Due to the fact that there were hot air balloons and everything else, he wanted to explore beyond that and go to the next level, which then in turn made him want to start tinkering with rockets.
The correct answer is B) to explore the last frontier.
What caused scientists such as Robert Goddard, Konstantin Tsiolkovsky, and Hermann Oberth to experiment with rocket technology in the early twentieth century was to <em>explore the last frontier.</em>
The idea of exploration and go beyond our planet attracted many scientists that started to research and experiment with technology to launch rockets and to know more about space and the human possibilities to understand it. For instance, that is the case of American engineer Robert Hutchings Goddard whose research made him invent the liquid-fueled rocket.
The other options of the question were A) to launch of artificial satellites. C) to win their countries in the space race. D) to help their governments to spy their enemies. E) to gain victory in wars.
With the assassination of President Abraham Lincoln, Andrew Johnson became the 17th President of the United States (1865-1869), an old-fashioned southern Jacksonian Democrat of pronounced states' rights views.
