Winter Solstice falls on December 21 at 12:04 UT (17:04 local time). I am awed by Natural Phenomena. I'm sure you are too. I love to watch Lightening, the occasional Eclipses, Rainbows, Sunsets, Clouds, etc. Winter Solstice is one such event. I have made several posts about the Solstices and Equinoxes over the past years. Often when I greet friends with "happy summer solstice" or "happy winter solstice", they respond with a reference to pagan rituals. The recent events in the US by atheist groups have stirred the battle between Christians vs Science even more. Science is portrayed negatively and it needs better PR.
Science is not Perfect
Science follows a process - The Scientific Method. The process starts with a Natural Phenomenon - as that is it's purpose - to explain Natural Phenomena. An explanation to a Phenomenon is presented - this is called a Hypothesis. The Hypothesis is then proven using other Scientific Theories and Mathematics. The proof of the Hypothesis will predict results similar to the original Phenomenon. If the Hypothesis is able to accurately predict results for similar Natural Phenomena, conducted independently (by anyone), then the Hypothesis becomes a Scientific Theory. That is, the Hypothesis must be experimentally validated against similar Phenomena.
Science is not perfect as each Theory is based on assumptions. For example, Newtons Laws of Motion says that the acceleration of a body is proportional to the (resultant) force applied to it and inversely proportional to it's mass. And the Law assumes that the mass of the body is constant. Several centuries later Einstein proved that the mass of a body changes with it's velocity. This changing mass is called Relativistic Mass. The effect of Relativistic Mass is negligible with situations we encounter on Earth. Therefore Newton's Laws of Motion can be applied to explain relevant Natural Phenomena that occur on Earth.
Prejudice: Science is Anti-Christian
Science does not see Hypothetical Phenomena, despite rigorous mathematical proof. That is, if I am to prove mathematically, that there is a Hypothetical Force such as The Force in Star Wars, then I must find a Natural Phenomena that supports my theory. String Theory is not accepted as a Scientific Theory because it cannot be experimentally verified. The experiments which are being carried out at the CERN Large Hadron Collider and at Fermi Lab attempt to find particles predicted by String Theory. Until such time String Theory is a Hypothesis.
Christians believe in God. And God is not a Natural Phenomena. And Thus Science has nothing to do with God. However, Science is used to explain the Origin of the Universe and the Origin of Species. Which contradict literal statements in the Bible, which is believed to be the Word of God. Common sense would tell you that, since Scientific Theories such as the Big Bang and Evolution contradicts the Creating Story in the Bible, Science is seen as a threat.
The Big Bang Theory and Theory of Evolution are two theories that demand so much more accuracy in their predictions than any other Scientific Theory. Newton's Laws of Motion are only accurate at slow speeds. Are Christian Creationists critical about Newton's Laws of Motion being inaccurate?
Science Does Not See Faith
Faith is personal. A person's belief system can be made up of multiple entities. Some Christians believe that God created Earth but do not accept the Story of Creation as mentioned in Genesis Chapter 1. Then Hindu's and other religions will have their own version of how the Universe was created. Science cannot experimentally validate anything based on faith. Therefore Science does not see faith, simply because these elements of faith cannot be measured.
Science demands independent verification of results from a theory. That is, if I am measure the value of acceleration due to gravity in Colombo and Mervyn Silva wants to measure the acceleration due to gravity in Colombo, we both can do it and arrive at a similar result.
Richard Dawkings in one of his TV shows stood at post holding heavy metal ball of Lead. The ball was suspended by a steel cable. He released the ball and did not move. The ball approached him but did not touch him. Would you call that faith? If I am to repeat the same experiment I will be able to achieve the same result. So would you. The results Science predicts are independent of faith. I don't need faith in anything to predict that the heavy ball would not smash my head and spill blood, mucus and brain matter all over the place.
Religion is only able to say that miracles are possible if you have enough faith that it would happen.
Science, unlike religion, is something anyone can question without being discriminated against. However, if you are presenting new information, then you must follow the Scientific Method. You cannot make deductions based on faith, as faith does not exist in Science.
Science does not belong to Scientists just as much as Music does not to Musicians. Science is often seen as something complicated and boring. It's easy to understand Science. Start from it's purpose. Then understand it's philosophy - The Scientific Method. Don't be turned off by complicated equations and notations. They are used only to study Science.
Earth's Tilt
Back to the Topic of Winter Solstice.
We were taught about Earth's tilt. Earth's Axis of Rotation or the line which connects the North Pole and the South Pole, is tilted by 23.5°. But we did not bother to ask ourselves "tilted to what?", because that was not in the syllabus.
The Earth's (average) orbital plane about the Sun is called the Ecliptic plane. The Earth orbits around the Sun in an elliptical path.
What we did not learn in school was that Earth's tilt relative to the Ecliptic is not constant.
The Earth also has an axial tilt ranging from +23.44° to -23.44° relative to the Ecliptic. This tilt gives Earth it's seasons, which starts from Vernal Equinox, Summer Solstice, Autumnal Equinox and Winter Solstice.
Earth's Orbit
An ellipse is an eccentric circle that has two foci, similar to how a circle has a center. An ellipse can be drawn by tying the ends of a string to two pints (the two foci) and tracing a complete round with the string taught. There will an instance when the pencil is closest to one of the pins and another point when the pencil is furthest from that pin.
Planets orbit around the Sun in an elliptical path with the Sun in one of it's foci, in accordance to Kepler's Laws of Planetary Motion. The Sun is not at the center of the ellipse but it is on one of the foci. Therefore, planets orbiting around it would pass a position in it's path where it's closest to the Sun, known as Perihelion (147 million km) and another where it's furthest from the Sun, known as Aphelion (152 million km).
Celestial Sphere
The Celestial Sphere is an imaginary rotating sphere with Earth's center as it's center and Earth's rotation axis as it's rotation axis. Objects in the sky such as the Sun, Moon, stars, planets, etc., can be projected on to the Celestial Sphere. This is done so that there is some reference to these objects, similar to plotting countries in a World Map, using a set of coordinates.
There are several coordinate systems to describe locations of objects in the Celestial Sphere. The Equatorial Coordinate System is one such system. It locates objects relative to the center of the Celestial Sphere using two angles: the Declination Angle, δ and Hour Angle, H. The Declination Angle, δ is analogous to Latitude Angle and the Hour Angle, H is analogous to Longitude Angle.
An observer would not make any sense of Declination Angle and Hour Angle, until he/she transforms them to a local Horizontal Coordinate System. In the Horizontal Coordinate System, the observer's reference plane is his/her horizon, with objects measured in terms of Altitude Angle (Alt) and Azimuth Angle (Az). The Azimuth Angle is measured from due North towards East and Altitude Angle is measured from upwards from the observers horizon. It is clear that the Horizontal Coordinate System makes more physical sense to an observer.
However, it is impractical to refer to objects in Horizontal Coordinate System because the coordinates measured from Colombo would be different to those measured from the North Pole. Astronomers use Declination Angle and Hour Angle (or Right Ascension) to locate objects in the Celestial Sphere in an absolute sense.
The Declination Angle of the Sun, δSun can be approximately given by:δSun = 23.44 × sin((360×(284 + N)/365))
Where N is the day number. (eg. N=31+10=41 for Feb 10).
The above equation is an approximated Sine function and it's accuracy is sufficient for our deductions. And we can deduce the following:
- two instances when δSun = 0, know as Vernal Equinox
- and Autumnal Equinox
- an instance when δSun = +23.44°, known as Summer Solstice
- and an instance when δSun = -23.44°, known as Winter Solstice
Dates & Times of Earth's Seasons
The exact dates and times of these seasons have been accurately calculated by The Astronomical Applications Department of the U.S. Naval Observatory.
- 2008
- Perihelion: January 03 at 00:00 UT (05:30 local time)
- Vernal Equinox: March 20 at 05:48 UT (11:18 local time)
- Summer Solstice: June 20 at 23:59 UT (June 21 05:29 local time)
- Aphelion: July 04 at 08:00 UT (13:30 local time)
- Autumnal Equinox: September 22 at 15:44 UT (21:14 local time)
- Winter Solstice: December 21 at 12:04 UT (17:04 local time)
- 2009
- Perihelion: January 04 at 15:00 UT (20:30 local time)
- Vernal Equinox: March 20 at 11:44 UT (17:14 local time)
- Summer Solstice: June 21 at 05:45 UT (June 21 11:15 local time)
- Aphelion: July 04 at 02:00 UT (07:30 local time)
- Autumnal Equinox: September 22 at 21:18 UT (Sept 23 02:48 local time)
- Winter Solstice: December 21 at 17:47 UT (23:17 local time)
Relevance to Sri Lanka
There is no relevance to Sri Lanka the Solstices does not show visible Phenomena to regions outside the Antarctic and Arctic Circles.
On Winter Solstice:
- for locations on the Tropic of Capricorn, the Sun appears to be directly overhead at (Solar) noon
- for locations on the Antarctic Circle, the Sun will set at (Solar) midnight
- for locations bellow the Antarctic Circle, the Sun will not set
- for locations on the Arctic Circle, the Sun will not rise