10 Unsolved Problems of Modern Physics
Below we present a list of unsolved problems in modern physics.

Some of these problems are theoretical. This means that existing theories are unable to explain certain observed phenomena or experimental results.

Other problems are experimental, meaning that there are difficulties in creating an experiment to test a proposed theory or to study a phenomenon in more detail.

Some of these problems are closely interrelated. For example, extra dimensions or supersymmetry can solve the hierarchy problem. It is believed that the full theory of quantum gravity can answer most of these questions.

What will the end of the Universe be like?

The answer largely depends on dark energy, which remains an unknown member of the equation.

Dark energy is responsible for the accelerating expansion of the Universe, but its origin is a mystery. If dark energy is constant over time, we are likely to experience a “big freeze”: the Universe will continue to expand faster, and eventually galaxies will move so far apart that the current emptiness of space will seem like child's play.

If dark energy increases, the expansion will become so fast that the space not only between galaxies will increase, but also between stars, that is, the galaxies themselves will be torn apart; this option is called the "big gap".

Another scenario is that dark energy will decrease and can no longer counteract gravity, causing the Universe to collapse (the “big crunch”).

Well, the point is that, no matter how events unfold, we are doomed. Before that, however, there are still billions or even trillions of years — enough to figure out how the Universe will die.

Quantum gravity

Despite active research, the theory of quantum gravity has not yet been constructed. The main difficulty in its construction is that the two physical theories it attempts to link together—quantum mechanics and general relativity (GR)—rely on different sets of principles.

Thus, quantum mechanics is formulated as a theory that describes the temporal evolution of physical systems (for example, atoms or elementary particles) against the background of external space-time.

In general relativity there is no external space-time — it itself is a dynamic variable of the theory, depending on the characteristics of those in it classic systems

When moving to quantum gravity, at a minimum, it is necessary to replace the systems with quantum ones (that is, quantize). The emerging connection requires some kind of quantization of the geometry of space-time itself, and the physical meaning of such quantization is absolutely unclear and there is no successful, consistent attempt to carry it out.

Even an attempt to quantize the linearized classical theory of gravity (GTR) encounters numerous technical difficulties—quantum gravity turns out to be a non-renormalizable theory due to the fact that the gravitational constant is a dimensional quantity.

The situation is aggravated by the fact that direct experiments in the field of quantum gravity, due to the weakness of the gravitational interactions themselves, are inaccessible to modern technologies. In this regard, in the search for the correct formulation of quantum gravity, we have to rely only on theoretical calculations.

The Higgs boson makes absolutely no sense. Why does it exist?

The Higgs boson explains how all other particles acquire mass, but it also raises many new questions. For example, why does the Higgs boson interact with all particles differently? Thus, the t-quark interacts with it more strongly than the electron, which is why the mass of the first is much higher than that of the second.

In addition, the Higgs boson is the first elementary particle with zero spin.

“We have a completely new field of particle physics,” says scientist Richard Ruiz, “we have no idea what its nature is.”

Hawking radiation

Do black holes produce thermal radiation as theory predicts? Does this radiation contain information about their internal structure or not, as Hawking's original calculation suggests?

Why did it happen that the Universe consists of matter and not antimatter?

Antimatter is the same matter: it has exactly the same properties as the substance from which planets, stars, and galaxies are made.

The only difference is the charge. According to modern ideas, in the newborn Universe there was an equal amount of both. Shortly after the Big Bang, matter and antimatter annihilated (reacted to destroy each other and create other particles of each other).

The question is, how did it happen that some amount of matter still remained? Why did matter succeed and antimatter lose the tug-of-war?

To explain this inequality, scientists are diligently looking for examples of CP violation, that is, processes in which particles prefer to decay to form matter rather than antimatter.

“First of all, I would like to understand whether neutrino oscillations (the transformation of neutrinos into antineutrinos) differ between neutrinos and antineutrinos,” says Alicia Marino from the University of Colorado, who shared the question.  “Nothing like this has been observed before, but we look forward to the next generation of experiments.”

Theory of everything

Is there a theory that explains the values ​​of all fundamental physical constants? Is there a theory that explains why the laws of physics are the way they are?

Theory of everything   — a hypothetical unified physical and mathematical theory that describes all known fundamental interactions.

Initially, this term was used in an ironic way to refer to a variety of generalized theories. Over time, the term became established in popularizations of quantum physics to denote a theory that would unify all four fundamental forces in nature.

During the twentieth century, many "theories of everything" have been proposed, but none have been tested experimentally, or there are significant difficulties in establishing experimental testing for some of the candidates.

Bonus: Ball Lightning

What is the nature of this phenomenon? Is ball lightning an independent object or is it fed by energy from the outside? Are all ball lightnings of the same nature or are there different types?

Ball lightning is a luminous ball of fire floating in the air, a uniquely rare natural phenomenon.

To date, no unified physical theory of the occurrence and course of this phenomenon has been presented; there are also scientific theories that reduce the phenomenon to hallucinations.

There are about 400 theories that explain the phenomenon, but none of them have received absolute recognition in the academic environment. In laboratory conditions, similar but short-term phenomena were obtained in several different ways, so the question of the nature of ball lightning remains open. At the end of the 20th century, not a single experimental stand had been created in which this natural phenomenon would be artificially reproduced in accordance with the descriptions of eyewitnesses of ball lightning.

It is widely believed that ball lightning is a phenomenon of electrical origin, of natural nature, that is, it is a special type of lightning that exists for a long time and has the shape of a ball capable of moving along an unpredictable trajectory, sometimes surprising to eyewitnesses.

Traditionally, the reliability of many eyewitness accounts of ball lightning remains in doubt, including:

• the very fact of observing at least some phenomenon;
• the fact of observing ball lightning, and not some other phenomenon;
• individual details of the phenomenon given in an eyewitness account.

Doubts about the reliability of many evidence complicate the study of the phenomenon, and also create the ground for the appearance of various speculative and sensational materials allegedly related to this phenomenon.

Based on materials from: several dozen articles from

Will gravitational waves be detected?

Some observatories are busy searching for evidence of the existence of gravitational waves. If such waves can be found, these fluctuations in the space-time structure itself will indicate cataclysms occurring in the Universe, such as supernova explosions, collisions of black holes, and possibly still unknown events. For details, see W. Waite Gibbs's article "Spacetime Ripple."

What is the lifetime of a proton?

Some theories that do not fit the standard model (see Chapter 2) predict proton decay, and several detectors have been built to detect such decay. Although the decay itself has not yet been observed, the lower limit of the half-life of the proton is estimated at 10 32 years (significantly exceeding the age of the Universe). With the advent of more sensitive sensors, it may be possible to detect proton decay or the lower limit of its half-life will have to be pushed back.

Are superconductors possible at high temperatures?

Superconductivity occurs when the electrical resistance of a metal drops to zero. Under such conditions, the electric current established in the conductor flows without losses, which are characteristic of ordinary current when passing through conductors such as copper wire. The phenomenon of superconductivity was first observed at extremely low temperatures (just above absolute zero, - 273 °C). In 1986, scientists managed to make materials superconducting at the boiling point of liquid nitrogen (-196 °C), which already allowed the creation of industrial products. The mechanism of this phenomenon is not yet fully understood, but researchers are trying to achieve superconductivity at room temperature, which will reduce electricity losses.

How does the composition of a molecule determine its appearance?

Knowledge of the orbital structure of atoms in simple molecules makes it quite easy to determine the appearance of a molecule. However, theoretical studies of the appearance of complex molecules, especially biologically important ones, have not yet been carried out. One aspect of this problem is protein folding, discussed in Idea List 8.

What are the chemical processes in cancer?

Biological factors such as heredity and environment likely play a large role in the development of cancer. By understanding the chemical reactions that occur in cancer cells, it may be possible to create molecules to interrupt these reactions and make the cells more resistant to cancer.

How do molecules communicate in living cells?

For notification, molecules of the desired shape are used in cells, when the message is transmitted through “adjustment” in the form of complementarity. Protein molecules are the most important, so the way they are folded determines their appearance [conformation]. Therefore, a deeper knowledge of protein folding will help resolve the communication issue.

Where is cell aging determined at the molecular level?

Another biochemical problem of aging may be related to DNA and proteins involved in “repairing” DNA that is cut during repeated replication (see: List of Ideas, 9. Genetic Technologies).

How does an entire organism develop from one fertilized egg?

It seems that this question can be answered as soon as the main problem from Chap. 4: what is the structure and purpose of the proteome? Of course, each organism has its own characteristics in the structure of proteins and their purpose, but you will certainly be able to find a lot in common.

What causes mass extinctions?

Over the past 500 million years, complete extinction of species has occurred five times. Science continues to look for the reasons for this. The last extinction, which occurred 65 million years ago, at the turn of the Cretaceous and Tertiary periods, is associated with the disappearance of dinosaurs. As David Rop poses the question in his book Extinction: Was it genes or luck? (See: Sources for in-depth study), was the extinction of most organisms living at that time caused by genetic factors or some kind of cataclysm? According to the hypothesis put forward by father and son, Luis and Walter Alvarez, 65 million years ago a huge meteorite (about 10 km in diameter) fell to Earth. The impact he made raised huge clouds of dust, which interfered with photosynthesis, which led to the death of many plants, and therefore the animals that made up the same food chain, up to the huge but vulnerable dinosaurs. Confirmation of this hypothesis is a large meteorite crater discovered in the southern Gulf of Mexico in 1993. Is it possible that previous extinctions were the result of similar collisions? Research and debate continue.

Were dinosaurs warm-blooded or cold-blooded animals?

British anatomy professor Richard Owen coined the term "dinosaur" (meaning "terrible lizards") in 1841, when only three incomplete skeletons were found. British animal artist and sculptor Benjamin Waterhouse Hawkins began recreating the appearance of extinct animals. Since the first specimens found had iguana-like teeth, his stuffed animals resembled huge iguanas, causing quite a stir among visitors.

But lizards are cold-blooded reptiles, and therefore at first they decided that dinosaurs were like that. Several scientists then suggested that at least some dinosaurs were warm-blooded animals. There was no evidence until 2000, when a fossilized dinosaur heart was discovered in South Dakota. Having a four-chamber structure, this heart confirms the assumption that dinosaurs were warm-blooded, since the lizard heart has only three chambers. However, more evidence is needed to convince the rest of the world of this assumption.

What is the basis of human consciousness?

As a subject of study in the humanities, this issue goes far beyond the scope of this book, but many of our scientific colleagues are taking up its study.

As you might expect, there are several approaches to the interpretation of human consciousness. Proponents of reductionism argue that the brain is a huge collection of interacting molecules and that eventually we will unravel the rules of their operation (see the article by Crick and Koch “The Problem of Consciousness” [In the World of Science. 1992. No. 11–12]).

Another approach goes back to quantum mechanics. According to him, we are not able to comprehend the nonlinearity and unpredictability of the brain until we understand the connections between the atomic and macroscopic levels of the behavior of matter (see the book by Roger Penrose The New Mind of the King: On Computers, Thinking and the Laws of Physics [M., 2003]; and also Shadows of the Mind: In Search of the Science of Consciousness [M., 2003]).

According to the long-standing approach, the human mind has a mystical component that is inaccessible to scientific explanation, so that science cannot comprehend human consciousness at all.

In view of Stephen Wolfram's recent work on creating orderly images by repeatedly applying the same simple rules (see Chapter 5), it is not surprising that this approach is used in relation to human consciousness; This will give you another point of view.

What causes big changes in the Earth's climate like widespread warming and ice ages?

Ice ages, characteristic of the Earth for the last 35 million years, occurred approximately every 100 thousand years. Glaciers advance and retreat throughout the northern temperate zone, leaving memorials in the form of rivers, lakes and seas. 30 million years ago, when dinosaurs roamed the Earth, the climate was much warmer than today, so trees grew even near the North Pole. As already mentioned in Chap. 5, the temperature of the earth's surface depends on the equilibrium state of incoming and outgoing energies. Many factors influence this balance, including the energy emitted by the Sun, debris in space that the Earth navigates through, incoming radiation, changes in the Earth's orbit, atmospheric changes, and variations in the amount of energy the Earth emits (albedo).

This is the direction in which research is being conducted, especially given the recent controversy over the greenhouse effect. There are many theories, but there is still no true understanding of what is happening.

Is it possible to predict volcanic eruptions or earthquakes?

Some volcanic eruptions are predictable, such as the recent (1991) eruption of Mount Pinatubo in the Philippines, but others are inaccessible to modern means - still taking volcanologists by surprise (for example, the eruption of Mount St. Helens, Washington, on May 18, 1980). Many factors cause volcanic eruptions. There is no single theoretical approach that would be true for all volcanoes.

Earthquakes are even more difficult to predict than volcanic eruptions. Some well-known geologists even doubt the possibility of making a reliable forecast (see: List of Ideas, 13. Earthquake Prediction).

What happens in the earth's core?

The two lower shells of the Earth, the outer and inner core, are inaccessible to us due to their deep location and high pressure, which precludes direct measurements. Geologists obtain all information about the earth's cores based on observations of the surface and overall density, composition and magnetic properties, as well as studies using seismic waves. In addition, the study of iron meteorites helps because their formation process is similar to that on Earth. Recent results obtained from seismic waves have revealed different wave speeds in the north-south and east-west directions, indicating a layered solid inner core.

Are we alone in the Universe?

Despite the absence of any experimental evidence of the existence of extraterrestrial life, there are plenty of theories on this subject, as well as attempts to detect news from distant civilizations.

How do galaxies evolve?

As already mentioned in Chap. 6, Edwin Hubble classified all known galaxies according to their appearance. Despite the careful description of their current state, this approach does not allow us to understand the evolution of galaxies. Several theories have been put forward to explain the formation of spiral, elliptical and irregular galaxies. These theories are based on the physics of gas clouds that predate galaxies. Simulations on a supercomputer have made it possible to understand something, but have not yet led to a unified theory of galaxy formation. The creation of such a theory requires additional research.

Are planets similar to Earth common?

Mathematical models predict the existence of Earth-like planets ranging from a few to millions within the Milky Way. Powerful telescopes have discovered more than 70 planets outside our solar system, but most are the size of Jupiter or larger. As telescopes improve, it will be possible to find other planets, which will help determine which mathematical model best corresponds to reality.

What is the source of the Y-ray bursts?

Approximately once a day, the strongest γ-rays are observed, which are often more powerful than all others taken together (γ-rays are similar to visible light, but they have a much higher frequency and energy). The phenomenon was first recorded in the late 1960s, but was not reported until the 1970s because all the sensors were used to monitor compliance with the nuclear test ban.

At first, astronomers believed that the sources of these emissions were within the Milky Way. The high intensity of the radiation led to speculation about the proximity of its sources. But as data accumulated, it became obvious that these emissions were coming from everywhere, and were not concentrated in the plane of the Milky Way.

Detected in 1997 by the Hubble Space Telescope, the flare indicated that it came from the periphery of a faint galaxy several billion light years away. Since the source was located far from the center of the galaxy, it was unlikely to be a black hole. It is believed that these bursts of γ-ray radiation come from ordinary stars contained in the galactic disk, possibly due to the collision of neutron stars or other celestial bodies still unknown to us.

Why is Pluto so strikingly different from all other planets?

The four inner planets - Mercury, Venus, Earth and Mars - are relatively small, rocky and close to the Sun. The four outer planets - Jupiter, Saturn, Uranus and Neptune - are large, gaseous and distant from the Sun. Now about Pluto. Pluto is small (like the inner planets) and distant from the Sun (like the outer planets). In this sense, Pluto falls out of the general series. It orbits the Sun near a region called the Kuiper belt, which contains many bodies similar to Pluto (some astronomers call them Plutino).

Recently, several museums decided to deprive Pluto of its planetary status. Until more Kuiper Belt bodies can be mapped, the debate over Pluto's status will continue.

How old is the universe?

The age of the Universe can be estimated in several ways. One method estimates the age of chemical elements in the Milky Way from the radioactive decay of elements with known half-lives, based on the assumption that the elements are synthesized (inside supernovae of large stars) at a constant rate. Using this method, the age of the Universe is determined to be 14.5±3 billion years.

Another method involves estimating the age of star clusters based on certain assumptions about the behavior and removal of the clusters. The age of the most ancient clusters is estimated at 11.5 ± 1.3 billion years, and for the Universe - 11–14 billion.

The age of the Universe, determined by the rate of its expansion and the distance to the most distant objects, is 13–14 billion years. The recent discovery of the accelerated expansion of the Universe (see Chapter 6) makes this quantity more uncertain.

Another method has recently been developed. The Hubble Space Telescope, working at its limits, measured the temperatures of the oldest white dwarfs in the M4 globular cluster. (This method is similar to estimating the time elapsed after a fire burned out by the temperature of the ash.) It turned out that the age of the oldest white dwarfs is 12–13 billion years. Assuming that the first stars formed no earlier than 1 billion years after the Big Bang, the age of the Universe is 13–14 billion years, and the estimate serves as a check of indicators obtained by other methods.

In February 2003, data were obtained from the Wilkinson Microwave Anisotropy Probe (WMAP), which made it possible to most accurately calculate the age of the Universe: 13.7 ± 0.2 billion years.

Are there multiple universes?

In accordance with one possible solution discussed in Chap. 6 of the problem of the accelerated expansion of the Universe, we get a lot of universes inhabiting separate “branes” (multidimensional membranes). For all its speculativeness, this idea gives wide scope for all kinds of speculation. More information about multiple universes can be found in the book Our Cosmic Abode by Martin Rees.

When will the Earth have its next encounter with an asteroid?

Space debris constantly hits the Earth. And that’s why it’s so important to know what size celestial bodies fall on us and how often. Bodies with a diameter of 1 m enter the Earth's atmosphere several times a month. They often explode at high altitudes, releasing energy equivalent to the explosion of a small atomic bomb. About once a century a body 100 m in diameter flies to us, leaving behind a large memory (a noticeable impact). After the explosion of a similar celestial body in 1908 over the Siberian taiga, in the basin of the Podkamennaya Tunguska River [Krasnoyarsk Territory], trees were felled over an area of ​​about 2 thousand km 2.

An impact from a celestial body with a diameter of 1 km, occurring once every million years, could cause enormous destruction and even cause climate change. A collision with a celestial body 10 km across probably led to the extinction of dinosaurs at the turn of the Cretaceous and Tertiary eras 65 million years ago. Although a body this size might only appear once every 100 million years, Earth is already taking steps to avoid being caught off guard. The Near-Earth Objects (NEOs) and Near-Earth Asteroid Observations (NEAT) projects are being developed, according to which by 2010 it will be possible to track 90% of asteroids with a diameter of more than 1 km, the total number of which, according to various estimates, is within 500 -1000. Another program, Spacewatch, run by the University of Arizona, monitors the sky for possible Earth impact candidates.

For more detailed information, please visit the World Wide Web nodes: http://neat.jpl. nasa. gov, http://neo.jpl.nasa.gov and http://apacewatch.Ipl. arizona. edu/

What happened before the Big Bang?

Since time and space begin with the Big Bang, the concept of “before” has no meaning. This is equivalent to asking what is north of the North Pole. Or, as the American writer Gertrude Stein would put it, there is no “then” then. But such difficulties do not stop theorists. Perhaps before the “big bang” time was imaginary; there was probably nothing at all, and the Universe arose from a fluctuation of the vacuum; or there was a collision with another “brane” (see the question raised earlier about multiple universes). Such theories are difficult to find experimental confirmation, since the enormous temperature of the original fireball did not allow the creation of any atomic or subatomic formations that could exist before the expansion of the Universe.

Notes:

Occam's razor - the principle that everything should be sought for the simplest interpretation; Most often this principle is formulated as follows: “Unnecessarily one should not assert many things” (pluralitas non est ponenda sine necessitate) or: “What can be explained by means of less should not be expressed by means of more” (frustra fit per plura quod potest fieri per pauciora ). The formulation usually cited by historians, “Entities should not be multiplied without necessity” (entia non sunt multiplicandasine necessitate), is not found in Ockham’s writings (these are the words of Durand of Saint-Pourcin, c. 1270–1334, a French theologian and Dominican monk; a very similar expression appears for the first time found in the French Franciscan monk Odo Rigo, c. 1205–1275).

So-called topological tunnels. Other names for these hypothetical objects are the Einstein-Rosen (1909–1995), Podolsky (1896–1966) bridges, and the Schwarzschild neck (1873–1916). Tunnels can connect both separate, arbitrarily distant regions of space in our Universe, and regions with different moments of the beginning of its inflation. Currently, there is an ongoing discussion about the feasibility of tunnels, their permeability and evolution.

Kuiper Gerard Peter (1905–1973) – Dutch and American astronomer. The satellite of Uranus - Miranda (1948), the satellite of Neptune - Nereid (1949), carbon dioxide in the atmosphere of Mars, the atmosphere of Saturn's satellite Titan were discovered. Compiled several detailed atlases of photographs of the Moon. Identified many double stars and white dwarfs.

A satellite named in memory of the initiator of this experiment, astrophysicist David T. Wilkinson. Weight 840 kg. Byt was launched in June 2001 into a circumsolar orbit, to the Lagrange point L2 (1.5 million km from the Earth), where the gravitational forces of the Earth and the Sun are equal to each other and the conditions for precision observations of the entire sky are most favorable. From the Sun, Earth and Moon (the closest sources of thermal noise), the receiving equipment is protected by a large round screen, on the illuminated side of which solar panels are located. This orientation is maintained throughout the flight. Two receiving mirrors with an area of ​​1.4 x 1.6 m, placed back to back, scan the sky away from the orientation axis. As a result of the rotation of the station around its own axis, 30% of the celestial sphere is visible per day. WMAP's resolution is 30 times greater than that of the previous COBE (Cosmic Background Explorer) satellite, launched by NASA in 1989. The size of the measured cell in the sky is 0.2x0.2°, which immediately affected the accuracy of celestial maps. The sensitivity of the receiving equipment has also increased many times. For example, an array of COBE data obtained over 4 years is collected in just 10 days in the new experiment.

For several seconds, a dazzling bright fireball was observed moving across the sky from southeast to northwest. Along the path of the fireball, which was visible over a vast territory of Eastern Siberia (within a radius of up to 800 km), there was a powerful dust trail that persisted for several hours. After the light phenomena, an explosion was heard at a distance of over 1000 km. In many villages, shaking of the soil and buildings, similar to an earthquake, was felt, window glass was cracking, household utensils were falling from shelves, hanging objects were swinging, etc. Many people, as well as domestic animals, were knocked off their feet by the air wave. Seismographs in Irkutsk and in a number of places in Western Europe recorded a seismic wave. The air blast wave was recorded on barograms obtained at many Siberian weather stations, in St. Petersburg and a number of weather stations in Great Britain. These phenomena are most fully explained by the comet hypothesis, according to which they were caused by the invasion of the earth's atmosphere by a small comet moving at cosmic speed. According to modern ideas, comets consist of frozen water and various gases with admixtures of nickel iron and rocky substances. G.I. Petrov determined in 1975 that the “Tunguska body” was very loose and no more than 10 times the density of air at the surface of the Earth. It was a loose lump of snow with a radius of 300 m and a density of less than 0.01 g/cm. At an altitude of about 10 km, the body turned into a gas that dissipated into the atmosphere, which explains the unusually light nights in Western Siberia and Europe after this event. The shock wave that fell to the ground caused the forest to fall.

Gertrude Stein (1874–1946) - American writer, literary theorist!. Modernist. Formally, experimental prose (“The Making of Americans,” 1906–1908, published 1925) in the mainstream of literature! "stream of consciousness". Biographical book "The Autobiography of Alice B. Toklas" (1933). Stein owns the expression “lost generation” (in Russian: Stein G. Autobiography of Alice B. Toklas. St. Petersburg, 2000; Stein G. Autobiography of Alice B. Toklas. Picasso. Lectures in America. M., 2001).

A hint of the words there is no there, there from chapter 4! the 1936 novella (published 1937) “The Biography of Everyone,” a sequel to her famous novel “The Autobiography of Alice B. Toklas.”

ARTHUR WIGGINS, CHARLES WYNN

FIVE

UNSOLVED

PROBLEMS

SCIENCE

Drawings by Sidney Harris

WigginsA. , WinnH.

THE FIVE BIGGEST UNSOLVED PROBLEMS IN SCIENCE

ARTHUR W. WIGGINS CHARLES M. WYNN

With Cartoon Commentary by Sidney Harris

John Wiley & Sons, Inc.

The book talks about the biggest problems in astronomy, physics, chemistry, biology and geology that scientists are currently working on. The authors review the discoveries that led to these problems, introduce work to solve them, and discuss new theories, including string theory, chaos theory, the human genome, and protein folding.

Preface

We humans are huddled on a piece of rock called a “planet,” orbiting a nuclear reactor called a “star,” which is part of a huge collection of stars called a “Galaxy,” which in turn is part of the clusters of galaxies that make up the Universe. Our condition, which we call life, is inherent in many other organisms on this planet, but it seems that we alone have the tool of the mind to comprehend the Universe and everything that it has. We subsume our efforts to clarify the nature of the Universe under the concept of science. Such understanding is not easy, and the path to it is long. However, progress is evident.

This book will tell the reader about the largest unsolved problems of science that scientists are working on today. Despite the abundance of experimental data, they are not enough to confirm one or another hypothesis. We'll look at the events and discoveries that led to these problems, and then take you through how scientists at the forefront of science are trying to solve them today. Sidney Harris, America's premier scientific illustrator, enlivens our discussions with the humor inherent in his drawings, not only clarifying the ideas involved, but also highlighting them in a completely new way.

We also discuss here unsolved problems in the main branches of natural science, guided in our choice by the degree of their importance, difficulty, breadth of coverage and scale of consequences. Along with them, we included in the book a brief overview of some other problems in each of the affected branches of knowledge, as well as a “List of Ideas”, where the reader will find additional information about the background of some unresolved problems. Finally, we've included "Deeper Resources," which lists information resources to help you learn more about the subjects that interest you.

Special thanks to Kate Bradford, Senior Editor Wiley, the first to suggest such a book, and our literary agent Louise Ketz for her constant words of encouragement.

Chapter first

Vision of science

After all, it is common for an educated person to strive for accuracy for every kind [of objects] 1

to the extent permitted by the nature of the subject. It seems equally [absurd] to be content with the lengthy arguments of a mathematician and to demand rigorous proofs from a rhetorician.

Aristotle

Science ≠ technology

Aren't science and technology the same thing? No, they are different.

Although the technology that defines modern culture develops through science's understanding of the universe, technology and science are guided by different motives. Let's look at the main differences between science and technology. If science is caused by a person’s desire to know and understand the Universe, then technical innovations are caused by people’s desire to change the conditions of their existence in order to get food for themselves, help others, and often commit violence for personal gain.

People often engage in “pure” and applied science at the same time, but in science it is possible to conduct fundamental research without regard to the final result. British Prime Minister William Gladstone once remarked to Michael Faraday regarding his seminal discoveries linking electricity and magnetism: “It’s all very interesting, but what’s the use of it?” Faraday replied, “Sir, I don’t know, but one day you will benefit from it.” Almost half of the current wealth of developed countries has come from the connection between electricity and magnetism.

Before scientific advances become available to technology, additional considerations must be taken into account: what kind of device should be developed? possible, What acceptable build (a question essentially related to the field of ethics). Ethics belongs to a completely different area of ​​human mental activity: the humanities.

The main difference between science and the humanities is objectivity. Natural science strives to study the behavior of the Universe as objectively as possible, whereas the humanities have no such goal or requirement. To paraphrase the words of the 19th century Irish writer Margaret Wolfe Hungerford, we can say: “Beauty [and truth, and justice, and nobility, and...] is seen differently by everyone.”

Science is far from monolithic. Natural sciences are concerned with the study of both the environment and people themselves, since they are functionally similar to other forms of life. And the humanities study the rational (emotional) behavior of people and their attitudes, which they need for social, political and economic interaction. In Fig. 1.1 graphically presents these relationships.

No matter how much such a harmonious presentation contributes to the understanding of existing connections, reality always turns out to be much more complicated. Ethics helps determine what to investigate, what research methods and techniques to use, and what experiments are unacceptable because they pose a threat to human well-being. Political economy and political science also play a huge role, since science can only study what a culture tends to encourage as tools of production, labor, or whatever is politically acceptable.

How science works

The success of science in studying the Universe is made up of observations and ideas. This kind of exchange is called scientific method(Fig. 1.2).

During observations this or that phenomenon is perceived by the senses with or without instruments. If in natural science observations are made of many similar objects (for example, carbon atoms), then the human sciences deal with a smaller number of different subjects (for example, people, even identical twins).

After collecting data, our mind, trying to organize it, begins to build images or explanations. This is the work of human thought. This stage is called the stage putting forward a hypothesis. The construction of a general hypothesis based on the observations obtained is carried out through inductive inference, which contains a generalization and is therefore considered the most unreliable type of inference. And no matter how they try to artificially build conclusions, within the framework of the scientific method this kind of activity is limited, since at subsequent stages the hypothesis collides with reality.

Often a hypothesis is formulated in whole or in part in a language different from everyday speech, the language of mathematics. Acquiring mathematical skills requires a lot of effort, otherwise those who are ignorant of mathematics will need to translate mathematical concepts into everyday language when explaining scientific hypotheses. Unfortunately, the meaning of the hypothesis may suffer significantly.

Once constructed, a hypothesis can be used to predict certain events that should occur if the hypothesis is true. This prediction deduced from a hypothesis by deductive reasoning. For example, Newton's second law states that F = ta. If T equals 3 units of mass, and A - 5 units of acceleration, then F must equal 15 units of force. At this stage, mathematical calculations can be performed by computers operating on the basis of the deductive method.

The next stage is carrying out experience, to find out whether the prediction made in the previous step is confirmed. Some experiments are quite easy to carry out, but more often it is extremely difficult. Even after building complex and expensive scientific equipment to obtain highly valuable data, it can often be difficult to find the money and then the patience needed to process and make sense of the vast array of data. Natural science has the advantage of being able to isolate the subject matter being studied, whereas the human and social sciences have to deal with numerous variables depending on the different views (biases) of many people.

After completing the experiments, their results are checked against the prediction. Since the hypothesis is general, and the experimental data are particular, the result, when the experiment agrees with the prediction, does not prove the hypothesis, but only confirms it. However, if the outcome of the experiment does not agree with the prediction, a certain side of the hypothesis turns out to be false. This feature of the scientific method, called falsifiability (falsifiability), imposes a certain strict requirement on hypotheses. As Albert Einstein put it, “No amount of experimentation can prove a theory; but one experiment is enough to refute it.”

A hypothesis that turns out to be false must be revised in some way, that is, slightly changed, thoroughly reworked, or completely discarded. It can be extremely difficult to decide what changes are appropriate. The revised hypotheses will have to go through the same path again, and either they will survive or they will be abandoned in the course of further comparisons of prediction with experience.

The other side of the scientific method, which does not allow you to go astray, is playback Any observer with appropriate training and equipment should be able to repeat the experiments or predictions and obtain comparable results. In other words, science is characterized by constant double-checking. For example, a team of scientists from the National Laboratory named after. Lawrence University of California, Berkeley 2 attempted to produce a new chemical element by firing a powerful beam of krypton ions at a lead target and then studying the resulting substances. In 1999, scientists announced the synthesis of an element with atomic number 118.

The synthesis of a new element is always an important event. In this case, its synthesis could confirm the prevailing ideas about the stability of heavy elements. However, scientists from other laboratories of the Society for the Study of Heavy Ions (Darmstadt, Germany), the Large State Heavy Ion Accelerator of the University of Cayenne (France) and the Laboratory of Atomic Physics of the Riken Institute of Physics and Chemistry (Japan) were unable to repeat the synthesis of element 118. The expanded team of the Berkeley laboratory repeated the experiment, but he also failed to reproduce the previously obtained results. Berkeley rechecked the original experimental data using a program with a modified code and was unable to confirm the presence of element 118. They had to withdraw their application. This case shows that scientific search is endless.

Sometimes, along with experiments, hypotheses are also retested. In February 2001, Brookhaven National Laboratory in New York reported an experiment in which the magnetic moment of a muon (like the electron of a negatively charged particle, but much heavier) slightly exceeds the value predicted by the standard model of particle physics (for more on this model, see Chapter .2). And since the assumptions of the standard model about many other properties of particles were in very good agreement with experimental data, such a discrepancy regarding the magnitude of the muon’s magnetic moment destroyed the basis of the standard model.

The prediction of the muon's magnetic moment was the result of complex and lengthy calculations carried out independently by scientists in Japan and New York in 1995. In November 2001, these calculations were repeated by French physicists, who discovered an erroneous negative sign in one of the terms of the equation and posted their results on the Internet. As a result, the Brookhaven group rechecked its own calculations, admitted the error and published corrected results. As a result, it was possible to reduce the discrepancy between the prediction and experimental data. The Standard Model will once again have to withstand the tests that ongoing scientific research prepares for it.

Below is a list unsolved problems of modern physics. Some of these problems are theoretical. This means that existing theories are unable to explain certain observed phenomena or experimental results. Other problems are experimental, meaning that there are difficulties in creating an experiment to test a proposed theory or to study a phenomenon in more detail. The following problems are either fundamental theoretical problems or theoretical ideas for which there is no experimental evidence. Some of these problems are closely interrelated. For example, extra dimensions or supersymmetry can solve the hierarchy problem. It is believed that the complete theory of quantum gravity is capable of answering most of the questions listed above (except for the problem of the island of stability).

• 1. Quantum gravity. Can quantum mechanics and general relativity be combined into a single self-consistent theory (perhaps quantum field theory)? Is spacetime continuous or is it discrete? Will the self-consistent theory use a hypothetical graviton or will it be entirely a product of the discrete structure of spacetime (as in loop quantum gravity)? Are there deviations from the predictions of general relativity for very small or very large scales or other extreme circumstances that arise from the theory of quantum gravity?
• 2. Black holes, disappearance of information in a black hole, Hawking radiation. Do black holes produce thermal radiation as theory predicts? Does this radiation contain information about their internal structure, as suggested by gravity-gauge invariance duality, or not, as suggested by Hawking's original calculation? If not, and black holes can continuously evaporate, then what happens to the information stored in them (quantum mechanics does not provide for the destruction of information)? Or will the radiation stop at some point when there is little left of the black hole? Is there any other way to study their internal structure, if such a structure even exists? Is the law of conservation of baryon charge true inside a black hole? The proof of the principle of cosmic censorship, as well as the exact formulation of the conditions under which it is fulfilled, is unknown. There is no complete and complete theory of the magnetosphere of black holes. The exact formula for calculating the number of different states of a system, the collapse of which leads to the emergence of a black hole with a given mass, angular momentum and charge, is unknown. There is no known proof in the general case of the “no hair theorem” for a black hole.
• 3. Dimension of space-time. Are there additional dimensions of space-time in nature besides the four we know? If yes, what is their number? Is the “3+1” (or higher) dimension an a priori property of the Universe or is it the result of other physical processes, as suggested, for example, by the theory of causal dynamic triangulation? Can we experimentally “observe” higher spatial dimensions? Is the holographic principle true, according to which the physics of our “3+1”-dimensional space-time is equivalent to the physics on a hypersurface with a “2+1” dimension?
• 4. Inflationary model of the Universe. Is the theory of cosmic inflation true, and if so, what are the details of this stage? What is the hypothetical inflaton field responsible for rising inflation? If inflation occurred at one point, is this the beginning of a self-sustaining process due to the inflation of quantum mechanical oscillations, which will continue in a completely different place, remote from this point?
• 5. Multiverse. Are there physical reasons for the existence of other universes that are fundamentally unobservable? For example: are there quantum mechanical “alternate histories” or “many worlds”? Are there “other” universes with physical laws that result from alternative ways of breaking the apparent symmetry of physical forces at high energies, located perhaps incredibly far away due to cosmic inflation? Could other universes influence ours, causing, for example, anomalies in the temperature distribution of the cosmic microwave background radiation? Is it justified to use the anthropic principle to solve global cosmological dilemmas?
• 6. The principle of cosmic censorship and the hypothesis of chronology protection. Can singularities not hidden behind the event horizon, known as "naked singularities", arise from realistic initial conditions, or can some version of Roger Penrose's "cosmic censorship hypothesis" be proven that suggests this is impossible? Recently, facts have appeared in favor of the inconsistency of the cosmic censorship hypothesis, which means that naked singularities should occur much more often than just as extremal solutions of the Kerr-Newman equations, however, conclusive evidence of this has not yet been presented. Likewise, there will be closed timelike curves that arise in some solutions of the equations of general relativity (and which imply the possibility of backward time travel) excluded by the theory of quantum gravity, which unifies general relativity with quantum mechanics, as suggested by Stephen's "chronology protection conjecture" Hawking?
• 7. Time axis. What can phenomena that differ from each other by moving forward and backward in time tell us about the nature of time? How is time different from space? Why are CP violations observed only in some weak interactions and nowhere else? Are violations of CP invariance a consequence of the second law of thermodynamics, or are they a separate axis of time? Are there exceptions to the principle of causation? Is the past the only possible one? Is the present moment physically different from the past and future, or is it simply a result of the characteristics of consciousness? How did humans learn to negotiate what is the present moment? (See also below Entropy (time axis)).
• 8. Locality. Are there non-local phenomena in quantum physics? If they exist, do they have limitations in the transfer of information, or: can energy and matter also move along a non-local path? Under what conditions are nonlocal phenomena observed? What does the presence or absence of nonlocal phenomena entail for the fundamental structure of space-time? How does this relate to quantum entanglement? How can this be interpreted from the standpoint of a correct interpretation of the fundamental nature of quantum physics?
• 9. The future of the Universe. Is the Universe heading towards a Big Freeze, a Big Rip, a Big Crunch or a Big Bounce? Is our Universe part of an endlessly repeating cyclic pattern?
• 10. The problem of hierarchy. Why is gravity such a weak force? It becomes large only on the Planck scale, for particles with energies of the order of 10 19 GeV, which is much higher than the electroweak scale (in low energy physics the dominant energy is 100 GeV). Why are these scales so different from each other? What prevents electroweak-scale quantities, such as the mass of the Higgs boson, from receiving quantum corrections on scales on the order of the Planck scale? Is supersymmetry, extra dimensions, or just anthropic fine-tuning the solution to this problem?
• 11. Magnetic monopole. Did particles - carriers of "magnetic charge" - exist in any past eras with higher energies? If so, are there any available today? (Paul Dirac showed that the presence of certain types of magnetic monopoles could explain charge quantization.)
• 12. Proton decay and the Grand Unification. How can we unify the three different quantum mechanical fundamental interactions of quantum field theory? Why is the lightest baryon, which is a proton, absolutely stable? If the proton is unstable, then what is its half-life?
• 13. Supersymmetry. Is supersymmetry of space realized in nature? If so, what is the mechanism for breaking supersymmetry? Does supersymmetry stabilize the electroweak scale, preventing high quantum corrections? Does dark matter consist of light supersymmetric particles?
• 14. Generations of matter. Are there more than three generations of quarks and leptons? Is the number of generations related to the dimension of space? Why do generations exist at all? Is there a theory that could explain the presence of mass in some quarks and leptons in individual generations based on first principles (Yukawa interaction theory)?
• 15. Fundamental symmetry and neutrinos. What is the nature of neutrinos, what is their mass and how did they shape the evolution of the Universe? Why is there now more matter being discovered in the Universe than antimatter? What invisible forces were present at the dawn of the Universe, but disappeared from view as the Universe evolved?
• 16. Quantum field theory. Are the principles of relativistic local quantum field theory compatible with the existence of a nontrivial scattering matrix?
• 17. Massless particles. Why do massless particles without spin not exist in nature?
• 18. Quantum chromodynamics. What are the phase states of strongly interacting matter and what role do they play in space? What is the internal structure of nucleons? What properties of strongly interacting matter does QCD predict? What controls the transition of quarks and gluons into pi-mesons and nucleons? What is the role of gluons and gluon interaction in nucleons and nuclei? What defines the key features of QCD and what is their relationship to the nature of gravity and spacetime?
• 19. Atomic nucleus and nuclear astrophysics. What is the nature of nuclear forces that binds protons and neutrons into stable nuclei and rare isotopes? What is the reason why simple particles combine into complex nuclei? What is the nature of neutron stars and dense nuclear matter? What is the origin of elements in space? What are the nuclear reactions that move stars and cause them to explode?
• 20. Island of stability. What is the heaviest stable or metastable nucleus that can exist?
• 21. Quantum mechanics and the correspondence principle (sometimes called quantum chaos). Are there preferred interpretations of quantum mechanics? How does the quantum description of reality, which includes elements such as quantum superposition of states and wave function collapse or quantum decoherence, lead to the reality we see? The same thing can be formulated using the measurement problem: what is the “measurement” that causes the wave function to collapse into a certain state?
• 22. Physical information. Are there physical phenomena, such as black holes or wave function collapse, that permanently destroy information about their previous states?
• 23. The Theory of Everything (“Grand Unified Theories”). Is there a theory that explains the values ​​of all fundamental physical constants? Is there a theory that explains why the gauge invariance of the standard model is the way it is, why observable spacetime has 3+1 dimensions, and why the laws of physics are the way they are? Do “fundamental physical constants” change over time? Are any particles in the standard model of particle physics actually made up of other particles bound together so tightly that they cannot be observed at current experimental energies? Are there fundamental particles that have not yet been observed, and if so, what are they and what are their properties? Are there unobservable fundamental forces that the theory suggests that explain other unsolved problems in physics?
• 24. Gauge invariance. Are there really non-Abelian gauge theories with a gap in the mass spectrum?
• 25. CP symmetry. Why is CP symmetry not preserved? Why is it preserved in most observed processes?
• 26. Physics of semiconductors. Quantum theory of semiconductors cannot accurately calculate a single constant of a semiconductor.
• 27. The quantum physics. The exact solution of the Schrödinger equation for multielectron atoms is unknown.
• 28. When solving the problem of scattering two beams on one obstacle, the scattering cross section turns out to be infinitely large.
• 29. Feynmanium: What will happen to a chemical element whose atomic number is higher than 137, as a result of which the 1s 1 electron will have to move at a speed exceeding the speed of light (according to the Bohr model of the atom)? Is Feynmanium the last chemical element capable of physically existing? The problem may appear around element 137, where the expansion of nuclear charge distribution reaches its final point. See the article Extended Periodic Table of the Elements and the Relativistic effects section.
• 30. Statistical physics. There is no systematic theory of irreversible processes that makes it possible to carry out quantitative calculations for any given physical process.
• 31. Quantum electrodynamics. Are there gravitational effects caused by zero-point oscillations of the electromagnetic field? It is not known how to simultaneously satisfy the conditions of finiteness of the result, relativistic invariance and the sum of all alternative probabilities equal to unity when calculating quantum electrodynamics in the high-frequency region.
• 32. Biophysics. There is no quantitative theory for the kinetics of conformational relaxation of protein macromolecules and their complexes. There is no complete theory of electron transfer in biological structures.
• 33. Superconductivity. It is impossible to theoretically predict, knowing the structure and composition of a substance, whether it will go into a superconducting state with decreasing temperature.

• Translation

Our Standard Model of elementary particles and interactions has recently become as complete as could be desired. Every single elementary particle - in all its possible forms - was created in the laboratory, measured, and properties were determined for all of them. The longest-lasting ones, the top quark, the antiquark, the tau neutrino and antineutrino, and finally the Higgs boson, fell victim to our capabilities.

And the latter - the Higgs boson - also solved an old problem in physics: finally, we can demonstrate where elementary particles get their mass from!

This is all cool, but science doesn’t end when you finish solving this riddle. On the contrary, it raises important questions, and one of them is “what next?” Regarding the Standard Model, we can say that we don’t know everything yet. And for most physicists, one question is especially important - to describe it, let's first consider the following property of the Standard Model.

On the one hand, the weak, electromagnetic and strong forces can be very important, depending on their energies and the distances at which the interaction occurs. But this is not the case with gravity.

We can take any two elementary particles - of any mass and subject to any interactions - and find that gravity is 40 orders of magnitude weaker than any other force in the Universe. This means that the force of gravity is 10 40 times weaker than the three remaining forces. For example, although they are not fundamental, if you take two protons and separate them by a meter, the electromagnetic repulsion between them will be 10 40 times stronger than the gravitational attraction. Or, in other words, we need to increase the force of gravity by a factor of 10,000,000,000,000,000,000,000,000,000,000,000,000,000 to equal any other force.

In this case, you cannot simply increase the mass of a proton by 10 20 times so that gravity pulls them together, overcoming the electromagnetic force.

Instead, in order for reactions like the one illustrated above to occur spontaneously when the protons overcome their electromagnetic repulsion, you need to bring together 10 56 protons. Only by coming together and succumbing to the force of gravity can they overcome electromagnetism. It turns out that 10 56 protons constitute the minimum possible mass of a star.

This is a description of how the Universe works - but we don't know why it works the way it does. Why is gravity so much weaker than other interactions? Why is "gravitational charge" (i.e. mass) so much weaker than electrical or color, or even weak?

This is the problem of hierarchy, and it is, for many reasons, the greatest unsolved problem in physics. We don’t know the answer, but we can’t say that we are completely ignorant. In theory, we have some good ideas for finding a solution, and a tool to find evidence of their correctness.

So far, the Large Hadron Collider—the highest-energy collider—has reached unprecedented energy levels in the laboratory, collected reams of data, and reconstructed what happened at the collision points. This includes the creation of new, hitherto unseen particles (such as the Higgs boson), and the appearance of old, well-known particles of the Standard Model (quarks, leptons, gauge bosons). It is also capable, if they exist, of producing any other particles not included in the Standard Model.

There are four possible ways that I know of—that is, four good ideas—to solve the hierarchy problem. The good news is that if nature chose one of them, the LHC will find it! (And if not, the search will continue).

Apart from the Higgs boson, found several years ago, no new fundamental particles have been found at the LHC. (Moreover, no intriguing new particle candidates are observed at all). And yet, the found particle fully corresponded to the description of the Standard Model; no statistically significant hints of new physics were seen. Not to composite Higgs bosons, not to multiple Higgs particles, not to non-standard decays, nothing like that.

But now we've started getting data from even higher energies, twice the previous ones, up to 13-14 TeV, to find something else. And what are the possible and reasonable solutions to the problem of hierarchy in this vein?

1) Supersymmetry, or SUSY. Supersymmetry is a special symmetry that can cause the normal masses of any particles large enough for gravity to be comparable to other influences to cancel each other out with a high degree of precision. This symmetry also suggests that each particle in the standard model has a superparticle partner, and that there are five Higgs particles and their five superpartners. If such a symmetry exists, it must be broken, or the superpartners would have the same masses as ordinary particles and would have been found long ago.

If SUSY exists at a scale suitable for solving the hierarchy problem, then the LHC, reaching energies of 14 TeV, should find at least one superpartner, as well as a second Higgs particle. Otherwise, the existence of very heavy superpartners will itself lead to another hierarchy problem that will not have a good solution. (Interestingly, the absence of SUSY particles at all energies would disprove string theory, since supersymmetry is a necessary condition for string theories containing the standard model of elementary particles).

Here is the first possible solution to the hierarchy problem, which currently has no evidence.

It is possible to create tiny super-cooled brackets filled with piezoelectric crystals (which produce electricity when deformed), with distances between them. This technology allows us to impose 5-10 micron limits on “large” measurements. In other words, gravity works according to the predictions of general relativity on scales much smaller than a millimeter. So if there are large extra dimensions, they are at energy levels inaccessible to the LHC and, more importantly, do not solve the hierarchy problem.

Of course, for the hierarchy problem there may be a completely different solution that cannot be found on modern colliders, or there is no solution at all; it just might be a property of nature without any explanation for it. But science won't advance without trying, and that's what these ideas and quests are trying to do: push our knowledge of the universe forward. And, as always, with the start of the second run of the LHC, I look forward to seeing what might appear there, besides the already discovered Higgs boson!

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• gravity
• fundamental interactions
• tank