Classification

Cosmological medium

Conventional medium

Basic unit

Virtual particle-antiparticle pair

Atom or molecular

Investigation system

Large number virtual pairs

Large number molecules

Leading interaction

Virtual Van der Waals force

Van der Waals force

Inertia indexes

Vacuum mass density

Mass density

Elasticity indexes

Vacuum elastic modulus

Elastic modulus

Propagated waves

Cosmological acoustic wave

Conventional acoustic wave