Class 9 Universe | What is Light Year? | प्रकाश वर्ष | Conversion of One Light Year into meters.

What is Light Year (प्रकाश वर्ष)? Ans: A unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 million million miles). #lightyear #sujan #class10science This video includes 1. Definition of Light Year 2. Basic concept of Light Year 3. Realizing the true distance of one light year 4. How to convert light year into meters 5. How far is second nearest star Proxima Centauri from us? 6. Speech by Carl Segan THE PALE BLUE DOT 1. What is Light Year (प्रकाश वर्ष)? Ans: A unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 million million miles). 2. Is light year a distance or time? Ans: A light-year is a unit of distance. It is the distance that light can travel in one year. 3. What is the velocity of Light? Ans: Light moves at a velocity of about 300,000 kilometers (km) each second. 4. How much distance does light travel in one year? Ans: In one year, light can travel about 10 trillion km. 5. Which is the second nearest star after sun? Ans: Proxima Centauri 6. How far is Proxima Centauri? Ans:4.244 light-years (1.301 pc) 7. About Proxima Centauri: Proxima Centauri is a small, low-mass star located 4.244 light-years (1.301 pc) away from the Sun in the southern constellation of Centaurus. Its Latin name means the "nearest [star] of Centaurus". This object was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. 9. Who is Carl Segan? Carl Edward Sagan (/ˈseɪɡən/; November 9, 1934 – December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, poet and science communicator. His best known scientific contribution is research on extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Sagan assembled the first physical messages sent into space: the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extraterrestrial intelligence that might find them. Sagan argued the now-accepted hypothesis that the high surface temperatures of Venus can be attributed to and calculated using the greenhouse effect. Initially an associate professor at Harvard and later at Cornell, from 1976 to his death, he was the David Duncan Professor of Astronomy and Space Sciences at the latter. He wrote many popular science books, such as The Dragons of Eden, Broca's Brain and Pale Blue Dot, and narrated and co-wrote the award-winning 1980 television series Cosmos: A Personal Voyage. The most widely watched series in the history of American public television, Cosmos has been seen by at least 500 million people across 60 different countries. The book Cosmos was published to accompany the series. He also wrote the science fiction novel Contact, the basis for a 1997 film of the same name. His papers, containing 595,000 items, are archived at The Library of Congress. 10. Light Year (प्रकाश वर्ष): The light-year unit appeared a few years after the first successful measurement of the distance to a star other than the Sun, by Friedrich Bessel in 1838. The star was 61 Cygni, and he used a 6.2-inch (160 mm) heliometer designed by Joseph von Fraunhofer. The largest unit for expressing distances across space at that time was the astronomical unit, equal to the radius of the Earth's orbit (1.50×108 km or 9.30×107 mi). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660000 astronomical units (9.9×1013 km).Bessel added that light takes 10.3 years to traverse this distance.He recognized that his readers would enjoy the mental picture of the approximate transit time for light, but he refrained from using the light-year as a unit. He may have resented expressing distances in light-years because it would reduce the accuracy of his parallax data due to multiplying with the uncertain parameter of the speed of light. The speed of light was not yet precisely known in 1838; its value changed in 1849 (Fizeau) and 1862 (Foucault). It was not yet considered to be a fundamental constant of nature, and the propagation of light through the aether or space was still enigmatic. The light-year unit appeared in 1851 in a German popular astronomical article by Otto Ule. Ule explained the oddity of a distance unit name ending in "year" by comparing it to a walking hour। A contemporary German popular astronomical book also noticed that light-year is an odd name.In 1868 an English journal labelled the light-year as a unit used by the Germans.Eddington called the light-year an inconvenient and irrelevant unit, which had sometimes crept from popular use into technical investigations.