What amount of red, green, and blue light is necessary to make black? Explain your reasoning.

In the united states, tornadoes generally occur because of the freezing of ocean water underwater earthquakes meeting of cool and warm air masses shifting of warm and cool ocean currents

The star nearest to our sun is proxima centauri, at a distance of 4.3 light-years from the sun. how far away, in km, is proxima centauri from the sun?

Which of the following is not an appropriate unit for acceleration? (kg/12 mihr? m/min/sec cm/30c?