Albert Einstein

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Albert Einstein

When young Albert's father showed him a compass, he tried to imagine the mysterious force behind the needle, awakening his passion for physics.
Albert Einstein Archive © The Hebrew University of Jerusalem

Albert Einstein was the most famous scientist of the 20th century. His scientific breakthroughs were so breathtaking that his gentle, bemused expression and riot of white hair have come to symbolize genius in the popular imagination. Einstein did not seek fame, but when thrust into the spotlight he chose to use his renown to further the causes of freedom and human rights around the world. A heartfelt humanist, he mistrusted authority. His independent, nonconformist thinking enabled him to shrug off centuries of scientific tradition to come up with astoundingly original theories about the nature of the universe.

Einstein was born in 1879 in Ulm, Germany, into a nonreligious Jewish family. His father ran an electrical equipment business, while his mother imbued him with a love of music that would stay with him his whole life. Einstein was a quiet child, very observant and self–reliant. When he was five years old, he received a compass. Young Albert was fascinated by the fact that no matter which way he turned the compass, the needle always pointed the same direction. This was his introduction to scientific inquiry. "That experience made a deep and lasting impression on me," he wrote years later. "Something deeper had to be hidden behind things."

Einstein was fortunate to have people around him who encouraged his interest in math and science. His uncle Jakob Einstein, an electrical engineer, and Max Talmey, a medical student who was a regular guest at family dinners, often loaned him science books. When Einstein was 12, he taught himself geometry from one of these books.

Legend has it that Einstein was a poor student who flunked out of school, but this was not the case. He excelled at math and science, though he often got only mediocre grades in other classes. When Albert was 15, his family moved to Milan, Italy. Albert had only one year left in high school, so he stayed behind. But by this time, he had already developed a profound distrust of authority and a hatred of conformity. He loathed Germany's rigid education system, which was based upon rote learning. "It's a true miracle," he commented years later, "that modern education hasn't yet completely smothered the curiosity necessary for scientific study." If Albert had remained in Germany until he was 16, he would have been obliged to perform military service. The sight of soldiers marching through the streets had always frightened and appalled him, and he was not willing to join them. So Einstein left high school and Germany, and joined his family in Milan.

Einstein's family thought he should pursue a career as an electrical engineer, so after finishing high school in Switzerland, Albert enrolled in the highly regarded Swiss Federal Institute of Technology in Zurich. But Einstein already knew that his future was not as an engineer. His true passion was theoretical physics, a field in which he could delve into the most fundamental questions and in which imagination reigned supreme. "Imagination is more important than knowledge," he once said. "Knowledge is limited. Imagination encircles the world."

Einstein had little patience for the classroom setting, and when he graduated from the institute in 1900, he was the only member of his class not offered an assistant professorship at the school. After two years of taking whatever teaching and tutoring jobs he could find, Einstein accepted a position in the Swiss patent office in Bern. The job was neither prestigious nor demanding of his skills, but Einstein was delighted to have a steady income, and it gave him plenty of time to think. Working as a patent clerk, Einstein embarked on his extraordinary scientific career using nothing but pen, paper, and his mind.

While at the Swiss Federal Institute of Technology, Einstein had fallen in love with Mileva Maric, the only female student in his class. In 1902, before they were married, the two had a daughter. Their daughter's fate, however, remains a mystery. It is thought that she might have died of scarlet fever while living with her maternal grandparents. Albert and Mileva married the following year and eventually had two sons. Marriage was never a priority for Einstein, however, and he had frequent affairs during both this and his subsequent marriage.

"Gravitation elicits just as much respect among my colleagues as skepticism," wrote Einstein in 1914, while working on the Theory of General Relativity that would soon launch him into the spotlight.


Einstein was still working at the patent office in 1905, his annus mirabilis, or "miraculous year." That year, the 26–year–old Einstein published four papers in the prestigious German journal Annalen der Physik. That would have been a remarkable feat for anyone, particularly an unknown scientist who was not even working in academia. Einstein's papers revolutionized physics.

The first of these papers stated that light behaves as both a wave and a particle, an idea called the photoelectric effect. The second proved the existence and size of molecules, and explained their movement, called Brownian motion. The third was Einstein's Special Theory of Relativity, which showed that the speed of light is constant, regardless of the speed of the light's source, and that time passes at different rates for objects moving at different speeds. His final paper in his miraculous year gave science its most famous equation, E=mc2. This equation, in which E is energy, m is mass, and c is the speed of light, establishes that energy and mass are actually different forms of the same thing and that one can be converted into the other.

Although many scientists did not accept the Special Theory of Relativity right away, they were intrigued. Einstein now had a reputation within the scientific community, and in 1908, he left the patent office for a position as a lecturer at the University of Bern. The following years would see him move on to universities in Zurich and Prague before settling in at the University of Berlin. There, in 1916, Einstein completed his work on his revolutionary General Theory of Relativity, which delved into the issue of gravity.

Einstein proposed a way of thinking about gravity radically different from Isaac Newton's explanation of a force pulling objects toward each other. Einstein suggested that space and time are like a piece of cloth stretched taut; objects are like marbles on the cloth that create indentations, or distortions, that cause other objects to move toward them. Gravity is this distortion in the fabric of space and time. According to Einstein's theory, very massive bodies such as the Sun would cause even light to bend.

During a total solar eclipse in 1919, scientists observed that the position of the stars appeared to shift slightly as their light curved around the Sun, confirming Einstein's theory. Newspaper headlines trumpeted Einstein's triumph. "Revolution in Science, New Theory of the Universe, Newtonian Ideas Overthrown," stated the Times of London. Suddenly, Einstein was a worldwide celebrity. Everyone was interested in his new ways of thinking about the universe, and he was mobbed wherever he went. "I have become rather like King Midas, except that everything turns not into gold but into a circus," he said.

In a few short years, Einstein had profoundly changed physics. It was so clear that he would one day be awarded the Nobel Prize that in 1918, when he and his first wife, Mileva, were working out a divorce settlement, Einstein agreed that he would give her the prize money when he won. She didn't have to wait long. Einstein won the 1921 Nobel Prize in Physics, although not for his revolutionary work on general relativity, which was still controversial within the scientific community, but for his insights into the photoelectric effect.

By this time, Einstein had already witnessed the horrors of World War I. He had been one of the few prominent German scientists who hadn't supported Germany's nationalist ambitions during the war. The suffering caused by the war strengthened his pacifism. "My pacifism is an instinctive feeling," he remarked, "a feeling that possesses me because the murder of men is disgusting."



Daring, wildly ingenious, and passionately curious, Albert Einstein reinterpreted the inner workings of nature, the very essence of light, time, energy, and gravity.
Albert Einstein Archive © The Hebrew University of Jerusalem

But the rise of Nazism forced him to rethink his pacifism. Einstein was out of the country when Hitler took power in 1933. He never again set foot in his homeland. Einstein and his second wife, Elsa, settled in Princeton, New Jersey, where he accepted a position at the Institute for Advanced Study.

Einstein, who was concerned that Germany was developing an atomic bomb, wrote to President Franklin Roosevelt urging that the United States accelerate its own work on nuclear weapons to deter the Germans from using any they might develop. Two years later, the United States embarked on the Manhattan Project, its effort to build a nuclear bomb. Though it was Einstein's equation E=mc2 that had shown that the tiny mass of an atom could be converted into a powerful destructive energy, Einstein was never invited to work on the project. The U.S. government distrusted him because of his left–leaning politics‹by the time Einstein died, the FBI had a nearly 1,500–page file on him. Einstein never expected the atomic bomb to be used. He was horrified when the United States dropped two atomic bombs on Japan, which killed hundreds of thousands of people. "Woe is me," he said, after the first bomb fell on Hiroshima.

Though Einstein had long used his fame to promote peace and human rights, in the years after World War II, he became even more fervently politically active. He worked tirelessly for nuclear disarmament and spoke out against racism and McCarthyism. Despising nationalism, he promoted international cooperation and the work of the United Nations. He also supported the establishment of the State of Israel. In 1952, the Israeli ambassador to the United States suggested that he become the president of Israel, an offer he politely declined.

Einstein lived as quietly as possible in Princeton, given his celebrity. He had become a beloved figure, an expert on everything. He answered as many of the deluge of letters he received as he could, whether they were about science, politics, or a child's homework, and he surprised his steady stream of visitors with his self–deprecating good humor. Still, Einstein was uncomfortable with his fame. He told one reporter, "In the past it never occurred to me that every casual remark of mine would be snatched up and recorded. Otherwise I would have crept further into my shell."

During the last decades of his life, Einstein tried to uncover what is known as the Grand Unified Theory, a theory that can describe the entire physical world. Such a theory would connect all branches of physics, it would explain everything. "I want to know how God created this world," Einstein once remarked. "I am not interested in this or that phenomenon, I want to know His thoughts; the rest are details." Einstein never succeeded in coming up with a Grand Unified Theory, and it remains one of the burning questions for theoretical physicists.

Albert Einstein died from a burst blood vessel on April 18, 1955, in a Princeton hospital. Doctors had suggested surgery, but Einstein declined. "It is tasteless to prolong life artificially," he said. "I have done my share; it is time to go. I will do it elegantly."

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Black Hole

Stopping light from escaping

The force of gravity determines how high an object can go up when propelled at a given velocity. If the speed of the object is fast enough, it can escape the gravitational field and go off into space. A Black Hole has such a strong force of gravity that even light cannot escape its grasp.

Throwing a ball

When you throw a ball up in the air, the height it will go depends on how hard you throw it (or its initial velocity) and the force of gravity.

Looking at the Gravity Equations lesson, you can calculate how high the ball will go when thrown at a given velocity with the equation x = v² / 2g, where x is the height, v² is the velocity times itself or squared, and g is the gravitational acceleration of 32 ft/s² or 9.8 m/s².

Thus, if you throw a ball up at v = 9.8 m/s, it would go to a height of x = 4.9 m.

Since the acceleration of gravity on the Moon 1/6 that of on Earth, a ball will go 6 times higher on the Moon than on the Earth, with the same initial velocity. If you could throw a ball from the surface of the Sun, it would take a much greater velocity to go the same height, since the gravity on the Sun is so much greater.

Escape velocity for a rocket

If the ball or a rocket went at a high enough velocity, it would escape the gravitational field and go off into space. This is called the escape velocity.

Escape Earth

An object must go about 26,000 miles per hour to escape the Earth's gravitational field. That is approximately 7 miles per second or 11 kilometers per second.

Although Newton's gravitational equations are only approximates for distances close to Earth, the equation x = v² / 2g can be used to get a rough approximate of the distance where the object would escape the Earth's gravity. x = 6200 km or 4300 mi.

Escape Sun

The Sun has a mass 300,000 times that of Earth, so the escape velocity from the Sun is about 600 km/sec. That means that a rocket would have to travel at about 1,500,000 miles per hour to escape from the surface of the Sun.

(Obviously, a rocket or ball that was on the surface of the Sun would burn up, because of the intense heat. We are just using it as an example to illustrate the different escape velocities.)

Escape velocity far too low for light

Since light travels at 186,000 miles/second (300,000 km/sec), you can easily see that its speed exceeds the escape velocity of the Earth and even the Sun.

Size of Black Hole

For a sun or star to be a Black Hole, it would have to have so much mass and gravity that its escape velocity would be greater than 300,000 km/sec, such that even light would not escape.

Heavier than Sun

It is estimated that such a star would have to have a mass of 1,000,000 (1 million) times that of our Sun in order for it to be a Black Hole. If you could weigh the Sun and compare it to a Black Hole, it would be like comparing a grain of sand to a bowling ball.

Actually smaller

Surprisingly, the Black Hole might actually be smaller in diameter than our Sun. A Black Hole has such a strong force of gravity that it actually compresses its mass into a smaller object. Don't forget that the Sun is like a hot gas or liquid, so that the material could be compressed into a smaller space.

Properties

A Black Hole has some interesting properties.

Gains energy

Although it is a sun and very hot, none of its light escapes. That means a Black Hole does not lose mass or energy like our Sun does. In fact, it gains energy and mass by sucking in nearby matter.

Difficult to see

Since no light leaves the Black Hole, it does not shine like other objects in space. This makes it very difficult to find in the black background of space. Astronomers think they have found Black Holes by noticing background stars temporarily disappearing at different viewing angles. Still, they are not 100% sure that what they saw was a Black Hole or some obstruction in space.

Horizon

Since gravity decreases as the square of the distance from an object, there is a distance where the escape velocity of a Black Hole becomes less than the speed of light. This is called the Black Hole's horizon. Outside the horizon light is allowed to escape, but inside that horizon, nothing could escape. Scientists have visualized what would happen at and near that horizon.

Summary

A Black Hole has so much gravity that even light cannot escape it. The escape velocity of a planet or star depends on its gravity. The gravity of a Black Hole is a million times that of our Sun and thus it has a million time the mass of the Sun. Astronomer only think they have seen Black Holes in observations through their telescopes.

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