Empirical Earth · The Sky — Sun, Moon & Stars

Mars’s backward loop and brightness swings

The claim

“Mars stops, moves backward in a loop, and swings wildly in brightness — a real orbit can’t do that, so heliocentrism needs made-up epicycles.”

What is measured

Apparent retrograde is a perspective effect of a faster Earth lapping Mars: predicted by heliocentrism, seen only at opposition, on a ~780-day cycle. The ~50× brightness swing and 3.5″→25″ disk track the Earth–Mars distance closely, and a fixed “dome light” has no reason to do either.

What would show this is wrong

a superior planet showing a retrograde loop at a time other than opposition, or Mars holding constant brightness and angular size while its Earth–Mars distance changes, either of which would break the heliocentric prediction. (A geocentric model must instead postulate a bespoke epicycle to mimic every loop.)

Sources

  1. Mars fact sheet — orbital period 686.98 d, rotation 24.6 h, obliquity 25.19°. NASA NSSDCA planetary fact sheet: Mars sidereal orbit 686.98 days (1.88 yr), sidereal rotation 24.62 h, axial ti link
  2. Oppositions of Mars — ~780-day synodic cycle; close ~56 / far ~400 Mkm. Perihelic oppositions approach ~55.8 million km (disk ~25″, magnitude ≈−2.8); near conjunction Mars is ~400 million km link
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