I'll try to make this brief and more of a programming question than a physics question-- since I'm nearly positive my physics is correct. I've written a simulation/code for a mass attached to six springs oscillating in 3-dimensions. The springs are each attached on the standard cartesian x-y-z axis. Take their anchor points to be + or - a on the x-axis. + or - b on the y axis, and + or - c on the z-axis. Now take a = b = c. Now, we should expect that given some initial displacement ONLY in the x-direction, there should be some oscillations only in the x-direction. This is true in my code, but I'm getting extremely small variations in the y and z directions.. oscillations on the order of 10^(-20). One of the functions is as follows : double result = 0.0, f1 = 0.0, f2 = 0.0, f3 = 0.0, f4 = 0.0; f1 = b * ((y + b) / sqrt(x*x + y*y + z*z + 2.0*b*y + b*b) + (y - b) / sqrt(x*x + y*y + z*z - 2.0*b*y + b*b)); f2 = a * y * (1.0 / sqrt(x*x + y*y + z*z + 2.0*x*a + a*a) + 1.0 / sqrt(x*x + y*y + z*z - 2.0*x*a + a*a)); f3 = c * y * (1.0 / sqrt(x*x + y*y + z*z + 2.0*z*c + c*c) + 1.0 / sqrt(x*x + y*y + z*z -2.0*z*c + c*c)); f4 = 6.0 * y - (f1 + f2 + f3); // printf ("%e %e %e %e\n", f1, f2, f3, f4); result = - wo * wo * f4; return (result); Now, since given the initial conditions the first time through this function, as expected since y = 0, then f2 = 0 and f3 = 0. BUT, f1 does not equal zero! If we evaluate f1 for y = 0, then analytically equals zero, but the commented out print statement tells me something on the order of approximately 10^(-20). Is this just C being stupid and storing values wayyyy out in the decimals places or am I going crazy here? Have I just been staring at it too long and missed something stupid?