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5 readings

Two-Road Estimates

How many, how much and how long, worked along two roads with separately sourced inputs and the gap between them printed; no length or size comparison charts.

Chromolithograph of the Milky Way rising over a dark sea, with a sailing ship and rocks in silhouette, after É. L. Trouvelot, 1881

Two-Road Estimates

Fermi Paradox: Voyager-Speed Ships Could Cross the Galaxy

At Voyager 1's 16.6 km/s, a non-stop ship would cross a 100,000-light-year Milky Way in about 1.8 billion years, inside Earth's 4.54 billion.

Image credit

"Part of the Milky Way (Plate XIII, The Trouvelot Astronomical Drawings)" by É. L. Trouvelot — https://commons.wikimedia.org/wiki/File:Trouvelot_-_Part_of_the_Milky_Way.jpg — Public domain in the US (published 1881) and in the EU (author died 1895, life+70); modified: cropped to 16:9, keeping the lower sky and horizon; plate margins and printed title removed

Photograph of a young mechanic in a sleeveless shirt bent over a steam pump, pulling a large wrench on a bolted plate, by Lewis Hine, 1920

Two-Road Estimates

Kardashev Scale: 2022 Energy Use Is About 5x the 1964 Type I

Image credit

"Power house mechanic working on steam pump" by Lewis Hine — https://commons.wikimedia.org/wiki/File:Lewis_Hine_Power_house_mechanic_working_on_steam_pump.jpg — Public domain in the US (published before 1931) and in the EU (author died 1940, life+70); modified: cropped to 16:9, keeping the head, arms and wrench; the upper pipes and the legs removed

Photograph of the Sun, a pale disk with several groups of dark sunspots, on a brown ground inside a printed frame, by Lewis M. Rutherfurd, 1870

Two-Road Estimates

Dyson Sphere: Dyson Meant a Swarm, by Wright’s Account

Image credit

"Gezicht op de Maan. Photographie directe de la lune" by Lewis M. Rutherfurd — https://commons.wikimedia.org/wiki/File:Gezicht_op_de_Maan_Photographie_directe_de_la_lune_(titel_op_object),_RP-F-2001-7-30-1.jpg — Public domain in the US (published before 1931) and in the EU (author died 1892, life+70); modified: cropped from a photograph of the book page to 16:9, keeping the whole disk; the printed caption is outside the crop

Color lithograph of two Giza pyramids across a desert plain, with rocks and small figures in front, by Louis Haghe after David Roberts

Two-Road Estimates

How Many Blocks in the Great Pyramid? 2.3M May Be a Division

Image credit

"Egypt and Nubia: Volume I - No. 3, Pyramids of Gizeh" by Louis Haghe, after David Roberts — https://commons.wikimedia.org/wiki/File:Louis_Haghe_-_Egypt_and_Nubia-_Volume_I_-_No._3,_Pyramids_of_Gizeh_-_1953.526_-_Cleveland_Museum_of_Art.jpg — CC0 1.0 (https://creativecommons.org/publicdomain/zero/1.0/); modified: cropped to 16:9, removing plate margins and the foxed upper sky; imprint line kept