So 'Chigaku' is short for 'Chikyuukagaku'...
But the most interesting-sounding field is 'space', isn't it?
Both 'Chigaku' and "Chikyuukagaku" mean 'earth sciences'. By the way, 'economics' is short for 'Manage the world (nation) and care for the people'.
The Japanese phrase for economics consists of 経 (to manage) and 済 (to care for).
