The second and third generation quarks and leptons require large amounts of energy to be created. Particle accelerators like the Tevatron and the LHC have been built to create and study them. They can also be created when very high-energy cosmic rays strike Earth’s atmosphere. Some astrophysicists believe that stars exist that contain the strange quark. These particles also existed at times shortly after the Big Bang when temperatures in the universe were extremely high. Thus studying high energy collisions using accelerators is a way of studying what the universe was like when it was very, very young.