It would be hard to tell if the rest of the universe even existed. No electromagnetic radiation or cosmic rays are going to make it through the ice. They'd have

It would be hard to tell if the rest of the universe even existed. No electromagnetic radiation or cosmic rays are going to make it through the ice. They'd have to get all the way to neutrino telescopes or gravity wave detectors to sense anything outside their ocean, and why would they spend the resources? Humanity could see our moon and it still took us thousands of years to get there. Really they'd only do it if they managed indefinite population growth without poisoning their biosphere with waste products, and had to mine out the ice shell just for more living space. That would be tough: the equivalent would be if every square meter of the Earth's surface, including oceans, was as densely populated as Manhattan. That gets us up to 14 trillion people. Now make every building 10 km tall.