"Now there were exceptions to what we have just stated. The exceptions were the mathematicians who were involved in recording
astronomical data. Here we find the first use of the symbol which we recognise today as the notation for zero, for Greek
astronomers began to use the symbol O. There are many theories why this particular notation was used. Some historians favour
the explanation that it is omicron, the first letter of theGreek word for nothing namely "ouden". Neugebauer, however, dismisses
this explanation since the Greeks already used omicron as a number - it represented 70 (the Greek number system was based on
their alphabet). Other explanations offered include the fact that it stands for "obol", a coin of almost no value, and that it arises
when counters were used for counting on a sand board. The suggestion here is that when a counter was removed to leave an
empty column it left a depression in the sand which looked like O.
