Given that our solar system is now about 4.6 billion years old, when will we need to start worrying about the sun running out of hydrogen for fusion?

Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. if an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite

Scientists think that convection currents flow in earth’s a. continents. b. mantle. c. lithosphere. d. inner core.

What processes does carbon cycle through the biosphere?