Humanity's relationship to the Earth's environments in modern times has been marked by periods of time when groups of individuals have come together around shared viewpoint on an environmental issue.  They have expressed that view by taking action individually and as a community through outlets such as writings, philosophy and ethics, political action, and other kinds of behavior. Such "environmental movements" are often marked by broad changes in attitudes toward society's relationship with nature and specific changes in law. Environmental movements are also often associated with scientific discovery and the changes in education about environmental issues. Certain individuals or events often come to be recognized as "catalytic" or "symbolic" of an environmental movement. Examples include: John Muir, his writings, and the founding of the Sierra Club in 1892; the publication of "Silent Spring" by Rachel Carlson in 1962; and the First Earth Day on April 22, 1970. While these examples occurred in the United States, environmental movements have occurred throughout the world; sometimes with a distinct form within a particular country, and on other occasions  quickly becoming international.