Things weren’t looking too good for Albert Einstein. After graduating near the bottom of his class from Zurich Polytechnic in Switzerland in 1900, he’d applied to several professorship positions, only to be turned down time and time again. So, in 1902, he got a job at a government patent office in Bern, Switzerland, where he spent six days a week examining patent applications for new inventions—all while daydreaming and conducting thought experiments.

It was in that office that Einstein made his first great burst of scientific discoveries. In the span of just six months in 1905, the little-known 26-year-old published four scientific papers that revolutionized our understanding of time, space, and the entire universe. Those papers included the most famous equation in history: E=mc².

Today—120 years after what scientists and historians have dubbed Einstein’s “Year of Miracles”—this equation serves as “an emblem of the modern age,” says Peter Galison, historian of science and physics at Harvard University. Its influence, and the influence of Einstein’s other theories, can still be seen throughout modern science and technology—from our understanding of black holes to the development of GPS navigation and the atomic bomb (see “Einstein’s Legacy,” below).

E=mc² “came to symbolize  the power of knowledge of physics,” Galison says.

There’s a good chance that a poster of Einstein—with his messy gray hair and prominent mustache—is hanging in one of your school’s classrooms. So how did a lowly government patent clerk end up formulating the most well-known equation in history and become a global symbol of scientific brilliance?

In 1900 Albert Einstein graduated near the bottom of his class from Zurich Polytechnic in Switzerland. He’d applied to several professorship positions, only to be turned down time and time again. So, in 1902, he got a job at a government patent office in Bern, Switzerland.  He spent six days a week reviewing patent applications for new inventions—all while daydreaming and conducting thought experiments.

While working in that office, Einstein made his first great burst of scientific discoveries. In just six months in 1905, the little-known 26-year-old published four scientific papers that changed our understanding of time, space, and the entire universe. Those papers included the most famous equation in history: E=mc2.

Today—120 years after what scientists and historians have dubbed Einstein’s “Year of Miracles”—this equation serves as “an emblem of the modern age,” says Peter Galison, historian of science and physics at Harvard University. Its influence, and the influence of Einstein’s other theories, can still be seen throughout modern science and technology. His work influences everything from our understanding of black holes to the development of GPS navigation and the atomic bomb (see “Einstein’s Legacy,” below).

E=mc2 “came to symbolize the power of knowledge of physics,” Galison says.

There’s a good chance that a poster of Einstein—with his messy gray hair and prominent mustache—is hanging in one of your school’s classrooms. So how did a lowly government patent clerk end up formulating the most well-known equation in history? How did he become a global symbol of scientific brilliance?

It all started, Einstein later wrote, when he was 16 years old. After dropping out of his high school in Munich, Germany, where he loathed the strict teaching style, he attended school in Aarau, Switzerland. There Einstein wondered what would happen if he were to travel at the speed of light alongside a light beam.

That question would puzzle Einstein for years. It was also the type of imaginative thinking that made him so special, says Sylvester James Gates Jr., a physics professor at the University of Maryland.

“All of Einstein’s greatest science begins as parables,” Gates Jr. says. “He’d ask a very simple question . . . and then he would hold the question in his mind and return to it over and over.”

Einstein also possessed a skepticism of conventional thinking, which led him to some of his greatest breakthroughs, says Galison.

In the spring of 1905, while working at the patent office, he wrote to a friend that he had uncovered something “very revolutionary.” At the time, light was believed to be a wave. But scientists had also observed that light emitted from hot objects behaved similarly to a gas, which was made up of particles. How could that be? Einstein proposed a solution: What if light waves are actually made up of tiny particles, called quanta?

It all started, Einstein later wrote, when he was 16 years old. He dropped out of his high school in Munich, Germany, because he loathed the strict teaching style. He then went to school in Aarau, Switzerland. There Einstein wondered what would happen if he were to travel at the speed of light alongside a light beam.

That question would puzzle Einstein for years. It was also the type of imaginative thinking that made him so special, says Sylvester James Gates Jr., a physics professor at the University of Maryland.

“All of Einstein’s greatest science begins as parables,” Gates Jr. says. “He’d ask a very simple question . . .  and then he would hold the question in his mind and return to it over and over.”

Einstein also possessed doubt about conventional thinking, which led him to some of his greatest breakthroughs, says Galison.

In the spring of 1905, while working at the patent office, he wrote to a friend that he had uncovered something “very revolutionary.” At the time, light was believed to be a wave. But scientists had also observed that light emitted from hot objects behaved similarly to a gas, which was made up of particles. How could that be? Einstein proposed a solution. What if light waves are actually made up of tiny particles, called quanta?

That theory, which he described in a scientific paper, laid the foundation for the field of quantum mechanics—which deals with the tiniest bits of matter in the universe—and would earn him the Nobel Prize in 1921.

A month after that first paper, Einstein published another theory in which he provided the most powerful evidence yet for the existence of atoms, by studying the movement of minuscule particles in water. But it was his third paper, on the special theory of relativity, that would end up being arguably his most revolutionary—and finally provide the answer to the question he’d first pondered as a teenager a decade before.

Einstein’s special theory of relativity explained that time isn’t absolute. Instead, it’s relative; the faster you move, the slower time moves, compared with time experienced by a stationary observer. So, what would happen if you were to travel at the speed of light? Nothing. Einstein explained that you could never travel at the speed of light, because for any object doing so, time would slow to a stop.

Another consequence of special relativity that Einstein discovered was that mass and energy are different forms of the same thing. He described this in his now-famous equation, E=mc², which he published in his fourth paper of 1905, capping off his Year of Miracles. The equation states that energy (E) equals mass (m) times the speed of light (c) squared. This means that a tiny amount of matter—something as small as a penny—can be turned into a massive amount of energy. The equation would later explain the science behind nuclear power and nuclear bombs.

That theory, which he described in a scientific paper, laid the foundation for the field of quantum mechanics, which deals with the tiniest bits of matter in the universe. It would earn him the Nobel Prize in 1921.

A month after that first paper, Einstein published another theory in which he provided the most powerful evidence yet for the existence of atoms, by studying the movement of minuscule particles in water. But it was his third paper, on the special theory of relativity, that would end up being arguably his most revolutionary.  It would finally provide the answer to the question he’d first thought of as a teenager a decade before.

Einstein’s special theory of relativity explained that time isn’t absolute. Instead, it’s relative. The faster you move, the slower time moves, when compared with time experienced by a stationary observer. So, what would happen if you were to travel at the speed of light? Nothing. Einstein explained that you could never travel at the speed of light, because for any object doing so, time would slow to a stop.

Another consequence of special relativity that Einstein discovered was that mass and energy are different forms of the same thing. He described this in his now-famous equation, E=mc2, which he published in his fourth paper of 1905. The equation states that energy (E) equals mass (m) times the speed of light (c) squared. This means that a tiny amount of matter—something as small as a penny—can be turned into a massive amount of energy. The equation would later explain the science behind nuclear power and nuclear bombs.

Einstein knew, though, that as radical as his theories were, they were also incomplete. After all, his special theory of relativity didn’t take gravity into account. But one day, while sitting in his office in Bern, he conducted yet another thought experiment, which he would later call the “happiest thought in my life.” He imagined what would happen if a person were to fall from a building.

“He will not feel his own weight,” he later recalled thinking at the time.

Thus began Einstein’s years-long quest to develop his general theory of relativity. In doing so, he dared to challenge the founding father of modern physics: Isaac Newton. In 1666, Newton had written that gravitational pull is the hidden force responsible for everything from an apple falling to the ground to Earth’s orbit around the sun. But Einstein said that gravitational pull doesn’t exist in the way Newton imagined. Instead, massive objects, such as the sun, actually warp the space and time around them, bringing smaller objects closer. Einstein’s new theory of gravity upended 200 years of science.

“Newton, forgive me,” he wrote when discussing his new theories later in his autobiography.

Einstein knew, that while he had breakthrough theories, they were also incomplete. After all, his special theory of relativity didn’t take gravity into account. But one day, while sitting in his office in Bern, he conducted yet another thought experiment. He would later call it the “happiest thought in my life.” He imagined what would happen if a person were to fall from a building.

“He will not feel his own weight,” he later recalled thinking at the time.

Thus began Einstein’s years-long quest to develop his general theory of relativity. In doing so, he dared to challenge Isac Newton, the founding father of modern physics. In 1666, Newton had written that gravitational pull is the hidden force responsible for everything from an apple falling to the ground to Earth’s orbit around the sun. But Einstein said that gravitational pull doesn’t exist in the way Newton imagined. Instead, massive objects, such as the sun, warp the space and time around them. They actually bring smaller objects closer. Einstein’s new theory of gravity upended 200 years of science.

“Newton, forgive me,” he wrote when discussing his new theories later in his autobiography.

In 1919, astronomers proved Einstein’s general theory of relativity when they photographed light bending during a solar eclipse, demonstrating that the sun’s mass curved the path of light.

Proof of this theory changed centuries of widely held beliefs about the laws of physics and our universe. When the news broke in November 1919 that Einstein’s theory was right, it reverberated around the world. “Revolution in Science, New Theory of the Universe” a headline in The Times of London declared. The New York Times proclaimed: “Men of Science More or Less Agog.”

In 1919, astronomers proved Einstein’s general theory of relativity when they photographed light bending during a solar eclipse. The photograph demonstrated that the sun’s mass curved the path of light.

Proof of this theory changed centuries of widely held beliefs about the laws of physics and our universe. When the news broke in November 1919 that Einstein’s theory was right, it echoed around the world. “Revolution in Science, New Theory of the Universe” a headline in The Times of London declared. The New York Times proclaimed: “Men of Science More or Less Agog.”

Einstein skyrocketed to international stardom. Massive crowds turned up to hear him speak. His breathtaking leaps of thought and quirky personality made him the best known scientist in the world. His name practically became synonymous with the word genius.

 This latest scientific breakthrough held special meaning in the wake of World War I (1914-18), which had left cities across Europe in ruins and dramatically reshaped international power structures. To many, Einstein’s theory of the universe provided relief from all the death and destruction, demonstrating the positive capabilities of humankind.   

During World War II (1939-45), Einstein would again find himself at the center of the global conversation—this time for a very different reason.

Einstein had long considered himself a pacifist and had spoken out against the First World War. But the rise of Adolf Hitler’s Nazi Party in his home country of Germany deeply worried Einstein, who was Jewish. In 1933—the year that the Nazi government banned Jewish people from holding official positions, including at universities—he fled Berlin and eventually became a U.S. citizen. The Nazis would go on to murder more than 6 million Jewish people across Europe.

Einstein skyrocketed to international stardom. Massive crowds turned up to hear him speak. His breathtaking leaps of thought and quirky personality made him the best-known scientist in the world. His name practically became synonymous with the word genius.

 This latest scientific breakthrough held special meaning in the wake of World War I (1914-18). Cities across Europe were in ruins and international power structures had been reshaped. To many, Einstein’s theory of the universe provided relief from all the death and destruction. It demonstrated the positive capabilities of humankind.   

During World War II (1939-45), Einstein would again find himself at the center of the global conversation, but this time for a very different reason.

Einstein had long considered himself a pacifist. He had spoken out against the First World War. But the rise of Adolf Hitler’s Nazi Party in his home country of Germany deeply worried Einstein, who was Jewish. In 1933, the Nazi government banned Jewish people from holding official positions, including those at universities. Einstein fled Berlin and eventually became a U.S. citizen. The Nazis would go on to murder more than 6 million Jewish people across Europe.

In 1939, concerned that Germany might build an atomic bomb, Einstein wrote a letter to President Franklin D. Roosevelt, informing him that “recent work in nuclear physics” could be used “for the construction of extremely powerful bombs.” He thought the U.S. should support nuclear research.

In 1941, Roosevelt responded by launching what would come to be called the Manhattan Project, a top-secret program to develop nuclear weapons, led by physicist Robert Oppenheimer. Four years later, the U.S. dropped two atomic bombs on Germany’s ally, Japan. The bombings of the cities of Hiroshima and Nagasaki effectively ended the Second World War. But the price was steep. An estimated 200,000 people died from the initial blasts and the ensuing radiation.

Those deaths weighed heavily on Einstein’s conscience. He would go on to campaign for nuclear disarmament, as well as for civil rights and world peace. A year before he died, in 1954, he called his letter to Roosevelt the “one great mistake in my life.”

In 1939, concerned that Germany might build an atomic bomb, Einstein wrote a letter to President Franklin D. Roosevelt. He informed him that “recent work in nuclear physics” could be used “for the construction of extremely powerful bombs.” He thought the U.S. should support nuclear research.

In 1941, Roosevelt responded by launching what would come to be called the Manhattan Project. The top-secret program to develop nuclear weapons was led by physicist Robert Oppenheimer. Four years later, the U.S. dropped two atomic bombs on Germany’s ally, Japan. The bombings of the cities of Hiroshima and Nagasaki effectively ended the Second World War. But the price was steep and an estimated 200,000 people died from the initial blasts and the ensuing radiation.

Those deaths weighed on Einstein’s conscience. He would go on to campaign for nuclear disarmament, as well as for civil rights and world peace. A year before he died, in 1954, he called his letter to Roosevelt the “one great mistake in my life.”

The dropping of the atomic bombs triggered a nuclear arms race that continues to influence foreign affairs today. Einstein’s most lasting legacy, though, may lie in our understanding of the universe. His general theory of relativity explains the existence of black holes and laid the foundation for the big bang theory, which describes the formation of the universe from a single, expanding point 13.8 billion years ago.

Yet even Einstein didn’t have the answers for everything. In his final scientific quest, he attempted to find a “unified field theory” that could explain all the forces of nature. He never did—and died with his notes by his bedside.

Today astrophysicists are still grappling with big, unanswered questions, such as why the universe is expanding at an accelerated rate. And many scientists question how Einstein’s theory of gravity aligns with the discoveries of quantum mechanics, which he’d helped set in motion. Solving these puzzles may require a generation of scientists just as daring and imaginative as Einstein himself.

One hundred and twenty years after Einstein’s Year of Miracles, says the physicist Gates Jr., “we’re still trying to prove him wrong.”

The dropping of the atomic bombs triggered a nuclear arms race that continues to influence foreign affairs today. Einstein’s most lasting legacy, though, may lie in our understanding of the universe. His general theory of relativity explains the existence of black holes. It laid the foundation for the big bang theory, which describes the formation of the universe from a single, expanding point 13.8 billion years ago.

Yet even Einstein didn’t have the answers for everything. In his final scientific quest, he attempted to find a “unified field theory” that could explain all the forces of nature. He never did. He died with his notes by his bedside.

Today astrophysicists are still grappling with big, unanswered questions. They wonder why the universe is expanding at an accelerated rate. They also question how Einstein’s theory of gravity aligns with the discoveries of quantum mechanics, which he’d helped set in motion. Solving these puzzles may require a generation of scientists just as daring and imaginative as Einstein himself.

One hundred and twenty years after Einstein’s Year of Miracles, says the physicist Gates Jr., “we’re still trying to prove him wrong.”