The Wikipedia page on the First World War provides a comprehensive overview of the global conflict that took place between 1914 and 1918.

Nature is a prestigious weekly multidisciplinary scientific journal.

A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image.

A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope).

A telescope is an optical instrument designed to magnify and focus light for observation of distant objects.