O’Neill cylinder

O’Neill was inspired by the papers written by his students. He began to work out the details of a program to build self-supporting space habitats in free space.Among the details was how to provide the inhabitants of a space colony with an Earth-like environment. His students had designed giant pressurized structures, spun up to approximate Earth gravity by centrifugal force . With the population of the colony living on the inner surface of a sphere or cylinder, these structures resembled “inside-out planets”. He found that pairing counter-rotating cylinders would eliminate the need to spin them using rockets.This configuration has since been known as the O’Neill cylinder.

Янис Ксенакис
ヤニス·クセナキス
ANTIKHTHON
In 1971, Iannis Xenakis composed a work called Antikhthon. Commissioned by Balanchine for the New York City Ballet, this overwhelming composition refers to a hypothetical planet, proposed in the 5th century BC. by the Pythagorean philosopher Philolaus. “Antichthon” is the name that the Greeks gave to a hypothetical celestial object, the Counter-Earth, located between the Earth and the center of the Universe to prevent man from looking directly at Zeus, who had his throne there.

Empyrean: In ancient cosmologies, the Empyrean Heaven, or simply the Empyrean, was the place in the highest heaven, which was supposed to be occupied by the element of fire (or aether in Aristotle’s natural philosophy). The word derives from the Medieval Latin empyreus, an adaptation of the Ancient Greek empyros (ἔμπυρος), meaning “in or on the fire (pyr)”

Empyreum  (The Divine Comedy, Gustave Doré )

The Empyrean was thus used as a name for the firmament, and in Christian literature for the dwelling-place of God, the blessed, celestial beings so divine they are made of pure light, and the source of light and creation. Notably, at the very end of Dante’s Paradiso, Dante visits God in the Empyrean.