Daven Hiskey runs the wildly popular interesting fact website Today I Found Out. To subscribe to his “Daily Knowledge” newsletter, click here.

When you were little, your mom probably told you not to sit too close to the television, lest you irreparably harm your vision. But you can file this popular warning in the myth file, right next to "your face will get stuck that way"—in reality, sitting close to the TV won't hurt your eyes. So why do parents the world over still say this to their kids? Because there was actually a very brief period of time where sitting close to the TV could damage your eyes—at least, if you owned a General Electric TV in the late 1960s.

In 1967, General Electric informed the public that many of their color televisions were emitting excessive x-rays due to a “factory error." Health officials at the time estimated that the amount of radiation coming from these defective TVs was about 10 to 100,000 times higher than the rate considered acceptable. They recommended keeping children a safe distance away—but as long as you were a few feet away and didn’t watch TV for more than an hour at a time or so at close range, you were probably fine. General Electric recalled all of the defective TVs and fixed the problem by putting a leaded glass shield around the tubes, making up close and personal television viewing safe once again.

"It's not an old wives' tale; it's an old technology tale," Dr. Norman Saffra, the chairman of ophthalmology at Maimonides Medical Center in Brooklyn, told the New York Times. "Based on the world our grandmothers lived and grew up in, it was an appropriate recommendation."

At worst, sitting excessively close to the television these days will give you a headache and possible eyestrain. This can sometimes be a problem for kids, who often watch TV while lying on the floor; looking up at the television this way causes more eyestrain than looking straight at the TV or down at it. (The same applies for computer monitors.) Eyestrain can also occur when watching TV or looking at a computer screen where the light level of the screen is very different than the light level of the surrounding environment. Thankfully, eyestrain isn't permanently damaging, and is very easy to fix—just take a break from watching TV.

Check out more interesting articles from Daven over at Today I Found Out and subscribe to his Daily Knowledge newsletter here.