As you may already know, constants are not random numbers found in mathematical equations. These derived numbers play a crucial role in the evolution of various theories in physics. Planck’s constant is one of the fundamental constants that explains how quantum mechanics or different electronic devices work. In addition, Planck’s constant is used for analyzing various phenomena, ranging from stellar evolution to blackbody radiation. Still, the significance of the constant might not be evident at first glance. Here are ten reasons why Planck’s constant is so important:

**#1. Planck’s Constant Is a Fundamental Physical Constant**

Planck’s constant is a fundamental physical constant that characterizes various mathematical formulations of quantum mechanics. In 1900, Max Planck empirically derived a formula that allowed him to calculate the proportionality constant based on experimental measurements. The constant and the discovery of energy quanta facilitated the advancement of numerous physical theories. Planck’s constant is so important that Max Planck even received the Nobel Prize in 1918.

**#2. Planck’s Constant Is Used to Determine the Overall Energy of a Photon**

A photon is a massless subatomic particle that carries waves of electromagnetic radiation. Although photons do not have mass, they have energy and momentum. Therefore, a photon’s kinetic energy equals its total energy. To calculate the total energy of a photon, we use Max Planck’s equations. In the first form of the equation, we multiply Planck’s constant by the photon’s frequency. Another version of the equation allows us to determine the overall energy of a photon by multiplying Planck’s constant by the speed of light and dividing the resulting number by the wavelength of the photon.

**#3. Planck’s Constant Defines the Amount of Energy a Photon Is Capable of Carrying**

Planck’s constant defines the amount of energy a photon can carry. According to the theory, the energy transfer only occurs in whole integers and is transferred by discrete photons of light. In other words, electromagnetic energy is not capable of flowing continuously. For example, atoms can only vibrate at specific frequencies or at whole-number multiples of that particular frequency. While sharing particle-like behavior, photons behave as waves and move in a straight line instead of vibrating with any frequency.

**#4. Planck’s Constant Plays a Key Role in the Understanding of Quantum Mechanics**

Quantum mechanics is a study of the physical properties of nature that explains how the universe works at the scale of atoms and subatomic particles. Initially, physicists had been assuming that atoms could vibrate continuously at any frequency. After Planck assumed the opposite, things started to make sense. The assumption worked! The discovery facilitated further research in the field that was later called quantum mechanics. Without Planck’s constant, we would not have been able to understand the principles of quantum mechanics.

**#5. Planck’s Constant Allowed Physicists to Understand the Difference Between Classical Mechanics and Quantum Mechanics**

Classical mechanics is a theory that explains the motion of macroscopic objects. The laws that help us understand classical mechanics include Newton’s laws of motion, conservation laws, and force laws. On the other hand, quantum mechanics deals with the movement of atoms and subatomic particles. Before Max Planck derived Planck’s constant, physicists could not differentiate these two fields from each other. Luckily, Planck’s assumption was correct and Planck’s constant made it clear that classical mechanics and quantum mechanics are two contrasting theories.

**#6. Planck’s Constant Is Crucial for Understanding Atoms and Matter**

Planck’s constant is essential for understanding and describing the motion of atoms and subatomic particles. Without Max Planck’s discovery, we would be unable to explain how atoms, protons, neutrons, and electrons move. As a matter of fact, elementary particles, also known as quarks, behave under the laws of quantum mechanics. These particles move around the proton and neutron with the speed of light.

**#7. The New Size of a Kilogram Is Based upon Planck’s Constant**

Nearly 150 years ago, the exact weight of a kilogram was determined by a cylinder made from an alloy (90% platinum and 10% iridium). While this method was totally acceptable in the 19th century, technological advancements and the development of the pharmaceutical industry raised the need for more accurate measurements. At the 26th general conference on weights and measures in 2019, 60 countries voted for the redefinition of the size of a kilogram based on Planck’s constant.

**#8. Planck’s Constant Enables Scientists to Understand the Stellar Evolution**

Stellar evolution is a theory that describes how the structure and composition of stars change over time. Although we cannot really notice if the stars change at all, stellar evolution theory enables us to learn more about how stars are born, how they age, and how they die. In fact, the principles of quantum mechanics are essential for understanding what stellar evolution is and how it works.

**#9. Planck’s Constant Facilitated the Production of Various Electronic Devices**

The study of electronics incorporates the use of various electronic devices to control electron flow by rectification or amplification. Without an electric current, there would not have been any electronic devices. Besides, an electric current is created by the movement of electrons in an electrically conducting medium. Planck’s constant allowed scientists to describe how atoms and particles work, enabling them to produce electronic devices, such as circuits, transistors, oscillators, amplifiers, and transducers.

**#10. Planck’s Constant Is Used for Explaining the Rationale Behind Blackbody Radiation**

Planck’s radiation law describes how the spectral electromagnetic energy of radiation is emitted by a blackbody. The law explains the emitted radiation near thermodynamic equilibrium, and therefore, Planck’s radiation is often referred to as thermal radiation. Without Planck’s constant, we would not be able to understand how electromagnetic radiation is absorbed or emitted.