We Fell For The Oldest Lie On The Internet (And You Probably Did Too)

Chasing a Science Myth: The Truth About Your 100,000 km Blood Vessels

Let’s be honest: we all love a good "fun fact." You know the kind—quick, snappy, mind-blowing. Something like: "If you laid all your blood vessels end to end, they’d wrap around the world... twice!" It’s the kind of fact that makes you go whoa, nod appreciatively, and then repeat it at a party to sound smart.

Well... turns out we’ve all been duped.

Yep. This tidy little nugget of internet wisdom is one of the oldest and most widely spread scientific myths online. And, full disclosure: we totally fell for it too.

This wasn't just an "oops, we messed up." This was a year-long scientific detective story that took us through a wild web of outdated textbooks, forgotten journal articles, Nobel laureates, and even handwritten letters (because, apparently, people still write those).

The Internet Loves a Sexy Number

First off, we didn’t just pull the number from a sketchy meme. The 100,000 km stat is everywhere. Books, blogs, TED Talks, university websites—even science YouTube channels (including ones we've admired for years). It shows up with casual authority: "The human body contains about 100,000 kilometers (60,000 miles) of blood vessels." No source, no caveat—just vibes.

It’s such a sticky fact. Small human, big number. Simple. Memorable. Feels smart. But one day, someone asked us, “Where does that number actually come from?” And just like that, the whole thing started to unravel.

The Search Begins: Into the PubMed Abyss

We assumed it would take, what, an hour? Maybe two? Google it, find a citation, move on with our lives. Ha. Cute.

What we got instead was a digital hall of mirrors. Article after article repeating the number with zero sourcing. Some pointed to textbooks, which pointed to papers, which led nowhere. We dove into PubMed, expecting a slam dunk from modern science. Nope. Zero hits. Cue the dramatic zoom-in on our confused faces.

Eventually, we got desperate and started scouring biology textbooks from the '90s. A couple of references finally popped up: one from Steven Vogel’s Vital Circuits, and another from David Suzuki’s Looking at the Body. Both repeated the number. Neither provided a source.

So naturally, we wrote an actual physical letter to Dr. Suzuki (respect). He politely responded that he didn’t remember where the number came from—it had just always been there.

A 100-Year-Old Estimate… Based on a Jacked Dude?

Our lucky break came in the form of a 1959 article from Scientific American that referenced a 1922 book by August Krogh, a Nobel Prize-winning scientist. We tracked down the book (The Anatomy and Physiology of Capillaries) and found our holy grail.

Krogh’s estimate? Based on a 143 kg (315 lb) idealized bodybuilder-like human with 50 kg of pure muscle. He counted capillaries in animal tissue, made a few logical leaps, and landed at… 100,000 km. Boom. Just like that, a fun side calculation made by a Nobel-winning dude became a global internet truth bomb.

Here’s the kicker: Krogh was wrong. Not maliciously wrong, just… science-in-1922 wrong.

Modern science says the actual length of your capillaries is probably somewhere between 9,000 and 19,000 kilometers. Still wildly cool—but nowhere near enough to wrap around the Earth once, let alone twice.

Why Do We Keep Repeating This Stuff?

Because it's easy. Because it sounds awesome. Because nobody has the time to hunt down obscure sources from the early 20th century. And because once something catchy makes it onto a blog, a textbook, or a Wikipedia page, it spreads like wildfire.

It's not just about blood vessels. It’s about how so much of what we think we “know” online is second-hand info, copy-pasted without checking. And to be fair, that’s often how even professionals operate. It’s just not feasible to double-check every single number in your research. So we lean on trusted sources—and sometimes, those trusted sources leaned on their trusted sources... and so on.

This is how myths are born.

The Beautiful Lie

Honestly? We wanted the number to be true. It’s poetic. The idea that your fragile, squishy body quietly contains a vascular network long enough to circle the Earth twice? That’s myth-level cool.

But maybe that’s the warning in all this. The most seductive facts—the ones that feel perfect—are often the ones we should question the most.

After a year of chasing shadows through academic libraries, vintage journals, and 100-year-old anatomy lectures, we found the truth. It was buried, obscure, outdated—but it was there. And in the end, we came out of it with a new appreciation for what good science communication actually takes: curiosity, effort, and the willingness to admit when you got it wrong.

So yeah. Your blood vessels don’t wrap around the Earth twice. But if you’ve ever repeated that fact, you’re in good company. We did too.

Let’s just promise to check the next mind-blowing number before we build a whole narrative around it, okay?

Stay sharp, stay curious, and unravel more mind-bending truths at Land of Geek Magazine!

#science-myths #internet-facts #human-body-trivia #kurzgesagt-inspired #blood-vessel-fact