61244
The positions of celestial objects and events , as measured from Earth , change over time , so when measuring or predicting celestial positions , the epoch to which they pertain must be specified .
 Earth
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Earth