Happy September equinox!

The september equinox is today.

Depending on where you are on the planet, it could be morning or some part of the day. The center of the Sun will be visible from the north to the south. That is the moment when the sun rises and sets.

There is a lot of meaning to it. It is not fair to people living in the southern hemisphere when it occurs in the spring. The September equinox is why I call it that. A lot of people like to think of it as the first day of autumn but I don't think it's a good idea. Autumn really starts when September is hot and things don't start cooling down until October.

It is thought that the day when daytime and nighttime are the same is the equinoxes. Equal night is a misconception because day and night are not equal.

There are a few reasons for this. If the sun was a dot, the day and night would be the same length. It isn't a dot, it's a disk. When the upper edge of the Sun crosses the horizon and sets, the day begins and the night begins. The day is two minutes longer than the night because it takes the Sun about two minutes to move its own width.

The earth has air. The same effect that makes a spoon look broken when it sits in a glass of water is caused by light entering our air. The air bends the light so that it makes the Sun appear higher than it really is. Adding more time to the day is what it rises earlier than you would think.

The effects make the day last longer. You have to wait a few extra days in September to get the day and night of the same length. The equilux takes place on different days and times for different latitudes. Most of the people live at 40 north latitude.

The third effect? The exact moment of the equinox can happen at any time of the day, but it depends on a lot of factors. If the Earth had no air and the Sun were a dot, you wouldn't get an equal time for both days and nights.

Nature is messy and this is one of them. We like to draw lines between things, but they are not always clear.

I stick with the definition of astronomy. The Earth has two poles. The equator is halfway between them and we can divide it into latitude and longitudes. We can mark the north pole, the south pole, and the equator with that spherical grid. The Sun appears to move north and south over the course of a year due to the Earth's tilt. When it crosses the equator going north, it is the March equinox, and when it crosses the equator again going south, it is the June solstice.

One way to think of it is that the sun is directly over the equator on the equator. The sun is at its zenith at midday if you stand on the equator.

The Sun's motion in declination is the fastest at the equator, which means the length of day changes the most around that time. The Sun is setting earlier every day. I have to feed the horses at a certain time of day so that they have enough time to eat before we put them to sleep. Every calendar day around this time of year, the sun sets a couple of minutes earlier. It can be seen in just a week.

People feel removed from astronomy when they think that all this stuff doesn't affect them. It does all the time.

Every second of every day, you live on a planet in a universe full of stars and planets and dust and gas and magnetic fields, and this all affects you.

It is more enjoyable to understand that and appreciate it.

It is a happy equinox.

The Latin root origin of the word makes it a cooler word.