physical science

• Read "What is a Light Year"  under the Instructor Insights section. Or find it at:  http://earthsky.org/space/what-is-a-light-year 

Step 2- Respond to the following:

• What does a Light Year measure? Is it a unit of time? Explain.
• According to your reading, how old is our Universe? 
• Based on the two points above, what is the greatest distance light could have traveled since the universe formed?
  
• Why does the "Known Universe" tour STOP at a certain point? Why is this the farthest we can see?
  

• Discuss the main physical processes that occur in each layer of the sun.
• What makes the sun so hot? Describe the fusion process that allows it to produce all the energy we require to survive.
• Fusion is very hard to produce. What about the sun allows fusion to happen there?