What Is a Probable Mechanism for the Initial Triggering, and the Subsequent

question 22

Multiple Choice

What is a probable mechanism for the initial triggering, and the subsequent maintenance, of the density wave that forms the visible arms in spiral galaxies?

• A) equivalent of a massive "sound" wave generated at the center of the galaxy by the gravitational energy release at the initial formation of the galaxy, producing progressive compression of material that is shaped by galaxy rotation
• B) gravitational influence from the rotating central supermassive black hole at the galactic center of the arm material
• C) gravitational interaction from the close passage of another galaxy
• D) shock waves from supernova explosions of massive stars within the spiral arms

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Definitions:

Economies of Scale

Enterprises gain cost benefits from their operation size, as the cost for each unit produced typically drops when the scale enlarges because fixed expenses are distributed across a greater number of output units.

Efficient Scale

The level of production at which a firm can produce its product at the lowest average cost per unit.

Economies of Scale

Economies of scale describe the cost advantages that enterprises obtain due to their scale of operation, with cost per unit of output generally decreasing with increasing scale.

Economies of Scale

Cost advantages reaped by companies when production becomes efficient, as the cost per unit of output decreases with increasing scale.