1. Topic 1 Space Exploration
For Our Eyes Only
Topic 1
Space Exploration

2. Frames of Reference
A set of axes of any kind that is used to describe the positions or motions of things.
Example:
The equator and the prime meridian are the axes for the frame of reference to locate positions on Earth (latitude and longitude).

3. Frames of Reference
Depending on where you are your frame of can be different.
Example:
When you are travelling on a bus you feel stationary in relative to the bus. Yet the road seems to be moving toward you. This is because the bus is your frame of reference.
To a person standing on the side of the road you and the bus would be moving relative to the ground. This is because their frame of reference is the Earth.
Neither frame of reference is correct or incorrect; they are simply two different reference frames or points of view.

4. What Our Ancestors Saw
Celestial Bodies are objects that are seen in the sky (e.g. the Sun, Moon, stars and planets).
Ancient People watched the motion of the celestial bodies and it appeared that the stars revolved around the Earth.
They learned many things while watching the sky which include:
Stars make unchanging patterns in the sky
Patterns can look like objects. Ancients named these groups of stars and we refer to them as constellations.
Star Constellations

5. What Our Ancestors Saw
Each night stars rise and set 4 minutes later. This means that over time different stars are in the night sky. Since there are different stars in the sky over periods of months. This lead to the ability of people to predict changing of seasons which eventually lead to the creation of calendars.
Sun rises and sets at a rate different from the stars.
Moon rises and sets at a rate different from the stars. Moon shows phases.
Planets (Mercury, Venus, Mars, Jupiter and Saturn) rise and set at rates different from stars
Stars and planets appear to be in different places depending on where you are on Earth.
Ancient societies created stories to explain the origin and motion of celestial bodies
Star Constellations
NASA Photo journal

6. Sky Co-ordinates
Two co-ordinates are used to measure celestial bodies in the sky:
Azimuth: angle measured clockwise from north
Altitude: angle measured above the horizon in degrees
Altitude-Azimuth Co-ordinates:
Angles used to specify the co-ordinates of a celestial body
Locate a celestial body relative to a fixed Earth.
Co-ordinates for specific celestial bodies change depending on the time of the reading.

7. Sky Co-ordinates
Ability to measure positions of bodies in the sky depends on the technological devices:
Astrolabe: a device used to measure the altitude of an object
Invented by ancient Greeks
Compass: used to measure an object’s azimuth
Imported from Arabic world in about 1200 c.e.
Navigation was approved by these tools and great sea exploration of the world began.

8. The Stars as a Frame of Reference
With Earth as a reference point stars and planets appear to move in a circle above us at the same rate. Although this is not their actual movement. To track the actual movement of each celestial body (i.e. Sun, Moon and planets) you need to use the stars as a frame of reference. To track a celestial bodies actual movement you would record the objects position in reference to bright stars near the object on the first night. The next night you record the objects new position in relation to the same bright stars. If you continue to do this over several weeks you will start to see the objects true pattern of movement.

9. The Earth-Centred Model
Also known as the geocentric model of the universe.
The belief that the stars circle around the Earth.
Theory dominated for almost 2000 years.
Model is based on ideas of Greek philosopher, Aristotle.
Aristotle based model on mathematics and geometry of Pythagoras and Euclid.
Model:
provided means to predict dates and times of celestial bodies rising and setting.
required 55 inner spheres to account for observed motions
was difficult to explain why three planets sometimes reversed their direction (called retrograde motion)

10. The Sun-Centred Model
Also known as the heliocentric model of the universe.
Nicholas Copernicus proposed the model that the Sun was fixed and the Earth revolved around it.
Happened in the 1500s
This model is currently accepted today as how the universe is organized.
Models of Universe