 |  | Dear Friend of Scientific American,
Some of our favorite stories to publish are first-person accounts by scientists who made world-historical discoveries. We have two in our November issue. Our cover story celebrates the 50th anniversary of Lucy, the 3-million-year-old Australopithecus afarensis fossil that changed our understanding of human evolution. Paleontologist Donald C. Johanson found her bones in Ethiopia, and his co-author, Yohannes Haile-Selassie, has discovered several other hominin species, some of which lived at the same time as Lucy. Together, the past 50 years of discoveries have revealed a rich and varied human family tree. Astrophysicist Adam Reis is one of the discoverers of dark energy, the mysterious force that is speeding up the expansion of the universe. That allowed us to calculate the age of the universe and solve some other puzzles. But as he and theoretical physicist Marc Kamionkowski write, astronomers are now grappling with a "pesky inconsistency." Different measurements and predictions of how quickly space is growing disagree. This "Hubble tension" doesn't seem to be caused by measurement errors or other confounders. It looks real, which means there might be something wrong with our understanding of dark energy—and that's exciting. We have a package of stories on solutions for improving health equity, report on new progress for nasal vaccines (no needles!), and say it may be time to stop adding (or subtracting) leap seconds. Thanks so much for your support of Scientific American. Enjoy our November issue and more with our special offer: 30 days of unlimited digital access for $0!
Best wishes, Laura Helmuth Editor in Chief
| | | Half a century after its discovery, this iconic fossil remains central to our understanding of human origins. | Estimates of how fast the universe is expanding disagree. Could a new form of dark energy resolve the problem? | Patients, advocates, researchers and clinicians around the world are reducing bias and improving health care access for all. | Gentle nasal spray vaccines against COVID, the flu and RSV are coming. They may work better than shots in the arm. | We have been adding "leap seconds" to time kept by our atomic clocks, but soon we may have to subtract one. Are the tiny adjustments worth the bother? | To view this email as a web page, go here.
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