Suppose a future astronaut travels to a distance planet around a distant star. They collect rocks for dating the age of the planet and system. The astronaut compares the abundance of a certain radioactive element (half life of element = 500 million years) in the collected rocks to the abundance of the same element in a newly formed rock. They measure that there are 1/16th the number of radioactive atoms in the collected sample. How old is this planet? a. 8 billion years old.
b. 4 billion years old.
c. 1 billion years old.
d. 2 billion years old.
e. 16 billion years old.

Match your vocabulary word to its definition. 1. emigration 2. immigration 3. migration 4. overpopulation 5. sustainable development 6. under population 7. unsustainable development 8. urbanization the movement from one place to another the number of people exceeds the available natural resources in an area leaving one's homeland to settle in a new place the increase in the population of a city the movement of people to a new country the ability to meet current needs without reducing the ability to meet future needs resources being used up at a faster rate than they can be replenished birth rate insufficient to replace the existing population

Fertility and mortality rates are higher in more developed nations.

What id the primary human cause of the global warming a. storage of nuclear fuel rods b. burning of fossil fuels c. building of high-density housing d. violent conflicts over natural resources