Simplify the following text for a Grade 6 native English-speaking person.
Original: Science fiction studies has a long history dating back to the turn of the 20th century , but it was not until later that science fiction studies solidified as a discipline with the publication of the academic journals Extrapolation ( 1959 ) , Foundation - The International Review of Science Fiction ( 1972 ) , and Science Fiction Studies ( 1973 ) , and the establishment of the oldest organizations devoted to the study of science fiction , the Science Fiction Research Association and the Science Fiction Foundation , in 1970 .
Simplified: Isaac Asimov was a famous science fiction writer . He once said that science fiction is possible , but fantasy is not .