#2904: Physics vs. Magic explain

[Miss Lenhart is standing in front of a whiteboard and pointing to it with a stick. The whiteboard contains two lines of scribbles at the top, two drawings below them featuring a curve on the left and a circle on the right, and below them four additional lines of scribbles with smallest line of scribbles in the lower left corner.]

Miss Lenhart: Physics and magic are different in a very deep way.

[Close-up of Miss Lenhart pointing the stick to the left to a depiction of a projectile’s motion due to gravity. The path of movement is shown as a dashed line that first heads directly to the right but starts increasingly curving downward. There are five small circles at different points within the path. There are labels “V0” for an arrow pointing right on the left side of the leftmost circle, “F” for an arrow pointing downward below the leftmost circle, and “T0” to “T4” for the five individual circles from left to right.]

Miss Lenhart: Physics works by describing the forces that act on a system.

Miss Lenhart: To predict outcomes, we progressively apply those forces over time.

[Miss Lenhart is holding the stick down and standing in front of Jill and Hairy sitting at their desks. Jill has her hands on her desk while Hairy has his hands on his lap.]

Miss Lenhart: Magic specifies the outcome, but not the intermediate events.

Miss Lenhart: * “Ere the clock strikes twelve, you are cursed to slay your brother” * is magic, not science.

[Same setting as in the third panel, except Miss Lenhart is holding the stick slightly lower and Jill has her other hand on her lap.]

Miss Lenhart: … And that’s how we know thermodynamics is magic.

Miss Lenhart: Conservation laws are, too.

Hairy: What about Lagrangians?

Miss Lenhart: Deep magic. Speak not of them here.