January 2: The Earth At Perihelion: Later Sunrise And Sunset Explained


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Sherlock Holmes removed his hat and solved the case: "I never liked the hat." Photo credit hknong

Sherlock Holmes removed his hat and solved the case: “I never liked the hat.” Photo by hknong

Chapter One: We Learn Of The Mystery And Meet Holmes And The Mayor

Sherlock Holmes had been called by the Mayor of Little Bits, Texas to solve a mystery. The Mayor had noticed that on the day of the solstice, December 21, the sunrise in Little Bits was at 7:13 a.m. It was now New Year’s Eve, and the sun had risen that morning at 7:17.

The Mayor was a learned man who read Decoded Science on a regular basis, and he reasoned that if the sunrise was getting later that the days were getting shorter. But how could that be? Weren’t the days supposed to get longer in the northern hemisphere after the solstice?

So he had summoned the world famous detective, Sherlock Holmes, to solve the conundrum before the celebrating began, lest Little Bits fall off the edge of the earth or endure some other catastrophe.

Holmes arrived just in time for dinner, and the Mayor invited him to stay for pork bellies with stewed chitlins, but Holmes had to rush off to solve another case, so he simply pointed out that Little Bits was not unique — that in fact every almanac showed that the problem was northern hemisphere-wide in 2014, and extended into Europe and Asia also.

Holmes bade the Mayor good tidings for the night and promised to return on January 2, after the festivities had subsided, to explain the whole thing. He assured the Mayor that, like all geophysical phenomena, this one had a logical explanation.

Chapter Two: We Meet Sir Cedric Phentingmost Again

The Mayor was still anxious about the evening’s festivities, so he summoned Professor Sir Cedric Phentingmost of the British Institute of Myladesh, a world famous climate-change denier. When we last met Sir Cedric, he had degrees in philolology, philanthropy, cantankerosity, thermogynomics, internal combustion, and pastology — to which he has now added ones in spinology and retrotraction.

Sir Cedric guaranteed the Mayor that nothing would interfere with the celebration, but that important ‘stuff,’ as he put it, was going on. He promised to return on January 2 to meet Holmes – and assured the Mayor that the problem would be explained, though the outlook for the future, he said, is much more dire than even climate-change drum-beaters claim, though for a different reason. He then hurried off to a party at a local resident’s house.

Chapter Three: January 2, Perihelion, And The Mystery Unraveled

On January 2, 2015, a small group of reporters convened at the Mayor’s residence, along with Holmes and Sir Cedric. Pork bellies were passed around. The Professor was allowed the first presentation. He opened his notebook and produced papers with many scientific notations.

Waving the papers vigorously, Sir Cedric proceeded to explain that the earth’s rotation was slowing down, and therefore days were getting longer worldwide. He showed in meticulous detail how this would happen: The bulge in the oceans caused by the gravitational pull of the moon lags slightly behind a perpendicular line from the moon to the earth. Frictional effects are slowing the earth’s rotation and, since angular momentum of the earth-moon system must be conserved, speeding up the moon.

The moon, pointed out Sir Cedric, is spiraling off into space, while the earth is rapidly coming to a standstill. The proof? Sunrise is getting later by a significant fraction of a minute each day.

At this rate,” concluded Sir Cedric, “the earth will stop spinning entirely in about four years… My calculations do not yet show which part of the globe will receive sunlight and which will be forever dark.”

Sir Cedric then closed his notebook emphatically.

Convinced by Sir Cedric’s argument and his self-assured manner, the reporters turned to Holmes for confirmation as they typed headlines warning of an imminent drastic lengthening of the day, with untold consequences.

Holmes took off his hat (“I never liked the silly thing,” he would later explain) and announced that Sir Cedric was correct — up to a point. The days are getting longer due to friction among the moon, the earth, and the oceans. But the increase in the length of day is only one second every 50,000 years.

So then why is the sun rising nearly half a minute later every day, Smarty Pants?” bellowed an infuriated Sir Cedric.

Holmes produced an almanac of sunrise and sunset.

The answer is very simple: The ‘day’ as defined by the time between one sunrise and the next is increasing by a tiny amount each year. However, the ‘day’ as defined by the time between sunrise and sunset is now getting longer each day in the northern hemisphere and will continue to do so until the summer solstice.”

Holmes turned to the page in his almanac with times of sunrise and sunset in Little Bits. The time of sunset was getting later each day by more than the earlier time of sunrise. The days were getting longer, after all.

But how can this be?” asked the curious Mayor. “Will we soon have the sun rising at noon and setting at midnight?

“Not at all,” Holmes replied.

All planets have eccentric orbits. The earth's is only slightly eccentric.

All planets have eccentric orbits. The earth’s orbit is only slightly eccentric. Graphic courtesy of NASA.

Holmes proceeded to point out that on January 2 — that very day — the earth is at perihelion, its closest approach to the sun. “You see,” said Holmes, “the earth’s orbit around the sun is not round. It has what is called eccentricity — this is a technical term,” he added, pointedly staring at Sir Cedric.

On this date,” continued Holmes, “the earth is moving faster than at any other time. Since the rotation doesn’t change, except for that daily tiny fraction of a millisecond, Little Bits has to go an extra little bit — I believe that’s where it got its name — to face the sun again. Both sunrise and sunset get later.

“The effect will soon diminish, as the sun recedes from perihelion. In July, when the earth is at aphelion, farthest from the sun and moving more slowly, the times of sunrise and sunset will get earlier and all will be right with the world.”

I don’t believe a bit of this,” huffed Sir Cedric, and he stomped out of the room.

The Mayor thanked Holmes and asked if anyone would like some more pork bellies. But the reporters had to hurry off to announce that the world was safe for at least a little while longer.

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