pplpod

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

How do you take a picture of something defined by the fact that light cannot escape it? This episode follows the long road to imaging Sagittarius A*, the supermassive black hole at the center of the Milky Way. We start with Karl Jansky's accidental 1933 detection of radio static from the direction of Sagittarius while investigating interference for Bell Labs, then move through the 1974 interferometer work of Bruce Balick and Robert Brown, the origin of the asterisk in the name, and the 1994 velocity measurements that pointed to millions of solar masses packed into a tiny volume.

We then explain how the Event Horizon Telescope used aperture synthesis to link dishes across the planet, why the 2022 image of our own black hole took years longer to produce than the 2019 image of M87*, and what the S-stars orbiting the galactic center reveal. We cover S2's 2018 pericenter passage, the record-setting S4714, gravitational redshift confirming Einstein, the Nobel Prize awarded to Andrea Ghez and Reinhard Genzel, the G2 gas cloud that failed to be shredded, dramatic X-ray and infrared flares, and a star flung out of the galaxy entirely.

• Why interstellar dust makes the galactic center invisible in optical light and how infrared and radio see through it
• How rapidly orbiting gas around a Mercury-orbit-sized shadow blurred the Sagittarius A* image and required five years of processing
• Stars moving at 2.55 and 8 percent of light speed and the 4.297 million solar mass measurement they enable
• The G2 flop of 2014 and the theory that it was a merged binary star wearing a dusty disguise
• The temperature paradox: a black hole with Hawking radiation near absolute zero surrounded by gas at millions of degrees

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

On July 4, 1054, a new star appeared in the daytime sky, outshining Venus for nearly a month and lingering at night for almost two years. This episode follows the remnant of that explosion, the Crab Nebula, from its accidental rediscovery by comet hunters in the 1700s to its role as a modern astrophysical laboratory. We cover John Bevis's 1731 sighting, Charles Messier's frustration at a fuzzy patch in Taurus that refused to move, and how that annoyance produced the Messier catalog with M1 as its first entry. We also explain why the Earl of Rosse's inaccurate sketch gave the nebula a name that never fit.

From there we look at how astronomers used photographic plates and a blink comparator to measure the nebula's expansion, rewound the math to 1054, and matched it to records from the Song Dynasty, a Japanese poet, and a physician in Baghdad. We dig into the anomalous expansion rate that pointed to a hidden engine, the discovery of the Crab Pulsar in 1968, electron capture supernovae, synchrotron radiation, the unsolved missing mass problem, and how the nebula's position near the ecliptic lets scientists use it as a cosmic X-ray backlight.

• How Messier's search for Halley's Comet led to the first entry in his catalog of objects to ignore
• Measuring 1,500 kilometers per second of expansion and tracing it back nine centuries
• A city-sized neutron star spinning 30 times per second with a luminosity 148,000 times the Sun
• Why the visible gas and the pulsar add up to only four or five solar masses when the progenitor should have been nine to eleven
• Using transits of the Sun and Saturn's moon Titan across the nebula to probe the solar corona and Titan's atmosphere

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

In the 1840s a star in the southern sky suddenly became the second brightest in the night sky, then faded from naked-eye view within a few decades. It had not died. This episode builds a biography of Eta Carinae, a system roughly 7,500 light years away that started life with an estimated 150 to 250 solar masses and has spent centuries swinging between obscurity and spectacle. We trace its quiet years as a fourth-magnitude star logged by Edmond Halley, its place in Chinese astronomy, and the Great Eruption recorded by John Herschel and by the Boorong people of Australia.

We then explain the physics behind the show: the temperature-sensitive CNO fusion cycle that made the core boil, the supernova impostor event that ejected 10 to 20 solar masses to form the Homunculus Nebula, and the 5.54-year cycle discovered in 1996 that revealed a massive binary companion. We cover the colliding stellar winds that heat gas to 100 million Kelvin, the only known natural ultraviolet laser in the universe, and what a future core-collapse or pair-instability supernova would mean for Earth.

• Why the backward magnitude scale made a 150-plus solar mass star look ordinary for centuries
• How the Great Eruption of 1837 to 1843 relieved internal pressure without destroying the core
• The eccentric orbit of Eta Carinae A and B, from Neptune-like distances down to closer than Mars is to the Sun
• How Lyman-alpha radiation pumps iron ions in the Weigelt blobs to create stimulated emission on an astronomical scale
• What a magnitude negative four supernova could do to Earth's ozone layer, satellites, and astronauts, and why the star may already be gone

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

The Space Transportation System launched like a rocket, worked in orbit for up to two weeks as a laboratory and construction site, and glided home as an unpowered airplane. This episode traces the Space Shuttle from its origins in the post-Apollo budget squeeze, when Max Faget's vision of a fully reusable two-stage space plane collided with U.S. Air Force demands for a 60-foot payload bay and 29,000-kilogram lift capacity for spy satellites. We explain why eastward launches carry more than polar ones and how that compromise shaped a vehicle that could never be the cheap space taxi it was promised to be.

From there we get into the hardware: solid rocket boosters that could not be shut off, RS-25 engines running at 104 percent of their original rating, throttling down through Max-Q, 30,000 silica tiles that stayed cool enough to touch, and five redundant flight computers that voted on every decision. We cover the Canadarm, the evolving crew suits, the year-end rollover bug that kept the shuttle grounded over New Year's until 2007, and the cultural failures behind the Challenger and Columbia disasters, ending with the program's retirement in 2011 after 135 missions.

• How Air Force payload requirements and Nixon's 1972 approval locked in the shuttle's bulky three-part design
• What happens during ascent: 71.4 percent of thrust from the SRBs, cryogenic propellants, and engine throttling to survive maximum aerodynamic pressure
• The thermal protection system and the fly-by-wire General Purpose Computers with a separately coded backup
• The O-ring failure on Challenger, the foam strike on Columbia, and the normalization of deviance identified by sociologist Diane Vaughan
• Why the shuttle lacked a launch escape system and how its retirement left the U.S. dependent on Soyuz until Crew Dragon in 2020

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

On November 15, 1988, a 100-ton spacecraft dropped out of a violent storm over the Kazakh steppe, executed an unplanned three-percent-probability maneuver to bleed off excess energy, and touched down within meters of its target with nobody on board. This episode explores the Soviet Buran orbiter, a machine that looked like a copy of NASA's Space Shuttle but was engineered on a fundamentally different philosophy. We trace how over a thousand Soviet enterprises built a three-deck crew module designed for six cosmonauts and missions of up to three weeks, and why the orbiter carried no main ascent engines at all.

We dig into the Energia rocket that did the heavy lifting, the 38,600 heat tiles arranged to preserve laminar airflow during reentry, the 37K-based laboratory modules planned for the payload bay, and the lookup-table software that let 1980s hardware fly an autonomous 8,000-kilometer glide path. Then we follow the program's collapse alongside the Soviet Union, its cancellation in 1993, and the 2002 roof collapse at Baikonur's Building 112 that destroyed the orbiter and killed eight people.

• Why Buran's flight components were only about 20 percent of its mass and how the Energia rocket was designed as a modular heavy-lift system
• The thermal protection design: molybdenum disilicide coatings, uncoated tile backs to equalize pressure, and quartz fiber gap seals
• How mission 1K1 completed two orbits in 206 minutes without its planned AL-31 jet engines or robotic arms
• The Soviet doctrine of automation versus the American pilot-in-the-loop approach, and how pre-calculated scenarios handled a 38 mph crosswind
• The mothballing of Buran after 1993 and the fatal hangar collapse of May 12, 2002

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

Between 1961 and 1984 the Soviet Union sent 18 probes to Venus, and the planet crushed, cooked, and blinded them one after another. This episode traces the extreme trial and error of the Venera program, starting with engineers who as late as 1964 were still building buoyancy systems in case a probe splashed into a Venusian ocean. It covers the failed flybys of Venera 1 and 2, the first impact on another planet by Venera 3 in 1966, and the parachute probes Venera 4 through 6 that were crushed in the atmosphere while discovering it was overwhelmingly carbon dioxide.

The conversation explains how the American Mariner 5 used radio occultation to reveal surface pressures of 75 to 100 atmospheres, forcing the Soviets to retract the claim that Venera 4 reached the ground. That led to the brute-force titanium sphere of Venera 7, which crash-landed at 17 meters per second in 1970, toppled over, got stuck transmitting only temperature, and still became the first probe to send data from another planet's surface. The episode follows the five-ton landers of Venera 9 through 14, the first surface photographs in 1975, the maddening lens cap failures, Venera 13's record 127 minutes and first color images, and Venera 14's hammer striking its own ejected lens cap. It closes with the synthetic aperture radar mapping of Venera 15 and 16 and the Vega balloon missions.

• How scientists derived 90 atmospheres of pressure from a single temperature reading of 465 degrees Celsius
• Why a gamma ray spectrometer could analyze Venusian soil without touching it
• How phase change materials and crush rings kept five-ton landers alive
• Why thermal expansion fused the metal lens caps shut on Venera 11 and 12
• How 8-centimeter radar wavelengths pierced sulfuric acid clouds to map the northern hemisphere

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

The legend says American astronauts went on strike 270 miles above Earth. This episode uses declassified mission logs, psychological case studies, and crew interviews to separate myth from reality on Skylab 4, the 84-day mission flown by rookies Gerald Carr, Edward Gibson, and William Pogue starting in November 1973. It begins with the stuffed flight suits left as a prank by the previous crew, the mission patches mistakenly labeled Skylab 3, and the decision to hide Pogue's space sickness, a cover-up exposed when Mission Control listened to onboard voice recordings and Alan Shepard delivered a blistering reprimand.

The conversation follows the crushing workload scheduled on Earth-based timing, the failure of a control moment gyroscope and the thermal expansion trick engineers used to save a second one, the liquid salt and pepper squirted from syringes, and the Thanksgiving spacewalk. It then explains what actually happened during the so-called mutiny: an exhausted crew forgetting to turn on their radios for a single orbit, compounded by holiday scheduling confusion and a ground station hardware failure. The December 30 all-hands conference that Carr called the first sensitivity session in space led NASA to abandon hour-by-hour scheduling, after which productivity soared. The episode also covers the first recorded birth of a solar flare, comet Kohoutek spectroscopy, and the accidental photograph of Area 51.

• Why NASA sent an all-rookie crew and how Apollo 19's cancellation shaped the roster
• How spinning wheels steer a space station through conservation of angular momentum
• Why the New Yorker and a Harvard Business School case study cemented the strike narrative
• Why the CIA was furious about a handheld photo when spy satellites already existed
• How Skylab 4 shaped the rule that every ISS crew includes a veteran astronaut

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

In 1619 Galileo declared the northern lights were sunlight reflecting off high vapor clouds. He gave the phenomenon its name and got the physics completely wrong. This episode reveals auroras as visible evidence of an invisible battle between the solar wind, a stream of magnetized plasma traveling around 400 kilometers per second, and Earth's magnetosphere. It explains magnetic reconnection, why a southward-pointing interplanetary magnetic field lets the solar wind grab our field lines, how the stretched magnetotail snaps back like a slingshot, and how the magnetic loss cone funnels particles into the auroral ovals around the poles.

The conversation then decodes the colors: why high-altitude oxygen takes up to two full minutes to emit red light and only survives in near-vacuum, why collisional quenching leaves fast green emission to dominate the middle layer, and why nitrogen produces blues and purples at the bottom. It covers the citizen science discoveries of STEVE, a 3,000-degree ribbon of plasma that is technically not an aurora, and dune auroras spotted in Finland in 2020, along with the crackling sounds produced by discharging inversion layers. The episode closes with the Carrington Event of 1859, when telegraph lines ran on auroral current and paper tape burst into flames, folklore from Aboriginal Australia to Scandinavia, and the moon Io powering Jupiter's permanent aurora.

• Why Earth's magnetic shield is a dynamic bubble rather than a solid wall
• The neon sign analogy for how excited atmospheric gases produce light
• How a Facebook group of photographers gave STEVE its name before scientists built the acronym
• Why telegraph operators between Boston and Portland could send messages with batteries disconnected
• Why astronauts heading to Mars will face solar storms with no magnetic umbrella

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

On July 23, 1995, veteran observer Alan Hale in New Mexico and Thomas Bopp, looking through a friend's borrowed homemade telescope in Arizona, independently spotted the same fuzzy patch near star cluster M70. Hale emailed the Central Bureau for Astronomical Telegrams three times; Bopp drove to a Western Union and sent an actual telegram. This episode tells the story of the Great Comet of 1997, discovered at a record 7.2 astronomical units from the Sun with a nucleus roughly 37 miles across, six times the size of Halley's Comet, and visible to the naked eye for 569 days, shattering the nine-month record set in 1811.

The conversation explains why peak brightness lagged behind perihelion on April 1, 1997, what the comet's rare third tail of neutral sodium atoms revealed about the momentum of light, and how its heavy water ratio, twice that of Earth's oceans, forced scientists to rethink where our water came from. It covers the first detection of argon in a comet, proving its interior never warmed above minus 387 degrees Fahrenheit, and then turns to the darker side: the software error behind the companion object rumor spread on Coast to Coast AM, the Heaven's Gate tragedy, and the Nibiru conspiracy. It ends with the comet's previous visit around 2215 BC during the reign of Pharaoh Pepi II, Jupiter's gravitational reshaping of its orbit, and the memorial to Gene Shoemaker sent to the Moon.

• How Hale and Bopp confirmed a new comet by checking sky maps and watching for movement
• Why recovery images from 1993 showed the comet glowing at 13 astronomical units
• How solar heating lag explains peak brightness after closest approach
• Why Jupiter cut the comet's orbital period from over 4,000 years to about 2,399
• What a 37-mile comet impact would mean compared to the dinosaur-killing asteroid

Got something to say to this podcast? Send a voicemail, and you might hear yourself on the next episode!

Who owns the Moon, and could a nuclear weapon be orbiting above your house right now? This episode explores the Outer Space Treaty of 1967, the cornerstone of international space law, and the Cold War panic that produced it. It explains how intercontinental ballistic missiles collapsed the warning time for an attack from hours to minutes, how Sputnik's beep in October 1957 doubled as a demonstration that the R-7 could deliver a warhead anywhere, and why early negotiations collapsed over inspection demands and overseas missile bases before the 1963 Limited Test Ban Treaty and the Antarctic Treaty provided a workable model.

The conversation walks through the treaty's key provisions: space as the province of all mankind, the ban on sovereign claims that makes the Apollo 11 flag purely symbolic, astronauts as envoys of mankind, and Article 4's prohibition on weapons of mass destruction in orbit. It then examines the loopholes, including the kinetic bombardment concept known as Rods from God, the Article 6 rule that makes governments liable for private companies, the Taiwan ratification paradox, and the 1976 Bogota Declaration in which equatorial nations claimed geostationary orbital slots. The episode closes on the modern crisis over asteroid mining, the 2015 US Commercial Space Launch Competitiveness Act, the Artemis Accords, and the divide between commercial extraction and the common heritage of mankind.

• Why a tungsten rod dropped from orbit at Mach 10 does not technically violate the WMD ban
• How the treaty gained 118 parties after opening for signature in Washington, London, and Moscow
• Why an equatorial nation argued geostationary orbit was an extension of its territory
• The fishing-in-international-waters analogy used to justify space resource extraction
• Why developing nations argue domestic mining laws cannot overwrite an international treaty