This phrase identifies a specific resource: a PDF document titled “astro4u: an introduction to the science of the cosmos.” It suggests a textbook or introductory material designed to educate readers on the subject of astronomy and cosmology. The presence of the “.pdf” extension indicates a digital format suitable for electronic viewing and distribution.
Such a document offers a readily accessible pathway for individuals seeking foundational knowledge in astrophysics. Its availability as a portable document format enables convenient study across various devices. Historically, printed textbooks were the primary source for such education, but digital formats allow for wider dissemination, often at lower cost, and facilitate features such as searchability and embedded multimedia.
