Origins #3

The authors definitely have a friendly relationship with the audience. As implied in my other posts, Tyson and Goldsmith do a very good job of keeping the language light, friendly, and easy to understand, while the actual content is scientific and very educational. The authors bring up extremely interesting topics, though it might not seem that way to anyone not interested in science. One example is the properties of dark matter; the most common form of matter in the universe but also something that scientists no nearly nothing about. The authors describe, in very friendly language, how the only reason that astronomers are able to detect dark matter is through its gravitational pull. If not for dark matter, each galaxy in the universe would have only one sixth of the gravitational pull that it does. Scientists are able to calculate this number by finding the average speed traveled by all the stars in each galaxy. Any object in a galaxy needs to maintain a certain speed based on the gravitational pull of the galaxy; all objects need to maintain a speed that will allow them to not be sucked into the center of the galaxy or cause them to fly out of the galaxy. So scientists use this average speed to estimate the gravitational pull of a galaxy. When first finding the gravitational pull, it does not match up with the amount of "normal" matter in each galaxy; it is the gravitational pull of a galaxy with six times the amount of "normal" matter. So then dark matter comes into the equation; it makes up for the amount of missing matter that gives the galaxy its high gravitational pull.
I'm sorry if that was cinfusing, but the authors do a much better job of explaining it in the book. This information about dark matter is just some of the many compliated concepts that the book makes easy to understand.