Quantum world: Small scales, big questions - 1

Even though "quantum physics" sounds like a big deal, it is actually interested in the smallest things. When technology was not available or developed before 1900s, people either looked up to the sky or put objects under microscopes. This allowed general predictions about the nature. But more observations made more data available and it shaped the knowledge base when brought together with brilliant minds. You might want to check the first post about the universe and the second post about the gravity to be able to fully grasp this one. I will try to make this as interesting as i can by giving a brief history and explaining current situation with some interesting facts. Also you will find links inside this post if you start wondering about the subject and decide to dig deeper.

What is quantum?

The word is derived by quanta. Quanta basically means setting / determining certain levels for a range of data. Quantum is the word to describe the minimum level of data that contributes to a meaningful interaction. When you go deeper and deeoper in the nature, you come across with molecules and atoms. Then all the known physics rules change starting from that scale and things become really fuzzy. The scale we are talking about is around 10 to the minus 30. That is a zero and a comma followed by 30 zeros more :)

Why quantum physics?

If you have read the previous posts, you already know about the big scale and Einstein 's general relativity. But i have also mentioned that gravity is 1 of the 4 fundamental forces that we know and it is built on matter bending the fabric of the spacetime. Matter is consisted of atoms. So what happens when you go down the atoms? What are the rules there? Gravity basically breaks the consistency of the 4 forces because other forces can be explained with their own fields, which i will explain in another post. So our first concern is the size.

And the second concern is most of you probably know, the famous double slit experiment. It briefly says "where the heck did the particle go?" If you go down to small scales, particles start behaving differently. You can expect an atom to occupy some space or bend spacetime but the elements that create an atom (such as quarks, electrons, photons) are much different. They don't just obey the laws that we know, they have different and usually unusual properties. They are called quantum particles and most of the time people use the word particles for these sub-atomic particles. The double slit experiment proves that photons do not have to travel through one slit all the time. They act like they are waves passing through both of the slits at the same time. Therefore resulting a probability distribution that can be observed. The points on the screen is a result of the probability for the particle to hit that point.

What is observation?

I have said "can be observed" on purpose because the lighting on the screen can be observed by your eyes. But you may not know that if you directly observe the particles, they act like they are traveling through slits like usual balls that you throw. And that produces the expected double slit shaped bright area on the screen. So what is observation? What do they mean by observation? It looks like it is mere interaction to me. When the movement or direction of the particles affects some other participant, it means they are observed. This causes it to get a certain value (quantized value) instead of a probability value. Remember, sub-atomic particles are proven to be probabilistic instead of deterministic. But it is also proven that those particles can act like deterministic usual particles. This transition from probability to certainty is happening when you basically look at them. This is called "the wave function is collapsed to a certain value". Are they shy?

But there is one weird situation here too. We are humans and we have billions of atoms that come together to make us one human being. And we are the observers of these quantum experiments. Take the double slit experiment for example. Is the concept of observation really objective? Maybe it is biased? Is there a universal consciousness that can objectively observe a quantum state and cause it to become a certain quantized state? PBS digital studios have a video about it and they question whose observation is valid.

When did this start?

If it was too complicated, let me summarize it. Matter is consisted of atoms. We did not know there was a reality beneath it. We observed it and came across with troubles. Because our physics rules are built upon the deterministic features. But when you go sub-atomic, it is not deterministic. When did this happen? It was early 1900 years. Almost 1 century ago and it is still a trouble. It has accelerated with the industrial revolution and high tech equipments. As i have mentioned in the beginning, people thought about the universe or electromagnetism or gravity or atoms. But they can only guess or write papers about the deeper subjects like new particle models or new theories. When double slit experiment is conducted, it inevitably attracted curiosity from brilliant people. Until these days, there were numerous approaches to tackle this problem or to bring a new way of thinking to be able to analyze it. There are still candidate theories to explain this weird nature of nature and it will be in the next post. Let me tell you some of the people who took part in the developments of quantum mechanics.

Some people who played a role

This is roughly in chronological order. There were numerous scientists and thinkers who took place in the developments of quantum physics. I can only mention a couple of them here. You can take a look at the 5th Solvay Conference or find couple of them in the image below.

James Maxwell has proven that electricity and magentism are closely related and light is one form of electromagnetic radiation. This caused lots of confusion because it describes light as a wave. And that means it should be quantized. So Max Planck thought about this and formulated E = hv, where E is energy of photon, v is frequency and h is the Planck 's constant. That constant can be derived like in this video, but its importance is that it describes the smallest scale that a quantized value can increase or decrease. It is like a measurement unit.

And Werner Heisenberg formulated another aspect of particles. I have mentioned the photons going through slits and they change their behavior under observation. But Heisenberg adds that you can only know the position or the momentum of the particles for certain. There is no way to know both at the same time. The total probability makes up to 100 and if one of them is certain, the other one is completely unknown. This kind of explains the fuzzy logic under the quantum mechanics.

Erwin Schrödinger was mostly known by his thought experiment called Schrödinger 's cat. Remember the observation causing the wave to turn into a particle? He formulated this undeterministic nature with wave functions and explained it like this: If you put a cat into a box with 50% percent of radiation poisoning the cat is both alive and dead, until you open the box and observe what it is. Then it becomes 100% probability for one the quantized states. See it is all connected with fuzziness, quantization and observation.

This weird logic was not limited to behavior of particles. Turns out these naughty particles can turn into another particle by emitting or ejecting other particles with different properties. Yes this is very hard to understand. That is why Richard Feynman came up with his own diagrams. They are models to explain the metamorphosis of these strange particles and make it easier to work on these subjects.

Niels Bohr is another physicist who started somewhat away from quantum mechanics. He developed a model for atom with certain orbits or states for electrons around the nucleus. But it was hard to bring it together with electron 's undeterministic properties. The developments led Bohr to conclude the universe works with uncertain features. This was the rivalry between him and Einstein.

Einstein was working mostly on special relativity by following the path of Maxwell and he also formulated it. Because he was skeptical about the fuzzy world of quantum physics. This became the famous Bohr - Einstein debate. He tried to explain nature by certain events or states, whereas Bohr was trying to prove otherwise.

He states "Moon is there even i am not looking at it. God does not throw dice with universe." In the end, even though Einstein had hard time accepting quantum mechanics, he gave up the fight. And this debate created the interpretations of the quantum mechanics. It is the next subtitle.

But before that, of course these stories and the studies of these people are a lot deeper. There are lots of other scientists and these people lived most of their lives n the field of science. Some of these people directly or indirectly contributed to Manhattan project and the atom bomb. Some of them were involved with Hitler 's campaigns. That is a philosophical side of the technology. What did we gain by it, what did we cause with it.

Interpretations

Bohr says you can't know where the particle is. Heisenberg says you can't know momentum and the position at the same time. Schrödinger says the cat is both alive and dead. If you bring all these ideas together, you can create the most skeptic philosopher in the world :) Anyways, some people (including me) think there must be a fundamental consistent logic to explain the fuzzy looking properties and behaviors of the quantum world. They think our experiments and instruments are not enough to poke beyond it yet. That is why there are different interpretations of the quantum mechanics.

There is a really fun table here. According to this table, my interpretation is a mixture of "de Broglie–Bohm theory" and "many worlds interpretation" :) There are different aspects of these interpretations. For example, are they deterministic or do they include locality as a law or do they need hidden variable that does not exist in our knowledge and couple more questions. Even today, people are coming up with new interpretations but these are not hypotheses. They are different approaches to look at the problem and they have their own proposed experiments.

De Broglie–Bohm theory is one of the most widely accepted interpretations. Remember the double slit experiment. These people basically saying that there are already possible waves going through slits and particles are just following along it. Most of the nature can be explained with this mindset and there is no uncertainty when it comes to behaviors of particles. There is also Copenhagen Interpretation and it is almost the exact opposite of this approach. They say particles behave weirdly and you can never know for sure. The deterministic approach believes a higher level of order in place and the undeterministic approach believes particles are having their own initiative. One fun interpretation is many worlds interpretation. It states that every quantum observation causes you to jump to another branch of reality in many worlds that already exists. So yeah, there is a universe where you are the president but evidently you have chosen a different path :) I am on the team deterministic and i promise i will explain my idea of the whole universe some day here. But before that, you need to know the basics :) By the way, there is a concept of information in all this. Let's end this post with on the philosophical side of things.

It is about information, not actions

Maybe you have realized this. Before these quantum properties and experiments, the nature was mostly described with what it is doing. Apples are falling, planets are moving, light is traveling, objects are interacting and etc. Now we know it is obviously not about these actions. There are fundamental weirdnesses if you try to describe these actions. People are trying to explain the properties and trying to link them to actions. For example, matter bends spacetime and that is why there is gravity. If you apply this logic to quantum particles, you will realize they have fuzzy properties and those properties are known. Therefore they are the information that yields to actions and results. So the bottom line is, it is all about the information.

Quantum physics is trying to deal with the most elusive information in the nature. It shows us that if we understand the information and properly apply a model for it (what it is and where does it come from), we can also predict what action is it going to take. These days there are not many predictive theories to describe the universe. They are mostly descriptive. They usually describe what is happening, in other words, the action. But of course it is not an easy task. If you want to explain the state of the universe today, you have dead ends like black holes, the origin or the expansion of the universe or dark matter. This is why so many people are failing to come up with a properly working unified solution.

There is one unified approach. It is called String Theory. Briefly, it says the smallest packet of entity is a string and it creates the properties and they result in actions. The next post will have more technical details of quantum mechanics like particle models, entanglement, field theories and string theory. See you at the next post :)