Man began to explore space before he entered orbit - through the creation of science fiction stories another 400
- Is it true that the Sun is small by stellar standards?
Not certainly in that way.There are red giant stars that are a thousand times larger than the Sun - for example, UY Shield, AH Scorpio and W Cepheus. But there are other examples as well. For example, the star 2MASS J0523-1403, discovered in 2003, is the size of Jupiter (but 70 times more massive). Its mass is 15 times less than the sun - this is the limit for stars, below which nuclear reactions simply do not ignite.
- How do stars turn into black holes?
This fate awaits stars with a mass greater than 8–10solar. From gravitational collapse (that is, "collapse into itself") they are kept by the energy of nuclear reactions. But sooner or later, the fuel runs out: such stars first burn hydrogen, then helium, then carbon - and so on until the core turns into iron. At this, nuclear reactions in it stop, and compression begins under the influence of gravity. Once the mass of the iron core reaches the so-called Chandrasekhar limit (about one and a half solar masses), nothing can resist the collapse of a star into a black hole.
- What is a gas giant - does this mean that the planet does not have a solid foundation and cannot be landed on?
We are talking about very large planets, consisting inmostly hydrogen and helium. There are two of them in our solar system: Jupiter and Saturn. Whether they have a solid surface is a very interesting question that scientists are trying to answer using the Juno spacecraft. It is currently in orbit around Jupiter.
When diving to Jupiter, you will first have to go throughthe outer layer of cold, dense clouds composed of ammonia and water. The lower the observer goes, the higher the pressure and temperature in the atmosphere. At some point, the hydrogen will condense to a liquid state and form a huge ocean. Even deeper, and hydrogen under enormous pressure begins to behave like a liquid metal.
The Juno data suggests that the core of the planet does not have clear boundaries, it seems to be dissolved. Perhaps this happened because billions of years ago, the giant collided with another planet.
Collision of proto-Jupiter with another planet.a) before the collision - a solid core is visible. b) the time of the collision, c) ten hours after the collision. Due to the collision and further mixing, Jupiter's core turned out to be extended and "diluted". Figure adapted from Liu et al. (2019)
- Is it possible to go through a black hole to another dimension?
We do not know.Einstein's equations allow that a black hole corresponds to a reverse white hole, which can lead to a parallel universe (the Rosen-Einstein bridge). But to get there, you need to move at a speed faster than light. White holes themselves can manifest themselves in our Universe in the form of bright flashes of radiation in the gamma range - and they want to find them from the Fermi space gamma-ray telescope. Theoretical physicist Lee Smolin suggested that white holes are the Big Bang for other universes.
Penrose diagram. Above is a black hole and below is a white hole. And on the sides are two universes: ours and a parallel
And physicists Oleg Lunin and Samir Mathur proposedsolution for a black hole, based on superstring theory. In superstring theory, all known particles are vibrations of energy strings in multidimensional spaces. In a black hole, these strings and spaces are intertwined, forming a single structure, similar to a ball of wool spit out by a “multidimensional cat” from hyperspace.
On the right is an "ordinary" black hole with a singularity andevent horizon, on the left - a black hole obtained from string theory, without an event horizon and without a singularity (fuzzball - woolen ball). Art by Olena Shmahalo/Quanta Magazine
- How did ancient people discover galaxies if they didn't have modern telescopes?
The eye is a sensitive instrument.We can perceive sources in the sky up to the sixth magnitude. By the way, this scale was introduced by the Roman astronomer Cladius Ptolemy. In his catalog, the first magnitude denoted the brightest stars, and the sixth denoted the dimmest. Therefore, we see the Andromeda Nebula, which has a magnitude of 3.44, without a telescope. By the way, this galaxy was first described by the Persian astronomer and mathematician Abdurrahman al-Sufi about a thousand years ago. He also discovered the Large Magellanic Cloud.
- Why do they say that time is the fourth dimension? How many dimensions are open?
Until the twentieth century, scientists believed that timespace and physical processes are independent of each other. But in 1905, Albert Einstein created the special theory of relativity, according to which time and space can stretch and contract. A little later, his teacher Herman Minkowski connected space and time into a common four-dimensional space-time continuum.
Based on these ideas, Einstein developed a generaltheory of relativity. He wrote an equation describing how mass and energy can affect space-time, bending it, and how the motion of matter changes under these conditions. It turned out that space and time are participants in physical processes, and not a stage for them. That is why scientists believe that time is the fourth dimension.
As for the extra dimensions, the theorystrings allow their existence at the micro level, and the associated idea of cosmology on the brane (derived from the word "membrane") - on the contrary, on the very large. Small extra dimensions are sought at the Large Hadron Collider, large ones - in space, using the LIGO and VIRGO gravitational antennas and the Fermi-LAT space gamma-ray telescope. So far to no avail.
- Is it true that the clock on the top of a high mountain runs differently than on the surface of the Earth?
Time delay occurs in two cases:when an object is moving at high speed relative to an external observer; near the source of gravity (massive planet, black hole). An example with a clock from the second category. The mountain is on the surface of the Earth, which has gravity, and time on the top of the mountain will flow faster relative to an observer at sea level. True, this effect is very small: 83 nanoseconds per day in the Everest experiment.
But GPS satellites fly at an altitude of about 20 thousand meters.km. There, the gravitational acceleration of time is more significant. Time flows 40 microseconds per day faster than on the surface of the planet, and this must be taken into account. In this sense, GPS satellites are an excellent laboratory for testing the effects of the theory of relativity.
- How can time and space be curved?
We know that time and space warpbut how they do it is a difficult question. To answer it, we need to consider the action of gravity at the quantum level, but there is no universal theory for this yet.
There are separate approaches like string theoryor loop quantum gravity. The latter represents space not as continuous, but as consisting of closed loops of the gravitational field. On large scales it looks like the usual space of general relativity, and on small scales it looks like it consists of pixels. Mass and energy placed in such a loop space affects it and thus distorts it.
- Is it true that the vacuum is not actually empty, and that particles themselves arise in it?
According to field theory and the uncertainty principleHeisenberg, for very short periods of time, the vacuum can be in such an energy state in which it is able to generate paired particles. Scientists call them virtual. They are somewhat different from ordinary ones, but at the same time they obey quantum conservation laws.
We cannot observe virtual particles, theyare born in pairs and quickly annihilate without affecting us in any way. However, this equilibrium can be disturbed in some cases, for example, in the presence of a strong gravitational field, as in a black hole. Stephen Hawking showed that black holes can not only absorb, but also emit particles (mostly photons), and therefore evaporate. Before that, it was believed that nothing, not even light, could “escape” from a black hole.
- What is the Big Bang? Why did it happen?
This is a theoretical model that describesthe emergence of the modern Universe from a very dense and very hot state. In a picosecond (a trillionth of a second), fundamental interactions appeared in it: first gravitational, and then electromagnetic, weak and strong. Then, at very high temperatures, the birth of particle-antiparticle pairs began, and after that they annihilated, the product of which is a photon (light).
Luckily for us, an asymmetry arose:for a billion proton-antiproton pairs, one proton turned out to be "extra". All stars, galaxies, planets and ourselves are made of this one billionth part. For the next hundreds of thousands of years, light and matter were "entangled" and the universe was very opaque. About 400,000 years after the Big Bang, it cooled and atoms began to form. There were no free electrons left, and the Universe became transparent to light. There was a powerful burst of radiation, which we now observe as relic radiation (cosmic microwave background).
Why the Universe began to expand from a very compressed state, we do not know (as well as what was before the Big Bang). Perhaps the reason was the quantum fluctuations of the vacuum.
- Why can't spaceships fly at the speed of light?
From the special theory of relativity follows:to accelerate a massive object to the speed of light, you need to expend an infinite amount of energy. Which, of course, is impossible. Only massless particles - such as the photon - can move at the speed of light.
In 1994, Mexican physicist Miguel Alcubierreproposed the idea of a warp drive (as in the cult science fiction series Star Trek). Instead of traveling at FTL, the spacecraft must compress space-time in front of it and expand it behind it, while still being in a bubble of flat space-time. True, there were several unresolved issues. To create such a bubble, exotic matter with negative mass is needed. The good news is that a recent paper has found solutions for superluminal warp bubbles with a positive energy density. But the problem remains how to disperse the bubble itself at least to the speed of light and where to get a lot of energy without creating a black hole.
2D rendering of the Alcubierre engine
- What substance is more in the universe?
According to the latest data obtained by the spacePlanck Observatory, our Universe consists of only 5% of ordinary or, as scientists say, baryonic matter, that is, stars, galaxies, gas, and you.
A more significant part - 26% - isdark matter. It was discovered by studying the rotation of galaxies and their clusters. Mass and gravity were not enough to explain their "behavior". Therefore, it was necessary to introduce the concept of dark matter, which manifests itself only through gravity and does not otherwise interact with ordinary matter. In fact, it is not known what dark matter is.
On the left is a map of gamma radiation with an energy of 1–3.16 GeV at the center of our galaxy. Known pulsars signed. If we remove all known sources of gamma radiation, as shown on the right, then there will be an excess of radiation, which can be explained by the annihilation of dark matter
Finally, the most mysterious substance thataccounting for 69% is dark energy, about which we know almost nothing. It manifests itself primarily through the expansion of the Universe. In addition, scientists have concluded that the density of the Universe is close to critical. However, matter (regular + dark) is only 30% of the critical density. Where is the rest? This could be the energy of space or vacuum itself, or an additional unknown force, which is commonly called dark energy.
- How likely is it that there are other intelligent beings in our galaxy?
There are many indications that our galaxymust be filled with life. First, according to the Kepler space telescope, there are about 40 billion Earth-like planets that orbit sun-like stars or red dwarfs, and are also in the habitable zone (favorable conditions for the origin of life).
Secondly, life on our planet originatedalmost immediately after the formation of the Earth and has existed for 4 billion years. As for intelligent beings, it is somewhat more complicated. On a galactic scale, man exists for a negligibly short time.
American astronomer Frank Drake compiledan equation for estimating the number of advanced civilizations in our galaxy, but it has many unknowns. Therefore, the solution for it varies greatly - from 20 pieces to 50 million! The latter is unlikely, because there is also the Fermi paradox, which literally sounds like this: why do we not observe traces of advanced civilizations - satellites, various radio signals, and so on? Perhaps the conditions on our planet and in the solar system are still unique (for example, we have a huge Jupiter, which protects the Earth from large meteorites and asteroids with its gravitational field). That is, life, perhaps, is not a rule for the Universe, but a big exception.
- What will happen to the Universe at the end of its existence?
Now the most likely scenario israpidly expanding universe. In about a trillion years, all galaxies will fly away beyond the visible Universe. In 100 trillion years, the last star, a red dwarf, will explode. Within 10 quantillion years, the galaxies will fall apart, and their remains will begin to fall into black holes. What will happen to intelligent life? This is a very long era, and a super advanced civilization may find a way to use black holes as energy sources.
Sooner or later, even black holes will evaporateHawking radiation account (according to various assumptions, within 1040-10106 years). Of course, everything can end much faster if the density of dark energy increases over time. In this case, at some point, say in 20–70 billion years, the expansion rate of the Universe will be so high that all matter will rupture at the subatomic level. This scenario is called the Big Rip.
And if you look even further into the unimaginable future, then one day quantum fluctuations may again lead to the birth of the universe.
These answers may lead to new questions −space exploration is endless. You can delve into the topic with the help of the interactive course "Space Printing" from "Uchi.ru". It is for those who want to master the skill of touch typing and save the Universe from aggressor robots along the way.
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