The size of the object doesn't determine its mass. Mass is a measurement of the amount of matter of the object. Weight is the measurement of the pull of gravity on the object.
Yes, but when a portable cassette player doesn't weigh the same as a 30-foot tall robot, I'd say the mass has clearly changed.
Still relevant, though. Size-changing and mass-shifting are two different concepts, yes. But unless you want something small (like a cassette player) to weigh the same as the larger item (giant robot), mass-shifting must be applied.
Mass = amount of matter (M) Volume = amount of space occupied (V) Density = amount of matter per unit of space (M/V) Weight = Force exerted by gravity on the object (M * gravitational constant) For an object to shift in size, say, to grow or shrink, it must do one of two things: 1) It's density must change 2) It must add/decrease mass This is because mass, that is to say matter, cannot be created or destroyed, it can only change form, but in these forms it will still be matter. The size of an object doesn't determine it's mass as much as its DENSITY determines its mass. Meaning without mass shifting, you would either have Soundwave being a cassette player made of an extremely dense material that would require a crane to lift, or a robot so light he would blow over in a breeze, since his total amount of matter would be limited by the proper "mass" of one of his two forms.
