I built a Python orbit simulator that models satellite motion around Earth using Newtonian gravity and an optional atmospheric drag force. The atmosphere is represented with a simple exponential density model based on altitude, which allows a direct comparison between stable orbits with drag turned off and decaying orbits with drag turned on. Over time, I track altitude, speed, and total mechanical energy to show the difference between numerical error and real energy loss caused by drag. A major part of this project was improving the code so the motion looks smooth and physically reasonable and turning the results into clear 2D and 3D visualizations. The results show that even a simplified model can reproduce realistic-looking orbital decay and reentry behavior, while also making it clear what additional physics would be needed for more accurate predictions.