DR.Orbit vs ViGravitatis

Demonstration of how a mass (e.g. earth) can orbit around a gravitational well (e.g. sun). Use your finger to push the mass onto a trajectory that results in a stable orbit around the well. Use the options menu to introduce some drag (good to get rid of the mass), to bring up some eye candy or to influence the movement of the mass by tilting your iPad. Physics background: Gravitational forces act between masses. In this demonstration a big stationary mass is situated in the center of the screen. Its location is fixed and it is hidden behind a cap. If you put a small mass onto the screen, it begins accelerating towards the big mass until it disappears under the cap "into the drain". You can prevent your mass from going down the drain by giving it an initial push. Try experimenting with the directions of your pushes. If it is done right, the small mass will be falling around the big mass without - in theory - ever disappearing into the drain. But due to the not very accurate numerical methods used for the calculation of the trajectory of the mass, the reality in this demonstration might be different. This also applies to the background grid on the screen: It does not show the correct wraping of space caused by the big mass in the middle of the screen. Its shape is a compromise between aesthetics and numerics. Link to demonstration video: http://www.youtube.com/watch?v=pwXI-EiZE4o

The physics is fun! The law of gravity in particular. Explore it with ViGravitatis today and understand the trajectory of celestials tomorrow! Guide: Modes ViGravitatis provides two key modes: Creation and Simulation. In the Creation Mode, you have the full power to place anything in your space and anywhere. When you press Play, Simulation mode starts automatically. In this mode, you are limited to changing a few parameters of a selected celestial. Moreover, different capabilities are available when simulation is playing compared to when it is paused. Use the toggle with the hammer icon to switch between Creation and Simulation. Note that when you switch from Simulation to Creation, the space is reset to its initial state. Meaning that the positions and velocities of celestials are reset. The key scenario of using the app is to set up your scene in the Creation Mode and then check how it is changing during the simulation. Then, go back to Creation Mode, change a few initial parameters, and check again how it affects the simulation. Guide: Simulation Speed There are a few ways you can affect the speed of the simulation. First of all, it can be completely paused at any time. So, no objects are moving. But you can also change the accuracy of the simulation using the slider near the Play/Pause toggle. It can increase the speed of the simulation, sacrificing accuracy. So, at very high speeds, objects can start moving in a very surprising way, albeit inaccurately. On the other hand, you can change the “iterations count”. With greater iterations in total simulation runs, faster without any degradation in accuracy, but it will require more battery power of your device.