From tiny dust particles that slowly swirl together under the force of gravity, to distant stars that forge new elements, to the trillions of galaxies in our universe, we’ll explore the staggering ...

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 ...

With this scale and other tools, Hubble had found and measured 23 other galaxies out to a distance of about 20 million light years. The second key was the work of Vesto Slipher, who had ...

Subsequent advances revealed first the size of the Solar System, then the distances ... scale for the Milky Way. Well before Hubble, some people had proposed there might be a universe beyond our ...