ELI5: what exactly happens to your brain when you feel mentally exhausted?

This is my jam! Wait … not my jam, my PhD.

There are probably about three different types of mental exhaustion. One, that has already been explained (to the best of anyone’s ability) is sleepiness.

Basically, that is when you start feeling tired and want to sleep at the end of the day (or other times in the day if you didn’t get enough sleep). That is your brain telling you that you need to sleep for a while so that your brain can clean itself out and deal with memory consolidation. Although the purposes of sleep aren’t entirely understood, it is definitely totally necessary for brains to function and it plays a role in solidifying important memories (and forgetting irrelevant things).

Another type of mental exhaustion happens when you’ve just been engaging in difficult and unenjoyable mental work. So maybe you just finished a couple hours of awful homework, or had to be on your best behaviour during an uncomfortable lunch with racist grandparents. Or something like that. But you’ve been slugging along, doing something mentally difficult, and now you feel tired. Although sometimes people want to sleep after this, a lot of the time people really just want to take a break. You want to check Facebook, eat something, laze around at your house. That’s not the same thing as being sleepy, since you aren’t craving sleep, but people still refer to it as feeling “mentally tired”. Researchers in this field are converging around this being caused by shifting motivations. Basically, it’s good to spend some of your time doing things that you have to do, and some time doing things that you want to do. Someone in the thread mentioned something about the brain running low on glucose … that was an earlier theory, that has been pretty thoroughly dismissed. The quantities of glucose that your brain uses doing difficult math problem sets is less than you use walking around, but 10 minutes of intense math can make you crave Facebook much more than 10 minutes of walking. Glucose is also sent to your brain pretty darn quickly, so running out of brain “fuel” is not an issue. You can get rid of this type of fatigue by taking a sufficient break, preferably doing something that you enjoy doing! Meditation (as someone posted) has been shown to rejuvenate people, as has prayer, youtube videos, smoking cigarettes, reminding yourself about your values… the list goes on!

A third type of mental exhaustion, that was also mentioned in passing, is an attentional habituation. If you do a single task for an extended period of time, your brain start to attend less to the relevant information in the task. (Interestingly, doing a mentally taxing task not only makes you attend less to task-relevant information like the math question, but increases your attention to rewarding stimuli like food and comfortable chairs, which seems to support the above idea of a “trading off” of motivations). At least one paper has differentiated between this habituation type of fatigue and the previous fatigue (last paragraph), but they still might be overlapping in many contexts.

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ELI5: What's the difference between an Ave, Rd, St, Ln, Dr, Way, Pl, Blvd etc. and how is it decided which road is what?

Everything I found here is either rephrased from an urban planning textbook, wikipedia, or googles define function, I never claimed to be an expert on anything, what I gave here is essentially the most common occuring definition I could find, but many are used interchangeably, how a word is used in vernacular does not change an accepted definition.

A road has no special qualifiers. It connects point a to point b.
A street connects buildings together, usually in a city, usually east to west, opposite of avenue.
An avenue runs north south. Avenues and streets may be used interchangeably for directions, usually has median
A boulevard is a street with trees down the middle or on both sides
A lane is a narrow street usually lacking a median.
A drive is a private, winding road
A way is a small out of the way road
a court usually ends in a cul de sac or similar little loop
a plaza or square is usually a wide open space, but in modern definitons, one of the above probably fits better for a plaza as a road.
a terrace is a raised flat area around a building. When used for a road it probably better fits one of the above.
uk, a close is similar to a court, a short road serving a few houses, may have cul de sac
run is usually located near a stream or other small body of water
place is similar to a court, or close, usually a short skinny dead end road, with or without cul de sac, sometimes p shaped
bay is a small road where both ends link to the same connecting road
crescent is a windy s like shape, or just a crescent shape, for the record, above definition of bay was also given to me for crescent
a trail is usually in or near a wooded area
mews is an old british way of saying row of stables, more modernly seperate houses surrounding a courtyard
a highway is a major public road, usually connecting multiple cities
a motorway is similar to a highway, with the term more common in New Zealand, the UK, and Austrailia, no stopping, no pedestrian or animal traffic allowed
an interstate is a highway system connecting usually connecting multiple states, although some exist with no connections
a turnpike is part of a highway, and usully has a toll, often located close to a city or commercial are
a freeway is part of a highway with 2 or more lanes on each side, no tolls, sometimes termed expressway, no intersections or cross streets.
a parkway is a major public road, usually decorated, sometimes part of a highway, has traffic lights.
a causeway combines roads and bridges, usually to cross a body of water
circuit and speedway are used interchangeably, usually refers to a racing course, practically probably something above.
as the name implies, garden is usually a well decorated small road, but probably better fits an above
a view is usually on a raised area of land, a hill or something similar.
byway is a minor road, usually a bit out of the way and not following main roads.
a cove is a narrow road, can be sheltered, usually near a larger body of water or mountains
a row is a street with a continuous line of close together houses on one or both sides, usually serving a specific function like a frat
a beltway is a highway surrounding an urban area
quay is a concrete platform running along water
crossing is where two roads meet
alley a narrow path or road between buildings, sometimes connects streets, not always driveable
point usually dead ends at a hill
pike usually a toll road
esplanade long open, level area, usually a walking path near the ocean
square open area where multiple streets meet, guess how its usually shaped.
landing usually near a dock or port, historically where boats drop goods.
walk historically a walking path or sidewalk, probably became a road later in its history
grove thickly sheltered by trees
copse a small grove
driveway almost always private, short, leading to a single residence or a few related ones
laneway uncommon, usually down a country road, itself a public road leading to multiple private driveways.
trace beaten path
circle usually circles around an area, but sometimes is like a “square”, an open place intersected by multiple roads.
channel usually near a water channel, the water itself connecting two larger bodies of water,
grange historically would have been a farmhouse or collection of houses on a farm, the road probably runs through what used to be a farm
park originally meaning an enclosed space, came to refer to an enclosed area of nature in a city, usually a well decorated road.
mill probably near an old flour mill or other mill.
spur similar to a byway, a smaller road branching off from a major road.
bypass passes around a populated area to divert traffic
roundabout or traffic circle circle around a traffic island with multiple connecting routes, a roundabout is usually smaller, with less room for crossing and passing, and safer
wynd a narrow lane between houses, similar to an alley, more common in UK
drive shortened form of driveway, not a driveway itself, usually in a neighborhood, connects several houses
parade wider than average road historically used as a parade ground.
terrace more common in uk, a row of houses.
chase on land historically used as private hunting grounds.
branch divides a road or area into multiple subdivisions.

These arent hard and fast rules. Most cities and such redefine them their own way about what road can be called what.

Why you drive on a parkway and park on a driveway parkway originally referred to the decorations along that particular road, not the state of the cars on it, its similarities to a park being obvious. driveways were orignally much longer than they are now, so you actually would drive on them.

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ELI5: What does the TPP (Trans-Pacific Partnership) mean for me and what does it do?

This comic explains things very well.

Short short version:
“Free Trade” treaties like this have been around for a long time. The problem is, the United States, and indeed most of the world, has had practically free trade since the 50s. What these new treaties do is allow corporations to manipulate currency and stock markets, to trade goods for capital, resulting in money moving out of an economy never to return, and override the governments of nations that they operate in because they don’t like policy.
For example, Australia currently has a similar treaty with Hong Kong. They recently passed a “plain packaging” law for cigarettes, they cannot advertise to children anymore. The cigarette companies don’t like this, so they went to a court in Hong Kong, and they sued Australia for breaking international law by making their advertising tactics illegal. This treaty has caused Australia to give up their sovereignty to mega-corporations.

Another thing these treaties do is allow companies to relocate whenever they like. This means that, when taxes are going to be raised, corporations can just get up and leave, which means less jobs, and even less revenue for the government.

The TPP has some particularly egregious clauses concerning intellectual property. It requires that signatory companies grant patents on things like living things that should not be patentable, and not deny patents based on evidence that the invention is not new or revolutionary. In other words, if the TPP was in force eight years ago, Apple would have gotten the patent they requested on rectangles.

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ELI5: What about Coca-Cola is so hard to replicate? The flavor of lemon-lime, grape, orange, etc. sodas seem pretty consistent. But off brand cola is noticeably just not as good.

It’s not just about ingredients, the process is very important too.
Take sugar turned into caramel. The total length of time spent heating the sugar (total joules) and the temperature curve (at which point there were changes in heating) directly affects the flavor and texture. Too hot and it tastes burnt, too slow and it’s all runny.

In the 90s Ruffles sales collapsed for a few quarters for no apparent reason. Frito-Lay used some very advanced processes, that included photographing every individual chip and rejecting (using timed puffs of air) those that do not meet color, size and shape requirements.

The root cause of the sales dip was a switch to a different blend of cooking oil. There’s a delay between a change in process and a change in sales as new product makes its way out into the supply chain. A month later, sales started to really dip. They checked everything in the machines and the ingredients but the sales kept door dipping. It was only after a chance discussion with a consumer did they discover the oil change had altered the temperature curve, which in turn made the chips taste ‘burnt’ to some palates. But only some people could taste whatever new substance was now in the chip.

Too Long; Didnt Read > The process is as important as the ingredients and way harder to figure out, especially at scale.
Source: I’m a former PepsiCo employee.

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ELI5: How is Orange Juice economically viable when it takes me juicing about 10 oranges to have enough for a single glass of Orange Juice?

My father worked in various divisions of Tropicana for nearly 40 years, going from factory work and into corporate. He has more knowledge about the industry than nearly anyone in the world, though he retired several years ago.

Here’s what he has to say:

A standard box of oranges (as bought from a grower in Florida) weighs 90 lbs. That box when extracted by a processor will generate 5.5 to 6.0 gallons of orange juice. A typical box of oranges will supply 180 to 220 oranges … depending on the maturity and the variety of orange. That means that it takes about 34.8 oranges to produce a gallon of OJ.

Re cost …. the economics of “table fruit” that you buy to eat is different than the economics of field run processed fruit. Table run fruit is sorted for appearance, boxed, and sold at a premium. Some varieties of table fruit are also processed but mostly used as table fruit and sell at a significant premium to processed fruit. Valencia, Parson Brown, “Pineapple” oranges and Hamlins are the main varieties of oranges used in Florida to make OJ in processing plants. Extractor do not “grind up the fruit”. There are 2 types of extractors …. one “reems” the fruit like you do at home and the objective of the reem is to get all of the juice, pulp and inside of the orange without impacting the white interior of the fruit (albedo) which is very bitter. The peels and waste material are then sent to a feed mill where they are pressed to reduce liquid content and dried to make cattle feed. The pressed liquid is run through an evaporator to turn it into molasses and added back to the cattle feed to sweeten it up.

A comment in the string says “don’t let them tell you they don’t add water because they do”. They don’t add water to not from concentrate Orange Juice …. it is against the law and no reputable brand would do this. The cost of the oranges is so different because when you buy table fruit it is at most a bag …. processors sign contracts to buy whole groves of oranges …. sometimes buying millions of 90 lb boxes at a time. If you look in the commodity exchange … you will see “Orange Juice Concentrate Futures”. This is the price a processor is expecting to pay for a standard pound solid (about one gallon of single strength orange juice) in the future. That cost typically runs from $1.25 to $2.00 ….. for about 35 processing oranges. (See math at the top of this note)

Nuf said …

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ELI5: Why does it take 5 seconds for credit card/debit card companies to take money out of my account but 5 days for them to refund it?

Different systems… First you have to realize there is a difference between authorizations and postings.

A charge is only “real” against your account when it’s posted. It’s posted when the merchant does their batch close (typically) except for debit. When you do a credit transaction there is an authorization against your account but you don’t “owe” the money until it posts.

Refunds to debit if done at a POS terminal should be automatic (just like charges).

Refunds to credit take time because they go through the same path as charges. If it took 3 days for your charge to post you can be assured it will take 3 days for the refund to post.

Now why don’t they just authorize refunds? I suspect because when you auth a charge no money has changed hands yet. The bank [or credit company] still has the money they were lending you. It only goes to the merchant when they do a batch close and post the transaction. So if they did an auth refund there would be two copies of the same money. You’d have your refund and the merchant wouldn’t have had to cough up the money yet.

Now why do they take so long to do batch closes? Probably because each close costs money (+ transaction fees and percentages). So they do them every few days to save money.

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ELI5: Stephen Hawking's new theory on black holes.

All right, let’s say you have a friend named Simon, who’s a normal weight and loves junk food, and a friend named Albert, who’s extremely fat and also loves junk food. Since you’re buddies with Simon, you’d be able to guess what junk food they’re gonna eat next based on what they ate before and you’d also be able to guess what they had eaten based on the wrappers and boxes left over.

However, even though you’re buddies with Fat Albert, he’s just so huge that when he gets near enough something to eat, he swallows it wrapper and all.

You have no idea what he’d eat next or what he ate before because he swallowed anything and everything near him. BUT NOW, all of a sudden, you realize that Albert is not only fat, but he’s a messy eater. Because of this, you realize that there are crumbs, smudges, and pieces of the food left around his mouth. So you’re like, OH! Now I know what you ate. Maybe in time you could use that to learn his eating habits just like you know your buddy Simon’s!

So in this case, you’re Mr Hawking, and you realized that the black hole, Albert, although he seemed not to leave evidence of food (information), actually might leave that evidence at the edge of his mouth (the event horizon = the edge of the black hole). You can use that to figure out all sorts of things!
(Hopefully this helps people, this is my first post here!)

For people who are still a little confused by what the theory is, and why I talked about Simon: The original thing that we thought was what I described at the beginning, that for any normal scenario (a Simon) we would be able to get information, but in the case of a black hole (Albert), we can’t. But Hawking’s theory is your theory that if you look at the edge of his mouth, you can see the crumbs and figure out a pattern to how he’s eating just like you did with a normal case like Simon. In the same way, looking at the event horizon (the “edge” of a black hole) might let you get the information that we before thought was destroyed. Hope that makes sense!

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