Monday, August 02, 2010

Ramadan by CCD

This is a weekly post by Nidhal Guessoum (see his earlier posts here). Nidhal is an astrophysicist and Professor of Physics at American University of Sharjah.

Ramadan is almost here, so this is the time for the annual saga of “when do we start the month of fasting” (and later “when does it end?”) – according to the astronomers and/or according to the Muslim jurists/scholars… In a contribution I made to this blog a couple of months ago, I reported on a conference that had just taken place in Abu Dhabi on issues at the interface between astronomy and Islamic jurisprudence, including the topics of the determination of Islamic months and calendar, the calculation of prayer times in (high-latitude) places where the usual definitions do not apply, etc. I mentioned then the chaos that we continue to witness whenever an occasion like the start of Ramadan comes around.

Why is there a problem in knowing when a month (Ramadan or other) is supposed to start or end if, after all, months are defined by the motions and (apparent) positions of the Sun and/or the Moon with respect to the Earth? Well, there are two reasons for this problem: one minor and one major. The minor difficulty is that the astronomical problem is quite complicated because the month starts not when the Moon achieves “conjunction” (lining up) with the Sun and the Earth, but rather by the “visibility” of the new crescent, and this definition introduces atmospheric (local and seasonal) factors, not to mention human sighting capabilities and such. (Some jurists have suggested changing the definition to a purely astronomical one, i.e. one based on simple conjunction, but such scholars have remained an extreme minority.) Even with those complicated factors, we have made such great progress in the past few decades that we now can predict when and where (by small-size regions) the crescent will or will not be visible on any given night. The major problem that still remains is the literalistic insistence of many scholars (and traditionalists are still largely dominant in the Muslim world today) that predictions and determinations by calculations are not acceptable, that testimonies of actual sightings of the new crescent be the determining criterion for starting or ending the month. Moreover, Muslim jurists of each country and school of thought have to decide whether observations made in other regions (nearby or far away) can be accepted or not…

And so, as you can imagine, all this leads to chaos with conflicting, and oftentimes ridiculous/impossible reports being exchanged and debated on the eve of Ramadan, sometimes live on TV… We then get one country’s officials (the religious and the political establishment) announcing the start of the month for the next day, and other countries rejecting the claims and postponing the start till the following day; other countries will have started the month a day earlier on various criteria; and so on and so forth. We now regularly end up with the Muslim world forming a mosaic of dates for the start or the end of Ramadan over 3 or 4 different days…

Now, if that is not enough in terms of confusion and chaos, in recent times we have had the added complication of deciding whether the usage of telescopes and binoculars for sighting the crescent is (islamically) acceptable or not for starting and ending Ramadan. And of course, there are two camps on this issue – among the Muslim jurists, that is.

And that’s where the CCDs pop up – to add more complications and “fun” to the circus. Indeed, in the past few years, CCD/digital imaging, which of course has been used in Astronomy for decades now, came into the field of crescent observations. Why only in the past few years? Because it turns out that imaging a thin new crescent, which stays above the horizon only a short time (due to the thick with air, dust, humidity, and pollution), is conceptually an easy matter but practically a very complicated task requiring adequate setup, know-how, and practice. But now we do have a handful of people, some in Europe and some in the Arab world, who can image the crescent in broad daylight (see the accompanying image). Is that an acceptable way of establishing the start of Ramadan? The debate is raging right now, with the majority of Muslims (even the learned ones) weighing against it – though the tide is slowly turning…

This Ramadan promises to be an interesting case in point. Indeed, the (geocentric) conjunction of the Moon with the Sun and the Earth occurs on Tuesday August 10 at 03:08 GMT (astronomers say UT, universal time), and it will be impossible to see the crescent by any means on that evening in Asia, Europe, and the northern half of Africa; it will be possible to see it by telescopes in the southern half of Africa and North American as well as in most of Central America; and it may be visible by naked eyes in South America. So these different possibilities lead to all kinds of possible conclusions/decisions... But the interesting part is the fact that the crescent is expected to be somewhat easily imaged by CCD (digital camera and small telescope) during the day! I can’t wait for the debates – though I can already foresee the chaos in the decisions that will come with all this.

So what’s the solution to this state of affairs? An Islamic calendar, of course, which I’ll discuss next time.


Ali said...

"Indeed, the (geocentric) conjunction of the Moon with the Sun and the Earth occurs on Tuesday August 10 at 03:08 GMT."

I am not an astronomer and I have only pretty basic knowledge of astronomy. So my question may even be stupid. Yet, i will take the risk of asking. :)

Given that the Earth is a (relatively) vast expanse of land and water, could it be possible that this conjunction occurs more than once? I mean depending on where you are looking at the moon from, or in other words, depending the observers angle, is it not possible to have this conjunction occurring more than once?

Nidhal Guessoum said...

Actually, that's a very smart and pertinent question. Astronomers distinguish between the "geocentric" conjunction, when the moon crosses the plane that joins the center of the Earth with the center of the Sun from the "topocentric" conjunction ("topo" means "surface"), where a point or location on the Earth's surface gets aligned with the moon and the sun. The former is a unique moment, whereas the latter depends on each point/location.

Accurate calculations that are given for specific locations must use the topocentric conjunction, but if one is speaking in general (as I was in my piece), then the geocentric conjunction gives a good indication and measure of what's to occur.

I hope this gives some clarification, if not please do feel free to ask. I hope my writings help further people's understanding of various issues, and comments by the readers certainly bring some new perspectives for me.

Ali said...

Thanks for your answer, Nidhal.

I enjoy reading yours and Salman's posts here. They help to broaden my general knowledge with valuable stuff. Thanks for keeping us posted. :)

Now, to your answer.
So, while the topocentric alignment may depend on the observer's location, the geocentric alignment is unique you say.

But, because the sun, the Earth and the moon are all moving bodies, and because they move at different speeds (not as a complete system or a single unit), I can't help but wonder why the geocentric alignment is a unique event.

I am glad you don't mind me asking. I sometimes do have a lot of questions. :)

Nidhal Guessoum said...

Dear Ali,

Thanks for your kind comments and encouragements; I do try to make my posts informative, and believe me the readers' comments are always most welcome even for my own "3-d" view of things...

As to your question, well indeed the moon moves quickly away from the alignment (between the earth and the sun), so that moment of conjunction is brief and common to the whole earth. After that, both the moon and the earth will have moved (in opposite directions) w.r.t. the sun, and the alignment is broken. Hence the moment of geocentric conjunction is common, unique, and brief.

Best wishes--

Ali said...

Thanks Nidhal.
Tat was helpful. I was thinking may be we may actually be able to see the start of the day more than once depending on our alignment. :)

"the readers' comments are always most welcome even for my own "3-d" view of things..."

I remember one of my earliest interactions here was with emre on Islamic Science. But I was anonymous then. Ha ha.

About 3-d views ...
I nearly get a headache every time I try to imagine more than 3 dimensions. I try to tell myself that just like speed and velocity are not the same, there may be more than 3 dimensions. Time apparently is one of them.

Don't know about multiple dimensions but the multiuniverse theory is a weird concept. Sorry astronomers. :)

MSM Salih said...

What would be the average time difference between earliest topocentric conjunction and the last topocentric conjunction?

Nidhal Guessoum said...

That's a great question, and one for which I do not know the answer off hand. I would have to do some calculations. I will try to get back to you soon on this.
Best wishes. NG

Anonymous said...

Alhamdullilah Ramadan is here again