What was a major cause of the increasing economic differences between urban poor and suburban middle class?

Which empire was called "the sick man of europe? "

What is the name for the main idea behind the settling of western lands by americans in the early-1800s?

What important discovery was made by edmond halley and alexis clairaut, using newton's ideas of mathematics and gravity? they created the scientific method to outline how science should be conducted. they were able to find the orbit of a comet and predict the year of its return. they discovered the three newest planets--uranus, neptune, and pluto. they explained why objects appear to have color.