Lecture Notes: Human Size and Its Limitations

Introduction to Human Growth

Average Height Increase: In the past 150 years, average human height has increased by about ten centimeters (four inches) due to improved nutrition and medical care.
Genetic Blueprint: There is a genetic blueprint that dictates how tall a healthy human can grow, generally not exceeding 7 feet 6 inches.

Endocrine Disorders: Tumors near the pituitary gland can cause excessive growth.
Notable Tall Individuals:
- Igor Vovkovinskiy: 7 foot 8 inches, tallest living man in America.
- Sultan Kösen: 8 foot 3 inches, tallest living person globally.
- Robert Wadlow: Tallest person ever recorded at 8 foot 11 inches.
- Andre the Giant: A well-known figure, 7 foot 4 inches.

Genetic Limits: We are near the genetic limit for human height; manipulation may add only about 15 centimeters.
Square-Cube Law: As a shape grows, its volume increases faster than its surface area, posing structural challenges for larger sizes.
- Larger humans (>8 feet) would require different body proportions or stronger materials than bone.
Organ Functionality: Larger sizes would cause functional issues, such as insufficient heart capacity.

Example of Large Animals:
- Giraffatitan: One of the largest land animals, weighing 20-30 thousand kilograms.
- Bruhathkayosaurus: Potentially larger, but size is controversial.
- Blue Whale: Largest known animal, weighing 177,000 kilograms.
Environmental Constraints: Gravity and geometry limit size; buoyancy in water can support larger sizes.

Growth on Mars: Reduced gravity might allow humans to grow taller, but with weaker bone and muscle structure.

Sound: Maximum audible shout reaches about 5 kilometers.
Sight: Maximum visibility on Earth extends to the horizon (about 5 kilometers); in space, visibility depends on angular size.
Smell: Animals can detect scents from great distances, e.g., grizzlies from 30 kilometers away.

Human Body Light: Emits infrared and some visible light, tied to circadian rhythms.
Photons: Individual photons can travel indefinitely through space, making human light emissions conceptually infinite.

Physical and Biological Limits: Human size is constrained by biology and physics.
Impact Beyond Physical Boundaries: Humans impact their environment through sound, smell, and light beyond their physical form.
Metaphorical Immensity: Light emitted by humans can travel indefinitely, suggesting a form of immortality.

Note: The discussion includes references and examples to illustrate key points, such as notable individuals and animal comparisons.