Most will travel safely away from our solar system, but there is a chance that others may travel toward us. This then creates the possibility of a collision with Earth. The results of such a collision would be catastrophic. A large cloud of dust and debris would be sent into the atmosphere, blocking out any sunlight. Our world would be left in total darkness causing plants to die because of their inability to carry out photosynthesis. This would then disrupt the remainder of the food chain and result in mass extinctions. Through fossils and other testing, scientists know that mass extinctions occur roughly every twenty-six million years. The orbit of Nemesis is also roughly twenty-six million years. Scientists connected these periodical mass extinctions with Nemesis because of their similar periods. A great big clock in the sky is controlling biological destinies on Earth. (Raup 1986).
Details of the Nemesis Theory were first documented in Nature by Marc Davis, Piet Hut, and Richard A. Muller in 1984. However, speculation on this topic began in 1980. The article "Extraterrestrial Cause for the Cretaceous-Tertiary Extinction" published in Science by Luis Alvarez, Walter Alvarez, Frank Asaro, and Helen Michel was one of the first pieces published on the idea of an extraterrestrial impact that was responsible for the extinction of the dinosaurs. This idea was based on the findings of high levels of the element iridium in the period between the Cretaceous Period and the Tertiary Period. This is often referred to as the K-T boundary. The discovery of iridium was important because its presence in the Earth's crust is rare, but it's fairly common in certain meteorites. This discovery was made by Luis and Walter Alvarez, along with the help of chemists Frank Asaro and Helen Michel while working on a project in northern Italy. They then wanted to use this finding in order to determine the elapsed time during and between each period.
