Soon, though, I'll be getting them all out. Such exclamations let Hollywood pitch the excitement as audiences cringe in expectation. We are just beginning to enter that phase where reality modifies melodrama, and where world leaders begin constructing a reasonable reaction to an apparent threat. The threat is very real. Fortunately, only the first two are guaranteed to hit in your lifetime.
Asteroids are ubiquitous, but for the most part far removed from our everyday life.
Chunks of rock formed early in the life of the solar system, asteroids can range up to 1-2 km in size and travel up to 70 km per second. An Earth collision with one would release enough energy to affect our environment on a global scale. We can see strong evidence that asteroids struck the Earth in the past and caused wide-ranging change. These types of collisions are predicted to occur about once in 100 million years. This is perhaps the largest of the impacts that brought extinction to the dinosaurs and many of their contemporaries.