This includes adaptation to microgravity (or weightlessness), isolation, confinement, and radiation. Spacelab allowed scientists to perform experiments in microgravity in Earth orbit. Many of the experiments conducted investigated the astronauts' adaptation to extended periods of microgravity. Studies conducted on reproduction of mammals in microgravity include experiments with rats. The Zero Gravity Research Facility is a vertical vacuum chamber used for microgravity experiments. Pettit also performed experiments on board ISS related to clumping of solid particles in microgravity. Typically, researchers wish to conduct experiments in microgravity or above the atmosphere. There were also experiments on measuring microgravity. Astronauts usually stood to eat, as sitting in microgravity also strained their stomach muscles. These flights will provide approximately four minutes of microgravity for research payloads. The document purports to report on experiments to determine effective sexual positions in microgravity. "Leonardo" contained a collection of experiments for studying the physics and chemistry of microgravity. Another study examined mouse embryo fertilization in microgravity. A student experiment to study crystal growth in microgravity was also carried out. It included a laboratory for studying the effects of microgravity, and a solar observatory.