StarTalk Radio

Cosmic Queries – Galactic Grab Bag – Blue Steel

January 16, 2026

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  • The Moon's apparent 'wobble' is actually a libration caused by its elliptical orbit, allowing observers to see slightly more than 50% of its surface over time. 
  • Constellations visible in the night sky have significantly changed over the 150,000 years of anatomically modern human existence due to stellar motion within the solar neighborhood. 
  • The liquid state of Mercury at ambient temperature, unlike its neighboring elements on the periodic table, is a unique property tied to its specific atomic structure and the conditions of our laboratory temperatures, not a fundamental chemical property shared across its column. 

Segments

Podcast Introduction and Sponsorship
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(00:00:00)
  • Key Takeaway: The episode begins with advertisements for a new Star Trek series and Progressive insurance.
  • Summary: The segment starts with a promotion for the new series Star Trek: Starfleet Academy streaming on Paramount Plus, followed by a detailed advertisement for Progressive insurance, including savings statistics.
StarTalk Welcome and Segment Naming
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(00:01:15)
  • Key Takeaway: The hosts welcome listeners to StarTalk and discuss the origins and meaning of the ‘Grab Bag’ segment name.
  • Summary: Neil deGrasse Tyson and Chuck Nice welcome listeners to StarTalk. They discuss the segment name, which has previously been ‘Cosmic Potpourri’ or ‘Galactic Gumbo,’ settling on ‘Grab Bag’ as an assortment of miscellaneous items.
Clyde Tombaugh and Pluto Anecdote
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(00:02:31)
  • Key Takeaway: A humorous anecdote is shared about Clyde Tombaugh, the discoverer of Pluto, being told it was still a planet on his deathbed.
  • Summary: The conversation shifts to an off-topic story about Clyde Tombaugh, the discoverer of Pluto, who reportedly lived into his 90s and was told Pluto was still a planet just before he died. They also joke about the arrow pointing to Pluto in discovery photos.
Moon’s Libration Explained
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(00:04:09)
  • Key Takeaway: The ‘moon’s wobble’ is identified as libration, caused by the moon’s elliptical orbit causing variations in its rotational speed relative to Earth.
  • Summary: The first question from David Brian Smith asks about the moon’s wobble. Neil explains this is likely libration, caused by the moon’s elliptical orbit making it move faster when closer to Earth and slower when farther away, allowing us to see slightly more than 50% of its surface over a month.
Zoolander 2 and Movie Franchises
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(00:08:35)
  • Key Takeaway: Chuck Nice references his appearance in Zoolander 2 and jokes about his filmography ending franchises.
  • Summary: The discussion briefly touches on the ‘Blue Steel’ reference from the episode title, linking it to Chuck Nice’s appearance in Zoolander 2. Chuck then jokes that three of the four movie franchises he was in ended after his appearance.
Constellations and Stellar Movement
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(00:11:00)
  • Key Takeaway: Stars in the night sky are moving, meaning constellations recognizable today would look significantly different 100,000 years ago.
  • Summary: Jordan Metcalf asks if humans have always seen the same night sky. Neil confirms that stars move, and over 75,000 to 100,000 years, nearby stars would have shifted enough to make constellations like the Big Dipper unrecognizable.
Why Mercury is Liquid Element
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(00:14:03)
  • Key Takeaway: The hosts admit they don’t know the precise quantum reason why Mercury is liquid while its neighbors on the periodic table are solid, but note state depends on ambient temperature.
  • Summary: Teresina asks why Mercury is liquid when its neighbors on the periodic table (Gold and Thallium) are solid. Neil admits he doesn’t know the deep answer but explains that melting point is an intrinsic property, and that laboratory temperature variations can affect element states.
Water’s Triple Point on Mars
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(00:25:18)
  • Key Takeaway: On Mars, specific conditions of temperature and pressure allow water to exist in all three states (solid, liquid, gas) simultaneously at its triple point.
  • Summary: Neil adds a point about Mars, explaining that water can exist at its triple point there, meaning ice cubes could be floating in boiling water stably.
Terraforming Mars Challenges
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(00:26:40)
  • Key Takeaway: The main challenge for terraforming Mars is creating a sustainable atmosphere, not shielding against solar wind, which can be managed with engineering or underground habitats.
  • Summary: Jordan Belakanis questions the feasibility of terraforming Mars due to its lack of a magnetic field stripping the atmosphere. Neil suggests that shielding from solar wind is an engineering problem, whereas creating a self-sustaining biosphere is the much harder challenge.
Black Hole Evaporation and Visibility
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(00:45:36)
  • Key Takeaway: As a black hole loses mass via Hawking radiation, it shrinks and emits higher-energy radiation, culminating in a final burst of gamma rays, but it remains a black hole until it completely evaporates.
  • Summary: Nicholas Lenson asks if a black hole will eventually become too small to trap light. Neil explains that as mass decreases, the object remains a black hole, shrinking in size, and the energy emitted increases, leading to a final, catastrophic gamma-ray burst upon complete evaporation.