Editing 2904: Physics vs. Magic

{{comic
| number    = 2904
| date      = March 8, 2024
| title     = Physics vs. Magic
| image     = physics_vs_magic_2x.png
| imagesize = 740x294px
| noexpand  = true
| titletext = 'At the stroke of midnight, your brother will be hurtling sideways at an altitude of 150 meters' is a regular physics prediction about your nonmagical trebuchet, whereas 'you are cursed to build a brother-launching trebuchet' falls out of the Lagrangian.
}}

==Explanation==
This comic explores the distinctions between magic and physics through the perspective of [[Miss Lenhart]], a schoolteacher. She explains that {{w|physics}} involves the continuous application of forces to objects over time, whereas magic reveals the outcome without detailing the process. She illustrates her point with a magical curse example that dictates the recipient will slay their brother by midnight (or possibly noon), highlighting its lack of scientific basis due to the absence of a causal explanation. She further contends that the {{w|laws of thermodynamics}}, among other laws, fall into the category of magic, with {{w|Lagrangian (physics)|Lagrangians}} representing a deeper level of magic.

The humor in this comic arises from the observation that foundational physical laws, despite being empirically derived, lack explanations for their inherent truths. According to the logic presented in the second panel, these laws resemble magic as they specify outcomes without clarifying the means to achieve them. While some laws might be derived from others, ultimately, we accept certain principles as given, akin to magical reasoning.

The second panel references Newtonian mechanics, depicted as an initial value problem, which establishes a system's initial conditions and its temporal evolution based on specific rules. This formulation aligns with our intuitive understanding that the present is a known state and the immediate future is determined by present conditions. The final panel humorously juxtaposes this notion with various physics concepts that challenge our basic assumptions in progressively disconcerting ways.

Specifically, equilibrium thermodynamics, a major branch of thermodynamics familiar to students, makes predictions about a system's eventual state without accounting for its current state or intermediate behaviors. This perspective seemingly contradicts the principle introduced in the first panel, although the concept of inquiring about long-term stability without detailed process knowledge remains intuitively accessible.

{{w|Conservation law}}s, emerging naturally from Newtonian physics, present another conceptual challenge. While basic explanations involve calculus and elementary algebra, more advanced interpretations connect conservation laws to physical system symmetries in a highly abstract and enigmatic manner. These laws, therefore, make permanent statements about a system's state, independent of its evolution, challenging the initial principle in a manner that feels even more counterintuitive than thermodynamics. Notably, particle physics conservation laws, except in cases involving the {{w|Wu experiment|weak nuclear force}}, maintain certain system properties like charge, spin, and parity.

Lagrangian mechanics, a reinterpretation of classical physics equivalent to Newton's laws, diverges by considering both initial and final states to determine physically permissible trajectories. This approach directly opposes the first panel's principle, mirroring the magical definition by surprisingly and counterintuitively aligning the intuitive Newtonian perspective with the "magical" frameworks of Lagrangian and Hamiltonian mechanics. Therefore, the comic labels Lagrangians, central to Lagrangian mechanics and system dynamics description, as 'Deep Magic', highlighting their role in encapsulating physics' magical aspect.

Furthermore, the comic might hint at the teleological debate within physics, especially regarding the {{w|stationary-action principle}}'s potential teleological interpretations. This principle, foundational to deriving various equations of motion across physics fields, suggests a teleological element by inferring initial conditions from specified final conditions, challenging the conventional causality narrative.

The title text merges the comic's thematic elements, contrasting a nonmagical {{w|trebuchet}} prediction with the mystical implications of the curse, further blending the lines between physics predictions and magical foresight.

==Transcript==
:[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 "V<sub>0</sub>" for an arrow pointing right on the left side of the leftmost circle, "F" for an arrow pointing downward below the leftmost circle, and "T<sub>0</sub>" to "T<sub>4</sub>" for the five individual circles.]
: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.

{{comic discussion}}

[[Category:Comics featuring Miss Lenhart]]
[[Category:Comics featuring Jill]]
[[Category:Comics featuring Hairy]]
[[Category:Physics]]
[[Category:Trebuchet]]