For millennia, numerical systems started the number one. Although Babylonians and Greeks used a symbol to indicate an empty spot in a number, such as 907, the concept of nothingness reesained just that—nothing. It was circa A.D. 500, when India's great mathematician-astronomers Aryabhata (A.D. 475-550) and Varahamihira (A.D. 505- Mg) described "zero" as a quantity, which led to the transformation of mathematics from being not just a counting system but also a conceptual framework. During the next few centuries, Indian mathematicians worked out the laws for adding, subtracting, and multiplying by nothing. But it wasn't until the ninth century that the concept of zero finally came to the West through the written works of Persian mathematician al-Khwarizmi (A.D. 780-850). He brought the Indian numeral system to Baghdad, where he worked at the House of Wisdom, a major intellectual center during the Islamic Golden Age (A.D. 786-1258). AI-Khwarizmi is also known for developing algebra.