Measure three space-time intervals

This project must be done by individuals.

The goal of this project is for you to measure the time and place of pairs of events, and then to compute the space-time intervals (STIs) between those events. To receive full credit, you must calculate three different intervals:

one interval must have a positive real STI
one interval must have an STI of size zero
one interval must have an imaginary STI

In each case, you must clearly define two events -- describing the location and time of each one -- and then perform a calculation in which you compute the STI. For example, you might choose these two events:

I put on my right shoe
I sit down to eat breakfast

You would note/measure the location of each event, and the time at which each happpened, then compute the STI in the usual manner. Of course, it would be a good idea to convert all measurements to a single set of units first (perhaps meters, or seconds, or years -- depending on the events).

You will receive full credit for any measurement in which you "participate" in at least one of the events. If that doesn't seem possible or convenient, you may receive partial credit by choosing two well-measured events from any source(s) and going through the calculations.