Star Trails: A Weekly Astronomy Podcast · Single Malt Sky

Four Worlds, One Sun; Plus, a Total Lunar Eclipse

·28 min·1 clip

Mercury’s orbit was the clue that helped Einstein show gravity is geometry, not just a force.

The scale comes back home. After months with stars, globular clusters, nebulae, galaxies, and black holes, Drew uses the 100th episode to point the telescope back at our own solar system. March starts with the inner planets, and the tone is practical. These are not light year abstractions. They are worlds people can see, and spacecraft have reached them. Earth gets treated less like home and more like evidence. From an imagined alien viewpoint, the planet gives itself away through spectral lines, television broadcasts, radar pulses, communications, satellites, probes, and spacecraft heading out of the solar system. Then the Moon complicates the picture. Drew spends time on how strange Earth's companion is compared with the inner planets, especially beside the small irregular Martian moons Phobos and Deimos. The size comparison does real work here. The Moon is one-quarter Earth's diameter and more than one percent of Earth's mass, which is why some astronomers have called the pair a double planet. The barycenter is the useful hinge. The shared center of mass is not exactly at Earth's center, so Earth wobbles a little as the Moon moves around it. Rotation matters as well. Earth's 24-hour spin helps drive the magnetic field from molten iron in the core, which helps protect the atmosphere from the solar wind over deep time. Mars becomes the colder comparison. It can look Earthlike from far away, but that resemblance points back to atmosphere, shielding, and planetary luck. The sky report keeps the episode grounded. Drew points listeners toward the only total lunar eclipse of the year, something a backyard or balcony observer might actually watch. Neptune gets a patient closing note: binoculars, steady skies, and a Night Watch discussion saved for when the outer planets fit better. The milestone feels less like a victory lap than a return to the nearby worlds that make Earth feel familiar and odd at the same time.

As heard by us

A calm solar-system tour that folds in the year’s only total lunar eclipse and a clear look at Earth-Moon scale.

Star Trails uses its 100th episode to turn back to the solar system, moving from the inner planets to Earth and Mars as part of a March-long look at nearby worlds.

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Why you'd press play

You want a calm solar-system reset with a total lunar eclipse on the schedule.

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