The night sky in the desert.
The day sky in the desert
Night and day are complete opposite time periods.
exists x1 x2 x3.(n_desert(x3) & n_sky(x1) & of(x1,x2) & n_night(x2) & a_topic(x1) & in(x1,x3))
exists x1 x2 x3.(n_desert(x3) & n_sky(x1) & of(x1,x2) & n_day(x2) & a_topic(x1) & in(x1,x3))