In the City of Time by Gwendolyn Clare

From the author of the highly acclaimed Ink, Iron, and Glass series, this YA duology sends three science prodigies on a time-traveling adventure to save the Earth-if they don't accidentally destroy it first-in Gwendolyn Clare's In the City of Time.
In 1891, Willa Marconi's life falls apart when her mentor at the University of Bologna unexpectedly dies. She loses her laboratory access and her stipend, but she refuses to let anyone take her research away. While testing her prototype radio equipment, she detects a mysterious signal and pursues its origin.
In 2034, a cataclysmic event has rendered the Earth uninhabitable, and humankind survives by living inside of artificial worlds. Riley would do anything for Jaideep, who lost his parents in the collapse of the Bay Area pocket universe-and anything includes building a time machine so they can travel back to the 19th century, prevent the destabilization of the planet, and rewrite...

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