Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

The Joke

A physics professor stands at a blackboard under the heading "Funtime Activity: Ruining Students Forever." He declares: "The first thing a physics student must learn is vectors and scalars and the difference between vectors and scalars is that scalars don't exist." A confused student asks, "What about a number of apples?" The professor snaps back: "Ha! Oh, you're referring to 'distance in apple-space.'"

The joke is that the professor is reframing every example of a scalar quantity as secretly being a vector (or at least a component of one), thereby "proving" that scalars do not exist. When the student offers a seemingly obvious scalar -- a count of apples -- the professor dismisses it by reinterpreting it as a "distance in apple-space," turning even counting fruit into a vector quantity.

The Humor

The humor lies in the professor's gleeful, deliberate over-complication of a basic physics concept. In introductory physics, the distinction between scalars (quantities with magnitude only, like temperature or mass) and vectors (quantities with both magnitude and direction, like velocity or force) is one of the first things taught. The professor is taking a contrarian, technically-defensible-in-some-abstract-sense position and using it to confuse students on day one. The phrase "Ruining Students Forever" as the heading acknowledges that this is not good pedagogy -- it is intellectual trolling. The invention of "apple-space" is a perfect parody of how physicists can construct abstract mathematical spaces for anything, making simple concepts impenetrably complex.

References

In physics, scalars and vectors are fundamental concepts. A scalar is a quantity described by a single number (like mass, temperature, or speed), while a vector has both magnitude and direction (like velocity, force, or acceleration). The professor's argument has a grain of truth in advanced physics: in certain mathematical frameworks, what we call scalars can be viewed as trivial cases of more complex objects. The concept of abstract "spaces" (like Hilbert space, phase space, or configuration space) is genuinely used in physics to represent quantities in higher-dimensional frameworks, making the joke about "apple-space" a pointed parody of real mathematical physics terminology.