As improbable as it may seem, Comet Ison could impact the earth. Predicting a comet’s trajectory is similar to your local seven-day weather forecast. At times it’s spot on, other times it’s way off. The comet is expected to disintegrate when it makes its way pass the sun’s surface. The reality is, the comet will make its way towards earth, unless the sun destroys it completely. Close or far away no one knows at this point.
One unpredictable outcome could be that when the sun’s heat breaks the comet apart, fragmenting it to pieces, one of them could come straight toward the Earth. That piece could still be big enough to make most of life on earth extinct. The iconic part of this is, the day we find out if we will get hit is thanksgiving day. That’s the projected day it passes the sun. If nothing hits us the entire world will equally have something to truly be thankful for.
There are many possibilities and no certainties when it comes to a comet’s final impact. It’s like if a large glacier were to float across the ocean, no one with any certainty could predict its destination. Too many variables like water temperature, water current, wind, ice structure, weather and distance would make it impossible. If history is a great teacher then know, those who claimed to know the future were wrong more than they were ever right.