Question: Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it. It is used in the manufacture of lenses and windows. Common glass has a refraction index around 1.5. This may be modified by adding low-density materials such as boron, which lowers the index of refraction (see crown glass), or increased (to as much as 1.8) with high-density materials such as (classically) lead oxide (see flint glass and lead glass), or in modern uses, less toxic oxides of zirconium, titanium, or barium. These high-index glasses (inaccurately known as "crystal" when used in glass vessels) cause more chromatic dispersion of light, and are prized for their diamond-like optical properties.
Is there an answer to this question: Why are high-index glasses modified?

Answer: unanswerable


Question: Antarctica is colder than the Arctic for three reasons. First, much of the continent is more than 3,000 m (9,800 ft) above sea level, and temperature decreases with elevation in the troposphere. Second, the Arctic Ocean covers the north polar zone: the ocean's relative warmth is transferred through the icepack and prevents temperatures in the Arctic regions from reaching the extremes typical of the land surface of Antarctica. Third, the Earth is at aphelion in July (i.e., the Earth is farthest from the Sun in the Antarctic winter), and the Earth is at perihelion in January (i.e., the Earth is closest to the Sun in the Antarctic summer). The orbital distance contributes to a colder Antarctic winter (and a warmer Antarctic summer) but the first two effects have more impact.
Is there an answer to this question: What does temperature do with elevation?

Answer: decreases


Question: German philosophers have helped shape western philosophy from as early as the Middle Ages (Albertus Magnus). Later, Leibniz (17th century) and most importantly Kant played central roles in the history of philosophy. Kantianism inspired the work of Schopenhauer and Nietzsche as well as German idealism defended by Fichte and Hegel. Engels helped develop communist theory in the second half of the 19th century while Heidegger and Gadamer pursued the tradition of German philosophy in the 20th century. A number of German intellectuals were also influential in sociology, most notably Adorno, Habermas, Horkheimer, Luhmann, Simmel, Tönnies, and Weber. The University of Berlin founded in 1810 by linguist and philosopher Wilhelm von Humboldt served as an influential model for a number of modern western universities.
Is there an answer to this question: What did Engels develop in the 1900's?

Answer: unanswerable


Question: Manhattan was on track to have an estimated 90,000 hotel rooms at the end of 2014, a 10% increase from 2013. In October 2014, the Anbang Insurance Group, based in China, purchased the Waldorf Astoria New York for US$1.95 billion, making it the world's most expensive hotel ever sold.
Is there an answer to this question: The Waldorf Astoria hotel sold for how many dollars?

Answer:
1.95 billion