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 Subject: Seconds in a year Category: Science > Physics Asked by: freckles1000-ga List Price: \$2.00 Posted: 28 Aug 2003 19:16 PDT Expires: 27 Sep 2003 19:16 PDT Question ID: 250025
 ```The astronomical basis of our calendar year is the tropical year, from the solar position of a vernal equinox to the position of the next vernal equinox. This year contains 365.242199 days. How many seconds are in this year(2003)?```
 Subject: Re: Seconds in a year Answered By: robertskelton-ga on 28 Aug 2003 19:46 PDT
 ```Hi there, A day has 24 hours x 60 minutes x 60 seconds = 86,400 seconds per day. 365 x 86,400 = 31,536,000 seconds ://www.google.com/search?c2coff=1&q=365+times+86400+ All we have to do is add how many seconds are in .242199 days... 86,400 times .242199 = 20,925.9936 ://www.google.com/search?c2coff=1&q=86%2C400+times+.242199+ 31,536,000 + 20,925.9936 --------------- 31,446,925.9936 There are 31,446,925.9936 seconds in a topical year in 2003. The topical year only changes by about half a second every century, so that answer will be accurate to one second for many years to come. Best wishes, robertskelton-ga``` Clarification of Answer by robertskelton-ga on 28 Aug 2003 19:48 PDT ```Oops, see what happens when I don't use Google to make the calculation! It should read: There are 31,556,925.9936 seconds in a topical year in 2003.``` Clarification of Answer by robertskelton-ga on 28 Aug 2003 19:49 PDT ```The number I arrived at also appears within this document: http://www.idealliance.org/papers/xml2001/papers/pdf/05-04-06.pdf```
 `This is an easy rule-of-thumb: there are pi x 10^7 seconds in a year.`
 ```> ... rule-of-thumb ... Yes, give and take 0,5%...```
 ```I'm not sure how you are coming to the conclusion that there are pi x 10^7 seconds in a year. This hardly seems grounded on anything. 31,556,925.9936 (Calculated by other means) 31,415,926.535897932384626433832795 (pi * 10^7) When you approximate the number of seconds in a year you can look it as [number of days in year] * [seconds in a day] or you can: Calculate the circumference of the earth's orbit and divide by the speed of the earth's rotation. Like this: Radius of Earth's Orbit (r) = (1) Astronomical Unit circumference = 2*r*pi 2*1*pi = 6.283185307179586476925286766559 (The circumference = 6.28 AUs) An AU is approximated by 149,600,000 km convert AUs to km by multiplying (6.283185307179586476925286766559 * 149600000) = 939964521.95406613694802290027723 The earth's speed is estimated to be 29.7859 km/s The number of seconds in a year equals: circumference / Earths_speed 939964521.95406613694802290027723 / 29.7859 = (31557365.127596149082217522394059) The number of seconds = (31557365.127596149082217522394059) This is another dandy estimate. However the solution is only as good as the samples that support it. (see http://www.campusprogram.com/reference/en/wikipedia/e/ea/earth_1.html ) Indeed there are better ways like actually calculating the circumference of the ellipse that the earth's orbit is. But then we are still limited by the estimates given by samples (or other calculations). Otherwise we are caught in a case of merrygoround mathematics. By this I mean if the speed of Earth determined by using the circumference then how do we know what the circumference is. And if the circumference is determined by using the speed then how fast is the Earth traveling. Clearly we need a better way of determining how many seconds are in a year.```