Guiding principle: quantum gravity

One of the aims of fundamental physics is to obtain a theory that can combine gravity with quantum physics. As I mentioned before, theory space is vast. A successful venture into theory space needs a reliable guiding principle. Without any experimental result pointing out the direction we need to take, the selection of such a guiding principle for the formulation of a quantum theory of gravity is difficult.

Some people believe that quantum gravity is the domain of the Planck scale where quantum and gravitational effects coincide. It requires extremely high (experimentally unattainable) energy densities. It also assumes that such high energy densities allow things like black holes and worm holes to pop in and out of existence. That is however an unscientific notion. Things don’t just pop in and out of existence, least of them black holes, regardless of the energy density.

Moreover, there are no such things as worm holes. I don’t care that Einstein thought they may exist. The idea represents one of those cases where the mathematics is over extended to produce a spurious solution that, although allowed mathematically, has no physical meaning. So they cannot pop in and out of existence anyway.

Hence, it is unlikely that there is anything interesting happening at the energy scale represented by the Planck scale, or more accurately called the hypothetical Planck scale. Therefore, I would not recommend any statements about what happens at this hypothetical Planck scale as a reliable guiding principle for quantum gravity.

As a more reliable guiding principle, we need to address the question, what happens to the gravitational field produced by a quantum state? What I mean by a quantum state is a state of matter in which quantum effects are manifest. An example of such a quantum effect is entanglement. So the question in this case is, does the gravitation field become entangled with the quantum state, or is the gravitational field uniquely produced by some combination of the elements in the superposition that represents the entangled state?

We can address the question with our current theory of general relativity. In Einstein’s field equation for general relativity, the curvature tensor of spacetime is equated to the stress-energy tensor of the matter distribution. In the context of quantum theory, the latter becomes an observable – an operator that can be traced with the quantum state to produce the observed stress-energy tensor of the quantum state. Obviously, the observed stress-energy tensor does not represent the entanglement anymore. Therefore, the curvature of spacetime produced by such an entangled state is affected by a combination of the elements in the superposition and does not become entangled with the state.

What does this say about the guiding principle for quantum gravity? What it seems to say is that there is no need for quantum gravity. The spacetime that we live in is a background in which the intricacies of quantum physics play out without becoming involved. The only effect that the quantum state of matter has on the gravitational field is through a unique stress-energy distribution for the entire state.

This conclusion is based on the assumption that Einstein’s field equation is valid on the small scale of quantum physics. It has been tested at larger scale and so far no deviations have been found. Without any observed deviations, there is not strong motivation for expecting that it would not be valid at the scales of quantum physics.

However, there is one aspect that Einstein’s field equation does not explain. It shows the connection between the curvature of spacetime and the distribution of matter, but it does not explain how mass-energy curves spacetime. It does not give a mechanism for this process. Such a mechanism may be hiding in the quantum description of matter. If such a mechanism can be uncovered, it would lead to a more comprehensive theory that would “explain” the Einstein’s field equation.

The search for this mechanism may be somewhat different from a search for a theory of quantum gravity. However, it can be seen as a more focussed attempt at formulating a theory of quantum gravity. To find this mechanism, we can perhaps focus of fermions. I think there are still some mysteries associated with fermions that need to be uncovered. Perhaps that can lead us to an understand of the mechanism for the way that mass-energy curves spacetime.

When democracy fails

There is this idea that humanity has evolved to its highest possible level of existence; that the structures in our cultures are as good as they can be; that our understanding of how the world works is complete. It does not take much to poke holes in such an idea if you think about it carefully. But sometimes people don’t think about things carefully, they just take things for granted. And then they are very surprised when other people hold different ideas or when things don’t work the way they thought.

Often people say that there are no holy cows; that nothing is above scrutiny. But when you interrogate them, you find that there are concepts and idea that they cling to. Often the current way of thinking about things is a holy cow to such people. It is a contradiction that exists in the current way of thinking held by many people of which they are not even aware. It is like when people say that one should not believe things without scientific evidence and then they cling tenaciously to ideas that they believe without any scientific evidence. Or where they criticize people for not following the scientific method in their convictions and then go ahead and violate the tenements of the scientific method in their own conduct.

Humanity has come a long way and there is much that happened during their long history that one can study and learn from. It does not matter whether it is general history, the history of science, or art, or any other aspect of our cultures. We see that there has been many different ways in which people viewed the world and different ways in which they thought about the world and how it works.

I want to believe that there has been a general progression in this understanding, but I do not believe that our current understanding is the ultimate and that (assuming we survive beyond our current challenges) there is not improvement possible. In fact, I can already think of some improvements that are possible. Moreover, I do not believe that all previously held convictions are necessarily inferior to our current way of thinking.

One thing that can be improved is the way we view previous ways of thinking. There is a general tendency to criticize other world views, especially those from the past. It reveals a general arrogance and also ignorance, because such a tendency is blind to the fact that our currently held way of thinking may not be the ultimate. What universal criteria that are independent of any world view can be used to assess world views?

To expand this idea further, one can ask whether it would have been good if people during the bronze age would have had our current world view. Perhaps you would argue that it would not have been possible, because it would have required some knowledge that we have today, which they did not have then. What about some concepts that did not need the knowledge we have today, like a political system, for example democracy?

Raphael, The School of Athens

It is interesting to consider that democracy is a very old idea, having been introduced in ancient Greece. Still, monarchy remained the dominant political system for most of the time since then. For a while Roman was a republic and then it became an empire. If this idea of democracy, which is tacitly held as a such a holy cow today, is really so wonderful, how do we explain the fact that it only became fairly dominant quite recently?

What it reveals is that the journey by which humanity achieved a certain idea is as important as the idea itself. In other words, if we believe that some political system is great, then it doesn’t help to enforce this idea on a group of people unless they have taken the same journey to reach this idea. There are enough examples in the world today where people that have not gone through the necessary journey are introduced to an idea that work so well in other groups, where it does not work in this group.

So, my suggestion is that we should not only consider the current status quo, but also the arduous process by which the current status quo has been achieved. Thinking that we can save people from the arduous journey by gifting them directly with the “final” result, we may discover that we have gifted them with an abomination that introduces an unnatural situation leading to much strive and anguish. Instead, we should allow people to evolve along the natural path and stop judging this path as if you have some superior vision that supposedly knows better.

The way forward

It is a new year. Time to look ahead, having completed a project toward the end of last year. Well, it still has some things I can look at, but I did make a bit of a breakthrough (if removing an error that resolved an annoying divergence can be called a “breakthrough”). Now, it is natural to look further ahead and ask oneself where one is heading.

In my case, I still hope to develop a formalism that is powerful enough to formulate fundamental theories that incorporate the dynamics of the standard model with gravity. But wait, isn’t that what they are trying to do with string theory and all those other theories?

No, there is a difference. The idea is not to build the speculative aspects of a new theory into the formalism itself. It seems to me that all the currently popular attempts to formulate theories of fundamental physics incorporate speculative ideas into the mathematics of the formalism itself. If they fail, the whole thing fails and there is nothing to salvage.

The only physics that should be built into the formalism is physics that has been established as scientific knowledge. That is the situation with quantum field theory. It has special relativity built into it, because that has been confirmed experimentally. Thus it allows speculative new theories to be formulated.

The inclusion of special relativity may also be the reason why quantum field theory cannot model gravity, which goes beyond special relativity. The obvious thing is then to modify the part that involves the special relativity and to replace it with general relativity. Well that has been tried and did not work.

I think the reason why the obvious extension of quantum field theory to incorporate gravity did not work is because it does not incorporate the formulation of states. Gravity depends on the nature of states. Therefore, my idea is to replace the path integral formulation with a functional phase space. Such a functional phase space formulation allows the definition of arbitrary complicated states. Such a functional phase space formulation is an idea that has been bounced around in the literature, but I have not seen a complete formulation that can handle gravity.

“Post-empirical science”

The informed reader will know that the title represents an oxymoron. Without its empirical character science would not be science. It is very much what defines the cultural activity that we call “science” to be what it is.

Why then this glaring contradictory notion? It has popped up in the literature related to a recent “publicity stunt” where a simulation of a wormhole in a toy model was blown out of all proportions by being deemed to have created an actual wormhole. The simulation was done on a puny quantum computer incorporating merely 9 qubits.

Although this story has been hyped by various sources (and I am not going to give any links because I don’t want to mislead more people), many people have strongly criticized the story, including John Horgan, Scott Aaronson, Ethan Siegel, and Peter Woit. I can go on to try and clarify, but these posts are doing a much better job than I can.

Of course it is nonsense. A simulation is a numerical calculation of the physical process under study. It is not the real thing. And it does not matter whether the simulation is done with a classical digital computer or with a quantum computer. It is still just a simulation. Moreover, the amount of information that one can extract from 9 qubits is 9 bits, which is barely enough to specify one single ASCII character in a text document. So, no wormholes were created.

Perhaps the result they obtained from their simulation agreed well with what they expected to see, but that does not mean that it qualifies as being an experiment. Simulations and experiments are different things. Usually simulations are used when the direct calculations are too difficult. However, there is almost no limit on what one can simulate. It does not have to be something that can actually exist. If I have a set of equations that describe some weird imagined process that cannot exist in our universe, I can still program those equations into a computer and simulate it. For this reason, the results of a simulation can never take the place of an actual experiment.

What does this have to do with the notion of post-empirical stuff? Well, the problem lies in fundamental physics where it becomes progressively more difficult to perform experiments to learn about how things work. As a result, people are trying to motive that we start to learn about these things without having to do the experiments. That would have been great if it could work. Unfortunately, it has been tried before and found not to work. That was what the philosophers did before the advent of the scientific method. The nonsense they came up with still bounces around in the cultures of the world.

No! the day we cannot perform experiments to learn how this universe works is the day we stop learning more about our universe. A lot of people may go on coming up with stuff, but for sure, that stuff is worth nothing if it cannot be shown to work that way in our universe.

Unfortunately, there is already a lot of this going on, as this hyped wormhole nonsense demonstrates. It is related to several such non-scientific ideas that people work on and call physics, even though they don’t have much or any hope ever to show that it actually works that way through a scientific process.

The annoying thing is that there are prominent people in the physics community that are driving the hype. They’ve been doing this with other similar stories. Apparently, the reason for this hype is to induce funding agencies to give them more funding. Well, I think that if funding agencies can be led by their noses so easily, then the situation is more hopeless than I thought. These prominent people are not prominent for having done any solid scientific work. There are also other ways to become prominent. Well, I’ve ranted enough about people being prominent for the wrong reasons and don’t want to do it again.

Morality in a changing world

Current developments in the world makes one concerned about whether humanity or civilization will survive for much longer. If you are a person that is concerned about more than just yourself and those dear to you, then you would want to do something to improve the situation. (Perhaps you disagree that the current situation is anything to be concerned about. That is a debate for another day.)

An obvious aspect of the current situation that is threatening humanity is the way people behave. To improve matters, one would need to change people’s behavior. That begs the question: “what is considered good behavior?”, which brings in the notion of morality.

Sometimes one gets the impression that morality is consider to be an old out-of-date notion. However, if our survival depends on how people behave, then morality is definitely not an outdated notion. Nevertheless, morality itself changes with time and different cultures view it differently. So how can we argue that morality would have anything to do with the survival of humanity if it is so variable?

The purpose of this post is to explain that although it is variable in the ways stated above, morality has structure that ensures the survival of humanity. To support this explanation, I use a source which has dealt with morality authoritatively: the Bible. I realize that there are many people that do not consider the Bible as an authoritative source. For those people, I ask that you do not judge on the basis of the origin, but on the statements themselves, their intrinsic value and their implied consequences.

In the Bible, it is stated that the command to love your neighbor as yourself, represents the complete fulfillment of the law. In other words, this simple principle forms the foundation of all morality. So, although morality may vary from culture to culture, unless such moralities are founded on this principle, they are basically flawed.

That still leaves much that can change within the different moralities. Which one would be the correct one? That is the wrong question. A better way to pose a question would be to ask: how should we view the different moralities?

Here I want to use two more statements from the Bible: The one is “For with the measure¬†you use, it will be measured to you.” The other is “I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.” What is the common theme here? It means that moralities are based on how people define them. Each person should therefore live according to the morality within the context of that person’s culture. In other words, the morality that a person should adhere to is the morality as defined by the culture of that person.

The Bible does not say much about the concept of a culture and how we should view culture, at least not explicitly. But it does so by implication. If God created humanity, then obviously He also created culture and then one can conclude that culture was created with a definite purpose in mind. It is the mechanism that replaces the survival-of-the-fittest principle, valid for the animal kingdom, by the love-your-neighbor-as-you-love-yourself principle, which enables the development of a civilized humanity.

One last quote from the Bible: “Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. For truly I tell you, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished. Therefore anyone who sets aside one of the least of these commands and teaches others accordingly will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven. For I tell you that unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will certainly not enter the kingdom of heaven.”

These words can either be understood to refer to all the various commandments as explicitly stipulated in the various books of the Bible, including those in the Old Testament. Or it can be understood in the context of cultures as explained above. The most widely used understanding is probably the former, which leads to much animosity, because how can we still be expected to obey those old laws which were relevant in the context of those old cultures? However, in face of our current world and all the changes, I think it more valid to consider the latter understanding. It then states the importance of being obedient to every aspect of the morality of the culture within which you find yourself.

So, if we want to change the world to become a better world in which humanity or civilization has a better change to survive, let’s uphold the morality associated with the culture within which we find ourselves. Let’s communicate these moralities to everyone, especially to the next generation. Although moralities may change, we need to make sure that it never violates the principle of love: Love your neighbor as you love yourself.

Have a blessed Merry Christmas!