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WHAT IS QUANTUM PHYSICS?
Quantum Basics
What is quantum physics?
Quantum physics is an amazing branch of science that describes the behavior of matter and energy on size scales far smaller than anything we humans can see with our unaided eyes. It describes the interactions of elementary particles and fields – the tiniest, most fundamental constituents of matter and energy in the universe.
What is a quantum?
A quantum (plural “quanta”) is simply a set amount of anything – length, time, energy, momentum, electric charge, or whatever. The word is used in the scientific term “quantum physics” because on those tiny size scales, many quantities cannot appear in nature continuous values, and rather can only be observed at specific set values.
What is physics?
Physics is the study of space, time, matter, and energy, and how they interact with one another. Put another way, physics is the scientific study of the structure, content, and activity of and in the world and universe around us. Physics seeks to explain natural phenomena in terms of a comprehensive theoretical framework in mathematical form. Physics depends on well-built instruments, precise measurements, careful calculations, and the rigorous expression of results.
Why is quantum physics also called quantum mechanics?
Quantum physics originated when physics were conducting research describing the motions and interactions of particles and waves. This area of physics is known as mechanics. Thus, quantum physics is often also known as quantum mechanics. Gradually, scientists discovered that quantum physical phenomena occur in many other areas of physics, and also in other sciences like chemistry, biology, and astronomy.
Why is quantum physics so mysterious?
At the tiny size scales of quantum physics – usually much smaller than one-millionth of an inch! – the structure and behavior of matter and energy differs greatly from the way objects behave at human size scales. Without the aid of advanced technological tools, it is almost always impossible to see the effects of quantum physics – even though, ironically, quantum physics helps to explain how human eyes work. The universe appears to behave very differently at quantum scales compared to human scales, so “quantum” things seem mysterious. As it turns out, much of quantum physics is well explained scientifically and even quite ordinary.
Why is quantum physics important?
Although quantum physics describes how things work at tiny size scales, every object we know of – including people, planets, stars, galaxies, and the entire universe – is made of up tiny particles. By studying quantum physics, we learn how we're built, and thus how we live, how we interact with the world around us, and even how we fit into the entire universe in which we exist.
How does quantum physics affect me?
Quantum physics affects you and me in so many ways it's hard to count them all. Here are just a few examples. All of the modern electronic devices you use, including your computer and mobile phone, use the principles of quantum mechanics to work. All of the sunlight you see and feel was produced by quantum physics happening deep inside the Sun. And all of the DNA molecules that govern your life processes operate by the rules of quantum physics.
How do scientists study quantum physics?
Even though it may seem extra-mysterious, quantum physics is a branch of scientific inquiry in the same way that other branches of physics, astronomy, biology, and chemistry are. Physicists work to explain natural phenomena in terms of a comprehensive theoretical framework in mathematical form. Physicists approach quantum physics in the same way as they approach the other branches of physics – they just have to take into account the special properties of the universe at tiny size scales.
What does a quantum physicist do?
A quantum physicist can do a wide variety of things over the course of a day, or a year, or a career. Many conduct fundamental research in large laboratories or universities, advancing what we know about quantum physics while teaching others about the field. Many others work for corporations, in a wide variety of fields such as energy, engineering, electronics, and computers. Still others apply their knowledge of quantum physics, which is widely applicable to a huge number of different activities, in areas of society far from scientific work.
Why should I learn about quantum physics?
Quantum physics is one of the frontier areas of science today, and is a fascinating, fun, and useful thing to learn. Physics often called “the fundamental science” because it is the core of many other sciences such as astronomy, biology, chemistry, and geology. It is also the basis of many fields of applied sciences such as aeronautics and astronautics, engineering, computer science, and information technology. Quantum physics is thus fundamental in almost every high-tech pursuit. A strong knowledge of physics, especially quantum physics, is a powerful tool to have in today’s world.
Key ideas of quantum physics
What are some of the basic key concepts of quantum physics?
Three basic key concepts of quantum physics are wave-particle duality, energy quantization, and quantum uncertainty.
What is a wave?
A wave is a traveling disturbance that moves energy from one location to another without transferring matter. When regular motions back and forth for example, known scientifically as “oscillations,” occur in a medium or material, it creates waves that propagate away from the location of the oscillation. For example, a pebble dropped into a pool of water creates vertical oscillations in the water, while the wave propagates outward horizontally along the surface of the water.
What is a particle?
A particle is the general term for any single object. Particles can be elementary, which means they exist and move fully independently from other objects; or they can be composite, which means they are made up of smaller, simpler objects. Photons, electrons, atoms, molecules, pebbles, potatoes, and planets are all examples of objects that could be physically considered as types of particles.
What is wave-particle duality?
Quantum physicists realized about a century ago that waves and particles are very closely connected. In fact, in a quantum system, every particle is also a wave, and every wave is also a particle. In our daily lives, however, the particles we encounter do not appear to be waves at all, because their wavelengths are almost imperceptibly tiny. This duality between waves and particles remains one of the most challenging, yet fundamental, parts of quantum physics to understand fully.
What is energy?
Energy is a challenging concept to define, because it can take so many different forms, and objects can have energy in many different ways. One rather abstract definition of energy is a property that, when it is transferred between particles or physical systems, can produce motion, heat, or light. An object with energy can change itself or its environment.
What is energy quantization?
Energy quantization is the process of producing energy only in specific amounts. Normally, we think we can produce any amount of energy, large or small; in quantum physics, however, where the amounts of energy are generally tiny, only set amounts of energy can move within and between particles and systems. The amounts depend on the quantum properties of those particles and system.
Do we experience energy quantization in our daily lives?
In our daily lives, we do experience energy quantization, although not exactly in the sense described in quantum physics. For example, when you are climbing a staircase, you can stop and stand on the second or fifth or tenth stair, but you cannot stand at the height between the third stair and fourth stair. Each stair represents a level of gravitational potential energy; so while you are on the staircase, you are experiencing a kind of energy quantization.
Where is energy quantization observed to occur?
One important example of energy quantization – which is a key concept of quantum physics – appears in atoms and molecules. These particles can only gain or release energy in specific amounts; there can be many different such energy levels, but the total number is limited. The patterns of quantized energy in atoms and molecules have direct effects on everything from the properties of materials we use, to the colors of light emitted in lamps, to the existence of life as we know it.
What is quantum uncertainty?
Perhaps the most counterintuitive concept among the fundamental ideas of quantum physics is quantum uncertainty. Roughly speaking, it is the idea that certain quantities in physical systems cannot be known precisely until they are measured. Before the measurement of a quantity occurs, the quantities are only known as estimates or probabilities; after the measurement occurs, some other related quantity must actually be less well known than it was before. (See, I told you it was counter-intuitive.)
The birth of quantum physics
How did quantum physics begin?
Quantum physics first began when scientists started to notice that the laws of physics that described motion, matter, and energy – what today is often called “classical physics” – were incomplete. In other words, natural phenomena were observed that could not be explained by the scientific physical theories of the time. About a century ago – in the early 1900s – physicists began to understand several very important new ideas in physics, including wave-particle duality and energy quantization, that led to the birth of quantum physics.
What was an early experiment that suggested wave-particle duality?
Thomas Young's interference experiment, first reported in 1801, showed that light travels in waves. A modified version of the experiment, known today as the double-slit interferometer, showed that particles such as electrons, atoms, and molecules behaved the same way in the experiment that light does; that demonstrated the idea of wave-particle duality in a clearly visible way.
