2 3 1 Measurement of Large Large distances such as the

Last updated: 6/1/2023

2 3 1 Measurement of Large Large distances such as the distance of a pla or a star from the earth cannot be measu m directly with a metre scale An important meth of in such cases is the parallax method ar SU lo th O When you hold a pencil in front of you again some specific point on the background a w and look at the pencil first through your lefte A closing the right eye and then look at t pencil through your right eye B closing the eye you would notice that the position of th pencil seems to change with respect to the pot of on the wall This is called parallax T distance between the two points of observati is called the basis In this example the basis the distance between the eyes To measure the distance D of a far aw planet S by the parallax method we observe from two different positions observatories Aar B on the Earth separated by distance AB at the same time as shown in Fig 2 2 measure the angle between the two direction along which the planet is viewed at these t points The ZASB in Fig 2 2 represented symbol is called the parallax angle parallactic angle As the planet is very far away therefore approximately take AB as an arc is very small of bo length circle with centre at S and the distance D b D 1 Then