What is a light year?

Your physics tuition is always exciting. Isn’t it? Have you ever heard of the term light year? If not, today your physics tuition will give you some insight on light year. So, let’s start. Small distances like the length and breadth of a book or file, are calculated in centimetres or inches. But, for bigger distances we use meters or feet to measure them. Even bigger distances are expressed in kilometres or miles. But the distances of billions or trillions of kilometres cannot be expressed in these units. For these we need an altogether different unit. Light year, in fact, is a unit of distance used to measure the great distances between the earth and the stars.

A light year is defined as the distance travelled by light in one year. In vacuum light travels with a velocity of 300,000 km per second. At this speed light travels a distance of 18,000,000 km in one minute. This distance is called ‘light minute’. When we say that a particular heavenly body is at a distance of one light minute, it simply means that it is located at a distance of 18,000,000 km from earth. For example, the distance of the sun and our mother earth is 8 light minutes and 20 light seconds. This indicates that the real distance between the sun and the earth is equal to 150,000,000 km.

The distance travelled by light in one year comes out to be 9.46 trillion km or 5.88 trillion miles. This distance is known as one light year.

The nearest star, Proxima Centauri is at a distance of 4.25 light years. There are so many stars whose light takes thousands of years to reach our earth. So, it is convenient to express the distance of these stars in light years.

We hope you enjoyed this lesson from physics tuition. We will be back with more such interesting findings in our next physics tuition.

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