Concept in Definition ABC

On astronomy One of the most used units is the light year, which is a measure of distance. Specifically, it is the distance that light travels throughout a year. If we express this idea in numbers, a light year equals 946,728,000,000 kilometers, that is, 10 million million kilometers. This distance is exorbitant and difficult to assimilate, so it may be useful to try to explain it with an example, specifically with the distance between the Moon and the Earth. The Moon is a planet relatively close to ours, but it is located 384,400 kilometers from Earth, a distance that in the scale human is immense.

The light-year concept is not a measure of time (as is sometimes believed) but a measure of distance

This is so because if we take as a reference the velocity of light, we say, for example, that it takes 6,300 years for light to travel from the Crab Nebula to the Earth, which is to say that the Crab Nebula is 6,300 light-years from our planet.

The stars that we observe in the sky are so far apart that astronomers refer to their distances not in terms of kilometers but rather use the unit of light year

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Keep in mind that light is what moves with the most speed in the universe, specifically it travels a speed of 300,000 kilometers per second. This means that if we could travel at the speed of light we would go around the world 75 times in a single second. In other words, a second light is the distance that light travels in one second and a light-year is the distance that light travels in one year. To calculate a light year we should multiply the number of seconds in a year by the number of kilometers that light travels in one second.

Conclusions

We use small units of distance to calculate the time it will take to travel them and in daily life we ​​use kilometers or miles, although it must not be forgotten that historically other units have been used (league, foot, nautical mile and others). However, the light year is a measurement that is only applicable to the astronomical realm.

On the other hand, if there is a light year, there is necessarily a light hour, a light minute and a light second. If we think in light seconds, it takes a little more than a second for the light from the Moon to reach Earth. As for the sunlight, it takes 8.3 minutes to reach Earth. Finally, it is worth the pain remember that the Milky Way have a diameter 100,000 light years.

The light year is not the only astronomical measure to calculate distances, as there are also others, such as parallax or parsec (the parsec is equivalent to 3.6 light years).

Photos: iStock - frentusha / den-belitsky