1) Read the first two subsections on special relativity on the Einstein-online website(https://www.einstein-online.info/en/category/elementary/special-relativity-elementary/), and in a brief paragraph explain what is meant by the principle of relativity and how it relates to the concept of inertial frames.

2a) Read Subsections 3 and 5 and then compare the concepts of space and time vs. spacetime in the context of special relativity.

2b) In your words, describe Fig.1, explaining the different regions I, II, and III.