Aphelion and Perihelion

The sun and our relationship to it seems fixed, and so it is for a single lifetime. However, over millennia, the relationship between Earth and Sun varies considerably.

There are certain things that I have accepted as unchanging, especially when it comes to the physical source of life on this planet, the Sun. However, I have been realizing that although a person may not witness much change in our relation to the Sun during a lifetime, over longer periods, there has been and will continue to be surprising variability.

Not long ago, I heard the words, aphelion and perihelion for the first time. The orbit of the Earth around the Sun is elliptical—more like the shape of a football than a beachball—and the Sun is not exactly centered in that ellipse. There is a precise moment when the center of the Sun and the center of the Earth are as close to each other as they will get. This is called the Perihelion and this year it occurred on January 2nd. It stands to reason that the Earth will be at the opposite end of the ellipse exactly six months later, and so it is. Tomorrow, July 5th, we will experience the Aphelion, when the centers of Earth and Sun are as far apart as possible.

The difference between the two events seems significant. This year at Perihelion, the Earth and Sun were a mere 91,399,454 miles apart. Tomorrow, we will be 94,510,866 miles from the Sun (these are center to center measurements), a whopping 3,111,432 miles further from the sun than in January. To put that into perspective, that is about 125 trips around the equator or five trips to the moon and back.

That doesn’t seem to compute with what we experience here on Planet Earth. January is our coldest month and July is our hottest, yet the sun, our source of heat, is closer in January and further away in July? And even then, the hottest days usually aren’t around the Fourth of July, but weeks later (this year may be an exception to that).

A couple of things are going on. The first is called the lag of the seasons. The summer solstice—the longest day of the year—and the Aphelion occur when we are still recovering from winter. Most years, there is still winter snow lingering in the high shady places and oceans, reservoirs and land masses are still warming up—a long process. Once the winter chill has been truly vanquished, then the hemisphere can warm and we get the hottest days—the end of July and through August.

The second factor is more fundamental. The change in distance to the Sun really has little influence on our weather. It is the tilt of the Earth on its axis that matters and creates the seasons. During our summer, the Northern Hemisphere is tilted toward the sun. We receive more solar radiation because the Sun’s rays are striking the Earth at a more direct angle. Come December, the Northern and Southern hemispheres have “traded places” and we are angled away from the Sun and thus only receive sunlight at an oblique angle and we have winter.

What is amazing though, is that the orbit of the Earth isn’t perfect. Perihelion and Aphelion don’t occur at the exact same time each year. For the next five years, the Perihelion will occur on: January 2, 3,4,2 and 4 and the Aphelion will occur on July 5,4,6,4 and 3. In addition, there will be up to 6,500 miles difference from Perihelion to Perihelion and almost 9,500 miles difference between aphelions.

That isn’t the end of change though. In the year 1246, the December Solstice and the Perihelion occurred on the same day. Every 58 years since then, the date of the Perihelion and Aphelion have drifted by a day. In about the year 6430, 4,000 years from now, the Perihelion will occur on the same day as the March Equinox. This is all apparently due to the fact that about every 100,000 years, the Earth’s orbital path changes from elliptical to circular, proving that our relationship with the Sun is flexible, not unchanging.

Help Idaho Wildlife

When we traveled across the state in October 2017, most of the vehicles we saw using the wildlife management areas did not have wildlife plates. Buying wildlife plates is a great way for non-hunters and hunters alike to support wildlife-based recreation like birding.

C'mon folks, let's help Idaho's wildlife by proudly buying and displaying a wildlife license plate on each of our vehicles! 

See below for information on Idaho plates. Most states have wildlife plates so if you live outside Idaho, check with your state's wildlife department or vehicle licensing division for availability of state wildlife plates where you live. 

And tell them that you heard about it from Nature-track.com!

Wildlife License Plates

Idaho Wildlife license plates provide essential funding that benefits the great diversity of native plants and wildlife that are not hunted, fished or trapped—over 10,000 species or 98% of Idaho’s species diversity. Game species that share the same habitats (such as elk, deer, antelope, sage-grouse, salmon, trout) also benefit from these specialty plates.

No state tax dollars are provided for wildlife diversity, conservation education and recreation programs. Neither are any revenues from the sale of hunting or fishing licenses spent on nongame species. Instead, these species depend on direct donations, federal grants, fundraising initiatives—and the Idaho Wildlife license plates.

Both my vehicles have Bluebird Plates. I prefer the bluebird because the nongame program gets 70 percent of the money from bluebird plates, but only 60 percent of the money from elk and trout plates - 10 percent of the money from elk plates supports wildlife disease monitoring and testing programs (to benefit the livestock industry) and 10 percent from cutthroat plates supports non-motorized boat access.

Incidentally, in 2014, the Idaho Legislature denied the Department of Fish and Game the ability to add new plates or even to change the name of the elk and cutthroat plates (very specific) to wildlife and fish plates, a move that would have allowed for changing images occasionally and generating more revenue. It would seem that they believe that we Idahoans don't want a well funded wildlife program.

I think it is time we let the Legislature know that Idahoan support wildlife funding and that we would like to see these generic plates come to fruition.

"WOW. What a phenomenal piece you wrote. You are amazing." Jennifer Jackson

That is embarrassing, but actually a fairly typical response to my nature essays. Since The Best of Nature is created from the very best of 16 years of these nature essays published weekly in the Idaho Falls Post Register (online readership 70,000), it is a fine read. It covers a wide variety of topics including humorous glimpses of nature, philosophy, natural history, and conservation. Readers praise the style, breadth of subject matter and my ability to communicate complex and emotional topics in a relaxed and understandable manner.

Everyone can find something to love in this book. From teenagers to octogenarians, from the coffee shop to the school room, these nature essays are widely read and enjoyed.

Some of the essays here are my personal favorites, others seemed to strike a chord with readers. Most have an important message or lesson that will resonate with you. They are written with a goal to simultaneously entertain and educate about the wonderful workings of nature. Some will make you laugh out loud and others will bring a tear to the eye and warm your heart.

Readers Write:

"You hit a home run with your article on, Big Questions in Nature. It should be required reading for everyone who has lost touch with nature...great job!" Joe Chapman

"We enjoyed your column, Bloom Where Planted. Some of the best writing yet. The Post Register is fortunate to have your weekly columns." Lou Griffin.

To read more and to order a copy, click here or get the Kindle version 


Copies are also available at:

Post Register

Island Park Builders Supply (upstairs)

Barnes and Noble in Idaho Falls

Harriman State Park, Island Park

Museum of Idaho

Valley Books, Jackson Wyoming

Avocet Corner Bookstore, Bear River National Wildlife Refuge, Brigham City, Utah

Craters of the Moon National Monument Bookstore, Arco, Idaho