Examples of Companies/Tools Simulating Real World Processes

I had a look at the recent Request For Startups (https://www.ycombinator.com/rfs?utm_source=tldrnewsletter#using-machine-learning-to-simulate-the-physical-world) on the ycombinator site.

One of the topics that caught my eye was "USING MACHINE LEARNING TO SIMULATE THE PHYSICAL WORLD".

Does anyone know of companies or tools which provide such services? I'm particularly interested in specific use cases.