worldEdify™🌍 on Instagram: "Almost 1M thanks for following!🤍 What looks like a simple marble toy is actually a 700-year-old mathematical concept in action. This device demonstrates the Tusi Couple, where two perfectly synchronized circular motions combine to produce a straight-line path. Invented by 13th-century Persian scholar Nasir al-Din al-Tusi, it was originally used to explain planetary motion in astronomy. The steel balls only appear to move in a straight line, but their motion results