Comparing and Combining WMAP with Other Data

Since this is a meeting on inflation the title of this talk should probably have been ``The cosmos as a lab for inflation''. I will illustrate how, by combining WMAP observations of the cosmic microwave background (CMB) with smaller scales CMB experiments and large-scale structure surveys, it is possible to constrain inflationary models. WMAP data in combination with these external data sets, offers a window to the very early universe and the physics of inflation: enables us to confirm the basic tenets of the inflationary paradigm and begin to quantitatively test inflationary models. Understanding the complex physics and complicated systematics of the low redshift observations is crucial to make progress in this direction.