Question: when was the structure of the earth discovered
[{'answer': '1936', 'provenance': [{'wikipedia_id': '1417149', 'title': 'Structure of the Earth', 'start_paragraph_id': 21, 'start_character': 33, 'end_paragraph_id': 21, 'end_character': 37, 'bleu_score': 1.0, 'section': 'Section::::Structure.:Core.\n'}]}, {'provenance': [{'wikipedia_id': '1417149', 'title': 'Structure of the Earth', 'start_paragraph_id': 21, 'start_character': 0, 'end_paragraph_id': 21, 'end_character': 757, 'bleu_score': 0.984062469849008, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17301210505880346740}, 'section': 'Section::::Structure.:Core.\n'}]}]