feel out of touch. I want to see things blooming--magnolias, other blooming trees, daffodils, irises, etc. What parks can I drive to nearby that have a good concentration of this stuff? Neighborhoods with nice landscaping is OK too. I would prefer not to go to Baltimore for Reasons. DC is possible but I'd l like closer options.

The physics of maple sap reduction

daisyace — Mon, 15 Mar 2021 09:31:54 -0800

We use a wood stove for heat. We tap a single maple tree for fun. Before boiling the sap down in the kitchen, we passively reduce it most of the way in a pot on the wood stove. I'm wondering whether it reduces more if we do it in big batches or sequential small ones, and with or without a heat-powered fan. We use the wood stove to heat the house, and we don't change the temperature or run time for the benefit of the sap -- we just sit a pot of sap on top when we have a fire going anyway. On the wood stove, the sap evaporates, steams, and gets little bubbles on the bottom of the pot, but it doesn't boil. I'm wondering...

1. Is it more efficient to have a gallon or more of sap in the pot at once? Or to reduce one fraction, and then replace it with the next fraction? How many fractions would be most efficient? A couple of assumptions:
- We start the first batch of sap from refrigerator-temperature in the morning. We could queue up subsequent batches at room temperature first. But if batches are more efficient, is that the only reason why?
- We're using the same pot either way; it takes up most of the available flat surface we've got.

2. Is it more efficient to point our heat-powered fan (like this) at the pot?

This is just for fun, so we're not looking to buy anything or do anything less convenient to eke out more efficiency. But these couple of variables seem worth playing with, and they've also just piqued my curiosity.

Statistical conundrum

basalganglia — Sat, 13 Mar 2021 04:56:28 -0800

I have a set of anonymous survey data that was sent out via email and social media at two time points. Some of the people who filled it out at time point 1 probably did so again at time point 2, but because the survey was anonymous, I don't know the proportion of overlap. What is the best way to compare time point 1 and time point 2? There were hundreds of responses each time; > 400 people for time 1 and > 1800 for time 2. The overlap could range from 0 to 400+ (i.e. everyone at time 1 filled it out at time point 2, plus another ~1400 or so at time 2). Unfortunately I have no way of determining how paired/unpaired the data is.

My original thought was that since the sample size is so large, it would be ok to just do an unpaired t-test and note the potential for correlation in the limitations section of the paper. However, one reviewer has suggested something called a "optimal pooled t-test," which best I can tell involves weighting the paired and unpaired data slightly differently. Makes sense, but is that even doable without knowing how much overlap is in your sample? From this analysis of partially paired data, it looks like the unpaired t-test and pooled t-test are pretty similar -- pooled has more power for highly paired data, but if anything that implies that if I detect a difference between Time 1 and Time 2 with an unpaired test, the true difference will be even greater. Right?

In retrospect, I wish I had included a statistician in the study design before we even got started -- lessons learned! I have emailed for a local stats consult but it will be a few days before they get back to me, and I'm hoping for a little hivemind guidance so that I can make the most of my time with the stats person.

there must be a name for this.

snerson — Fri, 12 Mar 2021 12:08:18 -0800

occasionally, while going up or down stairs, I will forget how many steps there are. So I'll think I've hit the last stair, and move like I should be able to walk on a flat surface, and I'll stumble pretty badly when my foot doesn't connect with the ground where I expect. Ouch. A) I can't be the only person who does this, right? B) is there a more specific name for this phenomenon other than "spatial brain fart"?

Looking for an excellent, wide-ranging medical blog/newsletter

cnidaria — Tue, 09 Mar 2021 14:25:28 -0800

I love reading The Prepared -- a great manufacturing and engineering-focused email newsletter with lots of fascinating links to articles, videos, and other content across an extremely broad range of topics. I'm hoping to find a similar newsletter (or blog / link aggregator) but with a broad medical/human health focus (or perhaps life science generally). Any recommendations? Random sampling of the kind of stuff I'd love to see in my dream medical newsletter:

- adaptive engineering at home for a disability
- immunology papers on COVID and long COVID
- 3-D printing for growing ear tissue scaffolds for microtia
- lead poisoning / asthma / environmental health
- social determinants of health
- the logistics of organ transplantation
- the microbiome of the built environment
- decompression physiology and gas physiology
- the Global Microbiome Conservancy

Is the Johnson and Johnson COVID vaccine safe for those at risk of HIV?

Nelson — Fri, 05 Mar 2021 11:03:17 -0800

Is the Johnson and Johnson COVID vaccine safe for those at risk of HIV exposure? Back in October 2020 there was an article published in The Lancet highlighting a possible risk of increased susceptibility to HIV from adenovirus-5 vaccines like the Chinese and Russian Covid vaccines. The Johnson & Johnson vaccine is derived from adenovirus-26. Is there a reason to be concerned? The concern about risk comes from field experience. A 2007 HIV vaccine trial got derailed because they discovered that their Ad5 vaccine was actually causing some men to be more susceptible to HIV infection, in particular if they'd previously been exposed to adenovirus. The conclusion was that there was a risk Ad5 vaccines could create a population more at risk for HIV infection.

Fast forward to 2020 and Johnson & Johnson has moved forward with adenovirus vaccines for several diseases; Covid, HIV, and others. But I haven't seen anything that says this concern raised in the Lancet article has been addressed. Has it?

One complicating factor; the J&J Covid vaccine is based on adenovirus-26, not Ad5. I have no idea whether the HIV effect seen from Ad5 would also apply to Ad26 or not. (The Russian and Chinese vaccines are Ad5 vaccines.)

This December 2020 note says that the risk shouldn't be considered too serious because it's unlikely many people were previously exposed to the adenovirus being used for the vaccine.

This article in Poz magazine addresses the Ad5 concern, but then writes it off for now because their audience at the time was only likely to get an mRNA vaccine, not an adenovirus vaccine. That's no longer the case though.

PS: I'm 100% enthusiastic about Covid vaccines! I also have read enough to convince me the J&J vaccine is good for preventing serious Covid illness just like the mRNA vaccines (despite the confusing statistics on efficacy). My only concern is this specific interaction with HIV exposure. I will get a vaccine regardless, but I'm wondering if I should insist on one not derived from adenovirus

Is Jung as full of it as Freud?

Hactar — Fri, 05 Mar 2021 08:11:47 -0800

Are there any studies that actual try to test for universal archetypes out the collective unconscious? Especially any that work across cultural lines with cultures that have not been heavily impacted by the west? Whenever I see anything Jungian, I immediately put it in the same mental box as Freudian stuff, that is interesting in a literary critical sense and perhaps informing writing, but with no basis in reality.

I realize that I was basing this in the time of his writings and the rigor (well, lack there of) applied to psychology then combined with his being a student of Freud. I did a quick google search on collective unconscious/jungian archetypes and found papers that are either about using it in therapy published in Jungian journals or using it in a critical sense to examine writings. Wikipedia tells me it encompasses all humans and therefore for some reason cannot be studied and that Jung's archetypes are so fuzzy that they might as well be horoscopes.

So, is there any actual science of the mind there, or can I go back to dismissing this except in the broadest terms (most humans, due to having a given makeup of sensory organs, living in a patriarchy, and having things like parents, have somewhat similar formative experiences) like I do for Freudianism and the strong Sappir-Waldorf hypothesis?

(Also, I know that's a falsifiability issue in psychology, so I'll take things with a grain of salt.)

(Question inspired by the MBTI post on the blue.)

Safe to wear heated thermal garments while pregnant?

Anonymous — Wed, 03 Mar 2021 13:37:32 -0800

I'm going to be working at an outdoor job site for a few days. The employees will be given "thin electric heated thermals" to wear- basically battery operated long johns. I'm 17 weeks pregnant but my workplace doesn't know. Is this safe? Can I make it safer? We'll all have to be outside for about 8 hours, and every other person will be wearing the heated thermals, so if my cold tolerance is much less than everyone else's, that's a problem. I won't have leeway to leave the group, and there won't really be anywhere to go to warm up.

I have to wear a specific uniform for work - basically a warm fall outfit with layers - not terrible but not warm enough to be outside all day in the winter. I cannot add extra layers over it as all employees need to match.

So I pretty much have to wear the thermals but I'm a bit worried. My plan was:

Wear another layer against my skin below them
Wear wool and silk etc to stay extra warm
Be very familiar with how to turn the thermals off and take heat breaks
Drink lots of water
Pad my belly area with extra fabric so the heat is buffered over that area

Anything else I can do? Anything specific I should be aware of?