1. A gravity search adaptive apparatus for modeling a system, the apparatus comprising: a system modeling circuit configured to receive an input signal input to the system, to convert the input signal using a model parameter vector, and to output the converted signal; and an adaptive controller configured to calculate, using a gravity search adaptive algorithm for solving a problem of finding a global minimum of a cost function which is in the form of a quadratic function, the model parameter vector when an error signal, which is a difference between an output signal of the system and an output signal of the system modeling circuit, converges on a minimum power value, and to apply the calculated model parameter vector to the system modeling circuit, wherein the adaptive controller calculates a power value ε of the error signal, the power value ε being expressed as equation 104 below: 
 ε=σ y 2 −2 pw[k]+σ x 2 w[k] 2 (104), where w[k] is the model parameter vector resulting from k-th iteration of the calculation of the model parameter vector, p=E{x[k]y[k]}, σ x 2 =E{x 2 [k]}, x[k] is the input signal, y[k] is the output signal of the system, σ y 2 is E{y 2 [k]}, and E{•} represents an ensemble average.