Talk:Tropical year

Naming conventions
Karl, lets settle on a convention about Latin, Greek, English words. I think we should stick to whatever is current in English. If you start to Romanize or Hellenize English words, there is no end - anglosaxons completely screw up foreign words; e.g.:

equinox would be aequinox (equus = horse, aequus = equal (sic!))

Homer would be Homeros

Now the English word is perihelium, not perihelion; like the stuff is helium, not helion. -- Tompeters


 * This would be a good argument, except for the fact that it's "perihelion" in English. What dictionary are you using that says otherwise? --Zundark, 2001 Oct 25

— Preceding unsigned comment added by Zundark (talk • contribs) 11:43, 25 October 2001 UTC


 * OK, I screwed up -- Tompeters — Preceding unsigned comment added by Conversion script (talk • contribs) Revision as of 15:51, 25 February 2002 UTC


 * Bad example: Helium ends in -ium because it was first found spectroscopically in the sun and they thought it was a metal: and metals get -ium or -um on the end e.g. Thorium, Hafnium, Aluminium, Neodymium, Molybdenum. If the naming convention for noble gases was followed strictly, Helium actually should be called Helion, though no-ones going to rename it at this late date  - Malcolm Farmer

— Preceding unsigned comment added by Malcom Farmer (talk • contribs) 12:10, 25 October 2001


 * Thanx for pointing that out, I never noticed. Good to see someone writing Aluminium, americans usually say aluminum. — Preceding unsigned comment added by Conversion script (talk • contribs) Revision as of 15:51, 25 February 2002 UTC

Ephemeris Time
The article now says:
 * The time scale is Terrestrial Time (formerly Ephemeris Time) which is based on atomic clocks

I don't understand this. One could understand this as "Terrestrial Time was formerly called Ephemeris Time". This is not the case. Ephemeris Time is different from Terrestrial Time; and is not based on atomic clocks. Terrestrial Time is now used a lot where Ephemeris Time used to be used. But wouldn't the formulae be different in the past if they used Ephemeris Time in the past? Until someone who really understands this, sorts this out, I will delete the text in parentheses "(formerly Ephemeris Time)" -- Adhemar — Preceding unsigned comment added by 212.65.42.127 (talk • contribs) 09:34, 29 August 2005


 * You have some valid points. Although Terrestrial Time (TT) is based on atomic clocks, it is a uniform time just like Ephemeris Time (ET), which was defined relative to the motion of solar system bodies, especially the Sun and Moon. TT (1991) is the new name for Terrestrial Dynamical Time (TDT, defined 1976). It was renamed because TDT was not dynamical, i.e., it was not based on the motion of the solar system. ET was the time base used in all national ephemerides until 1983. The offset of TT from International Atomic Time (TAI) was intentionally chosen to be 32.184 s so that it would equal ET, and thus ET can be directly substituted for TT in most astronomical equations. This is indeed done by Jean Meeus in his "Astronomical Algorithms". I am replacing the objectionable phrase by "(formerly, Ephemeris Time was used instead)". &mdash; Joe Kress 03:20, August 30, 2005 (UTC)

Mean tropical year

 * $$365.242 189 669 8-6.153 59\times 10^{-6}T-7.29\times 10^{-10}T^2 + 2.64\times 10^{-10}T^3$$

Some values for the equation cited (in article);

MBG02 (talk) 12:33, 24 April 2022 (UTC)