Recently, u/KnowledgeAlarming615 asked the good people of r/ask, "What fact is common knowledge to people who work in your field, but almost unknown to the rest of the population?". Here are some of their answers:
1. "Coffee shops spend more on milk than coffee."
2. "There is no difference between a violin and a fiddle other than how you play it."
3. "Libraries throw away or recycle thousands of books routinely. A modestly-sized library might get rid of a thousand books a month."
4. "The maximum spacing between spindles in a railing is four inches because that's the average size of a baby's head."
"Most building officials will carry a four-inch sphere with them when doing inspections on new construction."
5. "Most things stamped with 'BPA-free' would never have contained it in the first place."
"Things like Ziploc bags or many reusable containers, for example, are made from polyethylene. They wouldn't ever contain BPA, which is a polycarbonate. It's purely a marketing sham to take advantage of the perception that BPA is bad."
"In a similar vein, when I lived in San Jose there was a small market I went to that had 'gluten-free' stickers on their plain rotisserie chickens."
"My grocery store labels water as gluten-free."
6. "Virtually every piece of copper, aluminum, or steel you come across has been chopped to bits, refined, and melted down dozens, if not hundreds, of times."
"Copper pipe? Probably started out as hundreds of different wires from various devices from around the world at one point."
"Metal is so metal..."
7. "Most 911 calls an ambulance receives on a daily basis are not remotely close to being emergencies."
"Can confirm. I used to work for the London Ambulance Service as a dispatcher. My job was to triage the situation to ensure our resources weren't being wasted on situations that could be addressed by other means. (ER, general practice).
On the other hand, there are medical situations that can go from a non-emergency to an emergency in the blink of an eye."
8. "Oil paintings take months to truly 'dry'. It's best practice to not add a sealant until six months to a year after it is dry to the touch."
"I took one painting class in college and you had to pick oil or acrylic at the start. The instructor said some older oil paintings took years to dry… I picked acrylic."
9. "An electrical engineer isn't an electrician."
10. "The instant you push the spin button on a slot machine, it knows if it's a winner or not. The machine also knows how much you're going to win."
"All that spinning of the wheels and appearance of choice in bonus play is simply for show."
"I was just coming here to comment this!
It doesn’t matter what number or treasure box or shell you select, nor what retriggers or wild reels appear… the amount you’ll win is determined the moment you spin by a random number generator that is constantly running in the background."
11. "Cement is an ingredient in concrete. Most people use the terms interchangeably, but that's incorrect."
12. "Tarmac is the material, apron is where planes park."
13. "Psychiatric patients aren’t a big money-generating portion of the medical field, because wealthy donors who give to charity for a specific medical condition they’ve had rarely want to admit to having been treated for a psychiatric condition."
"Psychiatry gets some of the least amounts of donor money from foundational grants and charities, which is helping to fuel the homelessness crisis."
14. "Sleep apnea can happen to anyone. Old people, overweight people, young people, skinny people, children, babies, athletes. Your insomnia has a very high chance of actually being sleep apnea."
15. "There is a surprising amount of infrastructure under your feet. You’d be surprised how much public utility runs underneath private property. Always call before you dig."
"I'm acutely aware of this today. Power and cable were taken out in my neighborhood by the people laying fiber."
16. "Turning your computer or phone off and on again will fix a solid 70-80% of all problems the device likely has."
"I work for a VERY large phone company that I cannot disclose, and can guarantee that this is 100% correct. Also, going into and then out of airplane mode to fix any type of cell service issue. Generally, this resets the connection to the closest tower on your network."
17. "An elevator will go up to the top of the hoist instead of crashing to the floor in most catastrophic failures due to the counterweights."
18. "I paint for a living. Always prime… primer and finish in one is a scam."
19. "No, I won’t remember serving you if you come back twenty minutes later for something else. I glance at your face, that’s it. Customers are very rarely memorable. You all become a blur."
"Yep. Worked in retail for years. If I remember you it's either because you're a very good customer or a very bad one. Guess which one is more common?"
20. "STD and STI epidemics are very common in old folk homes. Lack of proper sex education coupled with declining inhibitions due to old age and various ailments that cause dementia is a bad combo."
21. "The oil that is extracted from under the Earth's surface does not come from dinosaurs. It comes from tiny phytoplankton (diatoms) deposited on the shores and beds of inland seas, long before the age of the dinosaurs."
"Also, the oil itself is trapped inside microscopic-sized spaces within certain types of porous rocks (minerals such as sandstone and limestone) that are overlain by other non-porous types of rock (shale, mica, or salt, for instance) that prevent the trapped oil from migrating to the surface.
Oil does not exist in underground caverns or lakes or pools that we basically drain by poking metal straws into the ground."
22. "Vaseline is nothing more than a natural by-product of the oil extraction process, a waxy residue that builds up on oil rig machinery and must periodically be removed."
Editor's note: of course, the product is purified and refined before use.
23. "Boy bees can't sting (no stinger). And they're basically useless — the queen only needs one or two to mate with really, to keep the hive populated. They don't even forage for pollen."
"They do nothing but eat and wait for a very slim opportunity to mate with the queen. When temps drop in autumn/fall, they're evicted from the hive by the girls, then die."
24. "Due to the immense number of computers connected to the internet, we ran out of IP addresses* to hand out to each individual device (since the late '90’s if you can believe it)."
"To solve this, a method known as 'Network Address Translation' was implemented so that we could group devices behind a single central network device. That central network device is known as a router, though nowadays most people associate that with the WiFi network. Without our routers and NAT, things would be very different. Imagine having to wait for an address to free up before you could connect to your favorite website!
*There are more physical devices than there are public IPv4 addresses, however a “newer” standard known as IPv6 is slowly becoming the standard. There are trillions of trillions of IPv6 addresses so we will not be running into the same issues as IPv4 any time soon."
You can watch a video about this here (I'm genuinely mind-boggled):
View this video on YouTube
25. "Endometriosis can be genetic. One of the primary causes of endometriosis is the mutation in the CFTR gene; the same genetic mutation which causes cystic fibrosis."
26. "You need a master's degree to be a certified librarian. And we don't read all day."
27. "Room acoustics are more important to sound quality than your speakers (within reason)."
28. "There is no such thing as a perfectly functioning aircraft. Every plane you fly on has a multitude of maintenance issues, just not severe enough to affect the safety of your flight."
29. "Touching your fresh tattoo with your unwashed fingers is bad. It's absurd how many times we have to tell this to people."
31. "Most people are not good at detecting lies and consistently score no better than chance (50/50) when tested. The score goes up slightly when it's someone they know that they're talking to, but not much."
Shout out to u/KnowledgeAlarming615 and r/ask for having this discussion.
Note: Submissions have been edited for length and/or clarity.
Thumbnail credits: Getty Images / PBS / BBC / Channel 4