Imagine sitting down and picking up your favorite book. You look at the image on the front cover, run your fingers along the smooth cover of the book, and smell this familiar smell of a book as you turn the pages. For you, the book consists of a number of sensory manifestations.
But you also expect the book to have an independent existence behind these appearances. So when you leave the book on the coffee table and enter the kitchen, or leave your house to go to work, you expect the book to still look, feel, and smell, just as it did when you held it.
The expectation of objects to have their own independent existence — independent of us, and any other object — is actually a deep-rooted assumption we make about the world. This assumption dates back to the 17th century scientific revolution and is part of what we call it mechanistic worldview. According to this view, the world is like a giant machine with a clockwork, whose parts are governed by given laws of motion.
This worldview has been responsible for much of our scientific progress since the 17th century. But as an Italian physicist Carlo Rovelli claims in his new book Helgoland, quantum theory – the physical theory that describes the universe on the smallest scale – almost certainly shows this worldview as false. Instead, Rowell argues that we must adopt a “relational” worldview.
What does it mean to be relational?
During the scientific revolution, the English pioneer in physics, Isaac Newton, and his German counterpart, Gottfried Leibniz, disagreed on the nature of space and time.
Newton argues that space and time act as a “container” for the contents of the universe. That is, if we could remove the contents of the universe – all the planets, stars and galaxies – we would be left with empty space and time. This is the “absolute” view of space and time.
Leibniz, on the other hand, argues that space and time are nothing more than the sum of distances and durations between all objects and events in the world. If we remove the content of the universe, we will also remove space and time. This is the “relational” view of space and time: they are only spatial and temporal relationships between objects and events. The relative view of space and time was a key inspiration for Einstein when he developed a general theory of relativity.
Rowell used this idea to understand quantum mechanics. He argues that the objects of quantum theory, such as a photon, electron or other fundamental particle, are nothing more than the properties they exhibit when interacting with – in conjunction with – other objects.
These properties of a quantum object are determined experimentally and include things like object position, momentum, and energy. Together they make up the state of the object.
According to Rovelli’s relational interpretation, these properties are all there is to the object: there is no subject individual substance that “possesses” the properties.
So how does this help us understand quantum theory?
Think of the well-known quantum puzzle of Schrödinger’s cat. We put a cat in a box with some deadly agent (like a vial of poison gas) triggered by a quantum process (like the decay of a radioactive atom) and close the lid.
The quantum process is a random event. There is no way to predict it, but we can describe it in a way that tells us the different chances of an atom decaying or not over a period of time. Since the disintegration will cause the vial of poison gas to open and therefore the death of the cat, the life or death of the cat is also a purely accidental event.
According to orthodox quantum theory, the cat is neither dead nor alive until we open the box and observe the system. It remains a puzzle about what exactly it would be like for a cat to be neither dead nor alive.
But according to relational interpretation, the state of any system is always in relation to some other system. So the quantum process in the box can have an indeterminate result in relation about us, but have a definite result for the cat.
So it is perfectly reasonable for the cat to be neither dead nor alive to us and at the same time definitely dead or alive. One fact in question is real to us, and one fact in question is real to the cat. When we open the box, the condition of the cat becomes definite for us, but the cat has never been in an indefinite state for itself.
In relational interpretation there is there is no global, “God’s gaze” view of reality.
What does this tell us about reality?
Rowell argues that because our world is ultimately quantum, we need to listen to these lessons. In particular, objects such as your favorite book may have their properties only in relation to other objects, including you.
Fortunately, this includes all other items, such as your coffee table. So when you go to work, your favorite book continues to appear as when you hold it. However, this is a dramatic rethinking of the nature of reality.
From this point of view, the world is a complex network of interconnections, so that objects no longer have their individual existence, independent of other objects – like an endless game of quantum mirrors. Moreover, there may not be an independent “metaphysical” substance that makes up our reality that underlies this network.
As Rovelli says, “We are nothing but images of images. Reality, including ourselves, is nothing but a thin and fragile veil behind which … there is nothing.”
This article has been republished by The conversation under a Creative Commons license. Read on original article. Author from Peter Evans, ARC Discovery Early Career Research Fellow, University of Queensland