Cosmic distances are difficult to measure in ordinary meters and kilometers, so astronomers use other physical units in their work. One of them is called a light year.
Many fantasy fans are very familiar with this concept, as it often appears in films and books. But not everyone knows what a light year is, and some even think that it is similar to the usual annual calculation of time.
What is a light year?
In reality, a light year is not a unit of time, as one might assume, but a unit of length used in astronomy. It refers to the distance traveled by light in one year.
It is usually used in astronomy textbooks or popular science fiction to determine lengths within the solar system. For more accurate mathematical calculations or measuring distances in the Universe, another unit is taken as a basis - .
The appearance of the light year in astronomy was associated with the development of stellar sciences and the need to use parameters comparable to the scale of space. The concept was introduced several years after the first successful measurement of the distance from the Sun to the star 61 Cygni in 1838. 
Initially, a light year was the distance traveled by light in one tropical year, that is, in a period of time equal to the full cycle of seasons. However, since 1984, the Julian year (365.25 days) began to be used as a basis, as a result of which the measurements became more accurate.
How is the speed of light determined?
To calculate a light year, researchers had to first determine the speed of light. Astronomers once believed that the propagation of rays in space was instantaneous, but in the 17th century this conclusion began to be questioned.
The first attempts to make calculations were made by Galileo Gallilei, who decided to calculate the time it takes light to travel 8 km. His research was unsuccessful. James Bradley managed to calculate the approximate value in 1728, who determined the speed at 301 thousand km/s.
What is the speed of light?
Despite the fact that Bradley made fairly accurate calculations, they were able to determine the exact speed only in the 20th century, using modern laser technologies. Advanced equipment made it possible to make calculations corrected for the refractive index of rays, resulting in this value being 299,792.458 kilometers per second. 
Astronomers operate with these figures to this day. Subsequently, simple calculations helped to accurately determine the time that the rays needed to fly around the orbit of the globe without the influence of gravitational fields on them.
Although the speed of light is not comparable to earthly distances, its use in calculations is explained by the fact that people are accustomed to thinking in “earthly” categories.
What is a light year equal to?
If we take into account that a light second is equal to 299,792,458 meters, it is easy to calculate that light travels 17,987,547,480 meters in a minute. As a rule, astrophysicists use this data to measure distances inside planetary systems.
To study celestial bodies on the scale of the Universe, it is much more convenient to take as a basis a light year, which is equal to 9.460 trillion kilometers or 0.306 parsecs. Observing cosmic bodies is the only case when a person can see the past with his own eyes.
It takes many years for light emitted by a distant star to reach Earth. For this reason, when observing cosmic objects, you see them not as they are at the moment, but as they were at the moment of light emission.
Examples of distances in light years
Thanks to the ability to calculate the speed of movement of rays, astronomers were able to calculate the distance in light years to many celestial bodies. Thus, the distance from our planet to the Moon is 1.3 light seconds, to Proxima Centauri - 4.2 light years, to the Andromeda nebula - 2.5 million light years. 
The distance between the Sun and the center of our galaxy takes rays approximately 26 thousand light years, and between the Sun and the planet Pluto - 5 light hours.
A light year is the distance that light travels in one year. The International Astronomical Union has given its explanation of the light year - this is the distance that light travels in a vacuum, without the participation of gravity, in a Julian year. The Julian year is equal to 365 days. It is this decoding that is used in scientific literature.
If we take professional literature, then the distance is calculated in parsecs or kilo- and megaparsecs.
There are specific numbers that determine the distance of light hours, minutes, days, etc.
- A light year is equal to 9,460,800,000,000 km,
- month- 788,333 million km.,
- a week- 197,083 million km.,
- day- 26,277 million km,
- hour- 1,094 million km.,
- minute- about 18 million km.,
- second- about 300 thousand km.
This is interesting! From the Earth to the Moon, light travels on average in 1.25 seconds, while its beam reaches the Sun in just over 8 minutes.
The star Betelgeuse in the constellation Orion should explode in the foreseeable future (in fact, within a few centuries).
Betelgeuse is located at a distance of 495 to 640 light years from us.
If it explodes right now, then the inhabitants of the Earth will see this explosion only in 500-600 years.
And if you see an explosion today, then remember that in fact the explosion occurred around the time of Ivan the Terrible...
Earth year
An earthly year is the distance traveled by the earth in one year. If we take into account all the calculations, then one light year is equal to 63242 Earth years. This figure applies specifically to planet Earth; for others, such as Mars or Jupiter, they will be completely different. A light year measures the distance from one celestial object to another. The numbers for light years and earth years are so different, although they mean distance.
Scale
Video
Sources
Quick answer: not at all.
We are often asked very interesting questions, the answers to which are very non-standard.
You see one of these questions in the title. And really, how many earthly years are there in one bright year? You may be disappointed, but there is no real answer.
The fact is that a bright year is not a measure of time, but a distance measure. To be more precise, a light year is the distance of distance in a vacuum without gravity fields, one effect of the Julian year (equivalent to 365.25 standard days per 86,400 SI seconds or 31,557,600 seconds) by the International Astronomical Federation.
To do this, we take the 300 thousand kilometers per second mark (that's exactly the speed of light) and multiply it with 31.56 million seconds (many seconds per year) and we get a huge number - 9460800000 000 km (or 9.46 million kilometers). This fantastic number means a distance equal to a light year.
- 1 light month ~ 788,333,000,000 km
- 1 easy week ~ 197,083,000 km
- 1 daylight ~ 26,277 million km
- 1 light hour ~ 1,094 million km
- 1 light minute ~ about 18 million km
- 1 light second ~ 300 thousand km
To find out how many kilometers in a light year you need to use a simple web calculator.
In the left box, enter the number of light years of interest you want to convert. In the field on the right you will see the calculation result. Simply click the appropriate link to convert light years or miles to other units.
What is “bright summer”
The light year of the one-way system (St., ly) is equal to the distance traveled by light in a vacuum in one July year (365.25 days).
The term is mainly used in science and fiction, and in professional circles the term "parsecs" has been adopted, with the prefixes "kilo" and "mega".
and not before 1984, according to the bright year, to understand the distance with light traveled in the tropical year, now the value has changed by 0.002%, and the practical value of this difference is because very accurate measurements are not made in bright years. The speed of light is about 300 thousand.
km per second and a luminous year of about 10 trillion kilometers (9460.8800 million km). Regarding distances, for example, Sirius is 8 light years from its closest proximity to the star Proxima Centauri - 4.22 light years, and the diameter of the Roman road - our galaxy, which is 100,000 light years.
What is a "kilometer"
The kilometer kilometer (km, km) is a plural unit of reference distances, widely used throughout the world.
One kilometer 1000 meters, 0.621 miles, 0.9374 miles, 1094 yards, 3281 meters, 1.057 x 10 - 13 light years, 6.67 x 10 - 9 astronomical units.
Easy years
For hundreds of years, people have been inventing their own planet to invent more and more remote sensing systems. Therefore, it was decided to take into account a universal unit of one meter in length and a long measuring path of kilometers.
But in the next twentieth century, this created a new problem for humanity. People began to carefully study the universe - and it turned out that the size of the universe is so large that miles are simply not suitable here.
In ordinary units you can express the distance from the Earth to the Moon or from the Earth to Mars. But if you're trying to figure out how far the nearest star is from our planet, the number "grows" with an imperceptible number of characters per decimal point.
What is 1 light year?
It was obvious that a new space exploration unit was needed - and it was a bright year.
In a second, light travels 300,000 kilometers. Easy years — this is the distance whose light will travel exactly a year, and when translated into a more familiar system of numbers, this distance is 9,460,730,472,580.8 kilometers. It is clear that using a concise “simple flight” is much more convenient than using every huge number in the calculations.
Of all the stars closest to us, Proxima Centauri was only “4.2 light years away.” Of course, based on kilometer data there is an unimaginable amount. However, everything is relative - considering that the nearest Andromeda galaxy is separated from the Roman road by as much as 2.5 million light years, the star and the truth begin to seem very close neighbors.
By the way, using light years helps scientists understand in which corners of space it is reasonable to find intelligent life and where sending radio signals is completely useless.
After all, the speed of a radio signal is similar to the speed of light, so a greeting sent towards a distant galaxy would take millions of years to reach its destination. It makes sense to expect a response from neighboring “neighbors” - objects whose hypothetical response signals will reach ground-based devices even during a person’s lifetime.
1 light year - how many Earth years?
There is a common misconception that a light year is a unit of time.
Actually this is not true. This term has nothing to do with Earth years, it does not refer to them and only represents the distance that light travels in one Earth year.
Exploring their own planet, over hundreds of years, people invented more and more new systems for measuring distance segments. As a result, it was decided to consider one meter as the universal unit of length, and measure the long distance in kilometers.
But the advent of the twentieth century presented humanity with a new problem. People began to carefully study space - and it turned out that the vastness of the Universe is so vast that kilometers are simply not suitable here. In conventional units you can still express the distance from the Earth to the Moon or from the Earth to Mars. But if you try to determine how many kilometers the nearest star is from our planet, the number “overgrows” with an unimaginable number of decimal places.
What is 1 light year equal to?
It became obvious that a new unit of measurement was needed to explore the spaces of space - and the light year became it. In one second, light travels 300,000 kilometers. Light year - this is the distance that light will travel in exactly one year - and translated into a more familiar number system, this distance is equal to 9,460,730,472,580.8 kilometers. It is clear that using the laconic “one light year” is much more convenient than using this huge figure in calculations every time.
Of all the stars, Proxima Centauri is closest to us - it is “only” 4.22 light years away. Of course, in terms of kilometers the figure will be unimaginably huge. However, everything is learned in comparison - if you consider that the nearest galaxy called Andromeda is as much as 2.5 million light years away from the Milky Way, the above-mentioned star really begins to seem like a very close neighbor.
By the way, using light years helps scientists understand in which corners of the Universe it makes sense to look for intelligent life, and where sending radio signals is completely useless. After all, the speed of a radio signal is similar to the speed of light - accordingly, a greeting sent towards a distant galaxy will reach its destination only after millions of years. It is more reasonable to expect an answer from closer “neighbors” - objects whose hypothetical response signals will reach earthly devices at least during a person’s lifetime.
1 light year is how many Earth years?
There is a widespread misconception that the light year is a unit of time. In fact, this is not true. The term has nothing to do with earthly years, does not correlate with them in any way and refers exclusively to the distance that light travels in one earthly year.
Light year- an unsystematic unit of distance measurement in astronomy.
Numerically, one light year equal to the distance light travels in one year.
More precisely, a light year is the distance that light travels in a vacuum, without the influence of gravitational fields, in one Julian year (365.25 days or 31,557,600 standard seconds).
In Russian literature, the light year is designated “St. g.", in foreign: "ly"
What is one equal to? light year:
Light year in kilometers: 9,460,730,472,580.8 km.
9 460 730 472 580 800 meters
63,241.077 astronomical units (AU)
1 light year is equal to 0.306601 parsecs.
In addition to the light year, there are also fractions of the light year: light month, light week, light hour, light minute and light second. They are rare, but it will be interesting to see how different distances are expressed in these units:
The light year is a fairly convenient unit of distance measurement in astronomy. The highest speed at which information can spread in our world is the speed of light. Therefore, distances expressed in light years simultaneously show how quickly one space object can affect another.
For example, you've probably heard that the star Betelgeuse in the constellation Orion is expected to explode in the foreseeable future (in fact, within a few centuries).
Betelgeuse is located at a distance of 495 to 640 light years from us.
If it explodes right now, then the inhabitants of the Earth will see this explosion only in 500-600 years.
And if you see an explosion today, then remember that in fact the explosion occurred around the time of Ivan the Terrible...
This example clearly shows how convenient the light year is - it simultaneously shows both distance and time.
Light year - how many Earth years is it?
How many Earth years are there in a light year? Quite a strange question, but sometimes it comes up... A light year is a measure of distance, as written above, and an earthly year is a measure of time. Therefore, the answer to the question, how many Earth years are in one light year, will be - none :-)
or tell your friends:Do you know why astronomers don't use light years to calculate distances to distant objects in space?
A light year is a non-systemic unit of measurement of distances in outer space. It is widely used in popular books and textbooks on astronomy. However, in professional astrophysics this figure is used extremely rarely and is often used to determine distances to nearby objects in space. The reason for this is simple: if you determine the distance in light years to distant objects in the Universe, the number will turn out to be so huge that it will be impractical and inconvenient to use it for physical and mathematical calculations. Therefore, instead of the light year in professional astronomy, a unit of measurement is used, which is much more convenient to operate when performing complex mathematical calculations.
Definition of the term
We can find the definition of the term “light year” in any astronomy textbook. A light year is the distance a ray of light travels in one Earth year. Such a definition may satisfy an amateur, but a cosmologist will find it incomplete. He will note that a light year is not just the distance that light travels in a year, but the distance that a ray of light travels in a vacuum in 365.25 Earth days, unaffected by magnetic fields.
A light year is equal to 9.46 trillion kilometers. This is exactly the distance a ray of light travels in a year. But how did astronomers achieve such precise determination of the ray path? We'll talk about this below.
How was the speed of light determined?
In ancient times, it was believed that light travels throughout the Universe instantly. However, starting in the seventeenth century, scientists began to doubt this. Galileo was the first to doubt the above proposed statement. It was he who tried to determine the time it takes for a ray of light to travel a distance of 8 km. But due to the fact that such a distance was negligibly small for such a quantity as the speed of light, the experiment ended in failure.
The first major shift in this matter was the observation of the famous Danish astronomer Olaf Roemer. In 1676, he noticed a difference in the time of eclipses depending on the approach and distance of the Earth to them in outer space. Roemer successfully connected this observation with the fact that the further the Earth moves away from, the longer it takes the light reflected from them to travel the distance to our planet.
Roemer grasped the essence of this fact accurately, but he failed to calculate the reliable value of the speed of light. His calculations were incorrect because in the seventeenth century he could not have accurate data on the distance from the Earth to the other planets of the solar system. These data were determined a little later.
Further advances in research and the definition of the light year
In 1728, the English astronomer James Bradley, who discovered the effect of aberration in stars, was the first to calculate the approximate speed of light. He determined its value to be 301 thousand km/s. But this value was inaccurate. More advanced methods for calculating the speed of light were produced without regard to cosmic bodies - on Earth.
Observations of the speed of light in a vacuum using a rotating wheel and a mirror were made by A. Fizeau and L. Foucault, respectively. With their help, physicists managed to get closer to the real value of this quantity.
Exact speed of light
Scientists were able to determine the exact speed of light only in the last century. Based on Maxwell's theory of electromagnetism, using modern laser technology and calculations corrected for the refractive index of the ray flux in air, scientists were able to calculate the exact speed of light as 299,792.458 km/s. Astronomers still use this quantity. Further determining the daylight hours, month and year was already a matter of technology. Through simple calculations, scientists arrived at a figure of 9.46 trillion kilometers—that’s exactly how long it would take a beam of light to travel the length of the Earth’s orbit.
