What does 1 light year mean? What is a light year equal to? Further advances in research and the definition of the light year

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 light years 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 other planets 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 have been 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.

An extra-system unit of length used in astronomy; 1 S.g. is equal to the distance traveled by light in 1 year. 1 S. g. = 0.3068 parsec = 9.4605 1015 m. Physical encyclopedic dictionary. M.: Soviet encyclopedia. Editor-in-Chief A. M. Prokhorov... ... Physical encyclopedia

LIGHT YEAR, a unit of astronomical distance equal to the distance light travels in outer space or VACUUM in one tropical year. One light year is equal to 9.46071012 km... Scientific and technical encyclopedic dictionary

LIGHT YEAR, a unit of length used in astronomy: the path traveled by light in 1 year, i.e. 9.466?1012 km. The distance to the nearest star (Proxima Centauri) is approximately 4.3 light years. The most distant stars in the Galaxy are located on... ... Modern encyclopedia

Unit of interstellar distances; the path that light travels in a year, i.e. 9.46? 1012 km... Big Encyclopedic Dictionary

Light year- LIGHT YEAR, a unit of length used in astronomy: the path traveled by light in 1 year, i.e. 9.466´1012 km. The distance to the nearest star (Proxima Centauri) is approximately 4.3 light years. The most distant stars in the Galaxy are located on... ... Illustrated Encyclopedic Dictionary

An extra-system unit of length used in astronomy. 1 light year is the distance that light travels in 1 year. 1 light year is equal to 9.4605E+12 km = 0.307 pc... Astronomical Dictionary

Unit of interstellar distances; the path that light travels in a year, that is, 9.46·1012 km. * * * LIGHT YEAR LIGHT YEAR, a unit of interstellar distances; the path that light travels in a year, i.e. 9.46×1012 km... Encyclopedic Dictionary

Light year- a unit of distance equal to the path traveled by light in one year. A light year is equal to 0.3 parsecs... Concepts modern natural science. Glossary of basic terms

light year- šviesmetis statusas T sritis Standartizacija ir metrologija apibrėžtis Astronominis ilgio matavimo vienetas, lygus nuotoliui, kurį vakuume nusklinda šviesa per 1 atogrąžinius metus. Žymimas šm: 1 šm = 9.46073 · 10¹² km. atitikmenys: engl. light... ... Penkiakalbis aiškinamasis metrologijos terminų žodynas

light year- šviesmetis statusas T sritis fizika atitikmenys: engl. light year vok. Lichtjahr, n rus. light year, m pranc. année lumière, f … Fizikos terminų žodynas

Books

There is no turning back. Set of 3 books, Alexey Lukyanov, Ivan Sergeevich Naumov. Set of 3 books. 1. "Tsunami. Book one. Earthshakers" 1999. Egor and Yusya Kruglov are left without adult care. Nothing good awaits them ahead. Disability has turned...
Fascinating astronomy, Elena Kachur. About the book In the new and long-awaited book, Chevostik and Uncle Kuzya go to the observatory! Here they will have a fascinating acquaintance with the celestial bodies that decorate our night sky. Together with...

A light year is the distance that light travels in one year. The International Astronomical Union gave 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 you 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.,
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.

Interesting fact about the nature of the universe

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 calculates the distance from one object celestial body to another. The numbers for light years and earth years are so different, although they mean distance.

On February 22, 2017, NASA reported that 7 exoplanets were found around the single star TRAPPIST-1. Three of them are in the range of distances from the star in which the planet can have liquid water, and water is a key condition for life. It is also reported that this star system is located at a distance of 40 light years from Earth.

This message caused a lot of noise in the media; some even thought that humanity was one step away from building new settlements near a new star, but this is not so. But 40 light years is a lot, it’s a LOT, it’s too many kilometers, that is, it’s a monstrously colossal distance!

From a physics course, the third escape velocity is known - this is the speed that a body must have at the surface of the Earth in order to go beyond the solar system. The value of this speed is 16.65 km/sec. Conventional orbital spaceships start at a speed of 7.9 km/sec and revolve around the Earth. In principle, a speed of 16-20 km/sec is quite accessible to modern earthly technologies, but no more!

Humanity has not yet learned to accelerate spaceships faster than 20 km/sec.

Let's calculate how many years it will take a starship flying at a speed of 20 km/sec to travel 40 light years and reach the star TRAPPIST-1.
One light year is the distance a beam of light travels in a vacuum, and the speed of light is approximately 300 thousand km/sec.

A human-made spaceship flies at a speed of 20 km/sec, that is, 15,000 times slower than the speed of light. Such a ship will cover 40 light years in a time equal to 40*15000=600000 years!

Earth ship (at modern level technology) will reach the star TRAPPIST-1 in about 600 thousand years! Homo sapiens has existed on Earth (according to scientists) for only 35-40 thousand years, but here it is as much as 600 thousand years!

In the near future, technology will not allow humans to reach the star TRAPPIST-1. Even promising engines (ion, photon, cosmic sails, etc.), which do not exist in earthly reality, are estimated to be able to accelerate the ship to a speed of 10,000 km/sec, which means that the flight time to the TRAPPIST-1 system will be reduced to 120 years . This is already a more or less acceptable time for flight using suspended animation or for several generations of immigrants, but today all these engines are fantastic.

Even the nearest stars are still too far from people, too far, not to mention the stars of our Galaxy or other galaxies.

The diameter of our galaxy Milky Way is approximately 100 thousand light years, that is, the journey from end to end for a modern Earth ship will be 1.5 billion years! Science suggests that our Earth is 4.5 billion years old, and multicellular life is approximately 2 billion years old. The distance to the closest galaxy to us - the Andromeda Nebula - 2.5 million light years from Earth - what monstrous distances!

As you can see, of all the living people, no one will ever set foot on the earth of a planet near another star.

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 Earth years are there in one light year? You may be disappointed, but the correct answer is not at all. How so?

The thing is that a light year is not a measure of time, but a measure of distance. To be more precise, a light year is equal to the distance that light travels in a vacuum, unaffected by gravitational fields, in one Julian year (equal by definition to 365.25 standard days of 86,400 SI seconds, or 31,557,600 seconds), according to definition of the International Astronomical Union.

Now let's try to calculate the distance of a light year. To do this, let’s take the mark of 300 thousand kilometers per second (this is the speed of light) and multiply by 31.56 million seconds (so many seconds in a year) and get a huge figure - 9,460,800,000,000 km (or 9,460,000 million kilometers). This fantastic figure means a distance that is equal to a light year.