Questions in the Science & Nature category.
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March 26

What is this generalization of formal grammar called?

I have been reading a little about formal grammar in the context of computer language parsing. I understand that a formal grammar G is defined as the tuple (N, Σ, P, S), where N are nonterminal symbols, Σ are terminal symbols, P are production rules, and S is the start symbol. N, Σ, and P are all finite sets. But what is it called if they're infinite? [more inside]
posted by biogeo at 10:43 AM - 5 answers

March 25

Best examples of interactive dichotomous keys

I am looking for examples of interactive dichotomous keys to use in a lesson on creating dichotomous keys. The few I've found have been... too cutesy and aimed at younger people. Do you know of any that are simple to follow, but not dumbed-down? [more inside]
posted by Acari at 4:56 PM - 4 answers

March 24

Blundering around in statistics

I am trying to understand some statistical data in a piece dealing with a historical text corpus and am in over my depth, which doesn’t take much doing. I’d be grateful for a simple explanation of what’s going on, plus the technical terms for this phenomenon, if it is one. [more inside]
posted by ogorki at 6:44 PM - 8 answers

March 21

Term for the mental image you form about radio personalities?

Is there a term for the phenomenon of imagining what a person looks like based on their voice? [more inside]
posted by Ms. Toad at 6:04 AM - 2 answers

March 13

I want to watch trout run

There's a park in the Bay Area that has a fish run to allow rainbow trout to migrate upstream. I've never seen fish migrating and I am oddly fixated on watching trout go up the fish run. Are there even trout in these streams anymore? [more inside]
posted by shapes that haunt the dusk at 4:35 PM - 5 answers

March 11

I, uh, have to, uh, think a long backspace very hard about the words

Why do I suck at dictating texts? I can speak at the rate I can think (or faster, oops), and I can type (key and touch) at nearly stream-of-consciousness speed, but dictating SMS messages is always a really fraught process. I find that I stumble over words, need to start over, miss important points and basically just fail for anything more complex than "yes" "no" "cheddar please". Why is that? Is there a cognitive reason? Am I using under-exercised parts of the brain or something? [more inside]
posted by TheNewWazoo at 2:14 PM - 5 answers

Film ID: Orca (killer whales) documentary

I watched a documentary last year online about a pod of orcas residing off the shores of Argentina and their hunting and social habits. There was a specific scene where the calf of the pod wanders into a kelp forest and when it discovers it is separated from the rest of the pod, it remembers to stay still and call out for help. The rest of the pod then respond to the calls. What is the name of this documentary? I've been searching for too long but none of the videos that pop up have this scene.
posted by BeHereNow at 8:14 AM - 0 answers

March 10

What is this Florida tree/plant with green fruits and cuneate leaves?

I've been trying for weeks to identify a Florida tree for my mom from a photo, and I'm stymied. Can you help figure out what type of plant this is? Tampa, Florida. March 3, 2017. [more inside]
posted by gemmy at 3:23 PM - 6 answers

Help me size an LED driver--I'm confused.

I'd like to build a shop light/tinker light out of cheap LED COBs, but I'm confused about how to size the driver. COBs have wattage, voltage and amperage ratings. To my understanding, to run 3 10w COBs, I would need a driver that puts out 30 watts. The voltage seems pretty straight forward, it's represented by a single number and the driver should be capable of delivering that. The amperage is where I get REALLY confused. [more inside]
posted by OmieWise at 12:24 PM - 3 answers

March 7

Gardening question: should I remove lawn from around a young tree?

After much lobbying, the council has planted some trees on the London housing estate where I live. Three years on, some are doing well, others less so. Some have been planted in grass-covered areas, and the grass has regrown up to the trunks. Could this be a major factor in why they're not growing very well? Is it likely to make much of a difference if I remove the grass around the base of the tree? Do I risk damaging the roots if I do?
posted by snarfois at 2:39 AM - 6 answers

March 5

How to calculate uncertainty when redistributing a population

I am trying to understand a statistical problem with resampling and variation, and I’m unsure of my terminology so it’s hard to search. I have a set of geographic areas with known populations, and I’d like to generate new areas with redistributions of those populations. I can assume that the population is evenly spread throughout the original areas, but this gives me numbers without any kind of confidence interval. What would I need to do to calculate variance or deviation for this problem? [more inside]
posted by migurski at 5:02 PM - 10 answers

How To Preserve a Beetle

How do you preserve a dead beetle for long lasting ornamental value? [more inside]
posted by glitter at 4:51 PM - 4 answers

March 3

Science, please

Is there any scientific evidence that PMS/hormones make women unreliable/unstable? [more inside]
posted by yawper at 7:01 AM - 17 answers

March 1

Can I be hypnotized?

I lost/hid/misplaced an expensive and sentimental piece of jewelry several months ago. I really think I hid it somewhere in my house but I've searched and searched with no luck. Is hypnosis to remember what I did with it a real thing? Maybe I just lost it outside the house. I know it was in my purse at one point. [more inside]
posted by tamitang at 7:19 PM - 8 answers

Tools & sites for Junior Rock Hounds in New England?

What things should I bring along on a hike with some kids (age 9 & 12) who are curious about looking for cool rocks after a great demo in school? [more inside]
posted by wenestvedt at 1:40 PM - 7 answers

February 26

Non-technical book about neural networks?

Is there a non-technical book that explains neural networks in sort of an introductory way for general readers? [more inside]
posted by Dr. Send at 8:36 AM - 12 answers

February 25

What are these ants doing?

Please explain this ant (and other small insect) behavior I'm witnessing. [more inside]
posted by BlahLaLa at 11:45 AM - 6 answers

February 24

What is the scientific principle that governs how big animals get?

After seeing the trailer for the latest King Kong movie, it got me thinking about why animals only get as big as they do. Is it because they evolve in an ecosystem and natural selection doesn't want you getting bigger than the food supply can managably feed? Is there a scientific principle that governs this that people have named? Is it a DNA thing? I guess I'm wondering what prevents gorillas from growing 100 feet tall. Could there ever be a mutation that allows this to happen? Thanks!
posted by Sully at 3:03 PM - 13 answers

February 22

How do chemical reactions in the brain create feelings?

Dopamine floating around in your synapses will make you feel g<ood. But how? [more inside]
posted by marvelousmellitus at 8:32 PM - 17 answers

Buoyancy question

i want to put an inflatable pool in my small backyard. Then I want to fill it with water and lie on its surface on an inflatable chaise/raft thing. [more inside]
posted by DMelanogaster at 2:33 PM - 10 answers

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