Human Understanding of both Earth and Space has Changed Over Time Unit E: Topic One

1.5 Describing the Position of Objects in Space

Frames of Reference

Frames of Reference A frame of reference is a set of axes used to describe positions or motions of things. The stars, the Sun and the planets do not rotate around the Earth, but seem to because the Earth is rotating on its axis. The Earth is our fixed frame of reference. On Earth, the equator and the prime meridian (latitude and longitude) are the axes used. But the motion of objects depends on your frame of reference.

Frame of reference worksheet

Stars as a Frame of Reference Ancient cultures tried to explain the motions of the stars and planets, with their frame of reference being the Earth. To track the actual motion of each celestial body in space, you need to use the stars as your frame of reference. To do this: make an observation of which celestial body you are studying include other stars in relation to it make subsequent observations and include those same stars Over a period of time you would be able to determine in which direction the celestial body you are studying is moving.

Altitude and Azimuth

Where in the sky is it? But how did they measure locations of celestial bodies in the sky? In order for scientists to understand the sky and what was going on, they had to observe, measure and calculate. To document the location of an object, scientists use altitude, azimuth and altitude-azimuth coordinates.

Altitude Altitude gives you the “how far above the horizon it is”. (0º to 90º) Stars straight up will be at 90º Points on the horizon will be at 0º Stars half way up the sky will be at 45º Zenith refers to the highest point directly overhead

Azimuth Azimuth determines which compass direction it can be found at in the sky. ( in degrees from 0º to 360º ) Stars in the north will have an azimuth of 0º East = 90º South = 180º West = 270º (clockwise)

http://astro. unl. edu/classaction/animations/coordsmotion/altazimuth http://astro.unl.edu/classaction/animations/coordsmotion/altazimuth.html

Determining Motion of Objects in Space Planet means “wanderer” in ancient Greek The path in the sky along which the Sun takes is called the ecliptic. The Celestial Sphere is the name given to the very large imaginary ‘sphere of sky’ surrounding the Earth. Celestial equator is directly above the Earth’s Equator

Activity: Altitude and Azimuth Note the star up in the corner of the room. Extend one arm out in front of you and make a fist. Close on eye and practice aiming along your arm so you can see the star. Start with one arm held horizontal to the floor. From your desk – estimate how many fists you need to “climb” to the object. Each fist is 10 degrees – Record how many degrees the altitude of the star is from your desk. Next estimate the compass direction. Use the compass directions given. Record the azimuth. Compare with your neighbour.

There are 5 hanging objects in the classroom There are 5 hanging objects in the classroom. Describe their coordinates using altitude and azimuth.   Show your data in a table for azimuth-altitude: Coordinate Object 1 __________ Object 2 __________ Object 3 __________ Object 4 __________ Object 5 __________ Altitude   Azimuth

Discussion Questions What similarities did you notice in your results? What differences? What was the accuracy of your results? Explain why you might have gotten a different result from a nearby student. Explain why you might have gotten a different result from a student farther away.