When did the first metal skates appear? Detailed answer

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When did the first metal skates appear? Detailed answer

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When did the first metal skates appear?

Already ancient people were fond of skating. They were made from the ribs or tubular bones of animals. The bone was sawn lengthwise, polished and holes were made so that it could be tied to the leg. Archaeologists have found such skates more than once during excavations.

Bone skates lasted a very long time. Shakespeare still found them in England, and in Norway and Iceland they rode bone skates even in the XNUMXth century. But at that time there were already other skates: they were made of wood, and upholstered with iron from below. And from the end of the XNUMXth - beginning of the XNUMXth century, all-metal skates began to be made in the Netherlands and England.

Author: Cellarius E.Yu.

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How are volcanoes formed?

In February 1943, in one of the regions of Mexico, people witnessed a rare and amazing sight: a new volcano was born in the middle of a corn field! In just three months, a cone-shaped mountain 300 meters high was formed. As a result, two cities were destroyed, and a vast territory was buried under a layer of ash and lava. How does the formation of volcanoes proceed?

First of all, it should be remembered that the temperature in the depths of the Earth rises as it approaches the center of the Earth. At a depth of 35-40 km, most of the rocks are in a molten state. When minerals change from solid to liquid, they increase in volume. As a result, new mountain ranges rise at various points on the earth's surface. This leads to a decrease in pressure in the thickness of the earth's crust, and huge lakes of magma - molten minerals - can appear under the newly formed mountains.

Magma rises up, filling the cracks that appeared in the process of mountain building. When the pressure in the underground lakes becomes too great, the stone vaults, unable to withstand it, bend upwards, and a new volcano is formed.

During the eruption that has begun, a mixture of hot gases, molten rocks and solid debris is pushed to the surface from the depths. Cooling, they form a cone-shaped top of the volcano, in the center of which there is a depression called a crater. In the middle of the crater there is a hole - a vent leading into the thickness of the earth's crust.

The material ejected through the vent to the surface is mainly a mixture of gases, however, along with them, a large amount of lava and solid particles that look like ash and cinders are also erupted.

Lava is actually magma flowing out of a volcano, but differs from the latter in its physical and chemical properties. Changes occur when magma rises to the surface and its temperature and pressure decrease dramatically.

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Asteroseismology as music for measuring distances to stars 03.01.2024

The team of astronomers used asteroseismology, studying the vibrations of stars, to more accurately measure their distances from Earth. Researchers focused on thousands of stars, analyzing measurements taken by the Gaia mission, designed to study the nearby Universe.

Ten years ago, the European Space Agency (ESA) launched the Gaia mission, which provided astronomers with unique data about the nearby Universe. The Gaia project, which has collected information on the position, distance and motion of nearly two billion stars, has become an important tool for the study of outer space.

The Standard Candles and Distances research team at EPFL, led by Professor Richard Anderson, set out to measure the current expansion of the Universe, counting Gaia as a key element in their research. The Gaia mission has increased the accuracy of parallax measurements by 10 times compared to ESA's previous Hipparcos mission. Today, astronomers use parallaxes to determine distances to stars, but this method becomes more difficult as distance increases.

Despite Gaia's success, measuring parallax is challenging, and scientists at EPFL and the University of Bologna in Italy have been working to check and correct small systematic errors to fully unlock the potential of Gaia's parallaxes. In their study, more than 12 wobbling red giants were analyzed, providing the most precise measurements to date.

Just as geologists use earthquakes to study the structure of the Earth, astronomers use asteroseismology, the study of the vibrations of stars, to gain information about their physical properties. The vibrations of stars are measured as small changes in the intensity of light, which are then converted into sound waves, creating the frequency spectrum of these vibrations.

“The frequency spectrum allows us to determine the distance to the star by providing asteroseismic parallaxes,” the scientists note. “In our study, we listened to the “music” of a huge number of stars, some of which are 15 light years away!”

To translate sounds into distance measurements, the researchers began by determining that the speed at which sound waves travel through space depends on the temperature and density of the star's interior.

"By analyzing the frequency spectrum of a star's vibrations, we can estimate the size of a star, just as one can determine the size of a musical instrument by the sound it makes, thinking about the difference in pitch between a violin and a cello," explains Professor Andrea Miglio, Professor at the Bolognese Department of Physics and Astronomy University, the third author of the study.

By calculating the size of the star in this way, astronomers determined its luminosity and compared it with the brightness visible on Earth. They then combined this information with temperature and chemical composition data obtained from spectroscopy and analyzed this data to calculate the distance to the star. Finally, the astronomers compared the parallaxes obtained in the study with those provided by Gaia to check the accuracy of the satellite's measurements.

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