How much does ‘nothing’ weigh?

The article goes into detail about the experimental setup. According to the article they are going to use cuprates mounted on a balance. The deviations in the balance are going to be read using laser interferometry. They are using cuprates so they can easily switch between a superconducting phase and an insulating phase. This is to measure if the virtual particles have a buoyancy force.

The reason why they want to test this is explained in the paragraphs above it. It also explains why this method was chosen and what the difficulties are.

I have no idea why you would categorize this as a human interest story.