Earth Is Spinning Faster and Days Are Getting Shorter, for Now

The planet’s rotation fluctuates as it travels around the sun, and measurements suggest we’re losing more than a millisecond during the long days of summer.

By Jacey Fortin

Origins

A 37,000-Year Chronicle of What Once Ailed Us

In a new genetic study, scientists have charted the rise of 214 human diseases across ancient Europe and Asia.

By Carl Zimmer

Even Grave Errors at Rehab Hospitals Go Unpenalized and Undisclosed

For-profit hospitals provide most inpatient physical therapy but tend to have worse readmission rates to general hospitals. Medicare doesn’t tell consumers about troubling inspections.

By Jordan Rau and Irena Hwang

The Surprising Scientists Hit by Trump’s D.E.I. Cuts

The N.I.H. has terminated hundreds of diversity grants awarded to young researchers, many of whom come from the very places that supported Trump.

By Kate Zernike

Math, Revealed

How Much of Our Math Series Did You Retain? Try This Quiz.

Test your knowledge of taxicab geometry, triangular numbers, the golden ratio and more.

By Steven Strogatz

Trump Seeks to Cut Basic Scientific Research by Roughly One-Third, Report Shows

An analysis by the American Association for the Advancement of Science shows the impact of the administration’s budget plan on the kind of studies that produce the most breakthroughs.

By William J. Broad

Trilobites

Snakes Use Smelly Musk to Keep Ants Out of Their Pants

Forget fangs full of venom — the backsides of serpents pack secretions volatile enough to kill insect invaders.

By Joshua Rapp Learn

Maya Ruler’s Tomb Is Unearthed in Belize, With Clues to His Ancient World

A rare mosaic death mask made of jadeite and vessels in the shapes of an owl, a monkey and coatimundi were found with the ruler.

By Alan Yuhas

Trump Is Gutting Weather Science and Reducing Disaster Response

As a warming planet delivers more extreme weather, experts warn that the Trump administration is dismantling the government’s disaster capabilities.

By Lisa Friedman, Maxine Joselow, Coral Davenport and Megan Mineiro

Around the World, Flash Flood Disasters Are the ‘Hardest Kind to Prevent’

Scholars and designers of early warning systems say that there are still huge gaps in our ability to predict flash floods and warn those at risk.

By Max Bearak and Hiroko Tabuchi

NASA Website Will Not Provide Previous National Climate Reports

An agency spokeswoman had initially stated that NASA would retain earlier assessments online for continuity.

By Rebecca Dzombak

Global Health

A Venerable AIDS Activist Returns to Battle

Zackie Achmat, once at the center of South Africa’s push for lifesaving H.I.V. treatment, has come out of retirement as U.S. funding cuts and his own government’s inertia revive old fears.

By Stephanie Nolen

Justice Dept. Demands Patient Details From Trans Medicine Providers

Doctors and hospitals were subpoenaed for private information on gender-related care for minors, the latest move by the Trump administration to stop the treatments.

By Azeen Ghorayshi and Glenn Thrush