# Who is Max Planck?

Max Planck was a Nobel Prize-winning German physicist. He lived from 1858 to 1947, dying at the age of 89. Credited with the founding of quantum theory in 1900, Planck is, along with Albert Einstein, considered one of the most significant physicists of the 20th century. His work in quantum theory launched a revolution in physics that continued until the 1970's.

Max Planck worked as a professor at the University of Berlin from 1892 until his retirement at 1926, and had a reputation as a conservative thinker. In 1894, he began to focus on the problems surrounding black body radiation, that is, the inherent spectrum of colors given off when a non-reflecting object is heated. He was commissioned to work on this problem by electrical companies who were looking for ways to build light bulbs that produce the greatest amount of light for the least amount of energy.

Trying to uncover the physics of light, Max Planck felt confounded. Up until 1900, everyone thought light was a continuous flow, indivisible down to the smallest level. Planck was a conservative thinker, and generally relied on accepted wisdom, but his calculations were confounded by representing light as continuous. Using Ludwig Boltzmann’s statistical interpretation of the 2nd law of thermodynamics as a base, Planck introduced the idea of quantization – representing light as discrete packets which would later be called photons. Later, asked about this decision, he called it, "an act of despair.. .I was ready to sacrifice any of my previous convictions about physics."

In Max Planck’s model of light, electromagnetic energy had to be emitted at discrete energy levels, multiples of a unit *E*, which was the product of the frequency of the radiation and a natural unit known as Planck’s constant. Indeed, we know today that light rays with higher frequencies and shorter wavelengths, such as x-rays, carry more energy than lower frequencies such as visible light and radio waves.

From Planck’s constant, physicists were able to derive a series of fundamental units, based not on human decision, but fundamental properties of the universe. Often, these numbers represent the largest or smallest possible value that makes sense under our current physical theory. For instance, at the Planck length, many times smaller than a proton, and the Planck time, an incredibly small unit, our understanding of quantum physics ceases to make sense. At the Planck temperature, many trillions of times greater than the temperature at the Sun’s core, all the fundamental forces of nature would unify and symmetries broken since the Big Bang would be restored. The Planck velocity is equivalent to the speed of light, and so on. When Max Planck discovered all these fundamental units, our understanding of the universe became much more digital.

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