Is the earth shrinking, expanding or staying the same?

Answer 1

Your question is somewhat ambiguous, so I'll arbitrarily interpret you question as to be refering to the mean radius of the surface of the earth (vs. it's mass, for example). This radius is shrinking due to secular cooling. The heat interior to the earth is maintained, over geological time scales, by radioactive decay of unstable isotopes throughout its bulk. As the isotopes decay, they decrease in radioactivity, giving off less heat over time. This means the earth gradually cools and shrinks due to thermal contraction (solids shrink when they cool). This has been inferred to cause the length of the earth's day to increase at a significantly slower rate than it otherwise would due to tidal drag (a spinning body generally speeds up if it contacts due to angular momentum conservation).

Answer 2

it's expanding by the amount of cosmic debris that enters the atmosphere every year. It's also shrinking slightly from some of the atmosphere that reaches escape velocity. Since both those quantities are such a small amount compared to the mass of the earth, for all intents and purposes the mass of the Earth is pretty much a constant.

Answer 3

It's growing. Several years ago I read in a science mag that scientists estimated Earth gaining approximately 19 tons per day from interstellar dust raining down on us. That help? ;-)=

Answer 4

good question........we loose elements to space all the time[ie.helium,hydrogen,etc.] most are lighter than air, on the other hand we gain others,[ie.cosmic dust,metiors,fragments,etc.]...in either case the amount is fairly negligable....this would make a good long term study!