Don’t introduce anything too radical, so no tunneling electron microscopes just yet. However, you should be able to use empirical science to debunk BS ideas and move things along that way.

For example, the phlogiston idea was proven wrong in the 1770s when people started burning metals and realized their mass increased in the process. Also, certain compounds can release oxygen, which can maintain a flame in an otherwise empty container. Sounds simple to us now, but back in those days, it was revolutionary.

The idea is that, you have to work within the framework available at the time.