This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
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Comments have been getting stuck in moderation here for longer than usual because my email alerts telling me a comment has been posted and needs to be approved have stopped arriving.
I'll try to get to the bottom of this (whether it's an issue with the blog software or my spam filters), but in the meantime, if you've tried to post a comment and it is taking a very long time to appear, feel free to email me (drdotfreerideatgmaildotcom) to alert me to the problem.