What is the most complex theory?

Answer 1

Well, an excerpt in interpretive philosophy / religion which is both complex as well as simple found in the link and quoted at length below from wikipedia touches upon our universe's return. Need one say more?

"In Tao the only motion is returning;

The only useful quality, weakness.

For though all creatures under heaven are the products of Being,

Being itself is the product of Not-being. " (chap. 40, tr. Waley)

http://en.wikipedia.org/wiki/Eternal_return

Another similar theme of the same complex theory of the workings of our universe is the eternal return, or what Mair (1990:139) calls "the continual return of the myriad creatures to the cosmic principle from which they arose." Eternal return (also known as "eternal recurrence") is a concept which posits that the universe has been recurring, and will continue to recur in a self-similar form an infinite number of times. The concept has roots in ancient Egypt, and was subsequently taken up by the Pythagoreans and Stoics. In the Hebrew Scriptures, the notion is supported in the book of Ecclesiastes.[1][2][3] With the decline of antiquity and the spread of Christianity, the concept fell into disuse, though Friedrich Nietzsche briefly resurrected it. In addition, the philosophical concept of eternal recurrence was addressed by Arthur Schopenhauer. It is a purely physical concept, involving no "reincarnation", but the return of beings in the same bodies. Time is viewed as being not linear but cyclical. The basic premise is that the universe is limited in extent and contains a finite amount of matter, while time is viewed as being infinite. The universe has no starting or ending state, while the matter comprising it is constantly changing its state. The number of possible changes is finite, and so sooner or later the same state will recur. Physicists such as Stephen Hawking and J. Richard Gott have proposed models by which the (or a) universe could undergo time travel, provided the balance between mass and energy created the appropriate cosmological geometry. More philosophical concepts from physics, such as Hawking's "arrow of time", for example, discuss cosmology as proceeding up to a certain point, whereafter it undergoes a time reversal (which, as a consequence of T-symmetry, is thought to bring about a chaotic state due to thermodynamic entropy). The oscillatory universe model in physics could be provided as an example of how the universe cycles through the same events infinitely. Peter Lynds has proposed a model in which time is cyclic, and the universe repeats exactly an infinite number of times. Because it is the exact same cycle that repeats, however, it can also be interpreted as happening just once in relation to time.[4]

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http://en.wikipedia.org/wiki/Tao_Te_Ching#The_Mysterious_Female

The Tao Te Ching or Dao De Jing(traditional Chinese: 道德經; simplified Chinese: 道德经; pinyin: Dàodéjīng), originally known as Laozi or Lao tzu (Chinese: 老子; pinyin: Lǎozǐ), is a Chinese classic text. Its name comes from the opening words of its two sections: 道 dào "way," Chapter 1, and 德 dé "virtue," Chapter 38, plus 經 jīng "classic." According to tradition, it was written around the 6th century BC by the Taoist sage Laozi (or Lao Tzu, "Old Master"), a record-keeper at the Zhou Dynasty court, by whose name the text is known in China. The text's true authorship and date of composition or compilation are still debated.[1] The Tao Te Ching is fundamental to the Taoist school (Dàojiā 道家) of Chinese philosophy and strongly influenced other schools, such as Legalism and Neo-Confucianism. This ancient book is also central in Chinese religion, not only for Taoism (Dàojiāo 道教) but Chinese Buddhism, which when first introduced into China was largely interpreted through the use of Taoist words and concepts. Many Chinese artists, including poets, painters, calligraphers, and even gardeners have used the Tao Te Ching as a source of inspiration. Its influence has also spread widely outside East Asia, aided by hundreds of translations into Western languages.