Physics Is No Longer To Explain The World, Rather Predict Its Future
ITMO University has become one of the sites for film screenings of the Contemporary Science Film Festival, which is traditionally held in several Russian cities in late autumn. ITMO has run the film "Into The Universe with Stephen Hawking. Lucky Imperfection", which tells about the physical aspects of time travel. Alexandr Chirtsov, Professor of Physics at ITMO, provided his commentary on the film. ITMO.NEWS interviewed Professor Chirtsov and got to know why classical physics gives only one of the possible approximate interpretations of the world, why the world does not always completely follow the formulated laws of physics and why theoretical physicists are constantly trying to come up with the right equations, providing the right solutions, while experimental physicists are looking for ways to refute them.
Myths and misconceptions common for popular science formats
It was mentioned in the film that it is impossible to move at a speed greater than the speed of light. However, it’s possible. For example, the X-rays and Gamma radiation of a sufficiently large frequency propagate in matter at phase speed which is higher than the speed of light in vacuum. However, it turns out that transmitting a message at such speed is impossible. The film also stipulated that our world is four-dimensional. But one must be more careful when making such assumptions. After all, the often mentioned picture of the world, traditionally called the four-dimensional spacetime is rather a graphic geometric picture illustrating non-trivial mathematical relations implied by the basic ideas of relativism.
It is quite handy, in the sense that it is easier for a person to perceive or remember even the very unusual images rather than remember some cumbersome formulas and equations. This is why this elegant four-dimensional space-time description was invented. But, in fact, one could add a lot more to this picture, for example, color. And if we move, then some colors will change because of the Doppler effect.
Moreover, even in classical (nonrelativistic) physics, the position of such a conventional object as our hands requires to be sketched with vectors of at least 82 components. It means, it is essentially described by an 82-dimensional vector. Therefore, we can assume that the space of our habitat has a number of dimensions substantially greater than three or four. It all depends on what task we are going to solve.
What about the unspoken statements in the popular science format, which need to be explained, but never really are?
So many statements on topics related to physics, the content of which sounded more like quasi-physics, were presented in the film. Any substantial information about the world around us that is not backed up by any convincing data or reference to the results of an experiment, I personally perceive as a fairy tale. And I advise it to all viewers: to question what they see. It can be either exciting or boring, depending on how it is featured in the film.
But even if in a popular science format fairy tales can be acceptable, I would like to, at least, get to know the context of this fairy tale and its concept. For example, it was mentioned that at the level of quanta there are certain "wormholes", in which jumps in time can occur. Maybe it was worded differently, but it’s not the point. What is this theory? Where did it come from? But not a word was said on that. Is it some development of the general relativity theory, or is it some kind of synthesis of STR or GTR with quantum mechanics? I’ll give you another example from the film: the spaceship (which, of course, exists only in fantasy), which is able to accelerate in 80 years to a speed that provides a noticeable slowdown of time inside of it.
Contemporary Science Film Festival at ITMO
I immediately got a question: what fuel will such a spaceship use? Since we don’t know which fuel it will use, it is impossible to calculate the acceleration time it will take to get close to the speed of light. If we are talking about regular rocket fuel, then in order to achieve the required speed, the mass of fuel this spaceship has to emit will be several times greater than the mass of the galaxy.
About the film "Into The Universe with Stephen Hawking. Lucky Imperfection" in general
I did not discover any new physics in this film. All the physics used in this film I studied back at school. This is a very alarming, if not unfortunate fact. As for the black holes located in the center of our galaxy, temporary "wormholes", then I, not being a cosmologist, science fiction writer or fantasy author, would've preferred to not make such bold statements. The fact is, we can’t conduct a physical experiment and test all the cosmic theories, even if they were proved mathematically.
For instance, why did Hawking confidently say in his film that there is a huge black hole in the center of our galaxy? Has anyone ever been there or can at least report any reliable observations? This is just a hypothesis, but they did not mention it. All the concepts describing space are just some of the possible interpretations of what is really happening out there. After all, once upon a time, people thought that the Earth was flat, and there were many "scientific" disputes on this topic: people discussed how many whales or how many turtles it stands on, etc.
Poster of the film "Into The Universe with Stephen Hawking. Lucky Imperfection". Source: kinoafisha.info
On the purpose of physics
The purpose of physics is not to explain the world anymore, but rather to predict its future. Physicists do not explain what is happening, but predict what will happen if you do certain things, or what you need to do to get to a certain point. The question is whether we believe in the equations by which we describe our reality. And all the visual images that we “adjust” to these equations are used in particular cases because it is more convenient for us to do so. For instance, you can say that you see me as a biological body, and I will say that I see you as secondary electromagnetic fields emitted by your body's atoms.
On the persistent mistake some theorists-mathematicians do
A very characteristic mistake of some theorists-mathematicians, as well as physicists, is the following: they believe that nature obeys the equations that they’ve created. Allegedly, the pen is falling down because there is the law of universal gravitation. No, the pen is falling down because this is how our world works, and Isaac Newton created the law of universal gravitation to describe this phenomenon. That is, he just described, using the language of mathematics, how this pen is falling, he namely created a formula for this.
But what if tomorrow I drop this pen and it starts to fly? Then we will have to cancel all Newtonian mechanics because the nature does not obey these laws anymore. For example, back in the 19th century, astronomers noticed that the orbit of Mercury's motion around the Sun precesses, that is, shifts. Basically, it violated the Newtonian mechanics. Einstein found the way out of it and described it in his General Theory of Relativity. According to his equations, Mercury should move just like this. But, probably, Einstein also adjusted his theory to the features of the motion of this planet.
Contemporary Science Film Festival at ITMO
On physical equations
Physicists have a belief that equations should be simple and symmetrical. They find their equations by chance and adjust them to reality. The equation is most likely correct if it is symmetric (a type of the algebraic equation - Ed.). For example, when Maxwell mathematically described the laws of electromagnetism, his formulas contradicted with the charge conservation law. It turned out that there was an infinite number of ways to correct the equations. Maxwell was right to have chosen the simplest method - symmetric equations. Later on, based on the laws he discovered, the radio was predicted and invented.
On the problems of the interpretation of physical phenomena
For example, classical physics can not answer a question like where does the force of radiation friction come from. This is the force which affects the electron due to its own electromagnetic radiation. Also, classical electrodynamics can not answer questions about where the electron mass comes from and what size an electron is. To do this, physicists tried to introduce such a concept as a point charge. However, if this concept was correct, then the energy and mass of the electron would be infinite.
Richard Feynman. Source: rebublic.ru
Let an electron be a "ball", but then it would be negatively charged from both sides. Accordingly, it would burst from the inside, and in order to prevent it, it would take such a powerful force that we simply do not know of. But all of these problems are well described and solved byquantum electrodynamics created by Richard Feynman. He came up with a new mathematical language, crafted specifically to solve the problems of quantum mechanics. However, we still do not know exactly how to interpret the shape and the size of an electron.
What do we do then? Physicists found a way out of this situation and it’s the following: let's agree that the mass of an electron will not be infinite, but equal to one. This is called renormalization. And then all the equations work! But the same renormalization does not work for strong nuclear interactions. Having said that, we mean that the General Relativity Theory and quantum mechanics do not correlate. The theorists are constantly on the lookout for this most universal theory of everything. It is for this purpose that particles are dispersed in the Large Hadron Collider: the scientists are trying to understand how the Universe actually works.
The “standard set” of terms every popular science aficionado needs to know
Therefore, I believe that it is necessary to use various affirmative expressions very cautiously in popular science lectures and films, especially when it comes to theories and mathematical hypotheses that have not been proven experimentally yet. In addition to that, popular science lectures should be conducted by professionals who have deep knowledge in their respective fields. This means an astrophysicist should provide commentary on a film about astrophysics. Otherwise, the listeners or viewers will not be able to develop a critical understanding of what they have heard or seen.
Contemporary Science Film Festival at ITMO
So, I often notice that at popular science lectures listeners, without really understanding the topic, ask questions, using some "standard set" of popular concepts like: black hole, event horizon, relativistic radiation, relativity theory, standard model, spin and so on, not always understanding the meaning of the terms they use. I’m not sure that there is much sense in such a popular science format. But it would be nice if at least 20% of the viewers would come home and read some scientific papers, and for starters - good physics textbooks on the topics covered in this colorful film. Despite my grumbling, there were, of course, many positive moments in it.
For example, there was an interesting and curious fact that I learned from the film: corrections are constantly introduced to the time readings of the chronometers installed on JPS-navigation satellites. It is necessary because time on the orbit and on earth passes with slightly different speeds. An interesting and informative technical fact pointing to the close connection of modern high-tech with seemingly purely abstract fundamental conclusions of physics!