To measure small distances, we use the unit of inches or centimeters. Like we measure the length and width of a book in inches or centimeters. Slightly larger distances, such as feet, yards or meters are used to find the length and width of the room. To measure distances larger than this, units like kilometer or mile are used. are measured.
Do you know what a light year is ?
The distance that light travels in one year is called a 'light year'. We know that light travels a distance of 3,00,000 kilometers or 1,86,000 miles in one second. At this velocity, light travels 18,000,000 km in a minute. Or will cover 11,160,000 miles. We call this distance a 'light minute'. Therefore, when we say that the distance of such a celestial body is one light minute, it means that that body is one crore eighty lakh kilometers away from our earth. For example, the distance of the Sun is 8 light minutes and 20 light seconds. This means that this distance is 150 million kilometers or 93 million miles. We can easily express the light minute in kilometers or miles but it becomes difficult to express the light year in billions of trillions of kilometers or even miles. One light year means 9,460,000,000,000 km. or a distance of 5,880,000,000,000,000 miles.
According to this unit of light year, the distance to the Moon is 14 light seconds, the distance to the Sun is 8 1/3 light minutes. The nearest star is Proxima Centauri at a distance of 4.25 light years (25,000,000,000,000) miles. There are many such stars in the sky like Andromeda, whose light takes millions of years to reach our earth at the speed of 1,86,000 miles or 3,00,000 kilometers per second. It is beyond our imagination to think of their distance in miles or kilometers. So we express these distances in light years only.
