Helgoland: Making Sense of the Quantum Revolution

by Carlo Rovelli

The joint properties of two objects exist only in relation to a third. To say that two objects are correlated means to articulate something with regard to a third object: the correlation manifests itself when the two correlated objects both interact with this third object, which can check. The apparent incongruity raised by what seemed like communication at a distance between two entangled objects was due to neglect of this fact: the existence of a third object that interacts with both the systems is necessary to give reality to the correlations. Everything that manifests itself does so in relation to something. A correlation between two objects is a property of the two objects—like all properties, it exists only in relation to a further, third object.

Color comes from the encounter between the frequencies of light reflected from the surfaces of the chair and the particular receptors in human retinas. It is not about the chair: it is a story between light, retina and reflection. Most other animal species do not see colors as we do.