Well, I let you be the judge. Here's a list of outdated facts that were commonly taught before the year 2000 but have since been updated, courtesy of ChatGPT:

Science / Space

Pluto is a planet.

Back then, Pluto was still the 9th planet. In 2006, the International Astronomical Union reclassified it as a “dwarf planet.”

The universe’s expansion was slowing down.

Many textbooks still suggested the universe might eventually collapse in a “Big Crunch.” In 1998, evidence of accelerating expansion was found, but it hadn’t fully filtered into school curricula by 2000.

Dinosaurs were cold-blooded and scaly.

In 2000, the “feathered dinosaur” revolution was just starting. Today, we know many theropods (including raptors) had feathers and were likely warm-blooded.

The continents “drift” slowly but are mostly stable now.

Continental drift was taught, but the understanding of plate tectonics was less developed in school-level detail. We now know tectonic activity reshapes Earth far more dynamically than was often taught.

Biology / Medicine

The human genome was incomplete.

In 2000, the Human Genome Project had just released its first draft. Many textbooks underestimated how complex genetics really is — for example, they suggested humans had ~100,000 genes, but it’s actually about 20,000.

Ulcers are caused by stress and spicy food.

That was the classic teaching. By the 1990s, scientists had already shown that ulcers are often caused by H. pylori bacteria, but the update wasn’t in most classrooms yet.

“Junk DNA” does nothing.

The idea that noncoding DNA was useless filler was common. Now we know much of it plays regulatory or structural roles.

History / Social Studies

The internet is a fad.

You may have heard skepticism about the internet being overhyped. Few predicted how deeply it would transform society in just two decades.

Christopher Columbus “discovered America.”

By 2000, it was still widely taught that Columbus “discovered” the New World, though evidence of Norse settlements (like at L’Anse aux Meadows) was already known — just not widely emphasized. Now, school curricula are far more likely to teach about Indigenous civilizations and earlier arrivals.

The Great Wall of China is the only man-made object visible from space.

This “factoid” was common in classrooms, but it’s false. The wall is not easily visible from orbit without aid, while cities, roads, and airports often are.