MANILA — The Northern Hemisphere, which includes the Philippines, will experience on Wednesday (Dec. 21 Philippine Standard Time) its longest night and shortest day this year.
“That is when the 2016 winter solstice in the Northern Hemisphere will happen,” said Dario dela Cruz, astronomy chief of the state weather bureau, PAGASA.
He noted that on that day, the sun at 6:44 p.m. will be at its southernmost position as seen from Earth so the forthcoming longest night’s duration will vary among Northern Hemisphere areas.
Such duration will span more time in areas that are farther from the equator, he said.
“In the Philippines’ case, that means the duration of the longest night will be most lengthy in extreme Northern Luzon and shortest in Mindanao,” he noted.
Extreme Northern Luzon and Mindanao are the country’s farthest and closest areas to the equator, respectively.
Solstice is the astronomical event during which the sun is at its greatest northerly or southerly distance from the equator, the imaginary line dividing Earth into the northern and southern hemispheres.
Parallel to the equator are imaginary lines of latitude circling Earth and running towards this planet’s north and south ends.
Among those lines are special navigational references called the Tropic of Cancer in the Northern Hemisphere and Tropic of Capricorn in the Southern Hemisphere.
Experts said every year, the sun shines over the Tropic of Cancer during the solstice occurring around June 21 and over the Tropic of Capricorn during the solstice happening around December 21.
The annual June astronomical event is known as the Northern Hemisphere’s summer solstice when night there is shortest and day is longest.
It is also the Southern Hemisphere’s winter solstice when night there is longest and day is shortest.
In contrast, the annual December astronomical event is the Northern Hemisphere’s winter solstice when night there is longest and day is shortest.
That event is likewise the Southern Hemisphere’s summer solstice when night there is shortest and day is longest.
Dela Cruz said during this month’s solstice, night will be about 13 hours and five minutes long in Basco municipality, capital of extreme Northern Luzon’s Batanes province.
Night then in Metro Manila will last about 12 hours and 46 minutes, he said.
For the Visayas’ Cebu City, he said night will be about 12 hours, 28 minutes long.
General Santos City in Mindanao will experience night that is about 12 hours, 14 minutes long, he said, noting that the duration of night is measured beginning sunset.
He also said that the duration of day during the December 2016 solstice will be only about 10 hours, 55 minutes in Basco; 11 hours, 14 minutes in Metro Manila; 11 hours, 32 minutes in Cebu City; and 11 hours, 46 minutes in General Santos City.
According to PAGASA, the solstice in December signals the onset of winter in the Northern Hemisphere and start of summer in the Southern Hemisphere.
“Earth has completed another annual circuit around the sun,” the bureau also said.
The solstice in June signals the onset of summer in the Northern Hemisphere and winter in the Southern Hemisphere, experts also said. Catherine Teves/PNA-northboundasia.com