Explainer: Quantum is the world of the super small | Science News for Students

Explainer: Quantum is the world of the super small

The public often misuses the term, but here’s what it really means
Sep 14, 2017 — 7:16 am EST
Quantum imagery

Quantum refers to the measurement and operations of particles and energy on subatomic scales. At this scale, things can appear as particles or waves and exist in more than one place at once.


The term quantum seems to come up all the time. There’s quantum computing and a quantum internet. Quantum encryption. There’s a whole field of quantum physics. And there’s even the phrase “quantum leap.” But what does that mean? Is such a leap especially tall? What's the big deal?

In fact, a quantum leap is amazingly small. The word quantum refers to the smallest amount of something that you can have. You can't break a quantum of something into smaller parts. A quantum is the most basic building block.

In 1900, German physicist Max Planck came up with a revolutionary idea. It had to do with energy — in the form of heat or light — as it radiated from a source. Planck argued that this energy was quantized. By that he meant it could only be found in amounts made up of whole numbers of those smallest amounts or building blocks. A photon is a quantum of light. You can't break a photon into smaller pieces. In other words, there’s no such thing as half a photon.

Planck went on to win the Nobel Prize in physics, the highest honor in this field. His work helped lay the foundation for quantum physics. This is an area of science that describes the behavior of particles at the smallest scales. Subatomic scales. (Subatomic is smaller than an atom.)

Still, some people use the word “quantum” to describe something surprisingly big. It's especially true with the phrases “quantum leap” or “quantum jump.” But quantum doesn't mean “big.” It's the exact opposite. So, when something does undergo a quantum jump, its energy changes — but not by much.

Power Words

(more about Power Words)

behavior     The way something, often a person or other organism, acts towards others, or conducts itself.

field     An area of study, as in: Her field of research was biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory.

Nobel prize     A prestigious award named after Alfred Nobel. Best known as the inventor of dynamite, Nobel was a wealthy man when he died on December 10, 1896. In his will, Nobel left much of his fortune to create prizes to those who have done their best for humanity in the fields of physics, chemistry, physiology or medicine, literature and peace. Winners receive a medal and large cash award.

particle     A minute amount of something.

photon     A particle representing the smallest possible amount of light or other electromagnetic radiation.

physicist     A scientist who studies the nature and properties of matter and energy.

quantize   To apportion things in units that can exist only as whole numbers; they can never exist as fractions of a unit.

quantum     (pl. quanta) A term that refers to the smallest amount of anything, especially of energy or subatomic mass.

quantum physics     A branch of physics that uses quantum theory to explain or predict how a physical system will operate on the scale of atoms or sub-atomic particles.

subatomic    Anything smaller than an atom, which is the smallest bit of matter that has all the properties of whatever chemical element it is (like hydrogen, iron or calcium).