Mass is a measure of the amount of matter in an object. Mass is usually measured in grams (g) or kilograms (kg). ... An object's mass is constant in all circumstances; contrast this with its weight, a force that depends on gravity. Your mass on the earth and the moon are identical.
Here Scrooge discerns another reason for the presence: his old friendship with Marley. In this moment, Marley's desire to help out his old friend has caused the ghost to appear.
