History of physics to simplify their production. In heliocentric models of the Solar system, the Earth orbits the Sun along with other bodies in Earth's galaxy, a contradiction according to the Greek-Egyptian astronomer Ptolemy (2nd century CE; see above), whose system placed the Earth at the center of the Universe and had been accepted for over 1,400 years. The Greek astronomer Aristarchus of Samos (c.310 – c.230 BCE) had suggested that the Earth revolves around the Sun, but Copernicus' reasoning led to lasting general acceptance of this "revolutionary" idea. Copernicus' book presenting the theory ("De revolutionibus orbium coelestium", "On the Revolutions of the
Earth in the Balance to react in time to save our skins”. Earth in the Balance Earth in the Balance: Ecology and the Human Spirit (, paperback ) is a 1992 book written by Al Gore, published in June 1992, shortly before he was elected Vice President in the 1992 presidential election. Known by the short title "Earth in the Balance", the book explains the world's ecological predicament and describes a range of policies to deal with the most pressing problems. It includes a proposed "Global Marshall Plan" to address current ecological issues. Written while his son was recovering from a serious accident, "Earth