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Your article posits that every 64 million years a mass die-off occurs due to increased cosmic rays. When will the cosmic rays again be at their maximum?

Robert Richards
Metairie, La.

The article failed to mention when the next cosmic-ray bath is due. Now, I’m worried that it might be so imminent that Science News didn’t have the heart to provide its readers the bad news.

Steve Bankhead
Watsonville, Calif.

Study coauthor Adrian Melott of the University of Kansas in Lawrence says that as we head to the north side of the galaxy, cosmic ray exposure will get gradually more intense and peak in about 14 million years .—D. Castelvecchi