You may have seen reports that a massive asteroid the size of a football field is hurtling toward Earth. Although the European Space Agency (ESA) has placed asteroid 2006QV89 on its Risk List, there's no reason to sound the alarms just yet. First of all, it's probably not as big as you think it is. The object is roughly 40 meters in diameter, according to the ESA. A football field is 48.5 meters wide and 109 meters long. The Risk List might sound scary, but that simply means that ESA calculated a non-zero impact probability. ESA says this particular asteroid...