At the turn of the century, why did most immigrants to the United States move and live in cities?

When it is a high tide in georgia, usa, where on earth is another place that is also experiencing a high tide

How can studying economics us make better choices about how to use scare resources

The first atomic explosion was detonated in the desert north of alamogordo, new mexico, on july 16, 1945. what percentage of the strontium-90 ( yr) originally produced by that explosion still remains as of july 16, 2016?