Earlier this month, on Feb. 6, a giant fireball came screaming through Earth’s atmosphere. But the chances that anyone actually saw it are few to none.

This fireball likely exploded with the energy equivalent to 13,000 tons of TNT, but it did so over the Atlantic Ocean more than 600 miles away from the nearest inhabited region.

So, if no one saw or heard this enormous explosion — which, to date, is the largest since the Chelyabinsk meteor rampaged over Russia in 2013 — why are we so sure that it happened?

NASA was the first to publicly report [2] the event, and you might think they would be the most likely to have made the discovery, but no. Even with all of its satellites and a program dedicated [2] to spotting potentially harmful meteors, asteroids, and comets, NASA didn’t actually detect the space rock, before or after it entered Earth’s atmosphere.

According to Phil Plait [3] — an astronomer and science writer for Slate — NASA was tipped off by another branch of the US government, possibly the military.

(Shutterstock) 

The government isn’t necessarily interested in space rocks, but when those rocks make an unexpected and relatively large boom anywhere in the world, it tends to spark interest.

While the government isn’t about to divulge how it saw this explosion, which was practically invisible to everyone else, Plait offered up a few ideas [3] in his post:

“I can think of three ways to detect a big fireball in this case: Satellite observations, which would image them directly; seismic monitors, which can detect the explosion as the sound wave from the blast moves through the ground; and atmospheric microphones, which can detect the long-wavelength infrasound from an event. This may have been detected by any combination of these (though since it was over the open ocean, seismic monitors seen unlikely).”

With some back-of-the-envelope calculations, Plait estimated that the meteor was no larger than 23 feet across, before it entered Earth’s atmosphere.

If the fireball had plunged toward a city instead of the Atlantic, Plait said it would have rattled some windows but, overall, left little to no damage in its wake.

Still, it’s slightly unsettling to know that our technology isn’t quite ready to spot these large fireballs ahead of time and provide a proper warning — even if it is just to say “Look up!”

http://finance.yahoo.com/news/theres-unsettling-reason-why-know-15360615... [4]