Prompt Cast
The Discovery of Galaxies and the Vastness of the Universe
TLDR In the 20th century, astronomers discovered that the universe is much larger than previously thought, with many points of light in the sky being collections of stars called galaxies. The Milky Way, initially believed to be a collection of distant stars, was found to be a spiral galaxy with a supermassive black hole at its center. The Hubble Deep Field Image revealed the staggering number of galaxies in the universe, estimated to be between 100 billion to a trillion, each containing hundreds of billions to trillions of stars.
Timestamped Summary
00:00
In the 20th century, we discovered that the universe is much larger than we thought and that many points of light in the sky are actually collections of stars called galaxies.
01:58
The Milky Way was initially thought to be a collection of distant stars, but measurements of its parallax revealed that it was something else.
03:51
The debate over whether spiral nebulae were part of the Milky Way or separate galaxies was a major controversy in early 20th century astronomy.
05:38
Spiral nebulae were proven to be separate collections of stars, called galaxies, and Edwin Hubble categorized the different types of galaxies.
07:22
The Milky Way is a spiral galaxy with a diameter of about 100,000 light-years, and it has a supermassive black hole in its center.
09:17
The Hubble Deep Field Image demonstrated the mind-boggling number of galaxies in the universe, with subsequent images showing the same thing, leading to the current estimate of between 100 billion to a trillion galaxies.
11:06
Galaxies are the fundamental units of the universe and there may be hundreds of billions to trillions of them, each containing hundreds of billions to trillions of stars.
