Over the next month many academic institutions will be moving all learning online. As scientists, we are often used to being able to demonstrate difficult concepts in the real world to emphasize points from classroom lessons. Watch the pencil, feather, and bowling ball all drop at the same speed, etc. Watch the gears mech and spin at different speeds. See density and buoyancy reflected in multilayer float stacks. This shift may present great difficulties for students and instructors used to a different learning environment.

For twenty+ years we've promised a shift to online learning and resources to aid understanding. Now it's become a necessity. Every department in every college has weeks for professors to develop online solutions. I believe these online forums are an excellent opportunity for us to share the resources we have found the most useful/valuable so that other instructors and students can continue to learn in a new environment.

So, from Calculus, to Physics, to Chemistry, to Biology, to the various flavors of Engineering, what online resources have you found to be the most effective tool for visualizing a learning concept?