Our Expert Voices conversation about the 2017 solar eclipse.

The eclipse affords us the opportunity to study Earth's ionosphere, a layer of partially charged gas 90 - 1000 km above the surface that helps to transmit satellite and radio signals around the planet and to protect life here by absorbing the Sun's extreme ultraviolet radiation. Disruptions in the ionosphere — from space weather, for example — can interfere with communication and navigation. During the eclipse, we'll be able to measure how the ionosphere responds to a dramatic reduction of UV radiation (up to 85%) and therefore better understand the details of how the ionosphere works.

A prediction: Recent computer simulations of the upcoming total solar eclipse over the continental U.S. predict the density of electrons in the ionosphere will be reduced by 50%, their temperature will drop by 15%, and the wind structure of parts of the atmosphere will be disturbed. That should produce an effect that can be detected by GPS receivers as far away as South America — a prediction that will be tested during the upcoming eclipse.

The bottom line: The solar eclipse will allow us to answer key questions about Earth's space environment that may in turn ensure the accuracy of vital systems we use daily.

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In photos: Deadly wildfires devastate California's wine country

The Shady Fire ravages a home as it approaches Santa Rosa in Napa County, California, on Sept. 28. The blaze is part of the massive Glass Fire Complex, which has razed over 51,620 acres at 2% containment. Photo: Samuel Corum/Agence France-Presse/AFP via Getty Images

More than 1700 firefighters are battling 26 major blazes across California, including in the heart of the wine country, where one mega-blaze claimed the lives of three people and forced thousands of others to evacuate this week.

The big picture: More than 8,100 wildfires have burned across a record 39 million-plus acres, killing 29 people and razing almost 7,900 structures in California this year, per Cal Fire. Just like the deadly blazes of 2017, the wine country has become a wildfires epicenter. Gov. Gavin Newsom has declared a state of emergency in Napa, Sonoma, and Shasta counties.

Updated 57 mins ago - Politics & Policy

Coronavirus dashboard

Illustration: Sarah Grillo/Axios

  1. Global: Total confirmed cases as of 12:30 a.m. ET: 33,880,896 — Total deaths: 1,012,964 — Total recoveries: 23,551,663Map.
  2. U.S.: Total confirmed cases as of 12:30 a.m. ET: 7,232,823 — Total deaths: 206,887 — Total recoveries: 2,840,688 — Total tests: 103,939,667Map.
  3. Education: School-aged children now make up 10% of all U.S COVID-19 cases.
  4. Health: Moderna says its coronavirus vaccine won't be ready until 2021
  5. Travel: CDC: 3,689 COVID-19 or coronavirus-like cases found on cruise ships in U.S. waters — Airlines begin mass layoffs while clinging to hope for federal aid
  6. Business: Real-time data show economy's rebound slowing but still going.
  7. Sports: Steelers-Titans NFL game delayed after coronavirus outbreak.

CDC: 3,689 COVID-19 or coronavirus-like cases found on cruise ships in U.S.

Cruise Ships docked in April at the port at Marina Long Beach due to a no-sail order in Long Beach, in California. Photo: Apu Gomes/AFP via Getty Images

There have been at least 3,689 COVID-19 or coronavirus-like illness cases on cruise ships in U.S. waters, "in addition to at least 41 reported deaths," the Centers for Disease Control and Prevention said late Wednesday.

Driving the news: The CDC released the data from the period of March 1 through Sept. 29 in an emailed statement confirming the extension of a No Sail Order for cruise ships through Oct. 31, as first reported by Axios' Jonathan Swan on Tuesday in his article revealing CDC director Robert Redfield was overruled in a push to extend the order into 2021.