What Gravitational Waves Reveal About the Universe, with Michelle Thaller

Michelle Thaller explains that, theoretically, a photon traveling at the speed of light doesn't experience time or distance in the same way we do. She references a Veritassium podcast for her understanding, highlighting that photons are frozen in a moment and can traverse vast distances instantaneously from their perspective. This concept challenges our conventional understanding of space and time.

Neil deGrasse Tyson clarifies that even though photons don't experience time, we can measure changes in their energy (redshift). This indicates that the photon has interacted with the expansion of the universe, losing some energy along its journey. This observation allows scientists to infer information about the universe’s evolution despite the photon's unique temporal perspective.

The discussion explores how photons appear to slow down when traveling through mediums like air or water. This isn't because the photon itself is moving slower than light, but rather due to interactions with atoms within the medium, creating a series of 'banking' events that effectively delay its progress.

To aid in comprehension, Michelle uses the analogy of a pool ball traveling across a table versus banking off multiple rails to reach a pocket. This metaphor illustrates how a photon's speed can remain constant while its path and perceived travel time change due to interactions with surrounding elements.

The eventual fate of the universe isn't a 'heat death,' but rather a 'cold death' as high-energy photons lose energy over time. This process leads to a gradual cooling and diminishing of available energy, ultimately resulting in a state where activity ceases. The term 'heat death' is therefore a misnomer, highlighting that it’s the loss of energy, not heat itself, that defines this cosmic endpoint.

Michelle and Chuck discuss a counterintuitive phenomenon: the sun’s corona, its outermost atmosphere, reaches temperatures of around 5 million degrees Celsius despite being far from the sun’s surface. This is explained by the low density of particles in the corona; while individual particles have high kinetic energy, their scarcity means they don't impart much heat to an observer – temperature loses practical meaning at these densities. NASA’s Parker Solar Probe orbits within this region and provides data despite the extreme temperatures.

To illustrate how temperature can be perceived differently depending on density, Michelle uses the analogy of a 500-degree pizza oven. While the oven itself is extremely hot, simply opening the door and briefly exposing your hand won't necessarily cause immediate burning because there isn’t sufficient contact with the dense metal surfaces inside. This highlights how temperature perception depends on both heat and density.

Eugene Parker, a pioneering astrophysicist, predicted the existence of the solar wind – a stream of charged particles emanating from the sun. The Parker Solar Probe, named in his honor, is currently orbiting within the sun's corona to study this phenomenon and understand how the sun’s surface temperature can be significantly lower than its outer atmosphere. The probe has also set a speed record exceeding 400,000 miles per hour due to the sun's gravitational pull.

The Parker Solar Probe's data is helping scientists understand the complexities of the sun’s behavior, including how its surface temperature (around 10,000 degrees Fahrenheit) gives way to millions of degrees in the corona. This involves intricate accelerations due to magnetic fields and shocks that increase particle speed; it demonstrates a significant gap in our understanding until direct observation through missions like Parker Solar Probe.

Michelle Thaller highlights the NICER mission, a Goddard-run project on the International Space Station. This mission uses X-ray telescopes to map the surface of neutron stars by precisely timing the arrival of X-rays. Neutron stars are incredibly dense objects, only about 20 miles across but containing twice the mass of our sun, allowing scientists to study their composition and even observe light bending due to extreme gravity.

A Goddard scientist reportedly prefers studying neutron stars over black holes because of the 'event horizon' that obscures information from black holes. With neutron stars, scientists can directly observe the surface and conditions, providing invaluable insights into extreme matter behavior not replicable in Earth-based laboratories.

The explanation of fast radio bursts involves synchrotron radiation, a process where rotating magnetic fields accelerate electrons. These accelerated electrons spiral around the magnetic field lines, emitting radio waves. This phenomenon requires a strong magnetic field and is crucial for understanding how neutron stars generate radio signals.

Different processes within the environment of a neutron star produce different bands of light, allowing various telescopes to observe them. The presence of jets further complicates the emission spectrum, highlighting the complexity of these celestial objects and enabling comparative analysis across multiple wavelengths.

Neil deGrasse Tyson emphasizes that ambition and a drive to explore are more crucial for success in scientific research than simply performing well on exams. He highlights that tests rarely assess genuine ambition, which is the key ingredient for pushing the boundaries of knowledge. This perspective encourages individuals to prioritize passion and perseverance over traditional measures of academic achievement when pursuing a career in science.

Michelle Thaller recounts her experience being placed in remedial math during college, stemming from the limitations of her public school education. Despite feeling inadequate initially, she persevered due to her deep fascination with space, ultimately driving her to overcome those early obstacles. This anecdote demonstrates that passion can be a powerful motivator for overcoming challenges and achieving success even when facing initial setbacks.

The conversation draws an analogy between learning science, particularly math as the 'language of the universe,' and learning a language like Spanish. Just as anyone can learn Spanish with dedication and consistent effort, they argue that anyone can grasp scientific concepts through persistent study and practice, regardless of perceived innate talent. This comparison aims to demystify science and make it more accessible to individuals who may feel intimidated by its complexity.

Neil deGrasse Tyson promotes the StarTalk Patreon community, highlighting that a mere $5 monthly contribution is less than NASA's budget. This playful comparison underscores the value of supporting independent science communication and emphasizes the affordability of becoming part of the StarTalk community to access exclusive content and engage with scientific discussions.

Michelle Thaller retired from NASA Goddard Space Flight Center in October 2024, marking the end of a long career dedicated to astrophysics. Following her retirement, she has transitioned to freelance work, engaging in lecturing with Smithsonian Journeys and enjoying the freedom to explore various scientific pursuits outside of a formal institutional setting.

NASA’s Goddard Space Flight Center in Maryland is its largest base, historically employing around 10,000 people. If it were to separate from NASA, Goddard would become the second-largest space program globally, demonstrating its immense scale and contribution to space exploration and scientific research.

The Goddard Space Flight Center played a crucial role in the development of significant space telescopes like the Hubble Space Telescope and the James Webb Space Telescope. The center is responsible for building various satellites, including weather satellites, demonstrating its extensive involvement in advancing astronomical observation capabilities.