Science Department

Science 9

Unit : Space
Time required: 2 days
Lesson : 8

Objectives

• use triangulation to determine the position of an object given information on the distance from three different points

Introduction

As our technology in telescope increases, it creates more questions like "Where are these stars?" How far away are they from Earth? How big is the universe? To find answers to these questions, astronomers develop methods to measure the distances to the stars.

Measuring with Triangulation

Imagine that you are standing on a beach and you are a from your friend. You look out and you see a fishing boat anchored out on the lake, not knowing if you can swim out that far, you can actually estimate how far it is! This is the method know as triangulation. Triangulation (also known as parallax technique) is a method of measuring distance indirectly by creating an imaginary traingle between an observaer and an object whose distance is to be estimated.

This is the same method astronmers use to measure stars.

How does Triangulation Work?

Take a look on page 388 of Science Focus 9 text and see the steps to triangulation.

1. Create a baseline.

You need to know the baseline distance between the two points

2. Measure the angles from the end of the baseline.

Measure the angle between the line to the object and the end of the baseline. You need two angles at either end.

3. Make a scale drawing of the imaginary triangle.

Note the scale drawing. They used 1cm = 20 m. Draw the baseline and the using a protractor and ruler, you draw a line from each end of the baseline at the angles you recorded. The point at which the two lines cross is the position of the object. Then use the scale drawing to measure the distance of the object in question.

Triangulation a Star

You can see that triangulation can be used for stars. In this case, the baseline is the diameter of the Earth. Astronomers would include two sightings of the nearby star are taken six months apart.

Distances are measured in units of AU or light years. One astronomical unit (AU) is the dostance from the Earth ot the sun (150 million km). But even this unit is not practical for measuring items in our system. Therefore, astronomers have creaed the light year - this represents the distnace that light travels in one year, a distance equal to about 63240 AU.

Assignment:

Use the method of triangulation, please complete scale drawings for page 392 in paint and solve for the distances to the following questions:

• page 392 #5
• page 436 #23