Post by Oz-T on Jun 21, 2017 11:51:20 GMT
Today is the solstice - summer solstice in the northern hemisphere, winter solstice south of the equator. It's the point in earth's annual orbit around the sun where our planet reaches one of its two extremes of 'tilt' toward the sun.
The practical effect of this is that it's the longest day of the year in the northern hemisphere because the sun rises earlier and sets later. The opposite happens in the southern hemisphere where it's the year's shortest day.
From a technical perspective, this is the day that the sun appears directly overhead at noon to anybody living near the Tropic of Cancer. The term solstice derives from sol (sun) and sistere (standing still) - and for good reason: the sun stops its progressive northerly movement each day and begins to head south again from this day onward. Because the earth is tilted at 23.4 degrees to the ecliptic (the plane of our orbit around the sun) this causes the solstices. It explains why we have the Tropic of Cancer placed at 23.4 degrees north of the equator, and the Tropic of Capricorn 23.4 degrees south. And it's the cause of our seasons.
If you are standing at the North Pole today, the sun would not set - it would appear near the horizon for 24 hours. Conversely, there would be 24 hours of darkness at the South Pole. If you live at the equator you have to wait until 22 September (equinox) to see the sun directly overhead at noon.
Solstices also occur on the other planets but their intervals are different to our two per year. Mars has approx one per year and Saturn has to wait 15 years for each one of a pair.
And there's one other aspect of Earth's northern solstice in June: it brings every hippy, druid, wizard and assorted fruitcakes to Stonehenge where they pay homage to the Sun God or whatever else takes their fancy. I think I'll stick to the easier topic of astronomy than try to explain that complex type of human behaviour...
The practical effect of this is that it's the longest day of the year in the northern hemisphere because the sun rises earlier and sets later. The opposite happens in the southern hemisphere where it's the year's shortest day.
From a technical perspective, this is the day that the sun appears directly overhead at noon to anybody living near the Tropic of Cancer. The term solstice derives from sol (sun) and sistere (standing still) - and for good reason: the sun stops its progressive northerly movement each day and begins to head south again from this day onward. Because the earth is tilted at 23.4 degrees to the ecliptic (the plane of our orbit around the sun) this causes the solstices. It explains why we have the Tropic of Cancer placed at 23.4 degrees north of the equator, and the Tropic of Capricorn 23.4 degrees south. And it's the cause of our seasons.
If you are standing at the North Pole today, the sun would not set - it would appear near the horizon for 24 hours. Conversely, there would be 24 hours of darkness at the South Pole. If you live at the equator you have to wait until 22 September (equinox) to see the sun directly overhead at noon.
Solstices also occur on the other planets but their intervals are different to our two per year. Mars has approx one per year and Saturn has to wait 15 years for each one of a pair.
And there's one other aspect of Earth's northern solstice in June: it brings every hippy, druid, wizard and assorted fruitcakes to Stonehenge where they pay homage to the Sun God or whatever else takes their fancy. I think I'll stick to the easier topic of astronomy than try to explain that complex type of human behaviour...