Lecture Notes: Basic Concepts of Physics

Introduction

• Focus on basic concepts: mass, length, and time.
• Discussion starts with perception without tools, mathematics, or instruments.

Mass

Smallest Mass Perception

• Smallest mass estimable by senses: approximately 1 gram.
• Possible to estimate fractions of a gram (e.g., nanogram, picogram).

Largest Mass Perception

• Heaviest mass estimable: about 100 kilograms (upper limit).
• Beyond 1000 kilograms, mass is unliftable; no sense of weight.

Length

Smallest Length Perception

• Smallest length perceivable by the naked eye: around 0.5 to 1 millimeter.
• Sharp resolving power: smallest around 0.1 millimeter (10^-4 meters).

Largest Length Perception

• Longest distance visible without instruments: approximately 10 kilometers.
• Distance perception relies on reference objects; without them, estimation is impossible.

Time

Smallest Time Perception

• Smallest time perceivable: around 0.1 seconds (blink of an eyelid).

Largest Time Perception

• Without external signals, perception of time can stretch to about 100 days.

Orders of Magnitude in Physics

• Middle dimensions: range of mass (10^-4 kg to 10^3 kg), length (10^-4 m to 10^4 m), time (10^-1 s to 10^7 s).
• Nature operates on a much larger scale than human perception.

Fundamental Constants and Limits

Smallest Mass Detected

• Smallest known mass: mass of an electron (about 10^-30 kg).

Largest Mass Estimation

• Largest mass: estimated total mass of the universe (around 10^52 kg).

Smallest Length and Time

• Smallest length known: Planck length (~10^-35 m).
• Smallest time known: Planck time (~10^-42 s).

Emergent Properties and Effective Theories

• Effective theories exist at various levels; complete understanding not necessary for application in daily life.
• Emergent properties arise when individual components combine (e.g., color in materials).
• Mass and energy interchangeable in relativistic quantum mechanics; complex phenomena arise at quantum scales.

Classical vs. Quantum Physics

• Classical dynamics: exploration of macroscopic objects and Newtonian mechanics.
• Quantum mechanics: governs behavior at atomic and subatomic levels; no need for classical mechanics in all situations.

Philosophy of Physics

• Debate on reductionism versus emergent properties; need for effective laws at different scales.
• Language of physics is mathematical, necessary for understanding phenomena beyond standard perception.

Conclusion

• Understanding of physics requires both intuition and mathematical tools; exploration of emergent properties is critical in modern physics.
• Questions regarding the nature of physical laws remain open for discussion as the course progresses.