Reading Date: Dec 12, 2022 ~ Dec 18, 2022
Contradictions and Our Attempt to Combining Them
General relativity and quantum mechanics cannot both be right, at least in their current forms, because they contradict each other. In general relativity, every thing is smooth, continuous, and deterministic. In quantum mechanics, every thing happens in quantum leaps, it is discrete and unable to predict the actual outcome, only probabilities.
Loop Quantum Gravity and Planck Star
One of the principal attempts to solve the problem is loop quantum gravity. It uses hypotheses already contained with general relativity and quantum mechanics, with suitably rewritten to make them compatible. General relativity says that space which we are contained is something dynamic, and it can be twisted and stretched. Quantum mechanics says that every field is made of quanta, and it has a fine granular structure. Combining these two tells us that space is also made of quanta. This quanta of spaces are called loops, or rings, and they are linked to one another, forming a network of relations that weaves the texture of space.
If loop quantum gravity is correct, then inside black hole, matter cannot collapsed to an infinitesimal point, cause there is only finite chunk of space. It will only become increasingly dense, up to the point where quantum mechanics have exerted a contrary counterbalancing pressure. The hypothetical final stage will give a Planck star, where the quantum fluctuations of space-time balance the weight of matter. A Planck star is not stable. Once compress to the maximum, it rebounds and begins to expand again, which leads to an explosion of the black hole. This explosion happens really fast. But since there is an enormous difference in the passage of time in black hole and the observer outside of the black hole, it may take a long time to see it from outside.
Our universe which originate in big bang may have actually been a big bounce.
Probability to the Heat of Black Holes
Heat always moves from hot things to cold. Entropy, which is defined on top of this, or is defined through number of configurations that we cannot distinguish, is the only fundamental equation of physics that distinguishs the past from the future. So why does heat pass from things that are hotter to things that are colder? It is because heat passes from hot to cold has a larger probability than from cold to hot explained by Boltzmann. Though we cannot predict what these molecules actual states (e.g. their speed, their position), it is sufficient for us to calculate the probability and predict the outcomes of those variables that we interact.
Heat is linked to probability; and probability in turn is linked to the fact that our interactions with the rest of the world do not register the fine details of reality. The flow of time or heat passes from hot to cold emerges in the context of statistics and of thermodynamics.
The study of probability (statistical mechanics) and the study of heat (thermodynamics) were extended to electromagnetic and quantum phenomena. This extension includes the gravitational field, however, has proved problematic. What is a hot gravitational field? We don’t know how to describe the thermal vibrations of a hot space-time. What is a vibration of “time” and “space”?
Time sits at the center of the tangle of problems raised by the intersection of gravity, quantum mechanics, and thermodynamics. A small clue towards combining these three comes from a calculation completed by Stephen Hawking. Using quantum mechanics, he successfully demonstrated that black holes are always “hot”. They emit heat like stove. It’s the first concrete indication on the nature of “hot space”. The heat of black holes is a quantum effect upon the black hole, which is gravitational field in nature. It is the individual quanta of space, the vibrating elementary grains of space, that heat the surface of black holes and generate black hole heat. This phenomenon is in a combination of gravity, quantum mechanics, and thermodynamics.
Us
How we describe the universe is directly related to how we get information from the outer world. The information that one physical system has about another has nothing mental or subjective about it. This communication between ourselves and the world is not what distinguishes us from the rest of nature.
So what is the difference between the other things from my own sensing and knowing and knowing that I exist? How can continuous exchange of information in nature produce our thoughts? Some theories like Integrated Information Theory attempt to characterize quantitatively the structure that a system must have in order to be conscious. Does this mean something in us escape the regularity of nature and allow us to deviate from it through the power of our freedom to think? The author’s answer is no. The laws of nature acting in our brains determines our behavior, not by external factors. (They proved this through observation in lab. To me, this isn’t something that we can answer now, maybe we just don’t know how to do that yet.)
There is not an “I” and “the neurons in my brain”. They are the same thing.