Equinoxes

“On March 20, 2009, at precisely 7:44 am EDT (March 20, 11:44 Universal Time), the Sun will cross directly over the Earth's equator. This moment is known as the vernal equinox in the Northern Hemisphere. For the Southern Hemisphere, this is the moment of the autumnal equinox.” http://www.infoplease.com/spot/riteofspring1.html

I promised several months ago (on the winter solstice) to write about the equinoxes at some point. As today is the vernal equinox, the official beginning of spring, here it is.

The term equinox is Latin for equal night. On the equinoxes (both spring – vernal and fall – autumnal) there are exactly 12 hours of daylight and 12 hours of darkness for every part of the planet from the North Pole through the Equator on south to the South Pole. These are the only two days a year when that is true.

The Sun’s apparent path in the sky, called the Ecliptic, is due to Earth’s orbit around the sun. The concept of the zodiac is related to this. The sun goes through different constellations (again from Earth’s perspective) during the course of a year. The planets roughly follow this path, too, which is why you’ll never find Mars in the far north of the sky (as viewed from the Northern Hemisphere), but you might see it in Gemini, the Twins (a winter constellation), or Sagittarius, the Centaur archer (a summer constellation).

The night sky has been mapped out like an extension of Earth. A projection of Earth’s North Pole into the sky is called the Celestial North Pole; a projection of the Equator is the Celestial Equator, and so forth.

On the equinoxes, the Ecliptic crosses the Celestial Equator. This means that the Sun will rise due East and set due West on those days. Because folks today do not pay much attention to where the Sun rises and sets, many may think that this is usually the case, but that is not true.

From the perspective of the continental United States, the Sun’s path changes in the following ways over the course of a year. On the winter solstice, the Sun rises the farthest south of east that it ever rises, goes up to the lowest altitude in the sky for the year, and quickly sets again in the farthest south of west position that it ever sets. For a position with a latitude of 38 degrees North (where I live), the Sun rises to be about 29 degrees above the Southern horizon at noon on the winter solstice. The Sun, during the next several months, seems to rise a little more north of its position from the previous day, until, on the vernal equinox, it rises due east, gets up to a middling height, and sets due west. From 38 degrees North, the Sun rises to be 52 degrees above the Southern horizon at noon on the equinox. That’s 23.5 degrees higher than it was on the winter solstice, because the Earth is tilted at an angle of 23.5 degrees. Not surprisingly, then, on the summer solstice, when the Sun is the highest that it will be all year, it’s at a height of about 75 degrees when viewed from the northern US.

Having always lived in the continental US, it was a unique experience for me to be able to see the Sun in the north in the middle of the day when I visited Costa Rica. The Sun had always been to my south at noon for my entire life. In the summer in Costa Rica, at a latitude of 9 degrees North, the Sun passes through the zenith (a point directly overhead) during early summer and stays in the northern part of the sky during much of the summer. The tropics of Cancer and Capricorn (at 23.5 degrees North and South latitude) are called that, because the sun passes through the zenith there one time per year. The sun passes through the zenith only on the solstice in June for the tropic of Cancer (its summer solstice) and the solstice in December for the tropic of Capricorn (its summer solstice, our winter solstice). That’s why the tropics are so warm. The Sun rises to be very high in the sky there every day of the year and the length of day does not change very much there over the course of the year.

I’m beginning to realize that I have gotten so used to teaching this with pictures that it is very hard to describe only in words. This all makes a lot more sense when there are pictures to go along with the explanations. I don’t have more time just now, but please feel free to ask questions or make comments, especially with help in making what I’m trying to say more clear for a non-astro person.

Thanks! And happy equinox!

Combining Math, Science, Astronomy and God

This follows from a note that Elizabeth Campbell wrote. Since I worked on my 25 random things this morning, I'm in a writing 'zone' or something, I guess. That's probably good, since school starts Monday. Before I get to my subject, perhaps part of why I'm writing is to take my mind off of what I'm in Madera to do. My friend's mom just passed and we are going through her mom's house, helping her keep what she wants, getting rid of junk, figuring out what to sell, etc. (This was part of my hoarding comments in the 25 things.) It's one of those things that must be done and which no one enjoys. I'm very grateful that I have a few days to be able to help her through this ordeal, hopefully helping her make it more manageable.

I have always seen God in the universe (and in big numbers, which directly follows for me). I think that that was/is a big part of my interest/attraction to astronomy. I feel like I have a small glimpse of what infinity means, because I have spent years contemplating the immensity of the universe.

Earth is small, as far as the universe (or even our own solar system, for that matter), goes, but it is, as far as we know yet, the only place where intelligent folks live. (I actually include dolphins in the 'folks' category. They have language, community groupings, etc.) I hope to be alive when we find other folks. We are each unique, though: number 1 in our own way. Even twins who have the same DNA are not even physically completely identical.

When I teach astronomy, I talk about the very big and the very small. Stars, immense as they are, use the energy of fusion - protons combining with protons to make Helium from Hydrogen. God is infinite, yet He knows each of us intimately. God doesn't forget anyone or anything in Her entire creation. This is actually why I think that there has to be intelligent life outside of Earth. If God truly is infinite, why would there be just one planet w/ sentient beings?

My astronomy mentor, Laurance Doyle, once gave this really great analogy to describe smallness versus uniqueness:
If all of the humans on the planet held hands and jumped into the ocean, it would rise 0.1 mm. Physically we are completely insignificant.
If you had a diamond that was the only one in a room, that might or might not be seen as important. If you had the only diamond in a city, perhaps that would be notable to some. If you had the only diamond on the planet, you would be seen as rich and special. You are the only you in the universe. You are truly blessed, interesting and important, because you are truly unique. Scripture says that the very hairs of our head are all numbered. God cares not just about us as individuals, but knows about the minutiae of our lives. God shows us what to know when we need to know it (if we're listening) and puts folks to help us along our path when we need it (often even if we're not listening).

I studied astronomy because of the glimpses of God's diversity and infinitude that it allowed me. After enough years, though, I realized that I just wanted to know God better, so I'm pursuing other paths that, I hope, will help me along that way. I still have a great deal to learn about how to go about sharing my experiences with God with others, so that they feel free to share theirs with me. I get confused about my purpose, sometimes, though, and start to try to get others to think like me. While I think that my path is right for me, who am I to try to convince someone else to take my path? (Hmm, things to ponder.)

I've got to go, but hopefully I'll come back to this subject - a bunch. It's one of my favorites, combining my two academic loves (and my soon to be two masters' - go figure).

The Winter Solstice and why Christmas is on Dec 25

Being an Astronomy teacher and a winter solstice baby, I enjoy solstices and equinoxes, but the winter solstice is my favorite. I have taught some 2000 students about these days over the last 8 years. I just did a rough count (not going back to look at resumes) and that's what I came up with. My dad mentioned that, in his 20 years of teaching, he's had many fewer students than I have in 8. Anyway, back to astronomy and ancient cultures.

The word solstice means 'sun stands still' from Latin - sol = sun and sistere = to stand still (thanks for this root word from wikipedia). If you mark where the sun rises every day and/or where it sets every day (and different cultures did one or the other or both), you will notice that the sun does not rise or set in exactly the same place every day. Today many people do not realize how much farther north the sun rises and sets in summer (in the Northern Hemisphere) as compared to the winter (in the NH) where it sets south of west (and rises south of east). (I'll just talk about the sun setting from now on, but the same principles apply to the sun rising. Also, I'm going to assume we're in the Northern Hemisphere, since everyone I know lives there, but the seasons are the opposite times of year in the Southern Hemisphere.)

As you get towards the winter solstice, Dec 21 or 22, the sun seems to slow down in its path towards the south. What I mean by that is that if you marked the position of the sunset every night from the autumnal equinox (Sept 20, 21, or 22, depending) through the winter solstice, you would notice that the sun sets farther south every night, but that the distance between the positions gets smaller and smaller. Finally, on the solstice, the sun seems to set in the same place for several days in a row - it is standing still. On about December 25, a careful observer will be able to notice that the sun has started moving north again from its 'winter house'. This is a reason for celebration for those who worship the sun as a god. (I would love to learn more about modern celebrations of this pagan holiday.) The ancient belief was that sun was happy with the people and had decided to return to the north. This meant that there would eventually be a thaw and springtime would come again. Without the thaw, there would not be a chance for planting again and the people would die. (Clearly they didn't live in CA, because people living in CA would not have died if spring never came again.)

The Christian celebration of Jesus' birth on December 25 probably came about as one of the two following scenarios: 1) early Christians, fearing persecution or death from being found out, celebrated quietly while the surrounding pagans celebrated loudly and they blended in or 2) early Christians wanted to convert pagans to worshiping Jesus from worshiping the sun, so they convinced them to worship the Son of God instead of the Sun on this day. In any case, there is NO archeological evidence that Jesus was born on Dec 25, or even in winter at all. The shepherds certainly would not have been standing out in a field with their flocks in freezing weather.

The 'star' that is glorified in modern Christmas carols, some going so far as to say that it shone day and night and told individuals about Jesus' coming, was probably not a single 'star', but a conjunction of planets gathering in the constellation of 'the people.' The ancient Israelites, like many peoples, had a set of the signs of the zodiac (groupings of stars that the sun and planets travel through). Having more than one planet in a single constellation at a time is noteworthy. Having two or three together in the sign of the people was important enough that even the 'wise men,' probably astrologers from Persia, would have recognized the significance. If there was a 'star' that shone day and night, King Herod, even being a bit slow, would have been able to find it on his own and would not have had to consult with the foreign astrologers (see Mark 2 in the Bible). No conjunctions have been found (using software that can replicate the motion of the planets backwards and forwards for thousands of years) that occurred in the wintertime, or in 1 BC. The probable dates for Jesus' birth are between 4 AD and 6 BC, probably in the springtime. Here's one article from earlier this month saying that it was June 17, 2 BC: http://www.dailymail.co.uk/sciencetech/article-1093053/Cancel-Christmas--Jesus-born-June-17-say-scientists.html.

That's enough for today. I'll do a piece on equinoxes soon.

Merry Christmas! (Does it really matter what day we celebrate it? There's plenty of archeological evidence that Jesus certainly existed and the Christ-idea is with us always.)