Ancient Discoveries and Numbers

The topic is measurement of time. The ancient people had one number, the number one. If you have no clock, no measurement for time, how the heck do you even know one day is longer than the next? The shadows were all they had to go by for Stonehenge and yet they discovered the longest and shortest days. The Greeks accurately measured the diameter of the earth by comparing the lengths of two shadows 500 kilometers from each other at the same time of the day. Consider how you would take this measurement. How would they know what time it was and how would they measure the distance and yet, one guy did it. And got it right. All with only one number, the number one.
By the time of Archimedes the Roman numbering systen was ruling the world. Calculations were impossible. The decimal numbering system required invention, in India.