ELI5: Why must I enter a CAPTCHA to pay a bill? Are they afraid a robot is going to enter a credit card on my behalf?

Answer 1: Yes, captchas are generally used to prevent automation by using (ro)bots. However, there are a couple of side effects. One would be that you can not “accidentally” pay the bill because you would have to enter the captcha first. A bot would also not just enter “a credit card” but instead do pretty much anything on there - like trying out different card numbers. Using a captcha verifies that you are human. When developers are unsure whether or not to use a captcha then they will usually go for it because you know, better have than not have.

Answer 2: I am a web developer and we do it because of the tremendous number of bots that randomly submit forms in an effort to spider our sites, and create junk as a result. A CAPTCHA dramatically lessens the amount of crap data we get.

 - without seeing the site in question, I must also presume the page does not require authentication (username/password) to use, which allows ‘bots in, causing the problems (and is likely a poor design).

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ELI5: What's the difference between someone who has a learning disability and someone who's just stupid/slow/dumb?

I would think of it in terms of a computer.

Stupid or dumb would just be someone with a slow processor. Everything works fine, it just doesn’t work that fast.

A learning disability would be a hardware defect. Maybe there is a problem in ram causing a corruption of data… the computer is working perfectly fast enough, it just encounters errors which make it difficult to complete a certain task.

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ELI5: When you have a cold, why does it always feel horrible in the morning and get better throughout the day?

Not a doctor, but I did just go to the doctor and had this explained to me. The reason you feel like shit in the morning is because you’ve been laying down all night, so the mucus just sits and builds up instead of draining. The sore throat is caused by infected mucus resting on the throat throughout the night, causing inflammation.

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ELI5: When knocked unconscious, what bodily function wakes a person back up? What determines when and how quickly it happens?

Definitely depends on what part of your brain needs to recover. I worked in an ER and our “go to move” was to take our knuckles and rub them vigorously across the sternum of a patients chest. (The bone between your breast) the pain wakes you REAL fast.

Comes in handy for less serious events like your buddy is black out drunk or gets knocked out at a bar.

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ELI5: How is lettuce able to be picked, shipped, processed, and shipped again, and still be green but if I don't finish a bag of premade salad in a week the lettuce turns brown?

Holding lettuce in water during processing and keeping them stored in a cool, low oxygen environment helps keep them fresh from picking to processing.
Once processed they are packed in air-tight sealed containers with a mix of gasses aimed at keeping their shelf-life and nice green colour.

Generally if you want to keep your salad pretty green store it iced-water in the fridge.

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ELI5: Don't password rules actually make brute forces easier? They can eliminate all attempts that lack letters in a row, that don't have numbers, that don't have weird characters. Seems like these rules shrink brute force dictionaries?

Let’s play a game called “guess the outfit before you see the person”. Every time you correctly guess the right outfit, you win $500.

The judges of the game noticed that a lot of smart players would default to “jeans and a solid black T-shirt, black shoes, white socks, no hat and no jewelry” over and over again, and they won a bunch of times. Not every time, but enough times to make some money. A lot of people wear this outfit very much like a lot of people have common passwords.

The judges start making more rules both visible to the players and the people wearing outfits. Now you must wear:
-a hat of some sort
-at least one piece of jewelry
-socks that don’t match
-a shirt that has at least two colors
Amazingly, it became harder for contestants to effectively guess the outfits, even though it was made clear of the requirements for the outfit (or password)

To reflect brute forces, imagine if you were allowed to guess until you got it right, move onto the next person whenever you like. In order to maximize the amount of money you could make every day, you would make a list of the most common outfits(less people wear hats and jewelry than those who choose not to wear them, so you’d just focus on the most common stuff: shirts of various popular colors, blue jeans or khakis, shoes of various colors. Wasting time guessing anything more complicated probably won’t win more games than sticking to the absolute basics, especially if people don’t like wearing jewelry or hats because it requires more effort on their level when getting ready in the morning(annoying tedious task similar to memorizing symbols and which letter is capital)

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ELI5: Why are shows like Dr.Oz allowed to give out health advice that isn't scientifically supported? How isn't this considered illegal?

He’s not really giving out health advice. Instead, he protects himself by merely reporting what others say. He’ll never say “Alice`s itchy feet will be cured by eating dryer lint.” Instead, he’ll quote a study like this: “According to a recent study by the Home Appliance Institute, 57% of people who eat dryer lint say their feet do not itch.” So it’s the authors of the study making the claim, except not really. The study authors are going to say something non-committal like “Although a positive correlation was found between dryer lint consumption and non-itchy feet, more study is needed and it will be several years before the production of dryer-lint based medicines.”

Dr. Oz can also shield himself by interviewing a guest about the problem instead of making any statement himself. “What options are there for people with itchy feet?” “Well, a recent study …” So, you’ll have to go through 3 or more layers of people to finally find someone who didn’t really say your itchy feet would be helped by the dryer lint anyway.

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