Thales [ about 600 BC ] Greek Philosopher.

The Ancients had a practice of crediting particular discoveries to men with a general reputation for having wisdom, and Thales is one of them. Thales is thought to be the first person that proposed explanations for natural phenomena which were materialistic rather than mythological or theological. He gave no role to mythical beings. Arguments could be put forward in attempts to discredit his theories. His hypotheses were rational and scientific. Aristotle acknowledged Thales as the first philosopher, and criticized his hypotheses in a scientific manner. 

Thales knew that the fossilized tree resin called Amber would attract small lightweight objects when it was rubbed with a woolen cloth. This was a demonstration of static electricity.  The Greek word for amber is Elektron.

Thales is also credited with discovering 5 geometry theorems:

A circle is bisected by its diameter.

The angles in a triangle with opposite two sides of equal length are equal.

Opposite angles formed by intersecting straight lines are equal.

The angle inscribed in a semi-circle is a right angle.

A triangle is determined if its base and two angles at the base are given.

Source: Encyclopedia Britannica

Note: The Emperhor Theodosius is thought to have had the scrolls emptied from the Library of Alexandria, destroying the Library along with the Pagan Temples of their time. Most of the Ancients knowledge base was lost to mankind by the middle ages (700 AD).