Today’s Appendix has a pretty simple goal: To get a glimpse of the fourth dimension--of time. We won’t be able to answer all of the questions posed above, but we can get a good start. And since we can’t go up into the 4th dimension, we’re going to have to start by going down into the second. And that’s where we begin with Today’s Appendix, coming in the form of a few shapes cut out of paper, clipped to the back of the very real, very physical book of Common Knowledge on Time.