Pre-Dawn Chart

Today, January 4th, is called Pre-Dawn Chart in the Universal Solar Calendar. Let's take a moment, then, to observe the sky and the paths of the objects moving across it.  

Yesterday was the perihelion, the day Earth makes its closest approach to the Sun this year. More specifically, the Earth was around 91.4 million miles from the Sun yesterday, about 3 million miles nearer to the Sun compared to when it's farthest away (the aphelion).Sunlight is about 7% more intense during the perihelion, which is comforting here in the Northern Hemisphere where it's winter. 

Imagine sitting next to a campfire on a chilly night. You lean forward, and you can feel the heat of the fire on your face.  You lean way in and the heat is so intense it's uncomfortable - you fear you might singe your eyebrows or eyelashes. But if you lean back, away from the flames, the heat is diminished and as you lean way back onto your elbows, you feel the chill of the night air again. By leaning in and then leaning back, we can get an idea of just how hot the campfire is without actually touching it and hurting ourselves. I'm sure we've all had this experience, or something similar to it.

As I grow older, years go by faster and faster. As we all know, when you're ten, a year is one tenth of your life (the longest duration of time you know), but when you're 50, it's only 1/50th of your life.  I'm 70 now, and years pass astonishingly fast.

It seems like just yesterday it was summer and it was almost uncomfortable to go out into the hot, sticky Georgia air.  And then suddenly, today it's winter, and I'm staying inside my heated home to avoid the chill outside.  It once seemed like an eternity between the skinny-dipping, shorts-and-t-shirt weather of June and July and the shivering, frost-on-your-moustache cold of December and January, but now the changes seem instantaneous and almost arbitrary. 

The changes in temperature happen so fast it's almost like leaning in toward and back away from a campfire. I can almost gauge just how hot the Sun is as the Earth careens from perihelion to aphelion. (Technically, what I'm experiencing is actually the directions of the Earth's axis relative to the Sun. That's why it's coldest in the Northern Hemisphere during the perihelion and hottest during the aphelion.) 

Others gained even greater insight by observing Earth's orbit than "the Sun is hot." The perihelion doesn't occur on the same day every year because the Earth's orbit doesn't follow the exact same track each year. Einstein’s theory of general relativity predicted that the direction of the perihelion should change by an additional 43 arcseconds per century, due to the curvature of space-time caused by the Sun’s mass. The shifts of Earth’s perihelion and its agreement with general relativity was one of the first tests that confirmed Einstein’s theory and challenged the classical Newtonian view of gravity.