Warning as threat levels for three US volcanoes are elevated due to possible eruptions
Scientists are keeping a close eye on three US volcanoes after their threat levels rose Thursday, suggesting eruptions may be ...
One large Milky Way galaxy or many galaxies?
In 1920, astronomers Harlow Shapley and Heber Curtis held a Great Debate. Shapley argued that the spiral nebulae were small and in the Milky Way, while Curtis took a more radical position that they ...