I appreciate the intent of revealing the all-encompasing nature of Math as the language for describing what we find wherever we look. It is too true that with a limited comfort level for math, we are very easily intimidated by cosmic scales and relationships.
I was especially impressed that you interpreted the factors, and demonstrated in such detail the reciprocal relationships inherent in the Lorentz Transformation. But then things fell apart in the detail on eccentricity of an orbit.
Just as movie producers employ a staff of "Continuity" observers to assure things like the placement of objects, time-indications on clocks, and so on are 'consistent' from one 'take' to the next, it is helpful to a reader if symbols representing specific values or properties of an illustrated relationship are kept consistent.
The discussion of Kepler's First Law lacks a similar level of instructional value. The boxed illustration on page 28 presents a formula, but no labels within the diagram to impart meaning to the factors in the equation. The specific mention within the body of the text offers no direct elaboration of the terms, either.
The wording of the explanation on page 27 introduces terms that may themselves be unfamiliar, or non-intuitive, like 'semimajor axis'.
So, if Mercury has an eccentricity of 0.20, the major axis of its orbit would have a length 5 times the spacing of its foci, but is that it's 'diameter'?
Then, help me with the illustration of Kepler's Second Law. In the first illustration within the box, the arc segments 'A' and 'B' appear to be equal, as they should be if the orbit is circular. But in the third illustration, they also appear to be equal! Which results in a HUGE understatement of the area swept by the 'string' discussed in the text during the planet's passage along the arc 'B'.
Given the point of the illustration is to counter the misunderstanding illustrated as the second case, it might have been better to err on the side of exageration, and show an arc 'B' that was clearly twice as long as arc 'A'. Yes, the picture reflects an increase in the angle subtended, but hardly an equality of swept area.
Don't be afraid to offer more of these. I believe establishing the 'meaning' of math in young minds is a critical step in promoting access to careers in astronomy and the other sciences. Making it plain that math is cool is of imense value to the entire human race.