Problem: Stars, planets, and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary: the density of atmospheric gas simply decreases with distance from the object. The Earth's atmospheric pressure drops to about 6998320000000000000♠3.2×10−2 Pa at 100 kilometres (62 mi) of altitude, the Kármán line, which is a common definition of the boundary with outer space. Beyond this line, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the Sun and the dynamic pressure of the solar winds, so the definition of pressure becomes difficult to interpret. The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre.
`Why does thermosphere past the Karman line vary so greatly?
The answer is the following: due to space weather

Problem: Memorization is a method of learning that allows an individual to recall information verbatim. Rote learning is the method most often used. Methods of memorizing things have been the subject of much discussion over the years with some writers, such as Cosmos Rossellius using visual alphabets. The spacing effect shows that an individual is more likely to remember a list of items when rehearsal is spaced over an extended period of time. In contrast to this is cramming: an intensive memorization in a short period of time. Also relevant is the Zeigarnik effect which states that people remember uncompleted or interrupted tasks better than completed ones. The so-called Method of loci uses spatial memory to memorize non-spatial information.
What is the spacing effect?
The answer is the following: shows that an individual is more likely to remember a list of items when rehearsal is spaced over an extended period of time

Problem: Parisian examples of European architecture date back more than a millennium; including the Romanesque church of the Abbey of Saint-Germain-des-Prés (1014-1163); the early Gothic Architecture of the Basilica of Saint-Denis (1144), the Notre Dame Cathedral (1163-1345), the Flamboyant Gothic of Saint Chapelle (1239-1248), the Baroque churches of Saint-Paul-Saint-Louis (1627-1641) and Les Invalides (1670-1708). The 19th century produced the neoclassical church of La Madeleine (1808-1842); the Palais Garnier Opera House (1875); the neo-Byzantine Basilica of Sacré-Cœur (1875-1919), and the exuberant Belle Époque modernism of the Eiffel Tower (1889). Striking examples of 20th century architecture include the Centre Georges Pompidou by Richard Rogers and Renzo Piano (1977), and the Louvre Pyramid by I.M. Pei (1989). Contemporary architecture includes the Musée du Quai Branly by Jean Nouvel (2006) and the new contemporary art museum of the Louis Vuitton Foundation by Frank Gehry (2014).
Who built the Louvre Pyramid?
The answer is the following: I.M. Pei

Problem: The major Allied participants were the United States, the Republic of China, the United Kingdom (including the armed forces of British India, the Fiji Islands, Samoa, etc.), Australia, the Commonwealth of the Philippines, the Netherlands (as the possessor of the Dutch East Indies and the western part of New Guinea), New Zealand, and Canada, all of whom were members of the Pacific War Council. Mexico, Free France and many other countries also took part, especially forces from other British colonies.
Did Mexico play a part in the war?
The answer is the following:
took part