Ezra: Well there's this episode about a counting contest between the Buddha and a mathematician named Arjuna where the prince is asked to calculate both a very big number and, yes, a very, very small number.
Me: Is that hard?
Ezra: Well, the small problem was to count the number of — I guess you could call them — atoms, the smallest possible unit, in a yojana.
Me: What's a yojanda?
Ezra: According to Alex Bellos, a journalist who included this tale in his new book Here's Looking at Euclid, a yojana is an ancient unit of length equivalent to around 10 kilometers.
Me: So the question is, roughly: How many atoms are there in a line 10 kilometers long?
Ezra: Kind of. And here, courtesy of the ancient texts, is his solution:
A yojana, the Buddha said, is equivalent to:
Four krosha, each of which was the length of
One thousand arcs, each of which was the length of
Four cubits, each of which was the length of
Two spans, each of which was the length of
Twelve phalanges of fingers, each of which was the length of
Seven grains of barley, each of which was the length of
Seven mustard seeds, each of which was the length of
Seven particles of dust stirred up by a cow, each of which was the length of
Seven specks of dust disturbed by a ram, each of which was the length of
Seven specks of dust stirred up by a hare, each of which was the length of
Seven specks of dust carried away by the wind, each of which was the length of
Seven tiny specks of dust, each of which was the length of
Seven minute specks of dust, each of which was the length of
Seven particles of the first atoms.
So here's the neat part: According to Alex Bellos, it turns out the Buddha's calculation got the size of an atom very close to right!
This was, in fact, a pretty good estimate. Just say that a finger is 4 centimeters long. The Buddha's "first atoms" are, therefore, 4 centimeters divided by 7 ten times, which is 0.04 meter x 7 to the minus 10 or 0.00000000001416 meter, which is more or less the size of a carbon atom.
Ezra: Well, remember, this is a legend so I wouldn't like, fall on my knees or anything...
Me: But still...
Ezra: Maybe the neat thing here lies in the notion that the civilization that gave rise to Buddhism was also the same civilization and culture that had a thing for and a means to express — usefulness aside — infinitely large and small numbers. A number describing the size of a carbon atom would be meaningless in a society that had no notion of atoms or building blocks of that scale.
Here's a group of ancient people (ancient Indians) trying not only to comprehend the infinite but somehow thought it important to name so many divisions of infinitely large and small.