Ancient solar alliegnments (UK)?

Question

I have noticed 3 ancient monuments in my area allign perfectly, the 2 furthest ones are 15.76 miles apart and about 300m high on hills. I am trying to work out whether they may have been deliberately aligned to mark an important sunset. (I pressume in spring as the far hill is called may hill) When i went and watched the sunset last sunday the sun missed the mark(to the right) . I was wondering if the sunset moves along the horizon throughout the year and what difference 4-5000yrs would make.

If there is some difference is there a calculation to compensate for any changes so i can find out if i am right.

Answer 1

Back in the 1960s Gerald Hawkins wrote "Stonehenge Decoded" which pointed out the solar alignments of that monument.  Mostly though they were aligned with sunrise, not sunset.  Since the position of sunrise and sunset moves north and south through the year, checking the alignment on any random day will probably not pick up anything.  If these do have an alignment it will probably be on the midwinter solstice (21 December) or the midsummer one (22 June).

On top of that there is the precession of the equinoxes where the poles of rotation of the Earth change direction in a cycle over about 28,000 years. Over the age of these monuments there will be a slight difference from when they were put up.

While it is possible that the name May Hill could be connected, it seems unlikely.  The equinoxes are in March and September.

Answer 2

Precession of the equinoxes

http://www.answers.com/topic/precession-...

n.

A slow westward shift of the equinoxes along the plane of the ecliptic, resulting from precession of the earth's axis of rotation, and causing the equinoxes to occur earlier each sidereal year. The precession of the equinoxes occurs at a rate of 50.27 seconds of arc a year; a complete precession requires 25,800 years.

Link below has some formulas, near bottom of page.

Good Luck with them

Answer 3

It isn't precession which affects the position on the horizon where the sun sets, it's the axial tilt of the earth. At present, the earth's equator is tilted 23.44 degrees to the plane of its orbit. 5,000 years ago, the tilt was 24.05 degrees. http://en.wikipedia.org/wiki/Axial_tilt

The northernmost position of sunset is at the summer solstice. At latitude 51 degrees north, in the present era, this sunset point is at azimuth 309.2 degrees, which means 39.2 degrees north of west. 5,000 years ago, due to the greater axial tilt, this point was 40.3 degrees north of west, i.e. just over 1 degree farther north, equivalent to about 2 sun diameters. At the equinox, in September, the sun sets due west, both now and 5,000 years ago. For dates in between June and September, the sun would have set proportionately farther north compared with today. For example, the sun currently sets at about 13 degrees north of west at the end of August, so 5,000 years ago, this figure would be about 13.3 degrees.

Of course, the month of August was unknown 5,000 years ago, so apart from the solstice and equinox points, it would be difficult to correlate other dates and setting points over this sort of timescale.