has it been explored?
Yes, most of human history, space was explored by observations made from the Earth's surface—initially with the unaided eye and then with the telescope.
Outer space
most of human history, space was explored by observations made from the Earth's surface—initially with the unaided eye and then with the telescope. 
the vast majority of human activity takes place in just one atmospheric layer. which one Troposphere what is it composed of? It contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. how did the outer space form? According to the Big Bang theory, the very early Universe was an extremely hot and dense state about 13.8 billion years ago which rapidly expanded. when was this theory published? UNANSWERABLE what effect it has on humans? Out in space, sudden exposure of an unprotected human to very low pressure, such as during a rapid decompression, can cause pulmonary barotrauma—a rupture of the lungs, due to the large pressure differential between inside and outside the chest.
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Outer space [SEP] Exploration and application
For most of human history, space was explored by observations made from the Earth's surface—initially with the unaided eye and then with the telescope. Before reliable rocket technology, the closest that humans had come to reaching outer space was through balloon flights. In 1935, the U.S. Explorer II crewed balloon flight reached an altitude of . This was greatly exceeded in 1942 when the third launch of the German A-4 rocket climbed to an altitude of about . In 1957, the uncrewed satellite Sputnik 1 was launched by a Russian R-7 rocket, achieving Earth orbit at an altitude of .