Starts With A Bang podcast

Meredith Rawls, a professor studying satellites and preserving dark, quiet skies, discusses the meteoric rise of megaconstellations and why 2019 changed everything. She covers visible sky brightening, threats to optical and radio astronomy, orbital crowding and crash‑risk scaling, reentry and atmospheric concerns, and governance gaps versus possible mitigation paths.

Out there in the Universe, we're most aware of what we see: of all the forms of light that arrive in our eyes, instruments, telescopes, and detectors. Much more difficult to see, as well as understand and make sense of, is the wide array of "stuff" that's present, but that isn't readily apparent to the apparatuses we normally use to reveal the Universe. From the dark bands of the Milky Way to the light-blocking materials in nebulae and clouds, all the way to lining the arms of spiral galaxies and the heavy, long-chained molecules found in protoplanetary disks, cosmic dust is perhaps our most enduring mystery.Sure, it gives absorption signatures that we can leverage, and at long enough infrared wavelengths, dust that gets heated has its own emission signatures, but we can generally only observe it in detail up close: within our own galaxy or in the nearest galaxies of all. That poses a huge challenge, because the origin of dust, including from a cosmic perspective, remains only very poorly understood. We may have identified many dust-producing sources in the Universe, and we may understand that the young Universe was a lot less dusty than our modern cosmos, but we still lack an understanding of how this has come to be the case. Thankfully, we have scientists on the case, like this month's guest: Dr. Elizabeth Tarantino of the Space Telescope Science Institute.In this fascinating interview, she takes us on a journey spanning gently dying stars, the formation of new stellar systems, the outskirts of our cosmic backyard, and to the farthest reaches of JWST as we try and piece this mysterious cosmic story together. Buckle up for an exciting and informative ride; you'll be glad you tuned in!(This image shows the Pillars of Creation within the Eagle Nebula, as assembled by two entirely different data sets. On the upper-right, a visible light view showcases how this dusty region obscures the stars behind it. On the lower-left, an infrared view showcases the stars, although reddened, that can be seen behind the dusty cloud. At still longer wavelengths, the dust would glow due to the heat inside of this region. Credit: NASA, ESA, CSA, STScI, J. DePasquale, A. Koekemoer, A. Pagan (STScI), ESA/Hubble and the Hubble Heritage Team)

Dr. Kate Storey-Fisher, a cosmologist at Stanford's Kavli Institute, dives into the intriguing world of large-scale structures in the universe. She discusses the emerging cracks in the standard cosmological model, focusing on the Hubble tension and questions about whether dark energy is constant. Kate explains the importance of combining multiple datasets, like galaxy clustering and baryon acoustic oscillations, to refine our understanding of cosmic parameters. Her work with the DESI collaboration hints at evolving dark energy, offering a fresh perspective on the universe's expansion.

All across the Universe, stars are dying through a variety of means. They can directly collapse to a black hole, they can become core-collapse supernovae, they can be torn apart by tidal cataclysms, they can be subsumed by other, larger stars, or they can die gently, as our Sun will, by blowing off their outer layers in a planetary nebula while their cores contract down to form a degenerate white dwarf. All of the forms of stellar death help enrich the Universe, adding new atoms, isotopes, and even molecules to the interstellar medium: ingredients that will participate in subsequent generations of star-formation.For a long time, however, we'd made assumptions about where certain species of particles will and won't form, and what types of environments they could and couldn't exist in. Those assumptions were way ahead of where the observations were, however, and as our telescopic and technological capabilities catch up, sometimes what we find surprises us. Sometimes, we find elements in places that we didn't anticipate, leading us to question our theoretical models for how those elements can be made. Other times, we find molecules in environments that we think shouldn't be able to support them, causing us to go back to the drawing board to account for their existence.Where our expectations and observations don't match is one of the most exciting places of all, and that's where astrochemist and PhD candidate Kate Gold takes us on this exciting episode of the Starts With A Bang podcast! Have a listen, and I hope you enjoy it as much as I enjoyed having this one-of-a-kind conversation!(This image shows the fullerene molecules C60 and C70 as detected in the young planetary nebula M1-11. This 2013 discovery was the first such detection of this molecule in this class of environment. Credit: NAOJ)

One of the great discoveries to be made out there in the grand scheme of things is alien life: the first detection of life that originated, survives, and continues to live beyond our own home planet of Earth. An even grander goal that many of us have, including scientists and laypersons alike, is to find not just life, but an example of intelligent extraterrestrials: aliens that are capable of interstellar communication, interstellar travel, or even of meeting us, physically, on our own planet. It's a fascinating dream that has been with humanity since we first began contemplating the stars and planets beyond our own world.Most of us, including me, personally, have assumed that this latter type of alien would not only be more technologically advanced than we are, but would also be far more scientifically advanced as well. That not only would they understand everything we presently do about the fundamental laws of physics, but far more: that they'd be a potential source of new knowledge for us, having equaled or exceeded everything we'd already gleaned from our investigative endeavors. And that assumption, as compelling as it might be, could be completely in error, argues physicist and author Dr. Daniel Whiteson.That's why I'm so pleased to bring you this latest episode of the Starts With A Bang podcast, where Daniel and I meet to discuss this very topic, with me taking the side of my own human-centered assumptions and Daniel taking a far more broad, philosophical, and cosmic approach: the same approach he takes in his new book, Do Aliens Speak Physics? And Other Questions About Science and the Nature of Reality. Have a listen to this fascinating conversation, see which set of arguments you find more compelling, and check out his book. You won't be disappointed!(This image shows the cover of Dr. Daniel Whiteson's and Andy Warner's newest book, Do Aliens Speak Physics? And Other Questions About Science and the Nature of Reality, which debuted on November 4, 2025! Credit: W.W. Norton & Company)

Join Dr. Olivia Cooper, a recent PhD and astronomy postdoc at CU Boulder, as she dives into the fascinating evolution of galaxies using data from the James Webb Space Telescope. She shares surprising findings about early, bright galaxies and the rapid maturation processes they undergo. Explore how multi-wavelength observations enhance our understanding and the critical importance of wide-field surveys like COSMOS-Web. Be captivated by the interplay between theory and observation in unveiling the rich diversity of cosmic structures!

Dr. Kielan Hoch, a postdoctoral researcher at the Space Telescope Science Institute, dives into the fascinating realm of exoplanets and their formation. He discusses groundbreaking imaging techniques, particularly those from the James Webb Space Telescope, that could one day help us see Earth-like worlds. Hoch also highlights the challenges faced by early-career scientists in securing funding and navigating a competitive landscape, stressing the need for systemic reform. This engaging conversation blends optimism and urgency as we ponder the future of exoplanet exploration.

Out there in the Universe, somewhere, a second example of an inhabit world or planet likely awaits us. It could be some other planet or moon within our own Solar System; it could be a spacefaring, interstellar civilization, or it could be an exoplanet around a different parent star. Although the search for life beyond Earth generally focuses on worlds that have similar conditions to Earth, like rocky planets with thin atmospheres and liquid water on their surfaces, that's not necessarily the only possibility. The truth is that we don't know what else is going to be out there, not until we look for ourselves and determine the answers.And yet, if you've been paying attention to the news, you might think that super-Earth or mini-Neptune type worlds, such as the now-famous exoplanet K2-18b, might be excellent candidate planets for life. Some have even gone as far as to claim that this planet has surefire biosignatures on it, and that the evidence overwhelmingly favors the presence of life within this planet's atmosphere. But the science backing up that claim has been challenged by many, including our two podcast guests for this episode: Dr. Luis Welbanks and Dr. Matthew Nixon.Beyond the breathless and sensational claims, what does the actual science concerning K2-18b in particular, and of biosignatures on exoplanets in general, actually teach us? What does the evidence indicate, and if we are going to find inhabited exoplanets, what will it take for us to actually announce a positive detection with confidence and less ambiguity? That's what this episode of the Starts With A Bang podcast is all about; I hope you enjoy it!(When an exoplanet passes in front of its parent star, a portion of that starlight will filter through the exoplanet’s atmosphere, allowing us to break up that light into its constituent wavelengths and to characterize the atomic and molecular composition of the atmosphere. If the planet is inhabited, we may reveal unique biosignatures, but if the planet has either a thick, gas-rich envelope of volatile material around it, or alternatively no atmosphere at all, the prospects for habitability will be very low. Credit: NASA Ames/JPL-Caltech)

Perhaps the strongest evidence we've ever acquired in support of the Big Bang has been the discovery of the leftover radiation from its early, hot, dense state: today's cosmic microwave background, or CMB. While there were many competing ideas for our cosmic origins, only the Big Bang predicted a uniform, omnidirectional bath of blackbody radiation: exactly what the CMB is.But it turns out the CMB encodes much more information than just our cosmic origins; it allows us to map the very early Universe from when it was just 380,000 years old, and gives us vital information about what has happened to light from that time over its 13.8 billion year journey to our eyes. It encodes information about our cosmic expansion history, about dark matter and dark energy, about intervening galaxy clusters, and about the material here in our own galaxy, along with much more. It is, arguably, the richest source of information from any one single observable in our entire Universe.Here to guide us through what CMB scientists are working on here in 2025, including what we've learned and what we're still trying to find out, I'm so pleased to welcome Dr. Patricio Gallardo to the show. We've got more than an hour and a half of quality science to go through, and by the end, I bet you'll be more excited about the upcoming Simons Observatory, designed to measure the CMB to higher precision than ever before, than you knew you should be. Enjoy!(This image shows the Large Aperture Telescope's colossal, 6-meter primary and secondary mirrors at the Simons Observatory in February of 2025. The telescope has already seen first light, and will soon begin delivering new CMB science as never before. Credit: M. Devlin/Simons Observatory)

When we search for life in the Universe, it makes sense to look for planets that are similar to Earth. To most of us, those signatures would look the same as the ones we'd see if we viewed our planet today: blue oceans, green-and-brown continents, polar icecaps, wispy white clouds, an atmosphere dominated by nitrogen and oxygen, and even the modern signs of human activity, such as increasing greenhouse gas emissions, planet modification, and electromagnetic signatures that belie our presence.But for most of our planet's history, Earth was just as "inhabited" as it is today, even though it looked very different. One fascinating period in Earth's history that lasted approximately 300 million years resulted in a planet that looked extremely different from modern Earth: a Snowball Earth period, where the entire surface, from the poles to the equator, was completely covered in snow and ice. This isn't just speculation, but is backed up by a remarkable, large suite of observational and geological evidence.So what was Earth like during this period? How did it fall into this phase, how did it remain trapped in that state for so long, and how did it finally thaw again? To help explore this topic, I'm so pleased to welcome PhD candidate Alia Wofford to the program, who conducts intricate climate models of early Earth to try to reproduce those early conditions. From that work, we're learning about what we should be looking for when it comes to potentially inhabited exoplanets, because Earth has been inhabited for around 4 billion years, and wow, has its appearance changed over all that time. Have a listen and see for yourself!(This illustration shows a frozen-over planet, but one that still possesses a significant liquid ocean beneath the surface ice. Many worlds in our Solar System may be described by this scenario at various points in cosmic history, including even planet Earth more than two billion years ago. Credit: Pablo Carlos Budassi/Wikimedia Commons)