Much of the fighting in World War I took place along the Western Front, within a system of opposing manned trenches and fortifications (separated by a "No man's land") running from the North Sea to the border of Switzerland. On the Eastern Front, the vast eastern plains and limited rail network prevented a trench warfare stalemate from developing, although the scale of the conflict was just as large. Hostilities also occurred on and under the sea and—for the first time—from the air. More than 9 million soldiers died on the various battlefields, and nearly that many more in the participating countries' home fronts on account of food shortages and genocide committed under the cover of various civil wars and internal conflicts. Notably, more people died of the worldwide influenza outbreak at the end of the war and shortly after than died in the hostilities. The unsanitary conditions engendered by the war, severe overcrowding in barracks, wartime propaganda interfering with public health warnings, and migration of so many soldiers around the world helped the outbreak become a pandemic.
What is the Western Front?
a system of opposing manned trenches and fortifications (separated by a "No man's land") running from the North Sea to the border of Switzerland.

Colonial records of French and Spanish slave ships and sales, and plantation records in all the former colonies, often have much more information about slaves, from which researchers are reconstructing slave family histories. Genealogists have begun to find plantation records, court records, land deeds and other sources to trace African-American families and individuals before 1870. As slaves were generally forbidden to learn to read and write, black families passed along oral histories, which have had great persistence. Similarly, Native Americans did not generally learn to read and write English, although some did in the nineteenth century. Until 1930, census enumerators used the terms free people of color and mulatto to classify people of apparent mixed race. When those terms were dropped, as a result of the lobbying by the Southern Congressional bloc, the Census Bureau used only the binary classifications of black or white, as was typical in segregated southern states.
What were slaves usually not allowed to do?
learn to read and write

The concept of emissivity is important in understanding the infrared emissions of objects. This is a property of a surface that describes how its thermal emissions deviate from the ideal of a black body. To further explain, two objects at the same physical temperature will not show the same infrared image if they have differing emissivity. For example, for any pre-set emissivity value, objects with higher emissivity will appear hotter, and those with a lower emissivity will appear cooler. For that reason, incorrect selection of emissivity will give inaccurate results when using infrared cameras and pyrometers.
Along with pyrometers, what devices can receive inaccurate results if emissivity is not set correctly?
infrared cameras