I've read the question titled "How is Docker.io different from a normal virtual machine?", but I'm still not certain how "virtual" docker containers are. For example, in a scientific setting, repeatability is very important. If an image produces a certain result on one machine, will the computation be exactly the same on another if using the same image?
(I don't really know at what level different operating systems, kernels, hardware, or architectures can alter calculations in practice, or at what layer Docker abstracts things, if at all.)