Parsec is a unit of measure for interstellar distance in space. Take Stanislaw Lem's “Onsite Inspection” as an example. Telegram from the group of search of the mind in space: “TAURUS GAMMA. PLANETS TO THE HELL BUT GLORY TO GOD OF THE UNPERSONS. IN PERIHELIA SWIMMERS IN AFELIA ICE. IT'S ALL PASSIVE ENTROPY AND NOTHING MORE. THE CREW SATURING UP THE THROAT QUICKLY LOOK AT ONE MORE PARSECK AND TO MOMMY. " And what is it, "Parsec", which the mind search group was going to run around?
From online calculators, we quickly learn that 1 parsec is 3.26 light years, 30 trillion. kilometers. Generally speaking, the value is strange. If it is comparable to light years, then why bother introducing it? It turns out that it's all about astronomers and parallax)))
Astronomers drew up star maps and tried to calculate the distances from the earth to various stars. In principle, all stars are considered stationary, since they are very, very far from us. But some of them are far away, while others are closer. And those that are closer, during the year slightly move against the background of distant stars back and forth. This apparent movement of stars in the sky is due to the Earth orbiting the Sun.
Distant stars are like a fixed screen. Due to the fact that the Earth moves in its orbit, nearby stars seem to shift from side to side. This effect (the apparent displacement of the star due to our movement) is called "parallax". And "parsec" is the distance to a star when it shifts by one arc second in six months.
Angles can be measured in degrees. Or you can divide the circle into 24 hours, every hour into 60 minutes, and every arc minute into seconds. One arc second is 0.00028 degrees. This is the distance to the star when it shifts by 0.00028 degrees due to the half-year parallax of the Earth - this is parsec. Conversely, if we fly away from the solar system so that the Earth's orbit fits into one arc second, we will find ourselves just at a distance of one parsec.
It is strange that there is "parsec": parallax for a second, but there is no "parmin", "pargrade" and "parchas")) And in general, why do you need to multiply entities unnecessarily, introduce another unit of measurement if it is translated into the usual light years and does not provide any advantage. Unless the reason is that it is necessary to translate from parsec into light years through the speed of light, and it is constantly being refined. That is, the distance to nearby stars in light years may change in the future, and "parsec" is a measured value. But it's still weird.
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Be that as it may, all people who create on the topic of space flights use parsecs to describe cosmic distances. And since 1 parsec is equal to 3.26 sv. years, then in the cinema the named value (say, 10 parsecs) can be quickly multiplied in the mind by three and flash: - Ha! If you count it, it's only 30 light years, you think!
(By the way, in "Inspection on site", whose telegram I brought, the group on the search for the mind screwed up. The sixth planet of Gamma Taurus was inhabited. The same planet Enteropia))
