Climate scientist who originated the Gaia hypothesis, which posits that the biosphere is a self-regulating entity that controls the chemical and physical environment around it. His work helped inspire the modern-day environmentalist movement.
He did not have enough to attend college out of high school, and instead went to work as a photographer.
A detector he created showed human-made pollutants in the atmosphere, inspiring Rachel Carson's famous book, Silent Spring.
He was born to a working class family, which believed strongly in education.
In his later years he said that he and many other global climate change activists, like Al Gore, were too alarmist.