An acclaimed new book racing with explorers and scientists to the ends of the earth in 1769 as they chase the planet Venus and unlock great secrets behind the sky. THE DAY THE WORLD DISCOVERED THE SUN tells a "truly excellent" (New Scientist) "scientific adventure tale" (Kirkus) that "vividly recreates the torturous explorations and enthralling discovery of three peripatetic and insatiably curious explorers.” (Publishers Weekly)



Opinion: How the Prime Meridian Changed the World

The world’s first GPS system was launched before the American Revolution — 250 years ago. A story by me for National Geographic.

"*The Day the World Discovered the Sun* … is a story that explains the inner workings and politics of 18th century voyages and the relationships between countries, explorers and astronomers. Anderson, author of *"Shakespeare" by Another Name"*, deftly weaves in multiple stories and perspectives of international interest. He also provides wonderful descriptions of a variety of cultures. … Some might compare this book to Dava Sobel’s *Longitude*, and it would make a great companion. HIGHLY RECOMMENDED [for] all levels of academic and general readers."

Choice: Current Reviews for Academic Libraries

Concord Monitor review - “Fascinating… adroit… makes each expedition come alive”

Today’s Concord (N.H.) Monitor contains a thumbs-up book review of The Day the World Discovered the Sun:

"In his book, Anderson explores the personalities and politics behind the transit observation expeditions, melding history and science in a fascinating story of the first large-scale international scientific effort. …

"Anderson makes each expedition come alive; the challenges and detours, hopes and hubris. These explorers and scientists went places even modern travelers find hard to reach, from the arctic circle to the tropics, in search of perfect viewing. They knew success would be elusive. Some had failed to observe a similar event in 1761, foiled by weather or in at least one case, disappearing forever. Political and economic conditions affected the expeditions as well, and Anderson adroitly fills in these details along with the science behind the missions.

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The 2012 Venus transit in a stunning HD video

On June 5, 2012 the world witnessed only the seventh Venus transit since the invention of the telescope in the early 1600s. NASA’s orbiting Solar Dynamics Observatory caught the whole transit in multiple wavelengths, capturing multiple jaw-dropping HD videos. Check it out. 

(Extra: The website TalkingPointsMemo has a slideshow of some nice, dramatic stills captured around the world of the Venus transit, while Kuriositas has a fine collection of stills too.) “A clever and very entertaining book” columnist Alaina Levine posted a piece today about The Day the World Discovered the SunHer takeaway:

"Today, while people across the Earth experience the transit, it’s important to remember that lovely Venus is not only important to us girls. In fact, in the 1700s, its transit helped sailors, scientists and kings understand our place in the solar system. The story of how this transpired is brought to light in a clever and very entertaining book called The Day the World Discovered the Sun, by Mark Anderson. People risked life and limb to crack the problem of longitude, the author shared with me, and the transit of Venus was “the crucial key to worldwide navigation.”  His book is an adventure tale, a story of human “drive and endurance” with voyages to the poles and everywhere in between to unlock a scientific mystery. Check it out!

"Venus of Longitude" - guest blog for

Today posted a guest blog post I wrote for them about the Venus transit voyages of the 1760s and the technological (not just scientific) motivations behind them:

"Rare as it is, the Venus transit has an outsized impact on the world. The transit launched the legendary careers of Captain Cook and Mason and Dixon — surveyors who wouldn’t have staked out the definitive line between American North and South without first proving themselves on a Venus transit voyage. …

The Venus transit also stands at the crossroads of perhaps the single greatest technological challenge in human history: practical navigation at sea.

"It on was this last point that I found a skewed account in recent popular histories — and ultimately tried to right the record a bit with my new book."

Played 10 times

WBUR’s Radio Boston today featured a piece on the 1769 Venus transit voyages and the remarkable accomplishments of the first “big science” project in human history

"In his new book, The Day The World Discovered The Sun, Anderson writes about the global chase to find the best places to measure the transit of Venus, an “Amazing Race”, 18th century style. He focuses on three scientific teams led by three unique men: France’s Jean-Baptiste Chappe; England’s Captain James Cook; and Vienna’s Father Maximilian Hell.

"The data they gathered came at a high cost. Lives were lost. But it achieved its ultimate goal. In 1771, astronomer Thomas Hornby collated the findings and first estimated the distance between the Earth and sun: 93,726,900 miles.

"He was off by less than 0.5 percent.

"“No one had ever traveled faster than the speed of the fastest horse. No one had been higher off the ground than the tallest cathedral spire,” said Anderson. “And yet they were able to inch out a measuring line into the solar system, and mark out the distance to the sun from all the planets with greater than 99-percent accuracy. It’s quite a testimonial to how the human spirit to know, and to come to know our world endures.””

Public Radio International’s program The World features a section about the Venus transit, the transit voyages of 1769 and The Day the World Discovered the Sun

Back in 1769, the transit of Venus was more than a curiosity. Scientists were trying to answer a key scientific question: how far away is the sun?

"Mark Anderson has written about that quest in a new book called The Day the World Discovered the Sun.

"Anderson says the key for scientists back in 1769 was to scatter to different locations around the globe. Each scientific team was assigned to measure how long it took for Venus to cross the sun’s face…"

"Venus’s Day in the Sun" - a guest blog for today posted a guest blog I wrote for them about why the Venus transit matters today

"When Venus passes in front of the Sun, a little bit the Sun’s light also passes through the tiny ring of Venus’s atmosphere at the planet’s outer edge. Just 0.001% of the Sun’s light during the Venus transit zips through our neighboring hothouse planet’s atmosphere on its way to Earth.

But isolating and examining that 0.001% of the sun’s light in detail will be very important. When Venus crosses the sun’s face during a transit, that 0.001% of the light carries spectral signatures—absorption lines—as tiny mementos of its passage through Venus’s atmosphere. During the 2004 transit, a team of nine French, Swiss, American, Spanish and German astronomers discovered by examining these absorption lines not only a strong signature of carbon-dioxide in the Venusian atmosphere but even the characteristic windspeeds at various altitudes above the planet’s surface. They spied on Venus’s weather from across the solar system…”

A web extra from PRI’s program The World (from WGBH, Boston) — reading an excerpt from The Day the World Discovered the Sun, chapter 6, “Voyage en Californie”