Parents have a bunch of catchphrases.

Things like, “Don’t eat with your mouth open” or “Don’t run with scissors." Another one you might recognize is “don’t sit too close to the TV; it’ll hurt your eyes." But it turns out that the science behind that one isn’t actually true—at least, not anymore. Your eyes might start to feel tired, but the TV won’t actually hurt them.

That idea came from some faulty televisions back in the late 1960s. About 50 years ago, General Electric accidentally released a line of color televisions that emitted X-rays from 10 to 100,000 times more than was considered safe. Talk about a manufacturing flaw.

Like most other old, boxy TVs, the GE ones used cathode ray tubes, or CRTs, to generate a picture. Inside the glass vacuum tubes, electrons were fired at a screen covered in red, green, and blue phosphors, a type of material that glows when hit by something like electrons. And when fast-moving electrons strike something in a vacuum, it generates X-rays.

To protect people from this radiation, engineers mixed lead into the glass ray tubes— but this batch of GE televisions was produced with faulty tubes. Two pieces were misaligned, which meant that the X-rays were deflected out of the bottom of the TV set and toward the ground right under the television, where some kid was probably singing along to The Flintstones theme song. A recall notice estimated that sitting under the TV for a total of 40 hours would expose someone to so much radiation that their skin would turn red and painful.

Which is... not great. But the good news is it doesn’t seem like anyone was hurt. Thankfully, modern LCD TVs don’t emit harmful radiation at all, so you can sit as close as you want.

But if you do spend too much time binging Netflix, you might still develop a headache. If you stare at the TV—or basically anything, including a book or your smartphone—for too long, you can tire out the muscles in and around your eyes and develop eye-strain. After a while, whatever you’re staring at will start to get wobbly and fuzzy, and you might get a headache or feel tired.

Fortunately there’s an easy fix: Go do something else, or at least just look away for a few seconds. Now, kids can focus on things close up much better than adults can without developing eye-strain, which is why they tend to get in the habit of sitting super close to screens—like televisions. And, in the 1960s, that might have been a problem.

But today, kids won’t get radiation burns by doing it, no matter what their parents say. So the next time you’re in the mood for a vintage movie marathon, you can sit wherever you’d like. But when Netflix asks you if you’re still watching, it might be time to give your eyes a break.

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