Earth closest to sun, moon farthest from Earth
Credit: NASA Johnson Space Center (NASA-JSC)
Wednesday, January 2, 2008
Tonight, around the stroke of midnight Universal Time, Earth will be at its closest point to the sun for this year.
Not long after, the moon will be at its farthest point from Earth for the month of January. The Earth’s closest approach to the sun for the year is called perihelion.
Every year, Earth’s perihelion comes during the first week of January. It happens because Earth’s orbit around the sun isn’t a perfect circle. Instead, it’s an ellipse, like a circle someone sat down on. We are some 5 million kilometers – or about 3 million miles – closer to the sun today than we are in July. That’s 5 million kilometers in contrast to our average distance from the sun of 150 million kilometers.
Really, it’s a very small change. That’s why Earth’s changing distance from the sun doesn’t create the change in the seasons. Instead, the seasons result from Earth’s tilt on its axis.
Right now, the southern part of Earth’s axis is tilting toward the sun, while the northern part of the axis is tilting away. Summer in the southern hemisphere. Winter in the northern hemisphere.
Yearly, the Earth reaches perihelion in early January. The moon returns to apogee about every 27.5 days. Every 4 years, lunar apogees and perigees fall on (or near) the same dates.
The Earth’s changing distance does affect the length of the seasons. Because the Earth goes fastest in its orbit when it’s closest to the sun, winter is the shortest season in the northern hemisphere and summer is the shortest season in the southern hemisphere. The winter season – which you might define as the period of time from the December solstice to the March equinox – is almost 5 days shorter than than the year’s longest season: the time from the June solstice to the September equinox.
Hi! I first listened to your show in March of 2007. That is when my brother and I dicided to photograph the Lunor Eclipes. Our first try was unfortunitly, unfuirtfull. Cape May NJ had to many clouds that night. But, it was still a wonderful experence. So we weated for five months until Aug. 2007. My brother couldn’t be with my but, my oldest sister and her ten year old grandson pitched right in. We were up at 1:00 am and arrived at Cape May Point at 3:30 am just in time. It was there I got my most fantabulous photographs of the lunor elcipes. Thank you for your show, keep up the great work. Olive
PS I am now look forward to the Feb, 2008 Lunor Eclipes. I am searching for night photograhy tip to make the experience something I can share with others. What state on the eastern seaboard do you thing would be the best to watch it from? I have a few other questions, during eclipes in March 2007 the moon was ecliped in the north east just above the point toward Cape May Farry’s lounch dock. However, in Aug. 2007, it was in the western ski directly over Delaware center right off the Cape May Point. How was the moons possion changed, Is there a website where I can track the orbits of the moon over a period of a year? There have been other time I have tracked the moon and everthought it at was wiewed at the same time nightly I found the moon in a different places in the ski periododicly. Why? time of day? Please clearify.
Olive,
For some tips on photographing the upcoming lunar eclipse, read Lunar Eclipse Photography by Fred Espenak. In New Jersey, the moon will be totally eclipsed from about 10 to 10:51 p.m. on Feb. 20. It’ll be in your southeast sky, roughly halfway between the horizon and straight overhead.
Clear Skies!
Bruce