Lex Fridman - Anna Frebel

1) Anna Frebel describes how the first supernova explosions generated heavier elements and changed the physics of gas clouds, allowing the next generation of stars to form, including smaller stars that have longer lifetimes. These early stars provide insight into the chemical and physical conditions of the early Universe, before the formation of galaxies. The Milky Way, for example, was formed from early stellar structures and systems that were absorbed over time through hierarchical growth. Frebel also explains what a galaxy is, and how the Milky Way is a spiral disc galaxy with 200-400 billion stars, with most of the material and stars in the disk.

2) Anna speaks about the structure of the Milky Way and how it can make us feel in awe and a part of it all. She talks about the vastness of space and the many possibilities there are for life forms and the conditions on different planets. However, she admits that the details of planet formation and the clumping process are not well understood and that patience is needed to advance our technologies to explore the mysteries of space further.

3) Anna discusses the mystery surrounding the formation of supermassive black holes in the center of large galaxies. While it is known that these black holes exist, researchers are not sure whether they caused or were created by the galaxies themselves. Frebel explains that the James Webb Space Telescope, which collects infrared light, is working to help solve this mystery and observe the early stages of black hole formation. Additionally, she notes that there are dozens of small dwarf galaxies that do not contain black holes, so researchers must investigate what made the Proto Milky Way different and more massive than other galaxies at its time.

4) Anna discusses her observational cosmology work and how it differs from theoretical physics regarding black holes. She explains that as an observer of stars, her work focuses on fundamental chemical and physical phenomena, which is not extreme physics like black holes. However, she does express interest in talking with her theory colleagues because they have an interesting intersection with her work. She believes that scientists, even in the same field, express themselves about science differently, making it difficult to communicate with each other sometimes. Nevertheless, it's satisfying when scientists come together to tackle scientific problems because, in the end, they can overcome their differences and make big discoveries in the sandbox of the universe.

5) Anna explains the process of stellar archaeology, which involves studying old stars to learn about the composition of the gas from which they formed. Smaller stars have longer lifetimes, and those that are 0.6 to 0.8 solar masses have lifetimes of 15 to 20 billion years. These stars are still observable today and are located in the outskirts of the Milky Way, having possibly formed in a nearby galaxy that the Milky Way absorbed.

6) Anna explains the importance of heavy metals in the evolution of stars. Every supernova explosion gives rise to elements up to iron, which is what came out of the first stars, and the many generations of supernova explosions that followed enriched the gas cloud from which the sun and the planets were formed. The heavy elements are created through neutron capture processes, and the supernova-made elements serve as excellent seed nuclei for the creation of heavy elements. Frebel's observations of the chemical composition of old stars allow her to unravel the processes and events that led to their creation and provide clues about the early universe.

7) Anna discusses the process of research and finding stories, not just numbers, as a scientist. She explains that her job is to find and interpret the story behind the chemical abundance of stars. She describes chemically pristine stars as those with the least amounts of heavy elements and how they illustrate the evolution of the universe and galaxy. Additionally, she talks about her love for stars such as the star HE 1327-2326 and the star Chief 15230901 that she helped discover and how they provide insights into the early days of the universe.

8) Anna discusses the discovery of second generation stars and their significance in revealing the nature of the universe's first stars. These stars were found to have huge amounts of carbon and very little iron, indicating that they must have been from the population three, or first stars. Working with theorist groups, they concluded that these first supernovae must have exploded differently than previously understood. This breakthrough has pushed the field to consider the implications for these early proto-galaxies and their potential disruption from these early stars.

9) Anna discusses the fallback mechanism that takes place during supernovae and how it can explain why certain elements, such as carbon, are more abundant than others, like iron, in the universe. A black hole will suck away some of the iron from the supernova, but the carbon is much further out and can escape. This mechanism can explain stars with a high carbon abundance but a low iron abundance. Frebel goes on to explain the importance of carbon in the formation of the first low-mass stars and how it enabled the development of humans and stable planets. She also briefly discusses Mildred Dresselhaus, a professor at MIT who pioneered carbon Nano work and the remarkable properties of carbon.

10) Anna discusses the wonder of carbon in not just the cosmos but for humans as well. She explains how our existence is a result of chemical evolution and how lucky we are that certain things fell into place. She also talks about the complexities and mysteries of the universe and how the biological evolution on Earth was facilitated by the chemical evolution of the universe. The discussion then shifts to the exciting discovery of HE 1523, a red giant star that has a different chemical composition, specifically an overload of heavy elements like thorium and uranium, which are useful in exploring the early universe.

11) Anna Frebel discusses the observation of the electromagnetic counterpart to the gravitational waves detected by the LIGO and Virgo gravitational wave observatories. Astronomers were able to observe the nucleosynthesis of heavy elements occurring following the collision of two neutron stars which created a super neutron star. The observation confirms that neutron star mergers are one of the sites for rapid neutron capture processes (r-process) to occur, resulting in the formation of heavy, neutron-rich nuclei. She also talks about her discovery of a small dwarf galaxy, Reticulum 2, which has ancient iron-deficient stars showing the signature of the r-process, indicating that it was a neutron star merger that went off in Reticulum 2 at early times that polluted the gas from which all our little stars formed.

12) Anna discusses her love for stars and how they serve different purposes depending on their location. While the SAS in the Milky Way provides better data because they are closer and brighter, dwarf galaxy stars provide valuable environmental information to pinpoint where certain processes could have occurred in the galaxy's formation history. Frebel uses spectrographs to observe stars and prefers the Magellan telescopes in Chile because of their unusually high efficiency. While most observatories now have staff to take observations for scientists, Frebel emphasizes the importance of data collection for astronomers.

13) Anna talks about her experiences observing the universe at observatories and how it creates a serene and magical environment. She mentions the beauty of the colors and the calmness of being on top of a mountain with less distractions, allowing her to focus just on data collection. She then describes her moments stargazing on the ground and feeling like a part of the universe. She talks about the unity of it all and how modern civilization often tries to separate itself from nature, but it is all one and the same.

14) Anna explains the process of how spectroscopy is used to gather data from starlight and how the dips in the spectrum indicate the presence and amount of different elements within the star. She also discusses the possibility of discovering life in the solar system and how it challenges our human-centric perspectives on what constitutes life and intelligence. Frebel emphasizes the humbling nature of the process, as life finds a way to survive and thrive in a variety of conditions, and encourages the exploration of different environments to expand our understanding of what life can be.

15) Anna discusses how the chemical composition of stars is determined through spectroscopy. By analyzing the absorption lines in a star's spectrum and measuring the strength of these lines, scientists can calculate the chemical abundances present in the star's atmosphere. Frebel explains that processing this data is fairly straightforward, and that she can quickly tell if a star is worth further study based on a summary plot of the key positions in the spectrum. She also talks about the tedious and time-consuming work that goes into discovering new stars, and how finding three of roughly the same kind can be considered a population, which helps advance the field of astronomy.

16) Anna discusses the challenges of conducting high-precision measurements in astronomy. She explains the process of low- and medium-resolution spectroscopy to identify candidates for high-resolution spectra, and a new technique involving images of stars taken with specific narrow filters. The difficulty lies in fishing out the desired information from the noise and identifying the needle in the haystack while dealing with limitations of telescopic size and brightness of stars. Frebel also recalls the excitement of discovering the most iron-poor star named HE1327.

17) Anna discusses the serendipitous discovery of the first process galaxy and the importance of luck in scientific breakthroughs. She also expresses her excitement about the future of telescopes like James Webb's Space Telescope, which will increase the resolution and precision of what can be detected in the universe. Although Frebel acknowledges the limitations of the field of stellar archeology, she believes that they have made significant progress in understanding the first billion years of the universe through observations of metal-poor stars. While the field is becoming more data-driven, Frebel still believes in the value of individual observations to build up intuition about the early universe.

18) Anna stresses the importance of properly formulating questions in scientific research. She explains how crucial it is for researchers to have a thorough understanding of the data and its limitations, and how it can affect their interpretations of the results obtained. Frebel also expresses her concerns with big data and statistical analysis, stating that although they have significant benefits, they may not be suitable for every type of research. She believes that the next level of discovery will involve filling in the details and finding the last puzzle pieces, which could lead to a more profound understanding of the universe and its intricacies.

19) Anna explains the difference between math and physics and how they apply to the question of the age of the universe and the Big Bang. While physics is limited by our physical nature and the models we construct, math is not, and it can push further than physics. However, physicists can use math to calculate numbers that may not make sense from a physical perspective, making sense only from a mathematical perspective. The Big Bang is still a mystery due to the difficulties in understanding what came before it, and physics and math are still working together to try and answer these questions.

20) Anna discusses the timeframe of the observations in her field of astronomy, the early chemical evolution of the universe, and the lack of planets around old stars. She also talks about the major contributions made by women in her field, specifically highlighting the work of the Harvard computers who were instrumental in carrying out large sky surveys. Despite having no formal education, these women made a significant contribution to the field by combing through big data of the day and making discoveries by being in tune with what they were doing. For example, Cecilia Payne calculated that the sun is mostly made of hydrogen and helium, which was a groundbreaking discovery at the time.