instruction:
This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
question:
The use of the term Middle East as a region of international affairs apparently began in British and American diplomatic circles quite independently of each other over concern for the security of the same country: Iran, then known to the west as Persia. In 1900 Thomas Edward Gordon published an article, The Problem of the Middle East, which began:
answer:
Where did the use of the term Middle East as a region of international affairs begin?


question:
On November 2, 2014, the Cubs announced that Joe Maddon had signed a five-year contract to be the 54th manager in team history. On December 10, 2014, Maddon announced that the team had signed free agent Jon Lester to a 6-year, $155 million contract. Many other trades and acquisitions occurred during the off season. The opening day lineup for the Cubs contained five new players including rookie right fielder Jorge Soler. Rookies Kris Bryant and Addison Russell were in the starting lineup by mid-April, and rookie Kyle Schwarber was added in mid-June. The Cubs finished the 2015 season with a record of 97–65, third best in the majors. On October 7, in the 2015 National League Wild Card Game, Jake Arrieta pitched a complete game shutout and the Cubs defeated the Pittsburgh Pirates 4–0.
answer:
When did the Cubs announce that Joe Maddon had signed a five-year contract to be the 54th manager?


question:
The concept of inertia can be further generalized to explain the tendency of objects to continue in many different forms of constant motion, even those that are not strictly constant velocity. The rotational inertia of planet Earth is what fixes the constancy of the length of a day and the length of a year. Albert Einstein extended the principle of inertia further when he explained that reference frames subject to constant acceleration, such as those free-falling toward a gravitating object, were physically equivalent to inertial reference frames. This is why, for example, astronauts experience weightlessness when in free-fall orbit around the Earth, and why Newton's Laws of Motion are more easily discernible in such environments. If an astronaut places an object with mass in mid-air next to himself, it will remain stationary with respect to the astronaut due to its inertia. This is the same thing that would occur if the astronaut and the object were in intergalactic space with no net force of gravity acting on their shared reference frame. This principle of equivalence was one of the foundational underpinnings for the development of the general theory of relativity.
answer:
What concept explains why objects continue in constant motion?