Science fiction is a vivid confirmation that physics can be of interest not only to scientists, but also to people far from research laboratories. Of course, in the books and the film they do not talk about scientific theories, but rather they present physical facts in an entertaining and interesting way. In this review, a dozen mysteries from the field of physics that scientists have yet to explain.
1. Rays of ultrahigh energies
Earth's atmosphere is constantly bombarded by high-energy particles from space called "cosmic rays". While they don't do much harm to humans, physicists are simply fascinated by them. The observation of cosmic rays has taught scientists a lot about astrophysics and particle physics. But there are rays that remain a mystery to this day. In 1962, during the Volcano Ranch experiment, John D. Linsley and Livio Scarsi saw something incredible: an ultra-high energy cosmic ray with an energy of more than 16 joules.
To clearly explain how much this is, we can give the following example: one joule is the amount of energy required to lift an apple from the floor to the table. All this energy was concentrated, however, in a particle a hundred million billion times smaller than an apple. Physicists have no idea how these particles get such an incredible amount of energy.
2. Inflationary model of the Universe
The universe is remarkably uniform on large scales. The so-called "cosmological principle" states that wherever you go in the universe, on average, there will be approximately the same amount of material everywhere. But the Big Bang theory suggests that large differences in density must have been observed at the time the universe began. Thus, it was much less homogeneous than the universe is today.
The inflationary model suggests that the universe that everyone sees today comes from a tiny volume of the early universe. This small volume suddenly and rapidly expanded, much faster than the universe is expanding today. Roughly speaking, it looked like a balloon was suddenly inflated with air. While this explains why the universe is more homogeneous today, physicists still don't know what caused this "bloat".
3. Dark energy and dark matter
It's an amazing fact: only about 5 percent of the universe is made up of what humans can see. Decades ago, physicists noticed that stars at the outer edges of galaxies were orbiting the center of those galaxies faster than predicted. To explain this, scientists speculated that there might be some invisible "dark" matter in these galaxies that caused the stars to spin faster.
After the appearance of this theory, further observations of the expanding universe led physicists to conclude that there must be five times more dark matter than anything that people can see (i.e. ordinary matter). Along with this, scientists know that the expansion of the universe is indeed accelerating. This is strange, because one would expect that the gravitational attraction of matter ("ordinary" and "dark") would slow down the expansion of the Universe.
To explain what balances the gravitational attraction of matter, scientists have suggested the existence of "dark energy", which contributes to the expansion of the universe. Physicists believe that at least 70 percent of the universe is in the form of "dark energy." However, to this day, the particles that make up dark matter and the field that makes up dark energy have never been directly observed in the laboratory. In fact, scientists know nothing about 95 percent of the universe.
4. The heart of a black hole
Black holes are one of the most famous objects in astrophysics. They can be described as regions of space-time with such strong gravitational fields that even light cannot penetrate from within. Ever since Albert Einstein proved in his theory of general relativity that gravity "warps" space and time, scientists have known that light is not immune to gravitational effects.
In fact, Einstein's theory was proven during a solar eclipse, which demonstrated that the sun's gravity deflects light rays from distant stars. Since then, many black holes have been observed, including the huge one at the center of our galaxy. But the mystery of what happens at the heart of a black hole is still unsolved.
Some physicists believe that there may be a "singularity" - a point of infinite density with some mass concentrated in an infinitely small space. However, there are still discussions about whether information is lost inside black holes, which absorb all particles and radiation. Although Hawking radiation comes from black holes, it does not contain any additional information about what is happening inside the black hole.
5. Intelligent life outside the Earth
People have been dreaming about aliens for centuries when they look at the night sky and wonder if someone could live there. But in recent decades, a lot of evidence has been found that this is not just a dream. For starters, exoplanets are much more common than previously thought, with most stars having planetary systems. It is also known that the time gap between when life appeared on Earth and when intelligent life appeared is very small. Does this mean that life must have formed in many places.
If this is so, then we need to answer the famous "Fermi paradox": why people have not yet made contact with aliens. Perhaps life is common, but intelligent life is rare. Maybe after a while all civilizations decide not to communicate with other life forms. Maybe they just don't want to talk to people. Or, oddly enough, perhaps it shows that many alien civilizations destroy themselves shortly after they become technologically advanced enough to communicate.
6. Travel faster than the speed of light
Ever since Einstein changed all of physics with his special theory of relativity, physicists have been convinced that nothing can travel faster than the speed of light. In fact, the theory of relativity says that when any mass moves at a speed close to the speed of light, then this requires huge energy. This is seen in the ultra-high energy cosmic rays mentioned earlier. They have extraordinary energy relative to their size, but they don't travel faster than the speed of light either.
Hardly limiting the speed of light may also explain why communications from alien civilizations are unlikely. If they are also limited by this factor, then the signals can go on for thousands of years. In 2011, the OPERA experiment produced preliminary results suggesting that neutrinos travel faster than the speed of light.
Later, the researchers noticed some errors in their experimental setup, which confirmed that the results were incorrect. In any case, if there is any way to transfer matter or information faster than the speed of light, it will undoubtedly change the world.
7. Way to describe turbulence
If you return from space to Earth, it turns out that in everyday life there are many things that are difficult to understand. For the simplest example, you do not need to go far - you can open a tap at home. If you do not open it fully, then the water will flow smoothly (this is called "laminar flow"). But if you open the tap completely, then the water will begin to flow unevenly and splash. This is the simplest example of turbulence. In many ways, turbulence is still an unsolved problem in physics.
8. Room temperature superconductor
Superconductors are one of the most important devices and technologies that humans have ever discovered. This is a special type of material. When the temperature drops low enough, the electrical resistance of the material drops to zero. This means that it is possible to obtain a huge current after applying a small voltage to the superconductor.
Theoretically, electric current can flow in a superconducting wire for billions of years without dissipation because there is no resistance to its current. In modern ordinary wires and cables, a significant part of the power is lost due to resistance. Superconductors could reduce these losses to zero.
There is one problem - even high-temperature superconductors must be cooled to minus 140 degrees Celsius before they begin to show their remarkable properties. Cooling to such low temperatures usually requires liquid nitrogen or something similar. Therefore it is very expensive. Many physicists around the world are trying to create a superconductor that can operate at room temperature.
9. Matter and antimatter
In a sense, people still don't know why something exists at all. For every particle, there is an "opposite" particle, called the antiparticle. So for electrons there are positrons, for protons there are antiprotons, and so on. If a particle ever touches its antiparticle, they annihilate and turn into radiation.
Unsurprisingly, antimatter is incredibly rare, since everything would simply annihilate. Sometimes it comes across in cosmic rays. Also, scientists can make antimatter in particle accelerators, but it will cost trillions of dollars per gram. However, in general, antimatter is (according to scientists) incredibly rare in our Universe. Why this is so is a real mystery.
It's just that no one knows why our Universe is dominated by matter and not antimatter, because every known process that changes energy (radiation) into matter produces the same amount of matter and antimatter. Wilder's theory suggests that there could be entire regions of the universe dominated by antimatter.
10. Unified theory
In the 20th century, two great theories were developed that explained a lot in physics. One of them was quantum mechanics, which described in detail how tiny, subatomic particles behave and interact. Quantum mechanics and the standard model of particle physics have explained three of the four physical forces in nature: electromagnetism and the strong and weak nuclear forces.
The other big theory was Einstein's general theory of relativity, which explains gravity. In general relativity, gravity occurs when the presence of mass bends space and time, causing particles to follow certain curved paths. This could explain things that are happening on the grandest scale - the formation of galaxies and stars. There is only one problem. The two theories are incompatible.
Scientists cannot explain gravity in ways that make sense in quantum mechanics, and general relativity does not include the effects of quantum mechanics. As far as one can tell, both theories are correct. But they don't seem to work together. Physicists have long been working on some solution that can reconcile the two theories. It is called the Grand Unified Theory or simply The Theory of Everything. The search continues.
And in continuation of the topic, we have collected more.
Now the most interesting. The picture has become more complicated, but you should not be afraid. Everything is very simple. Let's put a translucent mirror in front of the detectors (3) and (4), like what we used at the beginning. Next, let's send the reflected photons to another translucent mirror (to the left of the source in the diagram). An "idle" photon with a probability of 50% passes through a semitransparent mirror and enters the detector (3) or (4) OR, with a probability of 50% it is reflected from the PS, hits the PS on the left and hits with a 50% probability into (5) or from 50 % at 6). If the "idle" photon hit the detector (3) or (4), we know that the original photon passed from above or below, respectively. On the contrary, if detector (5) or (6) fired, we do not know which path the photon took. I emphasize once again - when (3) or (4) is triggered, we have information on which path the photon went. When (5) or (6) is triggered, there is no such information. With this intricate scheme, we erase the information about which path the photon took.
Now the most stunning result - if you select on the screen those points that appeared when (3) or (4) were triggered - there is no interference, but if you select a subset of points that were obtained when (5) or (6) was triggered, then they form an interference pattern ! Consider this result for a moment: the photon doesn't care if we "touch" it or not during the experiment. With the help of down converters, we get potential information about where the photon went. If it is realized (detectors (3) or (4)) - the picture is destroyed, but if we carefully erase it (detectors (5) or (6) work), then we manage to persuade the photon to interfere. Interference is destroyed not by a mechanical intrusion into the experiment, but by the presence of information. Scientists claim that such experiments were carried out not only with photons, electrons, but also with whole molecules.
The laws of our world are very strange and sometimes counter-intuitive. On a macroscopic level, it may seem that more or less everything is clear. But as soon as we start dealing with elementary particles, our entire everyday experience collapses. And what awaits us on the Planck scale, even the most daring science fiction writers cannot imagine.
It is known that until the end of his life, Albert Einstein did not accept quantum mechanics with its uncertainty, stochastic, random and chaotic processes. This rejection was expressed in Einstein's phrases: "God does not play dice" and "Does the Moon exist only because a mouse looks at it?". Those. Einstein stood on a clear position of the determinism of physical, including quantum processes. Einstein simply believed that physicists had not yet discovered those constants that affect the behavior of quantum particles.
P.S.: This experiment was not at all mental, but quite real and was carried out, although it looked more intricate and more complicated than I described here.
Nobody in the world understands quantum mechanics - this is the main thing you need to know about it. Yes, many physicists have learned to use its laws and even predict phenomena using quantum calculations. But it is still unclear why the presence of an observer determines the fate of the system and forces it to make a choice in favor of one state. "Theories and Practices" selected examples of experiments, the outcome of which is inevitably influenced by the observer, and tried to figure out what quantum mechanics is going to do with such interference of consciousness in material reality.
Shroedinger `s cat
Today there are many interpretations of quantum mechanics, the most popular of which remains the Copenhagen one. Its main provisions were formulated in the 1920s by Niels Bohr and Werner Heisenberg. And the central term of the Copenhagen interpretation was the wave function - a mathematical function that contains information about all possible states of a quantum system in which it simultaneously resides.
According to the Copenhagen interpretation, only observation can accurately determine the state of the system, distinguish it from the rest (the wave function only helps to mathematically calculate the probability of detecting the system in a particular state). We can say that after observation, a quantum system becomes classical: it instantly ceases to coexist in many states at once in favor of one of them.
This approach has always had opponents (remember, for example, “God does not play dice” by Albert Einstein), but the accuracy of calculations and predictions took its toll. However, in recent years there have been fewer and fewer supporters of the Copenhagen interpretation, and not the least reason for this is the very mysterious instantaneous collapse of the wave function during measurement. Erwin Schrödinger's famous thought experiment with the poor cat was just designed to show the absurdity of this phenomenon.
So, we recall the content of the experiment. A live cat, an ampoule of poison and some mechanism that can set the poison into action at a random moment are placed in a black box. For example, one radioactive atom, the decay of which will break the ampoule. The exact time of the decay of the atom is unknown. Only the half-life is known: the time during which the decay will occur with a probability of 50%.
It turns out that for an external observer, the cat inside the box exists in two states at once: it is either alive, if everything goes well, or dead, if the decay has occurred and the ampoule has broken. Both of these states are described by the cat's wave function, which changes over time: the farther, the more likely it is that radioactive decay has already happened. But as soon as the box is opened, the wave function collapses and we immediately see the outcome of the flayer experiment.
It turns out that until the observer opens the box, the cat will forever balance on the border between life and death, and only the observer's action will determine his fate. This is the absurdity that Schrödinger pointed out.
Electron diffraction
According to a survey of leading physicists conducted by The New York Times, the experiment with electron diffraction, set in 1961 by Klaus Jenson, became one of the most beautiful in the history of science. What is its essence?
There is a source that emits a stream of electrons towards the screen-photographic plate. And there is an obstacle in the way of these electrons - a copper plate with two slits. What kind of picture on the screen can be expected if we represent electrons as just small charged balls? Two illuminated bands opposite the slits.
In reality, a much more complex pattern of alternating black and white stripes appears on the screen. The fact is that when passing through the slits, electrons begin to behave not like particles, but like waves (just like photons, particles of light, can simultaneously be waves). Then these waves interact in space, somewhere weakening, and somewhere strengthening each other, and as a result, a complex picture of alternating light and dark stripes appears on the screen.
In this case, the result of the experiment does not change, and if electrons are passed through the slit not in a continuous stream, but one by one, even one particle can simultaneously be a wave. Even one electron can pass through two slits at the same time (and this is another of the important provisions of the Copenhagen interpretation of quantum mechanics - objects can simultaneously display both their "usual" material properties and exotic wave properties).
But what about the observer? Despite the fact that with him the already complicated story became even more complicated. When, in such experiments, physicists tried to fix with the help of instruments through which slit the electron actually passes, the picture on the screen changed dramatically and became “classical”: two illuminated areas opposite the slits and no alternating stripes.
The electrons did not seem to want to show their wave nature under the gaze of the observer. Adjusted to his instinctive desire to see a simple and understandable picture. Mystic? There is a much simpler explanation: no observation of the system can be carried out without physical impact on it. But we will return to this a little later.
Heated fullerene
Experiments on particle diffraction were carried out not only on electrons, but also on much larger objects. For example, fullerenes are large, closed molecules composed of tens of carbon atoms (for example, a fullerene of sixty carbon atoms is very similar in shape to a soccer ball: a hollow sphere sewn from five- and hexagons).
Recently, a group at the University of Vienna, headed by Professor Zeilinger, has tried to introduce an element of observation into such experiments. To do this, they irradiated moving fullerene molecules with a laser beam. After that, heated by an external influence, the molecules began to glow and thus inevitably revealed their place in space for the observer.
Along with this innovation, the behavior of molecules has also changed. Before the start of total surveillance, fullerenes quite successfully went around obstacles (showed wave properties) like electrons from the previous example passing through an opaque screen. But later, with the advent of the observer, the fullerenes calmed down and began to behave like completely law-abiding particles of matter.
Cooling dimension
One of the most famous laws of the quantum world is the Heisenberg uncertainty principle: it is impossible to simultaneously determine the position and speed of a quantum object. The more accurately we measure the momentum of a particle, the less accurately we can measure its position. But the operation of quantum laws, operating at the level of tiny particles, is usually imperceptible in our world of large macro objects.
Therefore, the recent experiments of the group of Professor Schwab from the USA are all the more valuable, in which quantum effects were demonstrated not at the level of the same electrons or fullerene molecules (their characteristic diameter is about 1 nm), but on a slightly more tangible object - a tiny aluminum strip.
This strip was fixed on both sides so that its middle was in a suspended state and could vibrate under external influence. In addition, next to the strip was a device capable of recording its position with high accuracy.
As a result, the experimenters discovered two interesting effects. Firstly, any measurement of the position of the object, observation of the strip did not pass without a trace for it - after each measurement, the position of the strip changed. Roughly speaking, the experimenters determined the coordinates of the strip with great accuracy and thereby, according to the Heisenberg principle, changed its speed, and hence the subsequent position.
Secondly, which is already quite unexpected, some measurements also led to cooling of the strip. It turns out that the observer can only change the physical characteristics of objects by his presence. It sounds absolutely incredible, but to the credit of the physicists, let's say that they were not at a loss - now Professor Schwab's group is thinking how to apply the discovered effect to cooling electronic circuits.
Freezing particles
As you know, unstable radioactive particles decay in the world not only for the sake of experiments on cats, but also quite by themselves. Moreover, each particle is characterized by an average lifetime, which, it turns out, can increase under the gaze of an observer.
This quantum effect was first predicted back in the 1960s, and its brilliant experimental confirmation appeared in a paper published in 2006 by the group of Nobel laureate in physics Wolfgang Ketterle from the Massachusetts Institute of Technology.
In this work, we studied the decay of unstable excited rubidium atoms (decay into rubidium atoms in the ground state and photons). Immediately after the preparation of the system, the excitation of atoms began to be observed - they were illuminated by a laser beam. In this case, the observation was carried out in two modes: continuous (small light pulses are constantly fed into the system) and pulsed (the system is irradiated with more powerful pulses from time to time).
The results obtained are in excellent agreement with the theoretical predictions. External light effects really slow down the decay of particles, as if returning them to their original, far from decay state. In this case, the magnitude of the effect for the two studied regimes also coincides with the predictions. And the maximum life of unstable excited rubidium atoms was extended by 30 times.
Quantum mechanics and consciousness
Electrons and fullerenes cease to show their wave properties, aluminum plates cool down, and unstable particles freeze in their decay: under the omnipotent gaze of an observer, the world is changing. What is not evidence of the involvement of our mind in the work of the world around? So maybe Carl Jung and Wolfgang Pauli (Austrian physicist, Nobel laureate, one of the pioneers of quantum mechanics) were right when they said that the laws of physics and consciousness should be considered as complementary?
But so there is only one step left to the duty recognition: the whole world around is the essence of our mind. Creepy? (“Do you really think that the Moon exists only when you look at it?” Einstein commented on the principles of quantum mechanics). Then let's try again to turn to physicists. Moreover, in recent years they are less and less pleased with the Copenhagen interpretation of quantum mechanics with its mysterious collapse of a function wave, which is being replaced by another, quite mundane and reliable term - decoherence.
Here's the thing - in all the described experiments with observation, the experimenters inevitably influenced the system. It was illuminated with a laser, measuring instruments were installed. And this is a general, very important principle: you cannot observe a system, measure its properties without interacting with it. And where there is interaction, there is a change in properties. Especially when colossus of quantum objects interact with a tiny quantum system. So the eternal, Buddhist neutrality of the observer is impossible.
This is precisely what explains the term "decoherence" - an irreversible process from the point of view of violating the quantum properties of a system when it interacts with another, large system. During such an interaction, the quantum system loses its original features and becomes classical, "obeys" the large system. This explains the paradox with Schrödinger's cat: the cat is such a large system that it simply cannot be isolated from the world. The very setting of the thought experiment is not entirely correct.
In any case, compared to reality as an act of creation of consciousness, decoherence sounds much more calm. Maybe even too calm. After all, with this approach, the entire classical world becomes one big decoherence effect. And according to the authors of one of the most serious books in this field, statements like “there are no particles in the world” or “there is no time at a fundamental level” also logically follow from such approaches.
Creative observer or omnipotent decoherence? You have to choose between two evils. But remember - now scientists are becoming more and more convinced that the very notorious quantum effects underlie our thought processes. So where observation ends and reality begins - each of us has to choose.
3) And since this is a quantum theory, space-time can do all of this at the same time. It can simultaneously create an infant universe and not create it.
The fabric of space-time may not be a fabric at all, but may consist of discrete components that only seem to us to be a continuous fabric on large macroscopic scales.
4) In most approaches to quantum gravity, space-time is not fundamental, but is made up of something else. These can be strings, loops, qubits, or variants of space-time "atoms" that appear in condensed matter approaches. Separate components can be disassembled only with the use of the highest energies, far exceeding those available to us on Earth.
5) In some approaches with condensed matter, space-time has the properties of a solid or liquid body, that is, it can be elastic or viscous. If this is indeed the case, observable consequences are inevitable. Physicists are currently looking for traces of similar effects in traveling particles, that is, in light or electrons that reach us from deep space.
Schematic animation of a continuous beam of light scattered by a prism. In some approaches to quantum gravity, space can act as a dispersion medium for different wavelengths of light.
6) Space-time can affect how light passes through it. It may not be completely transparent, or light of different colors may travel at different speeds. If quantum space-time affects the propagation of light, this too could be observed in future experiments.
7) Fluctuations in space-time can destroy the ability of light from distant sources to create interference patterns. This effect was searched for and not found, at least in the visible range.
Light passing through two thick slits (top), two thin slits (center), or one thick slit (bottom) exhibits interference, indicating its wave nature. But in quantum gravity, some expected interference properties may not be possible.
8) In areas of strong curvature, time can turn into space. This can happen, for example, inside black holes or during the big bang. In this case, the space-time known to us with three spatial and dimensions and one time can turn into a four-dimensional "Euclidean" space.
Connecting two different places in space or time through a wormhole remains only a theoretical idea, but it can be not only interesting, but also inevitable in quantum gravity.
Space-time can be non-locally connected to tiny wormholes that permeate the entire universe. Such non-local connections must exist in all approaches whose underlying structure is not geometric, such as a graph or a network. This is due to the fact that in such cases the concept of "proximity" will not be fundamental, but implied and imperfect, so that remote areas can be randomly connected.
10) Perhaps in order to unify quantum theory with gravity, we need to update not gravity, but quantum theory itself. If so, the consequences will be far-reaching. Since quantum theory is at the heart of all electronic devices, its revision will open up entirely new possibilities.
Although quantum gravity is often viewed as a purely theoretical idea, there are many possibilities for experimental verification. We all travel through space-time every day. His understanding can change our lives.
The mysteries of quantum physics can also be attributed to the number of unknown artifacts of the modern structure of the world. The construction of a mechanical picture of the surrounding space cannot be completed, relying only on the traditional knowledge of the classical theory of physics. An addition to classical physical theory, views on the organization of the structure of physical reality, is strongly influenced by the theory of electromagnetic fields, first constructed by Maxwell. It can be argued that it was then that the stage of the quantum approach in modern physics was laid.
It was connected, a new stage in the formation of quantum theory, and, with the shocking scientific community, the research works of the famous experimental physicist - Max Planck. The main impetus to the development of quantum physics began and was marked by an attempt to solve a scientific problem, the study of electromagnetic waves.
The classical concept of the physical essence of a substance did not allow to justify the change in many properties other than mechanical ones. The investigated substance did not obey the classical laws of physics, this posed new problems for research and forced scientific research.
Planck departed from the classical interpretation of the scientific theory, which did not fully reflect the reality of the phenomena taking place, offering his own vision and hypothesized about the discreteness of the radiation of energy by the atoms of matter. This approach made it possible to resolve many of the stopping points of the classical theory of electromagnetism. The continuity of the processes underlying the representation of physical laws did not allow making calculations, not only with a compromise error, but sometimes did not reflect the essence of the phenomena.
Planck's quantum theory, according to which it is stated that atoms are capable of emitting electromagnetic energy only in separate portions, and not, as previously stated, about the continuity of the process, made it possible to shift the development of physics as a quantum theory of processes. The corpuscular theory stated that energy is constantly radiated, and this was the main contradiction.
However, the mysteries of quantum physics have remained unexplored to the very foundations. It's just that Planck's experiments made it possible to develop an idea of the complexity of the structure of the surrounding world and the organization of matter, but did not allow us to finally dot the "and". This fact of incompleteness makes it possible even now to continue working on the development of theoretical quantum research by scientists of our time.
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