Our summer almanac 18.06.2010 – 24.06.2010

Sunrise, Sunset and the view from Earth

Sunrise and sunset times vary throughout the year. Days get longer from the winter solstice to the summer solstice. Then, just as astronomical summer begins, the days get shorter and the nights become longer.

Spring turns to Summer


The Longest Day
This week sees the summer solstice on June 21 at 11.28 UTC. Coordinated Universal Time (UTC) is a time standard based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the Earth’s slowing rotation. Leap seconds are used to allow UTC to closely track UT1, which is mean solar time at the Royal Observatory, Greenwich. UT1 is the principal form of Universal Time.

This is the longest day of the year and the beginning of the astronomical season of summer. The Sun rises to the north east of Basingstoke at about 03h 47m in the morning and sets at about 20h 25m in the evening in the north west. These times are GMT, so the local time of British Summer Time means that you need to add ONE hour to these times to see sunrise and sunset. Greenwich Mean Time (GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London. It is commonly used in practice to refer to Coordinated Universal Time (UTC) when this is viewed as a time zone, especially by bodies connected with the United Kingdom, such as the BBC World Service, the Royal Navy, the Met Office and others, although strictly UTC is an atomic time scale which only approximates GMT with a tolerance of 0.9 second.

At noon on the summer solstice the Sun reaches its highest point in our sky. Noon is 13h Local Time because in the UK, GMT is the official time only during winter; during summer British Summer Time is used. GMT is substantially equivalent to Western European Time.. From the spring equinox until the summer solstice the Sun moves northwards day by day. The Sun does not move northwards at the same rate of speed. At the beginning of spring the Sun moves very quickly north. At the summer solstice this rate of speed slows, like the swing of a pendulum at its limit. This means that this week the Sun seems to rise in almost the same place on the horizon. This is why we use the word solstice for this special day, as it comes from a Latin word “solstitium” meaning “Sun stands still”.

Stonehenge

Basingstoke is located on the old road (now called the A30 and that then turns into the A303) that runs to the west country and passes the ancient monument of Stonehenge.

The standing stones surrounding Stonehenge mark the point on the horizon where the sunrise takes place on the summer solstice. However, the special celebrations that take place upon the summer solstice these days were not the main event at Stonehenge 5000 years ago.

The diagram above shows how the Stonehenge monument has in recent years been interpreted as an astronomical design. It shows the direction of the sunrise on the summer solstice and the orientation of the stones. The most recent theory is that it is the orientation of the monument to the setting sun at the winter solstice that accounts for the arrangement of stones on this ancient site that has been used going back to at least 8000 years ago.

Recent archaeological investigations have shifted the emphasis from thinking about Stonehenge as either an astronomical device, or a temple of the dead but not forgotten ancestors, to the rings of bluestones that were brought all the way from Wales. The bluestones at Stonehenge were placed there during the third phase of construction at Stonehenge around 2300 BC. It is assumed that there were about 80 of them originally, but this has never been proven since only 43 remain.

The majority of them are believed to have been brought from the Preseli Hills (over 160 miles from Stonehenge) through our ancient ancestors organizing their transportation. How they achieved this is a mystery, but the most likely theory is they were brought by raft navigating along the coast of Wales and then pulled upstream along the River Avon. This would have been the most ambitious logistics project ever attempted by humans.

The bluestones were associated with the healing power of sacred springs. One very recent theory that has been supported by the most recent archaeological investigation at Stonehenge is that the bluestones were at the heart of the reason for the monument; healing power. The people who made Stonehenge were able to do so because they lived a whole way of life around the seasons of growing and harvesting in the ancient farming calendar. Mid-winter, the winter solstice was the beginning of the new year of growth, fertility and food production.

Calculating the time in Basingstoke

The clock on St Michael’s Church Basingstoke shows 1pm, but this is in fact midday when it comes to Greenwich Mean Time (GMT) because we are now in British Summer Time. In the UK, GMT is the official time only during winter; during summer British Summer Time is used.

Greenwich Mean Time is set for the world in Greenwich at the Greenwich Royal Observatory when the the sun reaches the highest point in the sky at noon.

GMT became the UK’s official time with the coming of the railways and the railway timetables in the 19th century.

Before the age of railways each town would set its clocks to local time, using a sundial to find out when it was the sun was at its highest in the sky.

The sundial on St Michael’s Church shows noon.

So why is the clock showing just over 4 minutes past the hour? Because Basingstoke is just over 4 minutes longitude west of Greenwich!



Canis Minor is a small constellation containing only two bright stars, Procyon and Gomeisa. Procyon is the eighth brightest star in the night sky. Procyon means “before the dog” in Greek, as it rises an hour before the ‘Dog Star’, Sirius, of Canis Major. Canis Minor has no deep sky object brighter than magnitude 15.

Near Chalk Ridge School 24.06.2010

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