Shuai Liu

Two transparent sheets with circles drawn on them. If you stack them exactly, the circles align. But give one sheet a slight twist, and a new pattern emerges: in some places the circles bunch together, in others they spread apart. That's roughly how moiré works — an unexpected pattern born from rotating two periodic structures.

Imagine three witnesses who saw the same event. Two tell the same story, the third tells a different one. Whom do you believe? This is exactly the situation in astronomy when measuring carbon in the star J0815+4729, an ancient object with a record-low iron abundance (carbon is one of the key elements used to infer the properties of the…