div class=ts-pagebutton class=gotoPage data-page=1Page 1button div class=ts-imageimg data-url=an-introduction-to-astronomy-57991fd133123htmlpage=1 data-page=1 class=ts-thumb lazyload alt=Page 1: An Introduction to Astronomy loading=lazy src=data:imagegifbase64iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAQAAADYv8WvAAAAD0lEQVR42mP8X8AwAgiABKBAv+vAXklAAAAAElFTkSuQmCC data-src=https:reader031vdocumentsnetreader031viewer2022020522575067e41a28ab0f07ad9f4dhtml5thumbnails1jpg width=140 height=200 divp© 1941 Nature Publishing Grouppdiv