8 biggest mysteries of physics that are still unsolved
Miscellaneous / / July 28, 2023
The main questions of life, the universe and everything else.
1. Why time only flows forward
In physics, there is the concept of "an arrow (or axis) of time." It describes the flow of time from the past to the future. And there is plenty of evidence that time favors a certain direction.
According to the second law of thermodynamics, in an isolated system, entropy (a measure of disorder) will increase with time. This meansthat processes in nature usually proceed in a direction where energy is distributed more evenly and the system becomes more disordered.
For example, when we break an egg, it does not regenerate by itself. You can't turn back time and do things the way they were. Entropy is merciless.
In addition, according to the general theory of relativity, over time, the Universe expands. Observations show that it has gone through a state of high density and low entropy in the past (this event we call the "Big Bang") and is moving towards a future state of high entropy.
In general, it is easy to see that time is irreversible and always moves in one direction. And scientists will never understand why this is so. And is it possible for time to flow backwards as well?
2. What is dark energy
The universe is expanding. She does it just like a balloon, only faster than the speed of light.
In the 1990s, astronomers discoveredthat the expansion of the universe only picks up speed over time, and does not slow down under the influence of gravity, as it should be in theory. This observation led to the suggestion that there is some form of energy that opposes gravity and contributes to the accelerated expansion of the universe.
Dark energy presumably fills the entire space-time structure of the Universe and is the main component of its energy content. But it cannot be directly observed or measured.
74% of our Universe is dark energy, 22% is dark matter, 3.6% is intergalactic gas, and another 0.4% is banal, uninteresting stars, planets and other small things.
Why the alignment is this way is not clear.
The very nature of dark energy is also remains a mystery to science. There are various theorieswho try to explain its origin, including the concepts of the quantum vacuum and the cosmological constant.
Meanwhile, dark energy is of great importance for understanding the fundamental properties of the Universe and its future fate. It depends on it whether the expansion of the Universe will continue indefinitely, slow down or even reverse in the future.
3. What is dark matter
Dark is a hypothetical form of matter that does not interact with electromagnetic radiation and therefore does not emit, absorb or reflect light. It cannot be detected with our ordinary instruments and instruments, which is why it is called so.
But there are many evidence the existence of dark matter in the universe. They are based on the gravitational influence it has on visible objects.
Dark matter, although invisible, affects the movement of stars, galaxies, and galaxy clusters.
Astronomical research showthat these objects move as if they were affected by additional mass, and this cannot be explained by the amount of matter that we observe. Therefore, dark matter holds galaxies and other giant structures together under the influence of its gravitational force.
In general, physicists will not understand what dark matter is, what particles it consists of, what its properties are, and whether it exists at all. Maybe the observed behavior of stars and galaxies is not related to any matter and it's just the oddities of gravity. Science hasn't figured it out yet.
4. Why are the fundamental constants the way they are?
Fundamental constants are numerical values that characterize the physical properties and interactions in the universe. They are basic and do not depend on specific systems of units.
Constants determine the basic properties and laws of nature, influencing the structure and development of the universe as a whole. All these numbers around 25. Among them:
- The speed of light in a vacuum (c) - determines the maximum speed at which information or interactions can propagate in the universe.
- Planck's constant (h), or quantum of action, - determines the relationship between the energy and frequency of particles and waves, conducting the boundary between the macrocosm, where the laws of Newtonian mechanics apply, and the microcosm, where the laws of quantum mechanics come into force. mechanics.
- Gravity constant (G) - determines the strength of the gravitational interaction between masses and affects the structure and movement of objects in the universe.
- Mass of an electron (mₑ).
- Elementary charge (e).
- Cosmological constant (Λ), which is also referred to as fundamental.
And scientists can’t understand why all these numbers have exactly the meanings they have, and not others.
Perhaps we can only observe meanings that are compatible with our existence, because life could only originate in such a universe. This is called the anthropic principle.
For example, the fine structure constant, which is usually denoted by the letter "alpha", defines strength of magnetic interactions. Its numerical value is approximately 0.007297. If the numbers were different, there might not be stable matter in our Universe.
And still, physicists puzzle over how the Universe with other physical parameters would change. Exist hypotheses, according to which the values of fundamental constants are random and determined by fluctuations in the early universe - just some set of numbers. This assumption implies that there are many Universes with different values of the constants. And we are just lucky to be in the one where these values are best suited for the development of life.
5. What's going on in black holes
Black holes These are areas of outer space with incredibly strong gravity. Beyond the black hole, the so-called event horizon, the gravitational pull is so strong that no matter, not even light, can escape.
At the very center of a black hole, physicists believe, there is a singularity - a point with infinite density and an infinitely strong gravitational field. But what it is, how it might look, and how exactly it works, no theory can explain.
Some scientists even supposethat the singularity may not be a point, but may have different shapes - this is true for rotating black holes. The so-called Kerr black hole, a hypothetical object described by mathematician and astrophysicist Roy Kerr, has an annular singularity. It will even be possible to fly through such a hole and survive. In theory.
But to accurately describe the physical processes inside the singularity, a unified theory is needed gravity and quantum mechanics, which has not yet been developed.
6. Why is there so little antimatter in the universe?
In ordinary matter, elementary particles, such as electrons and protons, have negative and positive charges, respectively. In antimatter, these charges are inverted: antielectrons (also called positrons) are positively charged, while antiprotons are negatively charged.
antimatter has the same physical properties as the ordinary one, including the mass, spin and other characteristics of the particles. But when an antiparticle meets a corresponding ordinary one, they can annihilate each other, turning into pure energy.
A liter of some kind of anti-hydrogen, when it comes into contact with air, will smell like an atomic bomb.
How good it is that the maximum amount of antihydrogen that they managed to synthesize scientists at a time - 309 atoms.
Astronomical observations showthat the universe and even the most distant stars and galaxies are made of matter, and there is very little antimatter in it. This difference between the number of baryons (particles made up of three quarks) and antibaryons (antiparticles made up of three antiquarks) in our universe is called baryon asymmetry.
If the Universe were completely symmetrical, then the number of baryons and antibaryons would have to be equal, and we would observe entire galaxies of antimatter. However, in reality, everything is made of baryons, and antibaryons have to be synthesized in particle accelerators not just by a teaspoon, but by an atom. Therefore, antimatter is the most expensive thing in the world.
According to the standard model of elementary particles, immediately after the Big Bang, there should have been an equal number of quarks and antiquarks in the universe. However, something happened, what exactly is not clear, but almost all antibaryons annihilated, and matter was formed from the remaining baryons. It is, in fact, what the universe consists of. And you, by the way, too. And scientists who still can't figure out why there's so little antimatter in space.
7. Is the vacuum stable?
Vacuum is space with the lowest possible energy, but contrary to its name, it is not completely empty. It still contains quantum fields that determine the behavior of elementary particles. Scientists believethat the true, or physical, vacuum that we know is the most stable state in the universe, as it is considered the global minimum of energy.
However, in theory there is a possibility that the state of the physical vacuum is a configuration of quantum fields, which is only a local, and not a global energy minimum. That is, the vacuum that we can observe in deep space or create in the laboratory is “false”. So, there can be "true".
And if a "true" vacuum exists, we're in big trouble.
If we assume that our Universe is in a state of not "true", but "false" vacuum, then the process of its decay to a more stable state becomes possible. The consequences of such a process can be the most terrifying and vary from subtle changes in cosmological parameters that depend on the potential difference between "false" and "true" vacuum, until the complete cessation of the functioning of elementary particles and fundamental forces.
If somewhere in space a bubble of "real" vacuum appears, this can lead to the complete destruction of baryonic matter or even an instantaneous gravitational collapse of the Universe.
In short, let's hope that our vacuum is the most reliable in the world. What else is left?
8. What will be the end of the universe
And since we are talking about such exciting global issues as the gravitational collapse of the Universe: physicists have compiled list the most interesting things that could happen to space in the future, but never decide which scenario is most likely.
According to the Big Bang theory, the universe arose about 13.8 billion years ago from a dense and hot state called a singularity, and since then everything has been growing and cooling. This theory explains well a number of observed phenomena, such as the cosmic background radiation and the expansion Universe. But what will happen next? Choose what you like best:
- heat death. Within this concept supposedthat over time the universe will become more and more cold and uniform. The energy in it will be exhausted, all processes, such as the formation of stars and thermal motion, will slow down and stop. This will lead to a state of maximum entropy, when all particles will be in a state of equilibrium and no further events in the Universe will be possible.
- big gap. Universe will continue expand. This means that galaxies and other space objects will increasingly move away from each other. If nothing changes, in the distant future, gravitational forces will no longer be strong enough to resist the pressure of dark energy. This will lead to the fact that at all levels of structure within the Universe, including galaxies, stars and atoms, there will be a force that exceeds their own force of attraction. As a result, all objects will be gradually broken into separate particles.
- Big squeeze. According to this scenario, the expansion of the universe, caused by the Big Bang, slow down and eventually reverses. The gravitational pull between galaxies, stars and planets will become the dominant force. The distance between them will continue to decrease until the Universe collapses back into a singularity, where the density and temperature become infinitely high. And there is not far from the new Big Bang.
But what kind of fate awaits space, is still unclear. Please wait a few more thousand septillion years.
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