Piezofluorochromism, the phenomenon of materials reversibly changing their fluorescent color when pressure is applied, is ...

When most people drop mail off at a mailbox or at a post office, they assume it is postmarked that same day. But according to a new rule from the United States Postal Service, that’s not the case ...

Gemstones like precious opal are beautiful to look at and deceivingly complex. As you look at such gems from different angles ...

The U.S. Postal Service is making new changes in 2026, including adjustments to the postmark process, which could result in late fees and penalties for anyone mailing time-sensitive documents such as ...