If you hold your face like that, it’ll get stuck that way.

At least, that’s what your elementary school teacher probably told you. (Also, why were you pulling so many goofy faces when you were supposed to be focusing on the math lesson?)

As an adult, of course, you see how ridiculous that claim turned out to be—unless you’re one of the few people whose faces did stay that way, in which case we are sorry, and recommend medical attention.

The point is, not everything your teacher taught you was, strictly speaking, accurate. Some percentage of it turned out to be bunk, simply disproven by science some time between your school days and this moment. Here are a few examples, along with the real facts behind these popular misconceptions.

Science marches onward!

Consider this a list of things you can tell your friends, just after introducing the subject with two of the most glorious words in the English language: “Well, actually…

1. Pluto Ain’t Just a Cartoon Dog

Listen: My Very Excellent Mother Just Served Us Nine Pizzas.

‘My Very Excellent Mother Just Served Us Nine’ doesn’t have quite the same ring to it.

Nope, we did not just lose our minds. That’s an old-school mnemonic device designed to help you remember the order of the planets, from closest to the sun to way out there. We’re talking Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus (hee hee), Neptune, and Pluto.

The problem is that, in 2006, the International Astronomical Union (IAU) decided that Pluto’s not a planet after all. It’s a “dwarf planet,” which doesn’t quite make the cut. And “My Very Excellent Mother Just Served Us Nine” doesn’t have quite the same ring to it.

If you’re a Pluto fan, you’ll be relieved to hear that there is still a debate about whether the celestial entity counts as a proper planet. According to NASA, though, it’s still just a dwarf planet—just half as wide as the United States itself, and far colder.

Pluto wasn’t always in our repertoire anyways; it was actually discovered as recently as 1930. Then an 11-year-old British girl named Venetia Burney decided that the new planet should be named after the Roman god of the underworld, because that’s the kind of stuff British 11-year-olds were into in the 1930s.

Venetia shared her idea with her grandpa, who forwarded it on to the Lowell Observatory, where the scientists who make these decisions were stationed at the time. They liked the sound of “Pluto.”

“Can’t be worse than ‘Uranus,’ which was Dave’s idea, if I recall,” those scientists may or may not have said. “Way to go, Dave.”

2. Diamond Is Density’s Best Friend

Quick, what’s the hardest material in the world? Did you say “diamond?” We bet you did, because we just planted that word in your mind.

In fact, though, the joke’s on all of us.

In 2009, scientists realized that two rare substances are even harder than diamonds. According to the Scientific American, “Wurtzite boron nitride and lonsdaleite [are harder than diamonds]. The first resists indentation with 18% more fortitude than a diamond, and the second—a whopping 58%.”

Still, no one’s claiming that wurtzite boron nitride is a girl’s best friend. And that’s not the only problem with the competition between these rare materials and diamonds.

A 2004 public letter from a group of crystallographers, published in the journal Nature, points out that the claims about these materials are based on simulated models—scientists just haven’t collected enough of the super-rare wurtzite boron nitride or lonsdaleite to perform physical experiments. In fact, the authors of the letter claim, “experimental measurements of their bulk properties, such as hardness, strength, toughness and abrasion resistance, is less than clear.”

Meanwhile, in 2015, a team of researchers at North Carolina State university aimed a laser into a lump of carbon and produced a substance they’re calling “Q-carbon,” which, while human-made, is also harder than a diamond. Say what you want about wedding rings: Diamonds just can’t win.

3. Burn the Witch!

Flashback to high-school English class: You’re reading Arthur Miller’s The Crucible. Or, at least, you are reading the CliffsNotes to Arthur Miller’s The Crucible. Either way, you are surprised to note that there was a lot more hanging than burning going on in that play. Because everyone knows that they burned witches at the stake during the Salem Witch Trials, right?

Life…No principle, however glorious, may justify the taking of it.

Well, actually…no. It turns out that Arthur Miller did his homework (and don’t you wish you did, too?).

Really, the women who were accused witchcraft in Salem were not burned; they were hanged.

Richard Trask, a historian who specializes in in Salem Witch Trials, wrote, “At the time of the trials, New England still followed English law, which listed witchcraft as a felony punishable by hanging—not burning at the stake. In Europe, however, the church labeled witchcraft heresy and did tie up suspected practitioners and light them on fire.”

Understandably, the confusion gave way to the more frightening prospect of being burned instead of hanged. Either way, we’re inclined to agree with Reverend Hale’s most famous line: “Life, woman, life is God’s most precious gift; no principle, however glorious, may justify the taking of it.”

4. The Labor of the Israelites

Folks of a certain age, who attended certain schools, all sat through Dreamworks Animation’s The Prince of Egypt when the teacher needed a break. Folks of an even more certain age probably watched the classic Charlton Heston vehicle The Ten Commandments.

Jews didn’t exist at the period when the pyramids were built.

Every year, those films make their rounds, perpetuating the ahistorical image of Pharaoh commanding Israelite slaves to build the pyramids in his honor.

Nope, never happened. Amihai Mazar, professor at the Institute of Archaeology at the Hebrew University of Jerusalem, explained the truth succinctly to U.S. News and World Report in a 2010 story.

If the Hebrews built anything, then it was the city of Ramses.

“No Jews built the pyramids because Jews didn’t exist at the period when the pyramids were built,” Mazar is quoted as saying.

In fact, recent archaeological finds suggest that Egyptians built the pyramids themselves. Workers were recruited from poor families in the north and south but were very respected, even earning crypts near the pyramids.

Slaves would not have been afforded such an honor, nor could they ever afford to pay for it themselves. So while the image of enslaved Hebrews toiling on the pyramids make good drama, they don’t make much historical sense.

“If the Hebrews built anything, then it was the city of Ramses, as mentioned in Exodus,” Mazar said. So at least Moses still gets to keep his line, “Let my people go!”

5. Backwards Toilets Down Under

Remember that kid in elementary school who proudly proclaimed that, when a toilet is flushed in Australia, the water spins and drains in the opposite direction as our toilets here in the U.S. of A? We hate to break it to you, but that kid was wrong.

The reasoning behind this supposed phenomenon is chalked up to the coriolis effect. The widest point on Earth is along the equator, and because of this, the Earth rotates faster there than at either of the poles. The difference in rotational speed causes objects in the northern and southern hemispheres to be deflected either to the right (northern hemisphere) or left (southern hemisphere). Makes sense thus far.

However, because Earth rotates fairly slowly for a planet, the coriolis effect isn’t strong enough to affect small appliances like your bathtub or sink.

The next time you hear someone bring this idea up, don’t do like Bart or Lisa in this classic Simpsons clip. Get your “Well, actually…” going.

6. Outer Space and the Original Wall

Okay, let’s move onto history class. One kid always drew The Great Wall of China as a subject for a presentation. And, inevitably, that kid said something along the lines of, “This is the only human-made structure that can be seen from outer space.”

Well, actually…

According to NASA, the Great Wall is really only visible from low Earth orbit—about 100 to 1200 miles up. From further up? Or from the moon? Not a chance.

Don’t let that get you down, though. Even if you can’t see the Great Wall from space, we’ve all seen photos of Earth at night, glowing with all the lights in major cities. All of that’s human-made, right?

7. Goodbye, Favorite Dinosaur (and Hello)

Every school kid has to pick a favorite dinosaur. In our experience, most go with Tyrannosaurus rex. At least, that was the case before Jurassic Park came along, with its hagiography of the Velociraptor.

Anyway, other favorites include good old Triceratops and, for the countercultural kids in the bunch, Brontosaurus, who is to dinosaurs roughly what Donatello is to the Ninja Turtles.

But in the 1970s, a pair of Carnegie researchers theorized that what the scientific community called Brontosaurus was actually just a more-complete version of an existing species, and one that no kid names as a favorite: Apatosaurus.

Brontosaurus is back, baby!

Let’s dial this story back to the beginning.

In 1877, paleontologist Othniel Charles Marsh discovered a partial skeleton, unfortunately lacking a head, which he named Apatosaurus. When he found the skull of Camarasaurus, he used it to complete the skeleton. Two years later, Marsh’s bone-hunters sent him a nicely intact skeleton that, while it resembled Apatosaurus, Marsh thought was different enough to get a new name: Brontosaurus (which, by the way, means “thunder lizard”—awesome).

By 1903, researchers began to suspect that the Brontosaurus was really just another Apatosaurus. The 1970s Carnegie folks took a look at the old skeletons, realized that the original Apatosaurus skull was wrong, and consigned the Brontosaurus to the dustbin of paleontology, which is hard to find, since paleontology deals mostly in dustbins to begin with.

But wait! Science marches onwards.

In 2015, studies from Oxford University scientists and by paleontologists at the New Universt of Lisbon both concluded that the original fossils of the Brontosaurus and Apatosaurus were different enough to belong to different species, after all. Brontosaurus is back, baby!

Let this be a lesson to all of us speakers of sentences that begin with, “Well, actually…

Two can play at that game, and the answers keep changing.