Antipodes
This is a silly gem of no consequence with exactly one feature: to find the antipodes of a given place on Earth.
Both latitude/longitude coordinates and place names are accepted as input. If a place name is used, it is geocoded with the Geocoder gem.
Antipodes.for(47.6062095, -122.3320708) #=> [-47.6062095, 57.6679292]
Antipodes.for(-47.6062095, 57.6679292) #=> [47.6062095, -122.3320708]
Antipodes.for('Beijing') #=> [-39.90403, -63.592473999999996]
Antipodes.for('Buenos Aires') #=> [34.6037232, 121.6184069]
While it would be cool to get a corresponding place name (instead of lat/lon), it’s neither practical (most places don’t have land antipodes, since most of Earth is covered in water) nor possible given the current range of geocoding options.