I was reading this article: http://www.eurekalert.org/pub_releases/2016-08/ac-irj082916.php The following paragraph has me scratching my head, wondering what they are talking about: "The team studied what happened to the current passing through the exotic material zirconium pentatelluride (ZrTe5) when exposed to a very high magnetic field. Measuring a current in a high magnetic field is a standard way of characterising the material's electronic structure. In the absence of a magnetic field the current flows easily through ZrTe5. This is because in ZrTe5 the electrons responsible for the current have no mass. However, when a magnetic field of 60 Tesla is applied (a million times more intense than the earth's magnetic field) the current is drastically reduced and the electrons acquire a mass. An intense magnetic field in ZrTe5 transforms slim and fast electrons into fat and slow ones. " What do they mean the electrons responsible for the current have no mass? I thought electrons always have mass (i.e. ~1/1800th mass of a proton)?