Answer:
If a spacecraft is in space for a long time, radiation is a problem. Designers must figure out a way to protect astronauts from the radiation.
Superposition is the geologic principle which explains why the bottom stratum in a section of rock is the oldest. The word literally means placing one thing on top of another where the lower strata are the older.
Answer:
The Gold Rush was the largest mass migration in U.S. history. In March 1848, there were roughly 157,000 people in the California territory; 150,000 Native Americans, 6,500 of Spanish or Mexican descent known as Californios and fewer than 800 non-native Americans
It's becasue human populations are concentrated in areas that are lacking proper resources.
