Measurements of large distances
- 1. Measurements of large distances Class 11 Project for Physics by Yash Joshi Measurements of large distances
- 2. Units For measuring large distances I. Astronomical Unit (AU): The mean distance between the earth and the sun is 1 AU i.e. 1.496 × 1011. II. Light Year (ly): The distance travelled by light in vacuum in one year i.e. 9.46 × 1015 m. III. Parallactic Second (Parsec): It is the distance at which an arc of length 1 astronomical unit subtends and angle of 1 second of arc. 1 Parsec = 3.26 ly.
- 3. Method of triangulation • Triangulation is a surveying method that measures the angles in a triangle formed by three survey control points. Using trigonometry and the measured length of just one side, the other distances in the triangle are calculated. The shape of the triangles is important as there is a lot of inaccuracy in a long skinny triangle, but one with base angles of about 45 degrees is ideal. • Each of the calculated distances is then used as one side in another triangle to calculate the distances to another point, which in turn can start another triangle. This is done as often as necessary to form a chain of triangles connecting the origin point to the Survey Control in the place needed. The angles and distances are then used with the initial known position, and complex formulae, to calculate the position (Latitude and Longitude) of all other points in the triangulation network. • Although the calculations used are similar to the trigonometry taught in high school, because the distance between the survey points is generally long (typically about 30 kilometres) the calculations also allow for the curvature of the Earth.
- 4. The Parallax Method • Parallax is the displacement or the change in the apparent position of the object when viewed from two different points of view. The two points of view have their own line of sights and parallax is measured as half of the angle between the two lines of sights. • When you are traveling in a vehicle and you look around as you are moving, you will see that objects in the distances appear to move more slowly than the objects closer to you. This is the effect of parallax. Nearby objects have a larger parallax than the distant objects, so the parallax can be used to determine distances. • The phenomenon of parallax, when combined with triangulation, will yield the location of the object with considerable accuracy. Astronomers regularly use the parallax method to measure the distances of the closer stars.
- 5. Calculating the distance using parallax method
- 6. Thank You! References: • http://www.eso.org/public/outreach/eduoff/aol/market/coll aboration/solpar/ • https://en.wikipedia.org/wiki/Triangulation_(surveying) • https://en.wikipedia.org/wiki/Parallax • https://www.icsm.gov.au/education/fundamentals- mapping/surveying-mapping/surveying-methods • ~Yash Joshi 11B