Podcast Summary
Exploring the mysteries of the universe with astrophysicist Matt O'Dowd: During the episode, Matt O'Dowd discusses the mysteries of the universe, including quasars, black holes, and the potential impact of the big rip. He also shares insights from his film 'Inventing Reality' about humanity's quest for fundamental truths in physics and neuroscience.
During the next episode of StarTalk, astrophysicist Matt O'Dowd, an expert in black holes, quasars, and other cosmic phenomena, will discuss the mysteries of the universe, including the threshold of a quasar and the potential impact of the big rip on black holes. Matt, who teaches at Lehman College and is an associate at the American Museum of Natural History, also hosts and writes for the PBS Space Time YouTube channel, is currently working on a film called "Inventing Reality" that explores humanity's quest for the fundamental truths of nature from both a physics and neuroscience perspective. In the discussion, Matt and Neil Tyson, the host of StarTalk, share their expertise in various areas and answer questions from Patreon members, including one about the energy density surrounding a black hole and Hawking radiation. Matt explains that the development of 20th century physics is deeply connected to the study of black holes, and the answer to the question about the fate of material falling into a black hole involves a summary of concepts like general relativity, quantum mechanics, and Hawking radiation.
Black holes emit Hawking radiation, not completely black: Black holes lose mass and preserve information through Hawking radiation, resolving the paradox of quantum information destruction
Black holes, which are the collapsed cores of stars where gravity is so strong that light can't escape, are not completely black as once believed. Instead, they emit Hawking radiation due to quantum phenomena near the event horizon. This radiation causes black holes to lose mass over time and allows the information about what fell into the black hole to be preserved and eventually "remembered" or retrieved. This discovery resolved the paradox of how quantum information could be destroyed. Hawking radiation is not exactly coming out of the black hole but rather from the energy field in the vicinity of the black hole, using the gravitational energy density created by the black hole. Despite the unclear mechanism of its creation, Hawking's arguments were crucial for the consistency of the universe.
Black holes increase in entropy as they grow: Black holes follow the second law of thermodynamics by increasing in entropy as they consume matter, hiding information and leading to the discovery of the holographic principle, which suggests that all info of a volume can be encoded on its surface
Black holes follow the second law of thermodynamics by increasing in entropy as they grow. This is due to the fact that as a black hole consumes matter from the universe, the information about the consumed matter becomes hidden, increasing the amount of hidden information and thus the entropy of the black hole. This relationship between a black hole's entropy and its surface area led to the discovery of the holographic principle, which suggests that the information of the interior of a volume can be completely encoded on the surface of that volume. This discovery has significant implications for our understanding of the universe. Additionally, the discussion touched upon the idea that black holes may have negative mass or energy due to the dimensions getting twisted inside the black hole, causing the black hole to shrink slightly. However, the exact nature of this phenomenon is still not fully understood.
Accounting for time dilation in cosmic events: Time dilation, caused by relativistic effects and the expanding universe, affects clocks differently in various locations. Adjusting for time dilation is essential for accurate calculations and discoveries in astronomy.
When discussing cosmic events in distant galaxies, it's essential to account for time dilation due to relativistic effects and the expanding universe. This means that clocks tick differently in different locations, and fast-moving objects appear to tick slower. For example, quasars, which are super massive black holes, can be studied by taking this into account and making the necessary adjustments using simple algebra. This is important because without accounting for time dilation, calculations and observations can be inaccurate. Researchers have made such adjustments in the past, leading to significant discoveries, such as the first measurement of time dilation in a supernova light curve. Overall, understanding and accounting for time dilation is crucial for accurately studying and interpreting phenomena in the universe.
Discovering Quasars from Black Holes: Quasars are not necessarily close to us and can form around black holes of various sizes, creating a super bright glow from heated gas.
While the discovery of dark energy by Nobel Laureate Brian Schmidt is significant, being an author on a Nobel Prize-winning paper does not require being the last author. Quasars can come from black holes of any size if there is enough matter around them to heat up, and they don't necessarily have to be extremely close to the Milky Way for us to see them. The sun has sunspots and other storms that can be larger than usual, but they are not black holes. The sun is massive and can hold a million Earths, so a black hole 20 times the size of Earth would not pose a significant threat. Quasars can form around decent-sized black holes, and the heat from the swirling gas around the black hole creates the super bright glow observed in quasars.
Stellar mass black holes forming x-ray binaries: Stellar mass black holes create x-ray binaries by 'filleting' or 'vampirizing' nearby stars, forming accretion disks that emit x-rays
Stellar mass black holes, which are remnants of massive stars and range from 10 to several tens times the mass of the sun, can form x-ray binaries when they fall into binary orbits with other stars. When these stars get too close, the living star's envelope can spill over into the black hole's influence, resulting in the black hole "filleting" or "vampirizing" the star. This process creates an accretion disk, which emits x-rays and forms what we call x-ray binaries. These mini quasars are relatively small compared to quasars, but they still emit significant light. The threshold between an active galactic nucleus and a quasar is not clear-cut, as definitions are muddy due to the vast distances and differences in gas supply, black hole size, and orientation of the accretion disk. Quasars were once prevalent in the universe, but many have consumed all their gas and are no longer active. The shortage of quasars nearby is due to the fact that the biggest galaxies, which once hosted quasars, have already consumed their gas and are no longer building them. However, there was a period in the universe's history, called the quasar epoch, when quasars were prevalent and corresponded to the building of the biggest galaxies. Today, quasars are mainly found in the early stages of galaxy formation.
Discoveries of quasars and the universe's vastness: Though quasars are rare in our vicinity, their discovery adds to our understanding of the universe's complexity. The significance of black holes' role in the universe's eventual fate remains uncertain.
While quasars, which are extremely bright sources of light in the universe, may not be common in the immediate vicinity of Earth, the universe is vast and we have observed many hundreds of thousands of them. The concept of rarity in the universe doesn't diminish the significance of these discoveries. Regarding black holes, it's speculative whether they will be affected by the eventual big rip of the universe, which could lead to the expansion of space and a decrease in density for black holes. However, it's uncertain if this process would allow for the emergence of life. These are complex phenomena that require ongoing research and exploration.
Impact of Dark Energy on Black Holes and the Big Rip Scenario: The debate continues on whether dark energy speeds up or slows down black hole evaporation, with potential implications for the Big Rip scenario. Gravitational lensing offers insights into distant objects and quasar structures.
The discussion revolved around the impact of dark energy on black holes and the potential implications of the Big Rip scenario. While some believe that the anti-gravitational effect of dark energy could cause black holes to evaporate more quickly, others suggest that the expansion of the universe and dilution of energy density around black holes could slow down the evaporation process. The use of gravitational lensing in astronomy was also touched upon, with the discussion focusing on how it allows for the observation of distant objects through multiple paths and the potential for probing the structure of quasars. Despite some disagreements, it was acknowledged that more calculations are needed to fully understand the complex interplay between dark energy, black holes, and the expansion of the universe.
Gravitational lensing provides insight into quasar structure and universe expansion: Gravitational lensing reveals quasar details and helps map their inner structures, while measuring time delays and path lengths can aid in understanding the universe's expansion history and potential dark energy rate.
Gravitational lensing, a phenomenon where the gravitational pull of a massive object bends the light from an object behind it, can provide valuable information about the structure and distance of celestial bodies. This is particularly useful when dealing with quasars, which can be reconstructed in detail due to the flickering effect caused by the alignment of a star inside the lensing galaxy with one of the pathways. This flickering, or time delay, depends on the size of the quasar and can be used to map out its inner structure. Furthermore, measuring these time delays and path lengths can help scientists understand the expansion history of the universe and potentially determine the rate at which dark energy is causing the universe to accelerate. However, the distinction between a massive planet and a failed star, such as the hypothetical object orbiting the red star Octurus, can be blurry, as the difference lies in their formation processes.
Origin stories of celestial bodies impact their classification: Binary star systems form when two stars originate together, while planets form around pre-existing stars. Galaxies, if they stopped rotating, would collapse into their central black holes.
The origin story of celestial bodies, whether they form together as a binary star system or one forms first and the other becomes a planet, significantly impacts their classification. For instance, if two stars form from the same giant cloud of gas and find each other, it's a binary star system, with one being a failed star. However, if a big star forms first, and a giant Jupiter-like planet forms in the leftover disk around that star, it's classified as a planet. The discussion also touched upon the implications of galaxies stopping rotation. If the Milky Way were to cease rotating today, every star would fall towards the supermassive black hole at the center. This could result in collisions and the whole galaxy being consumed by the black hole. Lastly, a question was raised about the Solar Gravitational Lens Mission, which could be an effective tool to study exoplanets and potentially discover life beyond our solar system. However, this mission has not yet occurred due to the challenges of sending a telescope to the specific location in the outer solar system where it would effectively focus light from distant objects using the sun's gravitational field.
Observing distant exoplanets with advanced telescope tech: Advanced telescope technology like coronagraphs and Einstein rings could potentially allow us to observe and map distant exoplanets' surfaces despite their stars' bright light, offering valuable insights into astrophysics.
Advanced telescope technology, such as the use of a coronagraph and an Einstein ring, could potentially allow us to observe and map the surface of a distant exoplanet, even with the bright light of its star in the way. This idea, though challenging due to the need to block the sunlight, has not been abandoned and is still a topic of discussion among scientists. Despite the difficulties, the potential rewards – including the ability to study the surface details of another planet – make it a worthwhile pursuit. Additionally, in the scientist's own words, there have been surprising findings in research that have expanded our understanding of astrophysics, even if they didn't necessarily revolutionize it for the researcher personally.
Discoveries that challenge our understanding: Intriguing discoveries aren't those that fit neatly into existing theories, but those that challenge our understanding and leave us puzzled, sparking further scientific inquiry
Learning from this episode of StarTalk Cosmic Queries is that the most intriguing discoveries for scientists aren't necessarily those that fit neatly into existing theories, but rather those that challenge our understanding and leave us puzzled. Neil deGrasse Tyson emphasized this point during the discussion, sharing an analogy of stumbling upon an unknown object in the dark. It's not the discovery itself that gets scientists worked up, but rather the mystery and uncertainty that comes with it. So, the next time you encounter something unfamiliar, remember that it might just be a stepping stone towards a groundbreaking scientific discovery. Keep asking questions and keep looking up!