1. John Adams’ July 2 Independence Day

Following the Continental Congress’s vote to separate from Britain, founding father John Adams wrote to his wife Abigail and predicted, “The Second Day of July 1776, will be the most memorable Epocha, in the History of America…I am apt to believe that it will be celebrated, by succeeding Generations, as the great anniversary Festival.” While Adams was certainly correct about Independence Day becoming a major American holiday, he got the date wrong by two days. The Continental Congress first voted aloud to break from the British on July 2, but they didn’t finalize and date the Declaration of Independence until July 4. Adams considered the original vote of independence on July 2 to be the more momentous occasion, and he even took part of the day off and went shopping when the Congress met again two days later. “The Colossus of Independence” later grudgingly accepted July 4 as America’s accepted birthday, and went on to become inextricably linked to the day after both he and Thomas Jefferson died on it in 1826.

2. Einstein and Nuclear Power

Albert Einstein in 1905 (Credit: Topical Press Agency/Getty Images)
Getty Images / Topical Press Agency
Albert Einstein in 1905. 

Albert Einstein’ famous equation E=mc2 showed that mass and energy could theoretically be transformed into one another, yet for many years he incorrectly argued that the process could never be controlled. In 1932, the great physicist claimed that ”there is not the slightest indication that nuclear energy will ever be obtainable. That would mean that the atom would have to be shattered at will.” Einstein believed that it was likely impossible to split the atom without using more energy than would be released, but he later changed his tune after the first experiments with uranium in the late 1930s. His deceivingly simple equation has since helped spawn power plants that generate electricity from the energy in fissionable materials, and as much as 12 percent of the world’s electricity is now provided by nuclear power.

3. John Maynard Keynes and the 15-hour workweek

John Maynard Keynes
Getty Images / George Skadding / The LIFE Picture Collection
John Maynard Keynes

In 1930, the famed British economist John Maynard Keynes wrote an essay on the future of labor called “Economic Possibilities for our Grandchildren.” In it, he claimed that increased levels of wealth and prosperity ensured that people in industrialized countries would only need to pop into the office for brief “three hour shifts or a fifteen-hour work week” by the year 2030. Keynes argued this new work model would allow humanity to “do more things for ourselves than is usual with the rich today, only too glad to have small duties and tasks and routines.” Appealing as it might sound, economic trends indicate that Keynes’ utopian “leisure society” won’t be arriving any time soon. While total wealth has indeed increased since 1930, so too have personal spending and income inequality. Work hours, meanwhile, have remained largely static for the last half-century, and trends in some countries indicate that people are likely to spend even more time on the job in the coming years.

4. Joseph C. Ives and the Grand Canyon

These days, Grand Canyon National Park in Arizona receives somewhere in the neighborhood of 5 million visitors each year. Those numbers would no doubt have come as a major surprise to Lieutenant Joseph C. Ives, a U.S. topographical engineer who was one of the first non-Indians to explore the canyon. Ives and his men first entered the canyon in March 1858 after being led to it by Mojave and Hualapai Indians, and they spent several days braving snows and treacherous climbs while trying to survey its rivers. A few years later, Ives wrote an extensive report on his mission in which he pronounced the Canyon a beautiful but essentially useless wasteland. “After entering it there is nothing to do but leave,” he wrote. “Ours has been the first, and will doubtless be the last, party of whites to visit this profitless locality. It seems intended by nature that the Colorado River…shall be forever unvisited and undisturbed.”

5. Irving Fisher and the Stock Market

Economist and Yale professor Irving Fisher spent the early 20th century as one of the undisputed wizards of Wall Street. Today, however, he is best known for making what is perhaps the most disastrously timed stock market prediction in history. The call came in early October 1929, in the days after stock prices leapt to dizzying new heights. Some claimed the jump was a sign that a massive crash was imminent, but Fisher was famously optimistic. As reported in the New York Times, he told guests at a dinner meeting that stock prices had reached “what looks like a permanently high plateau… I believe the principle of the investment trusts is sound, and the public is justified in participating in them.” Only a few weeks later, the stock market experienced a catastrophic crash. Thousands of investors—including Fisher—lost their fortunes in the ensuing hysteria.

6. Dewey Defeats Truman

On Election Day 1948, many prognosticators considered the results of the presidential election a foregone conclusion. Incumbent President Harry Truman was lagging far behind in the polls to the Republican Governor of New York, Thomas Dewey, and most analysts had the challenger winning in a walk. That night, as the votes were still being cast, a printers’ strike forced the the Chicago Tribune to call the race ahead of time to ensure their early edition made it to print. Following conventional wisdom, the editors went with Dewey, and the Tribune went to press with “DEWEY DEFEATS TRUMAN” emblazoned across its front page. Unfortunately for the Tribune, Truman went on to complete a major upset, winning the Electoral College 303 to 189. The paper made a desperate attempt to round up copies of their inaccurate early edition, but it didn’t take long before one found its way into the president’s hands. Two days after his historic win, an overjoyed Truman posed for a now-famous photo op while holding a copy.

7. General John Sedgwick at Spotsylvania Court House

Few predictions have been as swiftly or disastrously disproven as the one made by Civil War General John Sedgwick at the Battle of Spotsylvania Court House. On May 9, 1864, Sedgwick was leading the Union 6th Corps near the Confederate left flank when rebel sharpshooters began opening fire on his men from a distance of roughly 1,000 yards. Sedgwick noticed several of his troops taking cover in rifle pits or going to ground, and he began teasing them, saying, “What will you do when they open fire along the whole line? I am ashamed of you. They couldn’t hit an elephant at this distance.” When one of his soldiers told him that dodging an artillery shell had once saved his life, the general laughed and replied “All right, my man; go to your place.” Only moments later, Sedgwick was struck in the head by a sharpshooter’s bullet and fell to the ground with blood pouring from underneath his left eye. He died almost instantly, supposedly with a smile still on his face.