how the Machine works?

[deleted]

I can do it but I'm going to have to throw a chair at your monitor first. We need visuals.

There is no explanation. Just like in all Science-Fiction stories we are led to accept all things that aren't present in our "real" world. We never see how hyper-drives work in the Star Wars universe even though George Lucas creates a world where machinery relies on oils, fuels, and diode-reliant electronics, it's just that pesky detail about how Light-speed can be accomplished with 20th Century looking gadgetry. Same goes for artificial gravity.

Back to your question, even though it's not explained I think the movie overall did a good job of not wanting me as a viewer to question its viability as a technology. Not until after viewing the film did I stop to think why the government would only be using this type of machine for a specific terrorist attack when they could use it at any other historically significant event that affects not only US history but World history.