In SN 15.10 the Buddha said “One person roaming and transmigrating for an eon would amass a heap of bones the size of this Mount Vepulla, if they were gathered together and not lost.” So out of curiosity I immediately research and calculate how many lives we have lived in a typical eon.
The premises are:
- Lives that leave bones certainly only include human and animal forms
- An average mass of a human skeleton is 10 kg
- The average mass of a big mountain is 100’000 billions kg (Mount Everest is 810’000 billions kg)
So we have apparently lived at least 10’000 billions lives as human or animal in a single eon, this is just 2 out of 5 destinations.
An eon is indeed long. And that’s just one single eon.
In SN 15.7, the Buddha said “Suppose there were four disciples with a lifespan of a hundred years. And each day they would each recollect a hundred thousand eons. Those four disciples would pass away after a hundred years and there would still be eons that they haven’t recollected. That’s how many eons have passed.”
4 * 100’000 * 100 = 40 millions, so at least 40 millions eons have passed and still there are more.
About the length of an eon in term of years, there are many clues in the suttas, for example, in SN 6.4, the Buddha said to Baka the Great Brahma:
“But, Baka, the life span here is short, not long,
though you think it’s long.
I know that your life span
is two quinquadecillion years, Brahmā.”
The premises are:
- 2 quinquadecillion (sahassāna nirabbudāna?) years = 2 * 10^48 years or 2’000 billion billion billion billion billion years
- Life span of the Great Brahma is apparently equal to the length of a single eon.
These are all come together and make sense, even if you were to compare with the knowledge of modern science, scientists speculate that the universe will die when all of the protons have been decayed, and protons might have a half-life of 10^32 years. Hence, it could be in the range of 10^76 to 10^220 years
Sources:
An eon is indeed long. And that’s just one single eon.