The YouTube video “Exploring the Universe: Crash Course Big History #2” explains how the universe cooled after the Big Bang and became full of hydrogen and helium gas clouds. The force of gravity started pulling these gas clouds together leading to the formation of the first stars in the universe. The video discusses the vastness of the universe in terms of galactic islands, the cosmic horizon and multiple universes. The importance of stars on the creation of elements and complexity in the universe is also touched upon with supernovae explosions creating heavier elements, leading to the fertilization of the cosmos with their ashes. Overall, the video traces rising complexity in the universe, from cosmology to human history, and highlights the importance of basic chemistry in understanding our ancestry.
00:00:00 In this section, John Green explains how the universe cooled and became full of gaseous clouds of hydrogen and helium after the Big Bang. Gravity started pulling these pockets of gas together, which eventually led to the formation of the first stars. By a billion years after the Big Bang, the universe was full of billions of galactic islands, each containing hundreds of billions of stars and even more planets. Our galaxy, the Milky Way, with 200-400 billion stars, is expected to merge with its neighbor, Andromeda, in 3.75 billion years through a graceful dance of galactic proportions.
00:05:00 In this section, the video delves deeper into the vastness of the universe, discussing galactic islands, the cosmic horizon, and the possibilities of multiple universes. The Virgo Supercluster of galaxies, to which the Milky Way belongs, is around 110 million light years in diameter, and there are likely infinite superclusters in the universe. The cosmic horizon limits what we can see, but as we look further and further, we observe more primitive things like the first stars and galaxies. The universe is constantly expanding, and while our cosmic bubble is already huge, beyond it lies more universe that is expanding eternally. As the video shifts back to the topic of stars, the importance of size and lifespan is touched upon, along with how elements are formed when giant stars collapse.
00:10:00 In this section, we learn about the impact of stars on the creation of elements and the rise in complexity in the universe. Supernovae explosions create heavier elements of the periodic table and fertilize the cosmos with their ashes. Rising complexity is a unifying theme that spans across the entire story of the universe, from cosmology to human history, and it owes its existence to the tiny wrinkles in the early cosmos. Even basic understanding of chemistry is essential to understanding our ancestry, as almost everything we see around us originated in the belly of a star.