Another thing that interests me is the languages. I find Arabic is an ugly language when used in conversation but poetic Arabic and musical Arabic sound good. Is there a difference in classical and modern Arabic?
My father is also a big fan of Urdu even though I see no difference in conversational Urdu and Hindi.
Do Arabic, Farsi, Dari and Urdu share the same alphabet? Are any of them mutually intelligible i.e. keeping with the thread title, can an Afghan understand Farsi or can a Tajik speak Dari or can a Azeri and Baloch speak to one another? Do the Pashtuns and Tajiks of Afghanistan have the same language?
Because my Saudi Arabian friend can read a bit of Urdu and he hasn't a drop of Indian or Pakistani blood in him! I also heard South Arabians aren't Muslim and have a completely different language to Arabic!
@MD
Do Zoroastrians use Farsi in their congregations and prayers? If not, what's the language?
Classical Arabic is the preserved literary Arabic of the 7th or 8th Century. Modern Arabic is in practice almost entirely constituted by very divergent dialects, which may or may not be mutually intelligible.
Arabic, Farsi, Dari and Urdu use the same, or very similar, alphabets. Farsi/Persian, Dari and Tajik are the same language. Arabic and Urdu are very different to each other and to Persian. What do you mean by an Afghan? An Afghan might be Pashtun, Tajik, Uzbek... A Dari-speaking Afghan can understand Persian no problem. A Tajik too.
An Azeri and a Baloch, no I don't their languages would be mutually intelligible. The main language spoken by Pashtuns is Pashto, although there are many who speak Dari as a second or even a first language too. Pashto is not mutually intelligible with Persian.
There are groups in Southern Arabia which speak South Arabian languages, that are distinct from Arabic. But they're all still Arabs, and all still Muslims.