The Hubble constant is a constant used to describe the expansion of the Universe. It establishes a connection between the distance of a space object and the speed of its removal. has been getting bigger and bigger since it began expanding since the Big Bang 13.82 billion years ago. The universe is constantly expanding, and this expansion is constantly accelerating.
According to NASA, scientists are not only interested in the expansion itself and its acceleration, but also in the consequences of this process. If the expansion suddenly starts to slow down, it would mean that there is something in the Universe that is slowing its growth - perhaps it is hypothetical dark matter that cannot be detected by modern instruments. If the expansion of the Universe continues to accelerate, it is possible that dark matter is responsible for this phenomenon. In general, scientists do not yet understand the mechanism that causes space to change its volume. But dark matter is undoubtedly to blame for everything (since it has not been detected, which means everything incomprehensible in space can be attributed to it).
As of January 2018, measurements from several telescopes showed that the rate at which the universe is expanding varies depending on where you look. The part of the Universe closest to us (explored using the Hubble and Gaia orbital telescopes) has an expansion rate of about 73.5 kilometers per second per megaparsec. While the more distant Universe (measured by the Planck Space Telescope) is expanding slightly more slowly, at a rate of about 67 km per second per megaparsec. A megaparsec is a distance of one million parsecs, or about 3.3 million light years, so it's an incredibly fast speed.
Hubble discovery
The constant was first proposed by an American astronomer. He studied galaxies, and was especially interested in those that are farthest from Earth.
In 1929, based on data obtained by an astronomer that galaxies appeared to be moving away from the Milky Way, Hubble discovered that the further these galaxies are from Earth, the faster they are moving.
At that time, scientists decided that this phenomenon was just galaxies flying away from each other. However, today astronomers know that the entire universe is actually expanding. No matter where you are in space, you will observe the same phenomenon occurring at the same speed.
Hubble's original calculations were refined over the years as increasingly sensitive telescopes were used to make measurements, including Hubble and Gaia, whose data refined the value of the constant based on measurements of the cosmic microwave background - the constant temperature background of the Universe, sometimes even called the "afterglow" of the Big Bang.
Cepheids - beacons of the Universe
There are many types of variable stars, but the ones that are most useful for refining the value of the Hubble constant are called Cepheids. These are stars that regularly change their brightness over a specific interval, which usually ranges from 1 to 100 days (the North Star is among the most famous members of this group). measure the distance to these stars, measuring the variability of their luminosity.
The brighter a Cepheid appears, the easier it is to measure its distance. Some Cepheids can be seen from Earth, but for more accurate measurements it is best done in space.
Edwin Hubble was able to measure distances to Cepheids up to 900,000 light-years from Earth—an astonishing value at the time—in a space that was still relatively close to Earth. Further in space, the Cepheids become weaker and less and less visible. Only the launch of the Hubble Space Telescope was able to change the situation in the 1990s. In 2013, the Gaia space telescope appeared, which managed to accurately determine the positions and luminosity of about 1. His data also helped refine the value of the Hubble constant.
However, Cepheids are not ideal for measuring cosmic distances. They are often located in dusty areas (which obscure some wavelengths in the images). And the more distant ones are difficult to detect, because they glow faintly from our point of view.
According to Shoko Sakai, a research scientist at the National Optical Astronomy Observatory, astronomers are using other methods that complement measurements of distances to Cepheids, such as the Tully-Fisher ratio, which uses the discovered correlation between the brightness of a spiral and its rotation rate. “The idea is that the larger the galaxy, the faster it rotates,” he wrote. “This means that if you know the rotation rate of a spiral galaxy, you can use the Tully-Fisher relationship to determine its internal brightness. By comparing the internal brightness with the apparent value (the one actually observed - because the further away the galaxy is, the “darker” it becomes), we can calculate its distance.”
CONSTANT
CONSTANT, -aya, -oe; -yanen, -yanna.
1. full f. Unceasing, unchanging and the same at all times; everlasting. Live in constant work. P. theater visitor. Constant And constant(noun) (in mathematics: a quantity that, according to the conditions of the problem, retains the same value). Standing army(peacetime army). P. current(as opposed to variable, which does not change over time). P. capital(part of capital spent on means of production and remaining unchanged during the production process; spec.).
2. full f. Designed for the long term, not temporary. P. bridge. Full time job.
3. Not changeable, solid. P. view of things.
| noun constancy, -a, cf. (to 1 and 3 digits) and permanence, -i, w.
S.I. Ozhegov, N.Yu. Shvedova Explanatory dictionary of the Russian language
Synonyms
Dictionary of Russian synonyms
constant
continuous, uninterrupted, unceasing, unceasing; unchanging, stable, stable, constant; everlasting, eternal; unchangeable, unchanging, homogeneous, uniform, uniform, motionless, stationary, permanent; unchangeable, unbreakable, unchangeable, identical, even, seasoned, unshakable, unshakable, unceasing, unabated, tireless, tireless, unceasing, daily, everyday, faithful, faithful, stubborn, ordinary; pervasive, true to oneself, true to oneself, endless, regular, incessant, restless, monotonous, unchangeable, chronic, usual, sworn, fixed, inseparable, uninterrupted, hourly, every minute, irreconcilable, every second, year-round, durable, solid, non-condensing, long-term , persistent, endless, everlasting, inescapable, tireless, persistent, tenacious, once and for all established, not subject to change, uninterrupted, unwavering, sleepless, hopeless, unabsorbed, incessant, never absent, jury, round-the-clock, fixed, obligatory, personnel, hourly, year-round , unabated. Ant. unstable, fickle, variable, fickle, fickle, capricious; transient, changeable; heterogeneous, uneven; unstable, mobile, mobile, non-stationary; intermittent, temporary, sporadic; frivolous
Dictionary of Russian synonyms 3
constant
Unchangeable, unchangeable, indestructible, unchangeable, everlasting, identical, even; sustained, unshakable, unshakable, unceasing, unceasing, uninterrupted, uninterrupted, unflagging, tireless, tireless, unceasing; daily, everyday; loyal.
“It’s all due to my eternal thoughtlessness.” Turg. Maintain character, remain true to yourself. Prot. .
Dictionary of Russian synonyms 4
constant
hopeless, non-stop, non-absent, tireless, endless, uninterrupted, ceaseless, sleepless, unchangeable, faithful, eternal, everlasting, seasoned, long-term, daily, everlasting, sworn, personnel, constant, year-round, year-round, round the clock, persistent, unshakable, inescapable, unchanging, unchangeable, unchangeable, uncondensing, unabated, unabated, unbreakable, unshakable, uninterrupted, uninterrupted, unceasing, irreconcilable, indestructible, unchangeable, unmovable, unwavering, unceasing, unceasing, unabated, ordinary, identical, monotonous, permanent, everyday, ever-present, sworn, durable, uniform, regular, even, stable, stationary, persistent, firm, persistent, stable, chronic
permanent
permanent
constant
constant
constantly,
permanent
more permanently
more permanently
more permanently
Definition of DC current
Ideally, direct current does not change its value and direction over time. In reality, direct current is not a constant value in rectifier devices, since it contains a variable component (ripple).
Shape of DC components
In galvanic cells, direct current is also not constant, its value decreases across the load over time, thus, direct current is a conditional definition and when using it, changes in a constant value are neglected.
Direct current component (DC)
DC stands for Direct Current, translated as direct current. Graphically in the form of current you can see its changes over time or ripple. Such ripple occurs in the form of direct current in filtered rectifiers where small capacitances are used. In rectifier devices without the use of capacitors, the pulsation can be large.
The pulsating current at the output of a rectifier without capacitors is sometimes called pulsed current. The ripple current graph shows the DC component (straight line) and the AC component (ripple). The direct current component is defined as the average value of the current over a period.
AVG is the average value of the constant current. The alternating component of AC can be considered as the change in direct current relative to the average value. The ripple of the DC waveform is determined by the formula.
Where Iac is the average value of the alternating component of AC, Idc is the direct current component.
All of the above also applies to constant voltage.
DC current and voltage parameters
The intensity of the electric current is expressed as the number of charges moved over a period of time through the cross section of the conductor. One of the important parameters of direct current is the current value, which is measured in Amperes. The current intensity of 1 Ampere is to move a charge of one Coulomb for 1 second.
DC voltage is measured in Volts. DC voltage is the potential difference between two points in the same electrical circuit. Also important parameters for constant voltage are the ripple range and the ripple factor. The ripple range is the difference between the maximum ripple value and the minimum.
And the ripple coefficient is expressed in relation to the effective value of the alternating component (AC) of the current to the constant value of the component (DC). Also an important parameter of direct current is power P. Direct current power can be characterized by its operation over a certain period of time. Power is measured in Watts and determined by the formula:
According to this formula, the same power can be obtained at different currents and voltages.
Boltzmann's constant builds a bridge from the macrocosm to the microcosm, connecting temperature with the kinetic energy of molecules.
Ludwig Boltzmann is one of the creators of the molecular kinetic theory of gases, on which the modern picture of the relationship between the movement of atoms and molecules, on the one hand, and the macroscopic properties of matter, such as temperature and pressure, on the other, is based. In this picture, gas pressure is determined by the elastic impacts of gas molecules on the walls of the vessel, and temperature is determined by the speed of movement of the molecules (or rather, their kinetic energy). The faster the molecules move, the higher the temperature.
Boltzmann's constant makes it possible to directly relate the characteristics of the microworld with the characteristics of the macroworld - in particular, with thermometer readings. Here is the key formula that establishes this relationship:
1/2 mv 2 = kT
Where m And v— respectively, the mass and average speed of gas molecules, T is the gas temperature (on the absolute Kelvin scale), and k — Boltzmann's constant. This equation bridges the gap between the two worlds, linking the characteristics of the atomic level (on the left side) with volumetric properties(on the right side), which can be measured using human instruments, in this case thermometers. This connection is provided by the Boltzmann constant k, equal to 1.38 x 10 -23 J/K.
The branch of physics that studies the connections between the phenomena of the microworld and the macroworld is called statistical mechanics. There is hardly an equation or formula in this section that does not include Boltzmann's constant. One of these relationships was derived by the Austrian himself, and it is simply called Boltzmann equation:
S = k log p + b
Where S— entropy of the system ( cm. Second law of thermodynamics) p- so-called statistical weight(a very important element of the statistical approach), and b- another constant.
Throughout his life, Ludwig Boltzmann was literally ahead of his time, developing the foundations of the modern atomic theory of the structure of matter, entering into fierce disputes with the overwhelming conservative majority of the scientific community of his day, who considered atoms only a convention, convenient for calculations, but not objects of the real world. When his statistical approach did not meet with the slightest understanding even after the advent of the special theory of relativity, Boltzmann committed suicide in a moment of deep depression. Boltzmann's equation is carved on his tombstone.
Boltzmann, 1844-1906
Austrian physicist. Born in Vienna into the family of a civil servant. Studied at the University of Vienna on the same course with Josef Stefan ( cm. Stefan-Boltzmann law). Having defended his degree in 1866, he continued his scientific career, holding at different times professorships in the departments of physics and mathematics at the universities of Graz, Vienna, Munich and Leipzig. Being one of the main proponents of the reality of the existence of atoms, he made a number of outstanding theoretical discoveries that shed light on how phenomena at the atomic level affect the physical properties and behavior of matter.
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