[填空题]
Suppose a 12,500-kg y3dk*:, /0chqd pz wmuspacetd; gc(a yg3(hship left Earth at a speed of 0.99c. What is the spaceship's kighdy3g( ta; c(netic energy? Compare with the total U.S. annual energy consumption (about $10^{19} \, \text{J}$). KE = $ \times 10^{20} \, \text{J}$
