My understanding fits best with Jay's "Toss a heavy rock from a wheeled chair" analogy. By causing a violent reaction, you are basically speeding up your accelerant (fuel). But since it can only escape in one direction (i.e., the exhaust opening), you are in effect "throwing" your fuel.

Nobody seems to have a problem visualizing a gun firing in space, in that the bullet would exit the barrel but it would also propel the gun in the opposite direction. The only difference in the rocket is that the combusted fuel is not solid like a bullet...but it still has mass and momentum.

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I'm like one of those idiot savants...well, except for the savant part.

"A long time ago, yet somehow in the future"