Dirac Sea

In Episode 16, Shinji is pulled down into the "shadow" of the Angel Leliel. Ritsuko describes this space as a Dirac Sea (ディラックの海).

RITSUKO: "It's six hundred eighty meters in diameter with a thickness of three nanometers. The ultra-thin space is supported by an inwardly-directed AT Field. The inside is an imaginary space, called a Sea of Dirac. I think it's probably connected to another universe."

Dirac Sea is a real scientific term that is never fully explained within the series. It is a theoretical model of the vacuum as an infinite sea of particles possessing negative energy, that was invented by the British physicist Paul Dirac. For more information, see here.

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