There is only one empty set in existence, and all references to the empty set refer to the same thing. All physical reactions to the empty set are reactions to the same thing. This gives the empty set characteristics of a physical object.
Ectasian (Wikipedia)The Ectasian Period (from Ancient Greek: ἔκτασις, romanized: éktasis, meaning “extension”) is the second geologic period in the Mesoproterozoic Era and lasted from 1400 Mya ago to 1200 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.