What is the {material used} and the {has effect} of {Gravitational_wave} ?
What is a gravitational wave made of and what are it's effects?
What material is used in a gravitational wave and what is the effect of it?
SELECT ?g ?s WHERE { resource:gravitational_wave property:made_from_material ?g . resource:gravitational_wave property:has_effect ?s }
 SELECT ?ans_1 ?ans_2 WHERE { ?statement1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q190035> . ?statement1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P186> . ?statement1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?ans_1. ?statement2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q190035> . ?statement2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1542> . ?statement2 <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?ans_2. } 
SELECT ?ans_1 ?ans_2 WHERE { wd:Q190035 wdt:P186 ?ans_1 . wd:Q190035 wdt:P1542 ?ans_2 }
spacetime gravitational wave event