The figures in http://www.astro.virginia.edu/class/whittle/astr553/Topic16/t16_light_cones.html are very useful in understanding the various world lines in concordant diagrams. Is there any easy way to see how a velocity cone (at the observer's worldline) from a later time than the Big Bang look like? Is there any easy way to understand why the light cone has a steep (>2c) slope? Is it the 66.18c that we see in http://www.einsteins-theory-of-relativity-4engineers.com/LightCone7/LightCone.html at early time. In Cosmology, The Science of the Universe, two velocity cones are given, but the later cone seems to be steeper at the beginning. I guess I am also asking if there is an excel sheet or a program to make the concordance diagram from the conformal time diagram.