We know that the Earth's poles have reversed hundreds of times. It's a dynamic system inside the outer core and it has to reverse at times because that's just part of the way it works. We know it's done this most recently 780,000 years ago, so there are people who say it's overdue. We know that the core is becoming increasingly volatile. The North magnetic pole is absolutely running through the Northern Hemisphere at 55 kilometers a year to the northwest.
If you see the Earth today, don't forget to wish it a happy aphelion -- July 3 marks the day this year when our planet reached the point in its orbit that is the farthest from the sun. Earth doesn't revolve around the center of the solar system in a perfect circle. Because its orbit is more elliptical, there is a point that is closest to the sun, the perihelion, and a point that is farthest, the aphelion. Perihelion occurred on January 4 this year, and in the six months since then, Earth has reached the other extreme in its orbit, as it continues its perpetual journey around the sun. Today, specifically at 4:11 p.m. EDT, the Earth reached 94.5 million miles away from our star.
As the temperature drops and holiday decorations go up, winter seems to be just around the corner. According to astrological activity, we can determine exactly when we say goodbye to fall and cozy up to the coldest season of the year. The start and end dates of the four seasons are determined by the solar year, or tropical year, which represents the amount of time between two vernal equinoxes, or the time when the sun is approximately above the equator. During the vernal equinox, day and night are of about equal length. Between these equinoxes, the summer and winter solstices occur when one hemisphere is tilted closest and farthest toward the sun, respectively.
Break out the cozy sweaters and get ready to go pumpkin picking – as of 10:21 a.m. on Thursday, it is officially fall. The autumn equinox arrived on Thursday morning when the Earth reached a point in its orbit when neither the Northern nor Southern poles were angled towards the sun. In fact, at nearly half past 10 on Thursday morning, the sun shone directly on the Earth's equator, the imaginary line that divides our planet into two hemispheres. Twice each year, Earth reaches this unique position, giving us two days with days and nights that are equally long in both the Southern and Northern hemisphere. The very word equinox comes from Latin root words meaning "equal" and "night": a pairing that makes sense, given the 12 hours of sunlight and 12 hours of darkness that the world experiences on the spring and fall equinoxes, which occur in September and March each year.
Even if you brought a map, it won't do you much good if you don't have your bearings. Fortunately, the sun can point you in a general direction. We're told, "The sun rises in the east and sets in the west," but a more accurate saying is "The sun rises roughly east-southeast and sets roughly west-southwest, although the exact bearings will depend on the specific time of year." There's also the hemisphere flip to consider. In the Northern Hemisphere, the sun sits in the southern part of the sky, while in the Southern Hemisphere, it appears in the North.