Plot Ticks disappear when combining Plot with Graphics

Question

I'm attempting a simple Plot that I want to add asymptote markers to:

Module[{p, g},
 p = Plot[1/Sqrt[1 - x^2/4], {x, -2, 2},
   PlotRange -> {{-2.2, 2.2}, {0, 5}}];
 g = Graphics[{Line[{{2, 0}, {2, 5}}], Line[{{-2, 0}, {-2, 5}}]}];
 {p, Show[g, p]}]

With just the plot I get my tick marks

However, when I combine the plot and the pair of lines:

the tick marks on my axes disappear? Observe that it even the vertical ticks are gone, so this isn't an issue of them being pushed off the combined image.

Answer 1

Show picks the the options from the first graph and applies them to the second graph. The two lines have no tick marks as options so it removes them from the plot.

Module[{p, g}, 
 p = Plot[1/Sqrt[1 - x^2/4], {x, -2, 2}, 
   PlotRange -> {{-2.2, 2.2}, {0, 5}}, Background -> Green];
 g = Graphics[{Line[{{2, 0}, {2, 5}}], Line[{{-2, 0}, {-2, 5}}]}, 
   Background -> Red];
 Column[{Row[{p, " + ", g, " -> ", Show[p, g]}], 
   Row[{g, " + ", p, " -> ", Show[g, p]}]}]]