Passage: Science, also widely referred to as Science Magazine, is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals. It was first published in 1880, is currently circulated weekly and has a subscriber base of around 130,000. Because institutional subscriptions and online access serve a larger audience, its estimated readership is 570,400 people.The major focus of the journal is publishing important original scientific research and research reviews, but Science also publishes science-related news, opinions on science policy and other matters of interest to scientists and others who are concerned with the wide implications of science and technology. Unlike most scientific journals, which focus on a specific field, Science and its rival Nature cover the full range of scientific disciplines. According to the Journal Citation Reports, Science's 2015 impact factor was 34.661.Although it is the journal of the AAAS, membership in the AAAS is not required to publish in Science. Papers are accepted from authors around the world. Competition to publish in Science is very intense, as an article published in such a highly cited journal can lead to attention and career advancement for the authors. Fewer than 7% of articles submitted are accepted for publication.

Question: Who is Science magazine's main competition?
Nature