First, I'd like to make clear that this isn't exactly homework. I've been reading books about astronomy out of pure interest and I've bought myself an introductory astronomy textbook and I've been reading through it and answering all the questions. I've been doing fine... that is until I reached a "difficulty spike" or my brain decided to quit on me. For the past 2 days, I've been trying to find out how to do this: "From the information in the figure that accompanies the Making Connections box in this chapter, estimate the speed with which the particles in the CME in the final two frames are moving away from the Sun". The pictures they show are precisely these ones, same order and all: http://sohowww.nascom.nasa.gov/gallery/images/large/nov00cme.jpg This question is under a section called "Figuring For Yourself" meaning they really don't indicate anywhere in the book how to do this. I imagine this was intended so you could have an instructor to clue you along. I've searched online and have come across this (and many other sites that seem to copy & paste these): http://soho.nascom.nasa.gov/classroom/cme_activity.html There's just a few things that I don't seem to understand (I've been self-teaching astronomy and mathematics. My math wasn't exactly stellar in high school, but I'm working hard to fix it). In the SOHO site, it states "Select a feature that you can see in all five images, for instance the outermost extent of the bright structure or the inner edge of the dark loop shape. Measure its position in each image." My problem is...from where do I start my measurement? Am I supposed to measure only the feature itself, or am I supposed to start from the "far" end of the Sun's diameter and measure up to my chosen feature? I imagine its the feature only, but I am really unsure. I kept reading and saw this: v = (s2 - s 1)/(t2 - t1) where: s2 is the position at time, t2. s1 is the position at time, t1. Alright, looks simple (this is where my lack of math experience comes into play), but how exactly do I appropriately fit the time into that equation? Am I supposed to put it in minutes or hours? From 08:06 until 11:42 is 216 minutes. So I would be doing 216 - 0 (because my start time, t1, must be zero, right?). There's another question, but I don't exactly want this to be lengthy and I want to be able to solve this first. I'm not looking for direct answers, I just need a clue. Am I on the right track by going to the SOHO site? Or is it much simpler? To be sure, the book does say how fast a CME travles. It says it "travels outward at about 300 km/s" (though I've read that they can be anywhere from 200-1000km/s), which of course would make this question easy. But I assume they want it only judging from those pictures. I sincerely apologize if I've violated any forums rules, though I don't think I have.