calculation articles
What specific solar event did Eratosthenes note occurred in Syene during his measurement?
What did the $7.2^\circ$ shadow angle in Alexandria represent geometrically in Eratosthenes’ calculation?
What were the professional surveyors hired by Eratosthenes to measure the ground distance between cities called?
Besides astronomical observations, what visual evidence did ancient scholars use to support a spherical Earth view?
What crucial finding was confirmed by the French Academy of Sciences expeditions in the 1730s comparing Arctic and Equatorial latitude measurements?
What modern scientific reference surface accounts for the Earth's irregular gravity field and topographical variations?
What primary assumption did Eratosthenes make about the Sun's radiation in his geometrical calculation?
Which modern technique measures distances by timing the round trip of laser beams bounced off satellites?
Why is converting Eratosthenes' final calculated circumference (252,000 stadia) into modern kilometers subject to scholarly debate?
What term describes the necessary reference system in geodesy used to tie measurements together while accounting for the planet's actual flattened shape?
Who made the breakthrough measurement determining the true distance to the Andromeda Galaxy (M31) in the early 1920s?
What specific class of pulsating stars served as the essential 'standard candle' for measuring immense cosmic distances?
What profound relationship did Henrietta Swan Leavitt discover while studying the Magellanic Clouds?
What massive telescope did Edwin Hubble use at Mount Wilson Observatory to resolve individual stars in Andromeda?
What was the designation given to the specific Cepheid variable star Hubble identified in Andromeda?
Before Hubble's findings, what state of scientific understanding characterized the Andromeda Nebula?
What was Hubble's initial calculated distance estimate for Andromeda in the 1920s?
The concept that allowed Hubble to determine a star's actual energy output (absolute magnitude) using its pulsation cycle is known by what term?
What critical concept did Hubble secure by successfully bridging the distance measurement gap between our local stars and intergalactic space?