A physical environment is considered an area that is tangible and supports, influences, and develops life. On Earth, many different types of physical environments, natural and synthetic, have existed throughout its history. Furthermore, as scientific knowledge of the universe increases, scientists begin to search for true physical environments on other worlds.
Prehistoric Natural Physical Environments
Earth did not technically exist as a physical environment before 2.3 billion years ago. At this time, simple, single-celled bacteria appeared and produced oxygen making the Earth suitable for widespread life. The first members of the animal kingdom, organisms resembling modern-day mollusks, did not appear until around 545 million years ago. At this time, the Earth was covered in a warm, shallow ocean. Between the dawn of complex organisms and the emergence of modern humans, the Earth has experienced a great variety of physical environments including this early planetwide ocean, a supercontinent that formed during the Carboniferous Period and extreme climates unfit for most animal life.
Natural Physical Environments Since Human Evolution
A total of 190,000 years before present, the first modern human was born. When compared to prehistoric environments, the Earth has not changed drastically in the past 190,000 years. It did, however, experience an ice age that was at a maximum around 20,000 years ago. Today, the Earth has, on average, a temperate, accommodating environment for human standards. Today, anything that supports life, such as the atmosphere, the oceans and climate zones such as deserts, tundra and tropical rainforests, which exist worldwide, is considered a physical environment.
Human-Made Physical Environments
As humans have progressed through history, manmade environments have been created. Anything from palaces made for ancient rulers to modern cities are considered man-made physical environments because they sustain human life. Today, a complex man-made physical environment exists. Humans live in, interact in, and are influenced by a highly technological and developed society. Homes, businesses, and streets make up the man-made physical environments of the world. Previously natural physical environments, once manipulated, can become human-made physical environments. For example, forests, natural physical environments, that are cut down to make room for trails become man-made physical environments. (See References 3).
Extraterrestrial Physical Environments
Scientists are now searching for physical environments on other worlds. Some think that life may exist in our own solar system. A moon of Jupiter, Europa, may have a large water ocean below its icy surface. Some scientists further suggest that simple, bacteria-like organisms may exist in these waters. Elsewhere, astronomers are searching the skies for extra-solar planets, or planets outside of our solar system. In 1995, they found one. Unfortunately, it is unlikely that this planet supports life. Considering the size of the universe, however, it's possible that life exists elsewhere in the universe.