Does anyone know how long did it take for Gotama Buddha to appear in the world, after Buddha Kassapa? The interval between the 2 Buddhas
See: http://obo.genaud.net/dhammatalk/dhammatalk_forum/dhamma_talk/dt_019.previous.buddhas.htm for a table giving various features of the previous 7 Buddhas. The Direct answer to your question is that Kassapa and our Buddha were both born in this kappa, that is, world-cycle, or aeon. The kappa consists of a period of evolution, a period of stasis, a period of devolution and a period of stasis. This current period is the period of devolution (as if anyone had to tell you). It is not clear, but it is likely that Kassapa was born in the period of Evolution.
The kappa is described as: 10,395,902,500 years: 103,959,025 sesame seeds removed from a Magadhan Karika one at a time every hundred years (see Magadha Karika)
From MN 115:
"It is impossible, it cannot happen that two Accomplished Ones, Fully Enlightened Ones, could arise contemporaneously in one world-system—there is no such possibility."
And Ven. Bodhi's note citing the Commentary:
"MA: The arising of another Buddha is impossible from the time a bodhisatta takes his final conception in his mother’s womb until his Dispensation has completely disappeared. The problem is discussed at Miln 236–39."
Therefore the time period between Buddhas will vary depending on when the Sasana will completely disappear. I doubt anyone would know the exact date and time, but when the Noble Eightfold Path and its 3 Trainings of morality, concentration, and wisdom are completely neglected then we can be fairly certain that the Sasana is dead..
The Buddhas should do fulfill their Paramita to become Buddha. Also there cannot be 2 Buddhas at the same time. A Buddha comes when there is spiritual interest in the society and there is a balance of suffering and also comfort. So it is complex interaction of:
- ideal time and conditions to tech the Dhamma and set up the Sasana
- number of Bodhisattva and stages of their Paramita
- there is no existing dispensation