Normal ET pet., Please don't talk about turds, I like you and I want to keep on liking you. Speed can be measured in miles-per-hour or kilometers-per-hour. Temperature is generally measured in Fahrenheit or Celsius. Compression is the opposite of decompression, if you squish something you're probably compressing it. ComPRESSion and decomPRESSion are both PRESSure terms. Expansion is opposite (to me) to Compaction, both volume terms. Volume is all about how much space seomething takes up. When talking about a situation, a real scientist will tell you how fast it is going, as well as it's temperature, its state of compression and its volume. Say hello to your Dad from me. He sounds like a smart man. See how you get along with what I've told you and get back to me. I admire your thirsty mind! I think you'll do well! I totally enjoyed learning about jet engines. Only 25% of the air taken in is used for thrust. I had no idea!