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Extravoice
2011-Jan-03, 05:33 PM
Can anyone here help me find (or calculate) historic Earth perihilion dates? Despite my best attempt at using intertube search engines, I have been unsuccessful. :(

a1call
2011-Jan-03, 06:52 PM
http://www.usno.navy.mil/USNO/astronomical-applications/data-services/earth-seasons

From here:

Wiki article has info about current cycle.

Centaur
2011-Jan-03, 07:02 PM
Can anyone here help me find (or calculate) historic Earth perihilion dates? Despite my best attempt at using intertube search engines, I have been unsuccessful. :(

How far did you want to go back? Keep in mind that in October of 1582 the Catholic Church removed ten days from the calendar and reformed the rules for leap years. A particular year’s relationship to the leap affects the date of perihelion. And the amount of time between each perihelion passage hops about even more due to the fact that the Moon affects the Earth’s position. However, the time between perihelion passages by the Earth-Moon barycenter is fairly uniform. Also note that the Earth’s rotation has been slowing, which particularly affects the calculation of timings well in the past. And of course the moment of perihelion for a particular location on the Earth’s surface will differ from that for the Earth’s center.

Here’s a rough way to calculate the “mean” timings of the barycenter’s passages through perihelion. Consider a mean perihelion to have occurred on 2000 JAN 04.00699 TT (the .00699 is the fraction of a day past 00:00 TT; for your purpose TT is essentially the same as UT or GMT unless you're going back many centuries.) Each previous passage of the barycenter through perihelion will have occurred a mean 365.259636 days earlier. Again, keep in mind that the position of the Moon relative to the Earth near the time of perihelion can affect the precise timing of perihelion passage by more than a day.

Extravoice
2011-Jan-03, 07:49 PM
I want to go back to my birthday birth date, which is before 2000, but after 1582. :)

Centaur
2011-Jan-03, 07:53 PM
I want to go back to my birthday birth date, which is before 2000, but after 1582. :)

Can you be more precise?

Extravoice
2011-Jan-04, 02:17 AM
I hope you'll excuse me for not wanting to post my birth date on a public internet forum. How precise do you need? Is the fact that I'm a baby boomer (1945-1965) sufficient?

ETA: I could be more specific via PM if necessary.

Centaur
2011-Jan-04, 02:21 AM
ETA: I could be more specific via PM if necessary.

OK

jaffar
2011-Jan-04, 02:56 AM
it is so nice to to know that all the people here are so intelligent enough to discover things which not most of the people does. but i think counting the perihilion dates would be un necessary if you have not counted or even estimated oh how many more days which would the earth we live in would keep of standing.

a1call
2011-Jan-04, 03:13 AM
You can replace the year for your birth year here:

http://m.wolframalpha.com/input/?i=earth%20Perihelion%201844

Extravoice
2011-Jan-04, 01:07 PM
Thanks for your help, Centaur and a1call.

a1call
2011-Jan-04, 06:03 PM
Welcome Extravoice,
But for a more precise moment you will still have to use Centaur's suggested method.

a1call
2011-Jan-04, 06:18 PM
Strange, my last post did not raise the thread or attribute the last post to me in the main page of the Q&A!

pghnative
2011-Jan-06, 06:40 PM
I assume you hit "refresh", and not just the "back" button?

ETA -- I just replicated the error, confirmed with a refresh as well.