Mathematics Today -- One -- Mathematicsโ{128}{148}Our Invisible Culture -- Two -- Number Theory -- Groups and Symmetry -- The Geometry of the Universe -- The Mathematics of Meteorology -- The Four Color Problem -- Three -- Combinatorial Scheduling Theory -- Statistical Analysis of Experimental Data -- What is a Computation? -- Mathematics as a Tool for Economic Understanding -- Mathematical Aspects of Population Biology -- Four -- The Relevance of Mathematics -- About the Authors -- Further Reading