This app simulates the effects of gravity. You can fling particles at each other and watch them interact. Create solar systems and galaxies! Make a planet and fling asteroids into it! Add a black hole and watch everything get sucked in! You can even adjust the size, mass, and color of the particles! Zoom in and out and look around with two fingers!
During physics class this year, I wanted to explore the effects of gravity further after we learned about Newton's equations in class. It began as a personal project, only intended for my experiments, but I soon realized the project had potential. I polished the app, added features to easily adjust the properties of planets, and created a starry sky particle effect to use as a backdrop. My favorite feature of the app is the ability to create black holes. I based the black hole physics on real physics, but I had to adjust the speed of light in my calculations so that the user's initial black hole would be of a visible size. The user can create a black hole by setting the mass very high and the radius very low. The black hole looks different from other particles. They are pitch black, but I gave them a glowing white edge to make them visible against the black background. They will absorb other planets upon collision and will grow in mass and radius accordingly. The two hardest parts of the app were managing collisions with black holes, and optimizing the gravitational function to increase performance. The app is meant to be used by anyone from elementary school kids to working adults, and I have worked to make it user friendly so anyone can figure out its basic functions. The app has over 4000 downloads, and counting, from all over the world.