# [time-nuts] How many seconds in a year?

hasweb at has.org.nz hasweb at has.org.nz
Wed Oct 15 05:07:54 UTC 2008

```Neville Michie wrote:
> I have been thinking about my problem, the major part of the problem
>  is finding the right question.
> If leap seconds are applied to keep the meanderings of the planet in
>  phase with our mean time
> clocks, then what about our leap year days which are applied to keep
>  the seasons in phase with our
> calendars? Applying a whole day every so many years may keep the
> civil authorities happy,
> but when we all celebrate a new year we are not counting down the
> completion of a planetary cycle
> but the civil approximation to a new year.
> Now, having thought about it a bit more, the year is the completing
> of an orbit of our elliptical orbit around the sun.
> The start and finish of an orbit is defined by the inclined axis of
> rotation of the Earth crossing the plane of its orbit which is what
> causes the seasons.
> The elliptical orbit is moving, hence the precession of the
> equinoxes. As we can not measure a year
> by looking at a particular star crossing our meridian,
> we measure the year by watching a fictitious star crossing our
> meridian. This star (which used to be at the first point of Aries
> on the vernal equinox) is slowly orbiting around our solar system as
>  our tilted ecliptic precesses.
> cheers, Neville Michie
>
Neville

There are many definitions of a year all of which differ slightly from
each other.

You appear to have confused the precession of the equinoxes (better
described as the precession of the Earth's rotational axis i.e. the
Earth precesses like a top) with the precession of the apsides of its
orbit.

Bruce

```