Brain Makeover #5: The Quantum!

Big Idea #5: Everything Comes in Discrete Units and You Can’t Measure Anything Without Changing It.

Professor James Trefil (author of Science Matters, Why Science?, and 30 other books on science literacy) identified 18 key science concepts every adult should know to be a science literate. We’re here to reintroduce adults to science, in a fun way! It’s all part of our Brain Makeover project to increase adult science literacy. Here’s concept #4, presented by 76ers Cheerleader Lauren and explained by Professor James Trefil.  We’ll post one each week (more or less) and it to the Brain Makeover collection.

Here’s Professor Trefil with Big Idea #5: Everything Comes in Discrete Units and You Can’t Measure Anything Without Changing It.

In our everyday world matter seems to be smooth and continuous, but in the world of the atom things are different. There everything—mass, energy, spin, and so on—comes in discrete bundles called quanta. (The word is from the Latin for ‘bundle’.) The branch of science that describes this world is called “quantum mechanics,” and it differs in fundamental ways from the laws that describe familiar objects.

The main difference comes from the fact that when you want to detect a quantum (an electron, for example), the only way you can do it is to bounce another quantum off of it, and this interaction will change the object being measured. The mathematical statement of this effect is called the Heisenberg Uncertainty Principle, and it tells us that there are certain things we cannot know about quantum systems. We cannot, for example, know exactly where an electron is and how fast it is moving at the same time. Because of the Uncertainty Principle, objects in the quantum world are described in terms of probabilities, and the totality of probabilities describing a given object is called its wave function.

Recently, scientists working in quantum mechanics have been investigating a phenomenon known as entanglement. The wave function of two particles that have interacted at some point in the past never really separate from each other, so that the particles can continue to influence each other even though no signals can pass between them. Entanglement is expected to form the basis for new technologies, including secure communication systems and quantum computers.