Simplify the following text for a Grade 9 native English-speaking person.
Original: A Philosopher Lecturing on the Orrery , or the full title , A Philosopher giving a Lecture on the Orrery in which a lamp is put in place of the Sun , is a painting by Joseph Wright of Derby depicting a lecturer giving a demonstration of an orrery to a small audience .
Simplified: A Philosopher Lecturing on the Orrery is an 18-th century oil painting by Joseph Wright of Derby .