"More than 90 percent of those (extinction-level) asteroids, which are 1 kilometer, 0.62 miles, or larger, have already been identified by NASA and its partners."
How do they know it's 90%? I mean, if the denominator is unknown? If the denominator is known, then doesn't that mean they've identified them?
How do they know it's 90%? I mean, if the denominator is unknown? If the denominator is known, then doesn't that mean they've identified them?