Complex sentence: Height, width, and length constitute three-dimensional space, and time gives a total of four observable dimensions; however, string theories initially supported the possibility of ten dimensions--the remaining six of which we cannot detect directly.
Split into simpler sentences: Height, width, and length constitute three-dimensional space, and time gives a total of four observable dimensions. However, string theories initially supported the possibility of ten dimensions--the remaining 6 of which we cannot detect directly.