Our lives are full of little mysteries. Why is the week seven days long? Why aren't you supposed to put your elbows on the table? Why does toothpaste make orange juice taste terrible? And then there’s every kid’s favorite: Why is the sky blue? We’ve rounded up the answers to some of these quotidian questions, as well as a few weirder head-scratchers, from around the website. Reading the results should arm you with some answers as you go about your day — and help you prepare for the next time you encounter a curious kid.

Why Are Movie Previews Called “Trailers”?

Movie previews are called “trailers” because they were originally shown after the movie. In the early days of moviegoing, you didn’t just buy a ticket for one feature-length film and leave once the credits started rolling. You were instead treated to a mix of shorts, newsreels, cartoons, and, eventually, trailers — which, per their name, played after the movie rather than before — with people coming and going throughout the day. The idea for trailers came from Nils Granlund, who in addition to being a business manager for movie theaters worked as a producer on Broadway, which explains why the first trailer was actually for a play: 1913’s The Pleasure Seekers. Today there are production houses that exclusively make trailers and are handsomely rewarded for their efforts, sometimes to the tune of millions of dollars.

Why Does Catnip Make Cats High?

About 70% of cats are susceptible to the intoxicating effects of nepetalactone, the active compound in catnip. One whiff and these kitties are temporarily reduced to drooling, meowing messes, often rolling around in or rubbing their faces on the catnip source. That’s because nepetalactone is a volatile organic molecule that binds to receptors in a cat’s nose, stimulating neurons that activate the olfactory bulb, amygdala, hypothalamus, and other areas of the brain, causing a euphoric effect. The buzz seems to wear off after 10 to 15 minutes, leaving cats extremely chill thereafter.

Why Do We Say “the Best Thing Since Sliced Bread”?

n 1928, when inventor Otto Frederick Rohwedder of Davenport, Iowa, first released his bread loaf-slicing invention, the advertisement claimed it was “the greatest forward step in the baking industry since bread was wrapped.” Riffing on the theme, customers began to compare all later inventions to his, and the modern idiom evolved from there.

Why Do Brides Wear White?

Walk through any bridal shop and it’s obvious that white wedding dresses are the norm, but that wasn’t always the case. Historically, brides often repurposed their best dress as their wedding gown, and most were not white — specifically because white was exceptionally difficult to keep clean prior to modern washing machines and stain removers. Queen Victoria, who wore a lacy white gown at her 1840 wedding in place of the then-popular red, is often credited for popularizing bridal white(though Mary, Queen of Scots wore white during her 1558 Notre Dame wedding, and many lesser-known royals did before Victoria’s reign). Within a decade of Victoria’s wedding, dressmakers and etiquette books had run with the idea that white was virginal and pure, with the popular Godey’s Lady’s Book writing that a white dress was “an emblem of the innocence and purity of girlhood, and the unsullied heart which she now yields to the keeping of the chosen one.”

Why Is a Week Seven Days?

The seven-day week is a timekeeping oddity. Unlike days, months, and years, the week doesn’t align with any celestial reality, and it doesn’t divide elegantly into existing periods of time. For example, there aren’t 52 weeks in an average year — there are 52.1428571429. So how did this happen? Babylonians, the ancient superpower of Mesopotamia, put a lot of stock in the number seven thanks to the seven observable celestial bodies in the night sky — the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn. This formed the seven-day week, which was adopted by the Jewish people, who were captives of the Babylonians in the sixth century BCE. Eventually, it spread to ancient Greece and elsewhere thanks to the battle-happy Macedonian Alexander the Great. Efforts have been made throughout history to reform the seven-day week, but this oddball unit of time has become ingrained in many religions, including Judaism, Christianity, and Islam, rendering any sort of tweak pretty unlikely.

Why Is the Sky Blue?

Think about the atmosphere as a prism. In a prism, white light refracts through its polished surfaces and separates into the colors of the rainbow. The sun produces white light, so when its light travels through the atmosphere, it refracts a rainbow of colors. Each color comes from an electromagnetic wave. While red has the longest, slowest wavelength, blue and violet move in quick, short waves. As these colors pass through the atmosphere, they oscillate charged particles in air molecules like oxygen and nitrogen. Blue and violet are scattered in all directions at around 10 times the efficiency of red light, so they get the highest coverage area in our sky. Our eyes are more sensitive to blue than violet, which is why we see the sky as blue.

Why Is It Considered Rude to Point at Another Person?

When assisting theme park guests, Disney employees are trained to point with two conjoined fingers, index and middle. While the act reportedly doubles as a nod to Walt Disney’s smoking, the larger explanation is that standard pointing is considered rude in numerous cultures — especially if aimed at another person. A perception that dates back to Shakespeare’s time suggests pointing bringsunwanted attention to the recipient, implying that they’ve committed a wrong. Repeated pointing in Japan can even instigate hostility. And figurative “finger-pointing” is defined as “making explicit and often unfair accusations of blame.” In situations where you feel compelled to point, it is kinder to use an open palm, flight attendant-style.