who discovered it?
In 350 BCE, Greek philosopher Aristotle suggested that "nature abhors a vacuum", a principle that became known as the "horror vacui".
Outer space
In 350 BCE, Greek philosopher Aristotle suggested that "nature abhors a vacuum", a principle that became known as the "horror vacui". 
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. 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.
wiki:13607299
Outer space [SEP] Discovery
In 350 BCE, Greek philosopher Aristotle suggested that "nature abhors a vacuum", a principle that became known as the "horror vacui". This concept built upon a 5th-century BCE ontological argument by the Greek philosopher Parmenides, who denied the possible existence of a void in space. Based on this idea that a vacuum could not exist, in the West it was widely held for many centuries that space could not be empty. As late as the 17th century, the French philosopher René Descartes argued that the entirety of space must be filled. In ancient China, the 2nd-century astronomer Zhang Heng became convinced that space must be infinite, extending well beyond the mechanism that supported the Sun and the stars.