Tuesday, November 1, 2011

Moon phase animation

Assalamu’alaykum WW,

Remember we were split in concluding our Ramadan fast three months back? Some Muslims in South-East Asian countries performed Ied prayer on 30/8/2011, but some of them did it on 31/8/2011. Ever wonder why and how this happens? This moon-phase simulation might be useful for you to understand the complexity of astronomical phenomena graphically. A UTHM computer science student who is completing his PSM has helped me coding this, as part of my research. This is an exe file, so you just need to download it from my blog, extract it (winrar), and there it is, ready to run. Please DOWNLOAD here by opening Shared Documents and look for Moonphase Window.

The animation is composed of three modules.

The main module shows the position of three celestial bodies, the moon, the earth and the sun. You can drag the moon freely to show the phase of the moon at any position you like. You can also drag the man standing on the earth’s surface which actually representing the rotation of the earth along its axis and produces apparent movement of the sun and the moon so they look orbiting the earth.

The right module consists of two parts. The upper one is called “Moon Phase” that is showing the illuminated part of the moon that is facing to us on the earth’s surface regardless whether or not it is visible. The invisibility of the illuminated part of the moon is caused by: 1) When the sunlight is too bright e.g. during daytime so that it attenuates visibility quality of the moon, or 2) We and the moon are in different hemispheres so that we won’t be able to see it. The lower part is called “Horizon Diagram”. You can change its orientation so you can see the western, eastern, northern, or southern parts of our hemisphere by dragging it using mouse. It also shows the projected position of the sun and the moon onto the celestial sphere at radius of infinity in such a way that the moon and the sun at their apparent movement look in the same apparent orbit. This is exactly as indicated by Ya-Sin 38-40 in the Qur’an. Please note that the upper hemisphere where the man is standing is dark when the sun sets in the western horizon, and it is bright when the sun rises in the eastern horizon.

The bottom module has two parts as well. The left one “Animation Time Control” gives you options to run the simulation automatically at animation rate you like, or if you want to run the simulation manually by animation increment choice of you like (minutely, hourly, or daily). The right part, “Diagram Option”, is an option you may choose as benchmark (self explanatory).

In order to understand the disputed conclusion of last Ramadan, please start the simulation at sunset position (that is when the whole sun’s UPPER disk touches the horizon); however, put only the LOWER moon’s disk touches the horizon. You can obtain these positions by dragging the man and the moon in the central module by looking at the position of the sun and the moon in the “Horizon Diagram”. To some extents you might need to combine it by functioning “Animation Increment” control manually. At this position, the whole moon’s disk is still perfectly above the horizon and therefore the altitude of the moon is roughly 0.5 angular degrees. MABIMS (Malaysia, Brunei, Indonesia, and Singapore) countries put a prerequisite that the minimum moon altitude is 2 angular degree (there are additional prerequisites, but we do not discuss it here) in order to confirm the beginning of an Islamic month i.e. lunar month. However, for a pure proponent of astronomical calculation, this position (even less than 0.5 degrees) has already confirmed the commencement of an Islamic month because the hilal (crescent) has actually been born although it might not be visible to human eyes because its altitude is too low. In the mean time, you actually can see an illuminated slit in the “Moon Phase” diagram on your top right module. For the time being, define this as sunset of 29/8/2011.

Now, tick “show time tick-marks” in “Increment Animation” module and click the “hour increment” until the man is at observer’s local time of about 4:00 AM. Be reminded that the man is now at 4:00 AM on 30/8/2011. The crescent in “Moon Phase” module is also getting larger. However, the man and the moon are located in different hemispheres; therefore, the hilal is not visible although it was 300% wider than 9-10 hours ago (when the sun set). However, if you called your relatives or friends in Chile, at that particular time the sun was about to set in Santiago, Chile. At sunset on 29/8/2011 in Santiago, the hilal’s altitude was about 11 angular degrees in Santiago, much higher than the minimum 2 degrees required by MABIMS. At that particular moment in time, it was about dawn time (subuh) 30/8/2011 in Malaysia, and hilal’s altitude was about -37 angular degrees (below eastern horizon of Kuala Lumpur).

You may proceed clicking the “hour increment” until about 10:00 AM Malaysian time. If you called your friend in San Diego, it was about sunset in California, and the hilal was at an altitude of 3 angular degrees in San Diego. At that particular point in time (sunset on 29/8/2011 in San Diego), the hilal was actually located at an altitude of +34 angular degrees (above of eastern KL’s local horizon) on 30/8/2011 at about 10:00 AM. We should have been able to see an even larger hilal (about 500% wider); however, at 10AM, the sunlight intensity was just too strong, therefore the hilal was invisible either. Will you dare to say that the hilal has not been born because you are unable to see it?

It is therefore obvious that the hilal’s birth does not need to be confirmed by physical sighting except for illiterate people as clearly indicated in Rasul’s hadith. For those who are literate, rather than practicing moonsighting at random geographical points, one should have gone to either Santiago or San Diego to confirm the birth of the hilal. They should then text their brothers and sisters in South-East Asia to refrain from fasting as the hilal is already born (even pretty large). Remember, it is actually prohibited to fast on that day. Either way, one will not be able to construct an Islamic calendar; otherwise the maximum duration of the Islamic calendar is only exactly one month. Every month we have to do moonsighting, and Islamic calendar never exists. This is exactly the situation we have today. Please bear in mind also that cities for confirming the birth of the hilal are actually changing from one month to the next because the lunar date line (LDL) is also changing in somewhat random manner. Of course, astronomical calculation will be able to determine accurately which cities are to be used to confirm the hilal’s birth every month, even well in advance. At the end of the day however, you then have to trust astronomical calculation to confirm the birth of the hilal. Only with a robust astronomical calculation, an Islamic calendar for 100 years to come can be constructed accurately today, just like people are capable of determining solar eclipse that will happen 100 years from now.

This moon-phase simulation has not applied a robust calculation as its purpose is just to show graphical simulation of the moon phase by changing the associated parameters namely, position of the moon in its orbit, position of the man on the earth’s surface, etc. However, we are currently developing robust simulation software based on a robust astronomical software platform Stellarium (open source). Several benchmarks to further reconfirm the commencement of an Islamic month (from scientific and shariah view points) will be given as well. These two animation software, in addition to other software, will be provided as bonuses for my book (writing in progress) that isnya Allah will be published by Penerbit UTHM.

Please feel free to contact me should you find any shortcomings or difficulty in understanding the animation. DOWNLOAD HERE by opening Shared Documents and look for Moonphase Window


Tono Saksono