Hendrik Lorentz: Einstein's Mentor

 

Speaking about Professor Hendrik Lorentz, Einstein unhesitatingly said, "He meant more to me personally than anybody else I have met in my lifetime" – "Personally, he was the most important person among all those I have encountered in my life." Einstein's theory of relativity was developed from Lorentz's research.

Hendrik Antoon Lorentz was renowned for his work on the atomic theory of matter. In 1902, he received the Nobel Prize in Physics along with his student Pieter Zeeman.

Hendrik Lorentz was born on July 18, 1853, in Arnhem, Netherlands. Lorentz lost his mother at the age of four. Deprived of maternal affection, Lorentz grew up immersed in studies from a very young age.

Lorentz's father was very serious about Lorentz’s education. He enrolled Lorentz in a school with strict regulations at an early age. From there, Lorentz effortlessly moved on to an advanced high school course in 1866. In 1870, he enrolled at Leiden University and earned a bachelor's degree in mathematics and physics within two years. After graduating in 1872, he joined a night school in Arnhem as a science teacher. Alongside teaching, he continued his PhD research on the reflection and refraction of light.

In 1875, at the age of just twenty-two, Hendrik Lorentz earned his PhD. He then joined the Physics Department at Leiden University. Within a few years, he was promoted to Professor of Theoretical Physics. Before this, no university in the Netherlands had a position for a theoretical professor. Theoretical physics was just beginning to emerge as a separate branch of physics at that time. In this context, it can be said that Hendrik Lorentz was the first professor of theoretical physics in the Netherlands. Despite receiving attractive offers from many universities in Europe, he did not join any other institution. He spent his entire career teaching at Leiden University. Even after retiring from the university, he continued his Monday morning lectures, which were attended by Albert Einstein.

Einstein used to visit his friend Paul Ehrenfest at Leiden University. During these visits, Einstein would attend Professor Lorentz's Monday lectures, where Lorentz discussed recent discoveries and advancements in physics. Einstein drew significant inspiration for his own research from these lectures.

Initially, Lorentz worked on Maxwell's electromagnetic waves, particularly focusing on the principles related to electricity and light. Through Maxwell's theory, he provided a new explanation for the principles of light refraction and reflection in his PhD thesis. Lorentz established a relationship between the speed of light and the density and composition of the medium through which light travels.

Around the same time, Danish physicist Ludwig Lorenz discovered a similar mathematical relationship between the speed of light and the refractive index of the medium. This equation became known as the Lorentz-Lorenz equation, named after Hendrik Lorentz and Ludwig Lorenz. According to this equation, the medium through which light travels is composed of numerous electrically charged particles that constantly oscillate like waves. As light travels through the medium, these particles interact with the light waves. Today, we are all familiar with the particle theory of light. However, in 1879-1880, scientists had no clear understanding of atoms and their components—electrons, protons, and neutrons.

In 1881, Lorentz married Aletta, the daughter of Professor Johan Kaiser of the Academy of Fine Arts. Hendrik and Aletta Lorentz had two daughters and two sons. Their eldest daughter, Geertruida, later became a physicist like her father.

From Maxwell's equations, Lorentz developed an equation that laid the groundwork for the theory of the electron. In 1892, Lorentz proposed from his theoretical research that within any matter, there are tiny particles with either positive or negative charges. Lorentz theoretically proved that the oscillations of these charged particles result in the generation of electromagnetic waves. Maxwell formulated the theory of electromagnetic waves between 1850 and 1870. Around the same time Lorentz was establishing his electron theory, Heinrich Hertz succeeded in producing electromagnetic waves in the laboratory in 1888.

Contemporary scientists of Lorentz believed that there was a transparent, thin, invisible substance called ether in the air. Many scientists tried and failed to measure the speed of ether in the air, leading many to believe that ether was stationary and had zero velocity in the air. Lorentz also initially believed that ether existed and that light, sound, etc., travelled through it. However, the Michelson-Morley experiment in 1887 demonstrated that ether did not exist.

Despite the disproof of ether's existence, Lorentz did not fully accept this fact. He reinterpreted the failure to detect ether within the context of his electron theory research. He developed the theory of how the shape of an object changes due to its motion, which later became famous as the Lorentz transformation. Using the Lorentz transformation, Einstein discovered his theory of relativity.

According to Lorentz's atomic theory, when an object moves in a certain direction, its length contracts slightly in that direction. Although this change is very minute, it can be measured if the object's speed is extremely high. Lorentz suggested that the motion of an object alters the forces between the charged particles within the object.

Before the publication of the Lorentz transformation, Hendrik Lorentz had already received the Nobel Prize in Physics for his theory on the influence of magnetism on light. According to Maxwell's theory, German physicist Heinrich Hertz demonstrated the production of electromagnetic waves in the laboratory. Despite this experimental proof, Maxwell's equations remained somewhat incomplete as they did not account for atomic theory.

In his atomic theory, Lorentz introduced the concept of charged electrons, which determine the properties of conductive and non-conductive materials based on their flow. Lorentz's theory was experimentally validated by his student Pieter Zeeman. For this discovery, both Lorentz and Zeeman were awarded the Nobel Prize in Physics in 1902.

Lorentz's research following his Nobel Prize win was even more ground-breaking. According to the Lorentz transformation theory published in 1904, motion results in a variation of the electromagnetic forces between the charges of the particles within the moving object. As a result, a moving object contracts slightly in size. This work directly led to Albert Einstein's discovery of the Special Theory of Relativity in 1905.

Einstein and Lorentz (1921)

Lorentz's research opened so many new avenues in physics that scientists of his time recognized him as the greatest theoretical physicist. In 1905, he was elected a Fellow of the Royal Society. He received the Royal Society's Rumford Medal in 1908 and the Copley Medal in 1918. In 1911, he presided over the first Solvay Congress held in Brussels.

In 1919, the Dutch government appointed Professor Lorentz as the chairman of a high-level committee for sea control. Under his leadership, significant advancements were made in hydraulic engineering in the Netherlands.

After World War I, Lorentz took the initiative to re-establish scientific research cooperation among various European countries. He was one of the leading seven scientists on the Committee on Intellectual Cooperation of the League of Nations. In 1925, he was appointed the chairman of this committee.

Hendrik Lorentz passed away on February 4, 1928. He was so highly respected in the Netherlands that, to honour his memory, all telegraph and telephone services in the country were halted for three minutes.

In 1953, on Lorentz's centenary, Albert Einstein sent a message to Leiden University's commemorative event, writing, "Everybody felt his superiority, but nobody felt oppressed by it."

Lorentz was a profoundly humane and anti-war individual. During World War I, a German professor friend tried to convince him that humanity's fate would be determined solely by using might and force. Lorentz replied, "It is conceivable that you are right. But I would not want to live in such a world.”

 

References:

1. Nobel Prize Ceremony Speech
2. Encyclopedia Britannica: Hendrik Antoon Lorentz
3. Albert Einstein, "Ideas and Opinions," Rupa & Co., Delhi, 2009.
4. "Biographical Encyclopedia of Scientists," World Book, Chicago, 2003.
5. Wikipedia: Hendrik Lorentz