Hello my friends , I want to tell you about my first day at college , you may asking What is the relevance of this subject to science?. Wait for it . I am studying at faculty of science , Cairo university ,Egypt, physics department , and in my first day (like any one ) I met new friends talked to new people and attended my first lecture . it was about astronomy lecture , it was entitled “where are we?”. It is a simple question , but sometimes simple questions have the most amazing answer ,
We are here
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On that little blue plant ‘earth’ and the earth in the solar system which in the Milky way galaxy , but is that it. Definitely no . you an not imagine how big our universe is , first let me start from the beginning , the earth , do you know what is the distance between the earth and the sun ? , it is about 150 million kilometers it is a long distance is not it ? (wait to know light year). This distance called AU (Astronomical Unite) , and the distance from the sun to the last plant in the solar system is about 39.5 AU. Although it is a long distance, but the astronomers dealing with much larger distance so AU became un useful any more , they using light year , what is light year?, Well light year is is the distance that light travels in vacuum in one year , it is about9.5x1015 which means 9,500,000,000,000 kilometers it is that long , our galaxy (which one of thousands of the galaxies from one galaxy cluster ,and this galaxy cluster is one of many)is a barred spiral galaxy with a diameter between 100,00 and 1890,000 light years , can you imagine ?
Thank you for reading and thanks to @Suesa for this challenge
hope you enjoyed as much as I did