The geometry of the universe from high resolution VLBI data of AGN shocks

We propose to use the linear diameters of the shocks in AGN jets as standar d rods for estimating the geometry of the Universe. The unique feature of s hocks is that we can directly estimate their linear diameters from total fl ux density monitoring data and light travel time arguments. We demonstrate this method by using a small sample of 14 22 GHz VLBI observations. The acc uracy of the derived values (qo similar or equal to 0,Ohm (m) similar or eq ual to 0) compares favorably with traditional methods using much larger sam ples.