Spike is right, but he didn't use the KEY words: **Centre of Mass.** Gravity is a conservation force, true. What goes up must come down. Unless what goes up moves at 7 miles/second or faster (escape velocity of Earth).

What would happen if 600Meg ppl jumped all at the same time ( consider the technical diffuclties in the statement "all at the same time"), would be a : CentreofMass= (M1R1 +m2R2)/M1+m2, where M1=Earth mass ,

R1=Radius of Earth in meters. m2 =Total ppl mass (of 600Meg ppl), R2 =R1+jump height. (1 meter assume for simple calculation). Ok now we would expand the equation to get M1(R1+r1) and m2(R1+r2), where r2=jump height of 1meter and solve for r1.

simplifying the equation we get. r1=(m2Xr2)/M1, if r2=1m, then r1=m2/M1 or the ratio of jumpingpeople mass/Earth mass. r1 becomes indeed very small!!

What would happen is you'd get a wobble of whatever r1 works out to be during the jump. Then some minor decaying oscillation after the landing. Is 600 million enough, NO.

Edit : Sun_Jupiter Ex: put Sun in position 0, mass = 333,000 Earths. Jupiter in position 778,000,000 km, mass=318 Earths. Center of mass is 742,000 km from the Sun center, 96,000 km outside its surface. As Jupiter does its 11 year orbit, the Sun does a 1.5 million km orbit around the center of mass.

EDIT: I NEED TO GET OUT MORE puke:

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