Have it an alternate universe where our scientist have connected with their universe, kind of like Sliders. Then you could have them discover Tolkein had found a hole to the Hobbit universe, and his stories had been true.

You could even make it more interesting saying the hole between their Earth and ours had once been large and open all the time. And that life had moved freely between the two worlds without them even knowing it. But wizards and Elves noticed they didn’t have any powers on one side of the hole, so they stayed on the other side.

Eventually the hole shrunk and closed up, but every now and then it appears, and this is what Tolkein found. Our scientist discover alien ruins and a alien device that gives the wizards and Elves their powers. These aliens were also responsible for the connection between the two Earths. Take it from there.

Sorry, I am more into science fiction than fantasy, but I do enjoy Tolkein’s books.