1. Models
What is a model?

2. A scientific model  is a simplification
is a smaller or larger representation
(pattern, plan, replica, or description) designed to show the structure/function of the real thing
 can represent an object, system, or concept
 usually contains the smallest number
of parts that are necessary to
describe the real thing
 can be static or dynamic

3. A scale model can use the same or different materials as the original but the dimensions must be proportionate.
 scale given in key/legend (ex. 1” = 1 mi)
 can be a working model (cockpit simulator)
Examples:
maps
blueprints
architectural drawings

4. Examples of Scientific Models

5. Models of the Universe
Scientists have always searched for an explanation of how the universe was formed
Over the years many theories have developed
The balloon model represents what we presently know about the universe.
The Universe (balloon) is getting larger, and the galaxies (dots) are moving apart from each other.

6. Steady State Theory galaxies are not moving away from each other
new stars are being made from energy in the center of the galaxies
But if the balloon model is right, does Steady State make sense????

7. Big Bang Theory Proposed by Georges Lemaitre 1926
Galaxies are expanding in all directions
Must have started at a central location with an explosion
Does the balloon model work for this theory??

8. Oscillating-Universe Theory
universe has gone through periods of expansion and contraction
the universe is currently in a period of expansion
What would have to happen to the balloon for this theory to work?

9. Expansion Theory
universe is expanding faster than it did a few million years ago
1% growth every 200 million years

10. Limitations of Models

11. What are the limitations of these models?
Because a model is a simplification, it is necessary to realize that the final result may not give a completely true description of the object or system.
What are the limitations of these models?