On Aug. 10, 1972, an Earth-grazing fireball burst through the sky over North America. It didn't hit the ground, but instead it passed straight through the sky.
The fireball entered the atmosphere somewhere over Utah and passed northwards, leaving the atmosphere over Alberta, Canada about 100 seconds later.
Analysis of its trajectory showed the object was about 10 to 45 feet in diameter, depending on whether it was an icy comet or a denser, rocky asteroid.
Why it mattered
When we think of fireballs, we typically think of "shooting stars" during a meteor shower: a night sky spectacle that's brief but brilliant. But a daytime fireball is something else altogether.
Nighttime meteors are typically tiny particles of space dust or rocks that burn up as they streak through Earth's atmosphere. While they look impressive in the night sky, they're relatively dim. City streetlights or even a bright full moon can outshine them.
But a daytime fireball is caused by something large enough to be visible in the sky in broad daylight, something large and fast enought to light up a sky brighter than a sunlit day. That's what happened today in 1972.
Today, an event like the "Great Daylight Fireball" of 1972 (as it came to be named) would be visible to potentially millions of witnesses as it streaked over the United States and Canada, and we'd likely see social media flooded with images and video. There is at least one reported video of the 1972 event you YouTube, but nothing compared to what we'd see if it happened today.
