Sun will align directly over Kaaba, Islam's holiest shrine, on Friday

Muslim pilgrims perform the final walk around the Kaaba at the Grand Mosque in Mecca on November 30, 2009.

Story highlights

  • Phenomenon means Muslims can determine direction to pray simply by facing sun
  • Using shadows to determine Qibla dates to 12th century

Dubai, United Arab Emirates (CNN)It is Islam's holiest shrine -- and for a few moments on Friday, it will also be the easiest to find.

Astronomers say the sun will pass directly over the top of the Kaaba at the Grand Mosque in Saudi Arabia at 12:18 p.m. local time -- coinciding with the call to Friday prayers at the mosque -- and when it does, the cube-shaped structure, draped in black silk at the center of the world's most sacred Muslim site, will cast no shadow.
    Muslims across the world must face the direction -- known as the "Qibla" -- of the Kaaba when praying. Friday's alignment of the sun over the shrine, which happens twice a year, means the faithful can find the Qibla simply by facing the sun.
    "This celestial phenomenon will enable people all over the Earth who can see the sun at that moment to determine the direction of the Qibla through the simplest and easiest ways," Mulhim bin Mohammed Al Hindi, an astronomy researcher at King Abdulaziz University in Riyadh, told Saudi news agency SPA. "A man facing the sun (at that moment) will be heading to the Qibla with an accuracy of 100%."
    Those living near the Kaaba, however, will find it more difficult than the rest of the world to locate the direction the sun is traveling, and will have to rely on an ancient method to locate the sun. "They can determine the Qibla through the shadows of objects," Al Hindi said. "If a pen is situated vertically, the Qibla's direction will be the exact opposite to the pen's shadow."
    Using shadows to determine the Qibla dates back to the 12th century, according to Al Hindi. Facing the Kaaba -- Islam's holiest site and the destination for the annual pilgrimage known as the Hajj -- is one of the religion's chief requirements, in addition to performing ablution (ritual cleansing with water) and reciting verses of the Quran while praying.