Final answer:
Lansing initially intended to study journalism, but changed to astronomy after finding out that the journalism school was not opening for another year and rediscovering his childhood interest in the subject.
Step-by-step explanation:
Lansing initially planned to study journalism; however, he ended up studying astronomy. Upon his arrival at the University of Missouri at age 22 in 1907, he discovered that the journalism school would not open for another year. While browsing through the college catalog, he saw 'Astronomy' listed among subjects beginning with 'A' and, recalling his childhood interest in the stars, he decided to pursue astronomy for the following year. This change was prompted by the delay in the journalism program's availability and a rekindled passion for astronomy from his younger years.