While we commonly mark the first week of January as the commencement of the new year, it also marks two significant milestones in the passage of the earth’s journey around the sun.
You wouldn’t know it by winter’s chilly grip, but January 4 marks perihelion, earth’s closest approach to the sun. On this day, 92.187 million miles separate us from the sun, compared to aphelion, around July 4 each year, when the two are 93.375 million miles apart. Sunlight hitting the earth on perihelion is seven percent more intense than at aphelion, so were you out sunbathing at midday, you would burn that much quicker. But unless you were in the southern hemisphere, in the early throes of summer, you would still need to bundle up.
Despite the greater intensity of sunlight hitting earth, the three percent difference in distance between the extremes of perihelion and aphelion is not enough to break winter’s grip, which is held fast with the far fewer hours of daylight we enjoy this time of year.
Our seasonal weather is a result of earth’s 231⁄2-degree tilted axis, not our distance from the sun. During winter in the northern hemisphere, the north pole is tilted away from the sun. Our days are short, not even 10 hours long, and that makes it cold.
However, since solstice on December 21, our days have been growing longer, but only in the afternoon. December 7 marked the year’s earliest sunset, at 4:43:47, and since then we’ve gained more than 10 minutes at the end of the day. Almost a month later, January 5 marks the sun’s latest sunrise at 7:25:13. Thereafter, albeit imperceptibly at first, the sun will rise a little earlier each morning, but it will still be mid-February before it crests the horizon before 7:00.