An explosive mixture of saltpeter, sulfur, and charcoal, chiefly used in discharging projectiles from guns and for blasting. These will be used in the classroom to build the time-line skeleton. If the students miss any key event, be prepared to fill-in. When assigning homework, only give key event and make student find the year of discovery or event and by whom. Student groups present results of advanced homework, followed by discussion of each topic - teacher adds material not researched by groups.
Class then adds the title of their group's event on the timeline at the correct date.
Have students research the significance of 1957 as related to space flight.