If the equation E equals mc squared gives energy which is a scalar physical quantity how is this possible when multiplying a scalar and a vector results in a vector quantity?

Answer 1

Energy is a product of 1 scalar quantity which is mass and 1 vector quantity which is the velocity of light within a vacuum. The velocity of light in the equation is squared which returns an absolute value negating any sign it has. This results in both terms having no sign. A vector quantity must have both a direction and a magnitude. The product returned will always be a positive quantity which means it has no direction.