Surely, having heard in some fantastic action movie the expression a la “20 to Tatooine light years”, many asked legitimate questions. I will name some of them:

Isn't a year a time?

Then what is light year?

How many kilometers does it have?

How long will it take light year space ship with Earth?

I decided to dedicate today's article to explaining the meaning of this unit of measurement, comparing it with our usual kilometers and demonstrating the scales that Universe.

Virtual Racer.

Imagine a person, in violation of all the rules, rushing along the highway at a speed of 250 km / h. In two hours he will overcome 500 km, and in four - as many as 1000. Unless, of course, he crashes in the process ...

It would seem that this is the speed! But in order to circumnavigate the entire globe (≈ 40,000 km), our rider will need 40 times more time. And this is already 4 x 40 = 160 hours. Or almost a whole week of continuous driving!

In the end, however, we will not say that he covered 40,000,000 meters. Since laziness has always forced us to invent and use shorter alternative units of measurement.

Limit.

From a school physics course, everyone should know that the fastest rider in Universe- light. In one second, its beam covers a distance of approximately 300,000 km, and the globe, thus, it will go around in 0.134 seconds. That's 4,298,507 times faster than our virtual racer!

From Earth before Moon light reaches on average in 1.25 s, up to sun its beam will rush in a little more than 8 minutes.

Colossal, isn't it? But the existence of speeds greater than the speed of light has not yet been proven. Therefore, the scientific world decided that it would be logical to measure cosmic scales in units that a radio wave passes over certain time intervals (which light, in particular, is).

Distances.

In this way, light year- nothing more than the distance that a ray of light overcomes in one year. On interstellar scales, using distance units smaller than this does not make much sense. And yet they are. Here are their approximate values:

1 light second ≈ 300,000 km;

1 light minute ≈ 18,000,000 km;

1 light hour ≈ 1,080,000,000 km;

1 light day ≈ 26,000,000,000 km;

1 light week ≈ 181,000,000,000 km;

1 light month ≈ 790,000,000,000 km.

And now, so that you understand where the numbers come from, let's calculate what one is equal to light year.

There are 365 days in a year, 24 hours in a day, 60 minutes in an hour, and 60 seconds in a minute. Thus, a year consists of 365 x 24 x 60 x 60 = 31,536,000 seconds. Light travels 300,000 km in one second. Consequently, in a year its beam will cover a distance of 31,536,000 x 300,000 = 9,460,800,000,000 km.

This number reads like this: NINE TRILLION, FOUR HUNDRED SIXTY BILLION AND EIGHT HUNDRED MILLION kilometers.

Of course, the exact value light year slightly different from what we calculated. But when describing distances to stars in popular science articles, the highest accuracy is in principle not needed, and a hundred or two million kilometers will not play a special role here.

Now let's continue our thought experiments...

Scales.

Let's assume modern spaceship leaves solar system with the third space velocity (≈ 16.7 km/s). First light year he will overcome in 18,000 years!

4,36 light years to our nearest star system ( Alpha Centauri, see the image at the beginning) it will overcome in about 78 thousand years!

Our the Milky Way galaxy, having a diameter of approximately 100,000 light years, it will cross in 1 billion 780 million years.

And to the nearest one to us galaxies, spaceship rushing only after 36 billion years ...

These are the pies. But in theory, even Universe arose only 16 billion years ago ...

And finally...

You can start to wonder at the cosmic scale even without going beyond solar system because it is very large in itself. This was shown very well and clearly, for example, by the creators of the project If the Moon wereonly 1 pixel (If the moon were just one pixel): http://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html .

On this I, perhaps, will complete today's article. All your questions, comments and wishes are welcome in the comments below it.

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Light year

During the exploration of their planet, people needed various measures of measuring distances and segments. Initially, length measures were inaccurate, because different peoples had their own ways of measuring. Only in 1791, scientists from France introduced a measure that is still used today - the meter (from the Greek - "measure").
But at the beginning of the twentieth century, people began to turn their attention to the study of space. And the fact that the Universe has incredible distances, the already existing metric system turned out to be unsuitable for measuring such large distances. It is possible to measure in kilometers the distance from our planet to the Moon or to Mars, but if you measure the distances to other planets, and even stars, then there will be an incredible number of zeros in the figure.
And then scientists decided to introduce the term "light years".

How many light years?

In just one second, photons of light cover a length of 300,000 km. A light year is the number of kilometers that light travels in 12 months. In kilometers it will be - 9,460,730,472,580.8 kilometers ≈ 9.46 1015.
Of course, using the term "light years" is more convenient than using huge kilometers. But, of course, there are approximate values:
1 light second ≈ 300 thousand kilometers.
1 light minute ≈ 18 million kilometers.
1 light hour ≈ 1,080,000,000 kilometers.
1 light day ≈ 26,000,000,000 kilometers.
1 light week ≈ 181,000,000,000 kilometers.
1 light month ≈ 790,000,000,000 kilometers.

How many?

We assume that the spacecraft flies at the third cosmic speed (about 16.8 kilometers per second), then in 18 thousand years the ship will fly by one light year. And our galaxy the Milky Way, which is about a hundred thousand light years in diameter, the ship will fly by in almost 2 billion years!
The closest star to the Sun is Proxima Centauri. It is located at a distance of about four light years. If converted to kilometers, the figure is very large.
But if we compare the distance from Proxima Centauri to the nearest galaxy, the Andromeda Nebula, then the star is very close, since Andromeda is two and a half million light-years from the Milky Way. The spacecraft will be able to fly there in 35 billion years.

What else are light years useful for?

Using light years helps to understand where in the universe you can try to find intelligent civilizations. So scientists determine where it makes sense to send radio signals, and where not.
How it works: the speed of light is equal to the speed of a radio signal, and it turns out that sending messages to where they will reach in thousands, or even billions of years, is completely useless. It makes sense to look for "neighbors" through the sent signal, which will go on for at least one human life.

How many earth years are there in light years?

It is a fundamentally wrong belief that this term measures time. The light year has nothing to do with Earth time and is not related to it in any way. It denotes only a measure of the distances that light travels in 1 year on Earth.

Off-system unit of length used in astronomy; 1 S. g. is equal to the distance traveled by light in 1 year. 1 S. g. \u003d 0.3068 parsec \u003d 9.4605 1015 m. Physical encyclopedic dictionary. Moscow: Soviet Encyclopedia. Editor-in-chief A. M. Prokhorov. ... ... Physical Encyclopedia

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

LIGHTYEAR, 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- LIGHTYEAR, 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

A non-systemic 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. * * * LIGHTYEAR LIGHTYEAR, a unit of interstellar distances; the path that light travels in a year, i.e. 9.46x1012 km ... encyclopedic Dictionary

Light year- a unit of distance equal to the path traveled by light in one year. A light year is 0.3 parsec... Concepts of 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 aiskinamasis metrologijos terminų žodynas

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

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The distances between the stars are so great that measuring them in kilometers or miles is an exercise with endless zeros. The usual system of measurements is used to indicate distances in one system. For example, they say that the minimum distance from Earth to Mars is 55.76 million kilometers. With stars, everything is more complicated, and here the concepts of a light year and a parsec are usually used.

astronomical unit- a unit of measurement of objects of the solar system and the objects of the universe closest to it, adopted in astronomy. The astronomical unit is equal to 149,598,100 km (+- ~750 km), which is approximately equal to the average distance of the Earth from the Sun. Modern observations have recorded a gradual increase in the value by 15 cm annually, which is explained by the possible loss of mass by the Sun, the consequences of the solar wind.

Light year- the distance that light travels in one year, in meters, is 9 460 730 472 580 800. In fact, the light of the stars that we see on a cloudless night went to our planet for many centuries, and some of them no longer exist at all.

Parsec, also known as "parallax of an arc second" - this is the distance from which the average radius of the Earth's orbit (perpendicular to the line of sight) is visible at an angle of one arc second. If it is quite simple, then parsec = 3.26 light years.

It is interesting that in popular science and fantasy literature it is customary to use the concept of a light year, and parsecs are usually used only in professional writings and research.

(Galaxy UDFj-39546284 - the most distant galaxy from Earth (13.3 billion light years from Earth), in the image taken by the Hubble telescope looks like a red dot)

The nearest star to us is Alpha Centauri, which is located at a distance of 4.37 light years from Earth. But to the most distant galaxy (as of December 2012) from the Earth as much as 13.3 billion light years!. It turns out that when the sun of this very galaxy (known as UDFj-39546284) goes out, humanity will not know about it soon.

Quick answer: not at all.

Often we are 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 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 vacuum, without being affected by gravitational fields, in one Julian year (which is 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, take the mark of 300 thousand kilometers per second (this is exactly 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 the distance, which is equal to a light year.