Lecture on Basic Concepts in Physics: Mass, Length, and Time

Mass, Length, and Time Perceived by Our Senses

• No tools, mathematics, or physics; just our senses.
• Mass:
  • Smallest mass perceptible: ≈ gram, i.e., 10^-4 kg.
  • Heaviest mass perceptible: < 1000 kg, i.e., 10^3 kg.
• Length:
  • Smallest length visible: ≈ 0.1 mm, i.e., 10^-3 m.
  • Longest length visible: ≈ 10 km on a clear day, i.e., 10^4 m.
• Time:
  • Shortest time noticeable: blink of an eye, ≈ 0.1 s, i.e., 10^-1 s.
  • Longest time perceivable without instruments: < 100 days, ≈ 10^7 s.

Mass, Length, and Time with Instruments

• Mass:
  • Smallest detected mass: electron ≈ 10^-30 kg.
  • Largest detected mass: universe ≈ 10^52 kg.
• Length:
  • Smallest known length: Plank length ≈ 10^-35 m.
  • Largest known length: estimated radius of universe ≈ 10^26 m.
• Time:
  • Smallest measurable time: Plank time ≈ 10^-42 s.
  • Longest measured time: age of the universe ≈ 10^17 s.

Need for Instruments and Mathematical Tools

• Instruments like microscopes and telescopes extend our sensory perception.
• Mathematical tools help understand and predict phenomena beyond middle dimensions.
• Nature operates on scales way beyond human sensory perception.

Evolutionary Limits on Perception

• Our sensory perception tailored for survival.
• Reflex times, weight differences, and distances enough for ancestors' survival needs.
• Classical Newtonian physics derived from this limited perception range.
• Higher level behaviors and concepts require mathematical abstraction and instruments.

Classical, Quantum, and Relativistic Physics

• Classical Physics: Middle dimensions, deterministic laws (Newtonian mechanics).
• Quantum Mechanics: Microscopic level, probabilistic nature.
• Relativistic Physics: High-speed, gravitational effects.
• Relativistic Quantum Field Theory: Combines high speed with quantum effects, challenges with including gravity.

Effective Theories and Emergent Properties

• Effective theories like Newtonian mechanics work within specific parameters.
• Emergent properties arise when aggregating elements (e.g., color, phases of water).
• Boundaries between classical and quantum mechanics, non-relativistic and relativistic mechanics are areas of interest.

Collective Behavior

• Larger phenomena can arise from simple local interactions (e.g., laser from coherent photons).

Importance of Mathematical Language and Complex Numbers

• Mathematics, particularly involving complex numbers, necessary for modern physics.
• Reality of theoretical constructs like electric and magnetic fields without mechanistic models.

Future Course Coverage

• Focus on non-relativistic, non-quantum mechanical classical physics.
• Understanding of classical dynamics and its intricate structure.
• Later study on statistical physics and emergence of probabilistic laws.