I wasn't trying to be harsh on the author. I thought about this late last night and decided that the easiest way to explain the error could be that the author was employed by Physics World to compose interesting articles in layman's terms and that the author does not have a technical background and those persons at Physics World who were supposed to proof-read this work dropped the ball.
In checking the byline you can see that the author is a freelancer and if you follow the link to their site you can see that they do a lot of technical writing for multiple publications on a variety of subjects. It is possible that they had a tight deadline for article submission, more articles to write, etc so that this one was dumped to the machine just in time for publication but without enough time for a good review that would've spotted this slight error.
In checking the byline you can see that the author is a freelancer and if you follow the link to their site you can see that they do a lot of technical writing for multiple publications on a variety of subjects. It is possible that they had a tight deadline for article submission, more articles to write, etc so that this one was dumped to the machine just in time for publication but without enough time for a good review that would've spotted this slight error.