The schwarzschild radius of a black hole is r_s = 2 g m_bh / c^2.
derive the schwarzschild radius of the universe during the planck time, r_s, p.

According to social exchange theory, altruistic behaviors benefit the individual who performs them.

What is the measurement of how fast an object moves relative to a reference point?

Why is rain likely when warm, moisture-laden air meets cold air? a) the lighter warm air will rise and cool down, causing condensation and rain. b) the cold air moves faster and pushes the warm air away, causing condensation and rain. c) the moisture in the warm air condenses on contact with the cold air, causing rain to fall. d) the cold air mixes with the warm air, reducing its temperature causing moisture to condense.