Why is there more matter than antimatter?
In the modern understanding of practical physics, matter and antimatter are identical, but opposite. When they meet, they must destroy each other and leave nothing behind. And most of such mutual destruction has already happened in the nascent universe.
Nevertheless, enough matter remained in it to create billions and billions of galaxies, stars, planets and much more. This is due to mesons, composite (non-elementary) particles with a short half-life, consisting of quarks and antiquarks. B-mesons decay more slowly than anti-B-mesons, thanks to which enough B-mesons survive to create all the matter in the universe. In addition, B-, D- and K-mesons can vibrate and become antiparticles and vice versa constituent particles.
Research has shown that mesons are more likely to assume a normal state, although this may simply be because there are more normal particles than antiparticles.
Where is all the lithium?
Earlier, when the temperature in the universe was amazingly high, isotopes of hydrogen, helium and lithium were formed in abundance.
Hydrogen and helium are still incredibly abundant and make up most of the mass of the Universe, but the number of lithium-7 isotopes that we can now observe is only a third of the past. There are many different explanations for why this happened - including hypotheses involving hypothetical bosons known as axions. Others believe that lithium has been absorbed by the cores of stars, which our telescopes and instruments cannot detect. In any case, there is now no adequate explanation for where all the lithium went from the universe.
Why are we sleeping?
Although we know that the processes occurring in the human body are regulated by the biological clock that makes us awake and sleep, we do not know why this happens. Sleep is the time when our body regenerates tissues and performs other regeneration processes. And we spend about a third of our lives sleeping.
Some other organisms don't need sleep at all, so why do we need it? There are several different versions of why this is happening, but none of them is a complete answer to the question. According to one theory, those animals that sleep have managed to develop the ability to hide from predators, while others need to be constantly alert, and therefore they regenerate and rest without sleep. Much sleep research now focuses on why sleep is important and how it affects mental performance.
What is gravity?
Many people know that lunar gravity causes the ebb and flow, Earth's gravity keeps us on the surface of our planet, solar gravity forces the Earth itself to be held in orbit. But how can this phenomenon be explained?
This powerful force is created by matter, and larger objects can attract smaller objects. While scientists figure out how the force of gravity works, they are not even sure if it exists at all. Is gravity a consequence of the existence of gravity particles? Why is there so much empty space in atoms - that is, why are the nucleus and the electrons at a fairly large distance from each other? Why is the force holding atoms together different from the force of gravity? We cannot answer these questions at the present level of development of science.
"Well, where are they then?"
The observable Universe reaches 92 billion light years in diameter. It is filled with billions of galaxies with stars and planets, and Earth is now considered the only apparently inhabited planet. Statistically, the chance that our planet is the only one in the Universe where there is life is extremely small. Then why the hell hasn't anyone contacted us yet?
This is called the Fermi paradox (after the Italian physicist Enrico Fermi, the creator of the world's first nuclear reactor). Dozens of explanations have been proposed as to why we are still unfamiliar with extraterrestrial life, and some of them even seem to be true. So, we can talk for days about various missed signals, that aliens are already among us, and we do not know, or that they cannot contact us. Well, or there is a sadder option - the Earth is really the only inhabited planet.
What is dark matter made of?
About 80% of the mass of the entire Universe is dark matter. This is such a specific thing that does not emit light at all. Although the first theories about dark matter appeared about 60 years ago, there is still no direct evidence of its existence.
Some scientists believe that dark matter consists of hypothetical weakly interacting massive particles - WIMPs, (WIMPs, Weakly Interacting Massive Particle), which, in fact, can be 100 times heavier than protons, but do not interact with baryonic matter, under which our detectors are sharpened ... Others believe that dark matter contains particles such as axion, neutralino and photino.
How did life come about?
Where does life come from on Earth? How did this happen? Proponents of the "primordial soup" theory believe that the fertile earth itself formed more and more complex molecules, in which the first life appeared. These processes took place on the ocean floor, in volcanic craters, as well as in the soil and under ice. Other theories attach great importance to light and volcanic activity.
In addition, DNA is now considered the dominant basis of life on Earth, but it is also assumed that RNA may have been one of the first major forms of life. Another unresolved scientific question - are there any other nucleic acids besides RNA and DNA? Did life arise only once, or did it once begin, then was destroyed and then reappeared? Some believe in panspermia - according to this theory, microorganisms (embryos of life) were brought to Earth by meteorites and comets. Even if this is true, then where the life came from at the very source of panspermia is unknown.
How do tectonic plates work?
This may come as a surprise to you, but the theory of plate tectonics, moving continents and causing earthquakes, volcanic eruptions and even forming mountains, became widely known not so long ago (in the second half of the twentieth century). Although it has already been hypothesized that there was only one continent instead of six, fifteen hundred years ago, there was little support for this theory in the 1960s. Then the theory of spreading of the seabed prevailed.
According to this theory, the huge ridges dividing the earth's crust beneath each ocean mark the boundaries between tectonic plates gradually moving in opposite directions. As the plates move, molten mass from the mantle rises, filling a rift in the earth's crust, and then the seabed slowly moves towards the continent. But this theory was soon rejected.
In any case, scientists are still not sure what is causing these shifts or how the tectonic plates were created. There are many theories, but none of them fully reflects all aspects of this movement.
How do animals migrate?
Many animals and insects migrate throughout the year, trying to avoid seasonal changes in temperature and the disappearance of vital food resources or in search of neighbors.
Some migrate thousands of kilometers, so how do they find their way back a year later? Different animals use different navigation methods. For example, some are able to sense the earth's magnetic field and have a kind of internal compass. Either way, scientists still don't understand how these abilities develop and why animals know exactly where to go year after year.
What is dark energy?
Of all the scientific mysteries, dark energy is perhaps the most mysterious. While dark matter makes up roughly 80% of the mass of the universe, dark energy is a hypothetical form of energy that scientists believe makes up 70% of the entire contents of the universe. Dark energy is one of the reasons for the expansion of the Universe, although a large number of mysteries are associated with it, which have never been solved. First and foremost, what does dark energy actually consist of? Is it constant or are there some fluctuations in it? Why is the density of dark energy comparable to the density of ordinary matter? Is it possible to reconcile the data on dark energy with Einstein's theory of gravity, or should this theory be revised?