Yuga cycle

"A hundred to you, ten thousand years, two Yugas, three Yugas, four we make."

"The Aitareya Brāhmana (VII.15.4), describing the merits of exertion, has the picturesque phrases: "A man while lying is the Kali; moving himself he is the Dvāpara; rising, he is the Tretā; walking, he becomes the Krita.'""

"The waning strength and stability of Dharma in the four yugas is graphically depicted by representing it as a majestic bull which stood firm on its four legs in the golden age of the world (krtayuga) and lost one of its legs to [ either of] the succeeding two yugas, Tretā and Dvāpara, to stand tottering on a single leg during the present kaliyuga."

"In the great philosophy of Brahma, such violent turns of the scale are quite unknown. It embraces vast stretches of time, cycles of human ages, whose successive lives gravitate in concentric circles, and travel ever slowly towards the center...."

"The Hindu religion is the only one of the world’s great faiths dedicated to the idea that the cosmos itself undergoes an immense and indeed an infinite number of deaths and rebirths. It is the only religion in which the time scales correspond […] to those of modern scientific cosmology."