David Deutsch's Multiverse

Hi everyone,

I hope you are all doing well.

I have finally finished reading The Fabric of Reality by David Deutsch and since then I have also finally read Conscious by Annaka Harris.

In this email, I would like to talk a little about the former.

When David was a child, he was told that a long time ago it was possible to go out and learn everything that we humans know. That the sum of human knowledge was small enough that a single individual could understand it. He was told that since then our knowledge had become so vast and far-reaching that such a feat was no longer possible. He didn't like being told this.

He now argues that this isn't the case. As time goes onward there is the trend for the simplification and increased elegance of deeper and broader explanations. We can explain more with less abstraction. Knowledge that was once at the forefront of human inquiry is now routinely taught in high schools.

In this book, he details what he refers to as a theory of everything which he describes by interweaving four different strands of explanation.

Quantum physics
Epistemology
Theory of Computation
Theory of evolution by natural selection

I want to briefly describe each of them.

Hugh Everett's Many-Worlds interpretation of Quantum Physics

When you shine a laser through a thin slit, the light scatters in a way that is not described by classical physics. When we shine it through two slits, it scatters in a completely different way. Through three slits, a very different way and so on so forth.

The only way sense could be made from this phenomenon, is that something was interfering with the light (as it doesn't shine straight through the slit). More experiments and variations to the method were attempted to see when the interference occurs.

What was found was:

Whatever was interfering with the light, also travelled through the slits (as the pattern changed when a different number of slits were used)
What was interfering with the light's path, has the identical properties of light except that it cannot be detected directly.

It was deduced that what was causing the interference was in fact light. A kind of invisible light. In chapter 2 of the book, David initially refers to these as shadow photons.

The same equations that describe the results of these experiments to a very high level of precision, describe a multiplicity of worlds - a vast array of parallel universe of which ours is a member.

The shadow photons are indeed photons from other universes!

Every particle; neutrons, protons, electrons and all have many shadow counterparts in other universes.

Of course, all of the particles in our universe are also shadow particles in other universes. We call the collection of universes that make up reality; the multiverse.

All particles in the multiverse can only ever interact with:

Other particles in the same universe
Itself in other universes

From my understanding, there are two main interpretations of the finding in Quantum physics. The Copenhagen interpretation by Niels Bohr and Werner Heisenberg as well as the Many-World's interpretation by Hugh Everett.

In the Copenhagen interpretation, the idea of a multiverse is minimised and rather a realm of possibilities is described. It is said that there are many possible worlds and many possible states for particles to be in, which collapse into what we call reality.

The Many-Worlds interpretation takes the findings literally. The reason why it seems like there is a multiverse - that positing one predicts the outcomes of many experiments to a high level of precision - is because there is a multiverse.

David criticises the traditional Copenhagen Interpretation for a very simple reason.

The so-called possible photons actually collide with our "real photons" and produce measurable effects (the interference pattern).

How can a possible entity interact with an actual one?

Is the quantum picture of reality deterministic?

An interesting note that was made in a later chapter on time is if reality is deterministic. Let me explain.

Laplace's demon is an entity that knows everything about the universe. It knows the location and every variable of each and every particle in the universe. With this information, is Laplace's demon able to predict all future events?

That is; if you know everything about the universe in one state, can you predict all future states?

If the answer is yes, then determinism is true.

What does quantum theory say about this?

It says a single universe is not deterministic, that there is a genuine possibility for events to go in many different ways.

However, the multiverse as a whole is deterministic.

If you were to flip a coin, even knowing every variable about it, there would be genuine uncertainty as to how it would land. However, if we look at all of the copies of you flipping the coin across the multiverse, we can say for certain half of them will get heads and the other half will get tails.

I feel the need to give you a disclaimer here. I know very little about quantum physics aside from what I have read in the book. This email is a shadow of a shadow, it is my interpretation of David Deutsch's interpretation of it.

Have a watch of this video of the man talking about it himself here.

So I said I would briefly describe each of the four strands but ran out of words talking about quantum physics. Alas, I will have to get back to them in a future email.

Politics and the fourth wall

The second round of Democratic debates happened recently. I don't know very much about politics, let alone US politics. I haven't researched much into the policies that different candidates support nor can I say confidently I know who would make the best possible president.

But this is pretty cool, so I will tell you this.

Have you heard of Andrew Yang?

He is a 2020 Democratic Presidential Candidate and is running on a platform of Universal Basic Income.

Towards the end of the second Democratic debate he broke the fourth wall and criticised political discourse itself and the format of the debate itself.

"We're up here with makeup on our faces and our rehearsed attack lines, playing roles in this reality TV show... it's one reason we elected a reality TV star as our president."

The same sentiment was made by Steven Pinker made in Enlightment Now.

"Engagement with politics is like sports fandom in another way: people seek and consume news to enhance the fan experience, not to make their opinions more accurate."

People are prone to getting very cynical on the issue of how our society is run. I feel many have the tacit assumption that whoever is in power, they are bound to be corrupted or even that no matter the system human nature will get in the way.

There are deep problems in how the way we as a society play the game of politics and engage in political discourse. But does it have to be this way?

Has it occurred to you these may be solvable problems?

Thanks again for reading everyone,

Sashin