Phases of Venus
The phases of Venus are the variations of lighting seen on the planet's surface, similar to lunar phases. The first recorded observations of them are thought to have been telescopic observations by Galileo Galilei in 1610. Although the extreme crescent phase of Venus has since been observed with the naked eye, there are no indisputable historical pre-telescopic records of it being described or known.[1]
Observation
The
The planet also changes in apparent size from 9.9
Contrary to other planets its apparent magnitude around
History
The first observations of the full planetary phases of Venus were by
There is some controversy about Galileo's claim to first observing the phases of Venus: In December of 1610, Galileo received a letter from fellow scientist Benedetto Castelli, asking if the phases of Venus were observable through Galileo's new telescope.[5] Days later, Galileo wrote in a letter to Johannes Kepler saying that he had observed Venus going through phases, but took complete credit for himself. It is unclear, lacking copies of any earlier correspondence, whether Castelli was telling Galileo of it for the first time, or responding to Galileo having previously informed him of it.[6]
Curiously, Galileo's letter to Kepler was encrypted so that Kepler could not scoop Galileo before he had made more exhaustive observations: Galileo took a sentence stating that Venus went through phases:
- Cynthiae figuras aemulatur mater amorum (The mother of love imitates the shape of Cynthia)
And scrambled the letters into a strange anagram:
- Haec immatura a me iam frustra leguntur o.y. (These are now too young to be read by me)
Cynthia was a popular epithet for the Moon, the mother of love of course being Venus. He sent the anagram to Kepler, then a few months later sent the decoded version. This way he had proof of having made the observation, without Kepler being able to publish it earlier.[7][6] This technique of hiding encoded announcements in letters was not uncommon at the time.
Naked eye observations
The extreme crescent phase of Venus can be seen without a
See also
Notes
- ^ a b c Goines, David Lance (October 18, 1995). "Inferential Evidence for the Pre-Telescopic Sighting of the Crescent Venus". Retrieved 2010-08-11.
- ^ "NIGHT SKY~PHASES OF VENUS". www.souledout.org. Retrieved 2022-02-16.
- ^ "How Bright Are the Planets?". Sky & Telescope. 2020-05-26. Retrieved 2022-10-27.
- ^ Galileo's observations of the phases of Venus (slide 4)
- ^ Phases of Venus
- ^ a b "The Phases of Venus and Heliocentricity: A Rough Guide". The Renaissance Mathematicus. 2014-06-09. Retrieved 2022-02-16.
- ^ Galileo Galilei's Anagram
- ^ Williams, David R. (April 15, 2005). "Venus Fact Sheet". NASA. Retrieved 2007-10-12.
References
- Campbell, William Wallace (1916). "Is the Crescent Form of Venus Visible to the Naked Eye?". doi:10.1086/122498.
- Reinhardt, Carl (1929). "Notes and Queries: Phase of Venus seen with the Naked Eye". Bibcode:1929JRASC..23...48C.
- Goines, David Lance (1992). "Observer's Notebook: Naked Eye Crescent of Venus". Sky & Telescope. 83.
External links
- Observations and Theories of Planetary Motion
- The crescent Venus seen with the naked eye
- Owen Gingerich - Empirical proof and/or persuasion — lecture on Galileo's observation of the phases of Venus from a renowned historian of science
- YouTube animation of the phases of Venus predicted by the pure geocentric Ptolemaic model [1]
- YouTube animation of the phases of Venus predicted by the heliocentric model (and implicitly also by the geo-heliocentric models such as the Tychonic) [2]