/reality

name: mfe-reality
description: "Physical applications of mathematics. Constants, quantum mechanics, measurement — where abstract meets embodied."
user-invocable: false
allowed-tools: Read Grep Glob
metadata:
  extensions:
    gsd-skill-creator:
      version: 1
      createdAt: "2026-02-26"
      triggers:
        intents:
          - "physics"
          - "constant"
          - "quantum"
          - "particle"
          - "energy"
          - "momentum"
          - "wave function"
          - "measurement"
          - "uncertainty"
        contexts:
          - "mathematical problem solving"
          - "math reasoning"

Reality

Summary

**Reality** (Part V: Grounding) Chapters: 15, 16, 17 Plane Position: (0.3, -0.4) radius 0.35 Primitives: 44

Physical applications of mathematics. Constants, quantum mechanics, measurement — where abstract meets embodied.

**Key Concepts:** Quantum Operators (Observables), Planck's Constant, Wave Function, Dimensional Analysis, Atomic Number and Mass

Key Primitives

**Quantum Operators (Observables)** (definition): Observables in quantum mechanics are represented by Hermitian (self-adjoint) operators on Hilbert space. Position: X_hat psi = x*psi. Momentum: P_hat psi = -i*hbar*d/dx psi. The eigenvalues of an observable are the possible measurement outcomes.

• Represent a physical measurement mathematically
• Find the possible outcomes of a quantum measurement
• Determine whether two observables can be measured simultaneously

**Planck's Constant** (axiom): Planck's constant h = 6.62607015 x 10^{-34} J*s (exact, SI definition). The reduced Planck constant hbar = h/(2*pi). It is the quantum of action, setting the scale where quantum effects become significant.

• Determine the scale at which quantum effects matter
• Compute photon energy from frequency
• Calculate the de Broglie wavelength of a particle

**Wave Function** (definition): The wave function psi(x,t) is a complex-valued function that completely describes the quantum state of a system. The probability of finding the particle between x and x+dx is |psi(x,t)|^2 dx. The wave function must be normalized: integral |psi|^2 dx = 1.

• Describe the state of a quantum particle
• Compute probabilities of measurement outcomes
• Determine the time evolution of a quantum system

**Dimensional Analysis** (technique): Every physical equation must be dimensionally consistent: both sides must have the same dimensions in terms of fundamental quantities (length L, mass M, time T, charge Q, temperature Theta). A quantity Q has dimensions [Q] = L^a M^b T^c Q^d Theta^e.

• Check if a physics equation is dimensionally consistent
• Derive the functional form of a physical relationship from dimensional constraints
• Determine which variables a physical quantity can depend on

**Atomic Number and Mass** (definition): The atomic number Z is the number of protons in an atom's nucleus, uniquely identifying the element. The mass number A = Z + N where N is the number of neutrons. Atomic mass is measured in unified atomic mass units (u ≈ 1.661 x 10^{-27} kg).

• Identify an element from its number of protons
• Determine the number of electrons in a neutral atom
• Calculate atomic mass from isotope data

**Quantum Numbers** (definition): Each electron in an atom is described by four quantum numbers: principal n (1,2,3,...), angular momentum l (0,...,n-1), magnetic m_l (-l,...,+l), and spin m_s (+1/2 or -1/2). No two electrons can share all four quantum numbers (Pauli exclusion).

• Describe the state of an electron in an atom
• Determine the number of electrons in each shell and subshell
• Predict orbital shapes and orientations

**Electron Configuration (Aufbau Principle)** (algorithm): The Aufbau principle states that electrons fill orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, ... The filling order follows the (n+l) rule: lower n+l fills first; for equal n+l, lower n fills first.

• Determine the electron configuration of an element
• Predict chemical properties from electron arrangement
• Understand the structure of the periodic table

**Speed of Light** (axiom): The speed of light in vacuum is a universal constant: c = 299,792,458 m/s exactly. It is the maximum speed for information transfer and the conversion factor between space and time: E = mc^2.

• Convert between mass and energy
• Compute relativistic effects at high velocities
• Set the scale for electromagnetic phenomena

**Elementary Charge** (axiom): The elementary charge e = 1.602176634 x 10^{-19} C (exact, SI definition) is the magnitude of the charge of the electron and proton. It is the fundamental quantum of electric charge.

• Compute electromagnetic forces between charged particles
• Convert between energy in joules and electron-volts
• Quantize charge in atomic and molecular systems

**Physical Quantity** (axiom): A physical quantity Q is the product of a numerical value {Q} and a unit [Q]: Q = {Q} x [Q]. The numerical value depends on the choice of unit, but the physical quantity is invariant. Examples: length l = 5 m, energy E = 3.2 eV.

• Represent a measurable physical quantity with units
• Convert between different unit systems
• Ensure calculations preserve physical meaning

Composition Patterns

• Dimensional Analysis + reality-buckingham-pi -> Systematic derivation of dimensionless groups governing a physical system (sequential)
• Buckingham Pi Theorem + reality-dimensional-analysis -> Complete dimensional reduction of any physical problem to dimensionless form (sequential)
• Speed of Light + reality-plancks-constant -> Photon energy: E = hc/lambda, linking quantum and electromagnetic scales (sequential)
• Planck's Constant + reality-speed-of-light -> Natural unit system where hbar = c = 1 (parallel)
• Gravitational Constant + reality-speed-of-light -> Schwarzschild radius: r_s = 2GM/c^2, boundary of a black hole (sequential)
• Boltzmann Co