Lecture Notes: The Miller-Urey Experiment

Introduction to Spontaneous Generation

• Historical belief: Spontaneous generation (living creatures like maggots and rats "poof" into existence from rotting food)
• 1600s experiments disproved spontaneous generation
• 1800s: Law proposed - life only comes from life

Darwin and the Theory of Evolution

• Charles Darwin's theory: simple creatures can evolve into complex ones
• Posed the question: Can simple life forms originate from non-living matter?
• Darwin's idea of a "warm little pond" with chemical elements forming proteins

Oparin's Hypothesis

• 1924: Alexander Oparin's book "The Origin of Life"
• Proposed the idea of a primordial soup in early oceans
• Suggested chemical reactions in this soup could lead to living cells
• Early ocean as a collection of complex molecules from natural reactions

The Challenge of Studying the Origin of Life

• Lack of fossil evidence or time travel for direct observation
• Need for testable scientific hypotheses

Stanley Miller and Harold Urey's Experiment

• 1950s: Stanley Miller (graduate student) and Harold Urey (professor) at the University of Chicago
• Simulated early Earth's conditions in a lab apparatus
• Components:
  • Water (ancient ocean, boiled for evaporation)
  • Methane, hydrogen, and ammonia (gases in the atmosphere)
  • Condenser for rain simulation
  • Spark discharges to simulate lightning (energy source)
• Objective: Test if simple chemistry can lead to life's complex molecules

Results and Significance

• After one week: Ocean became brownish black
• Analysis found the formation of complex molecules like amino acids
• Amino acids previously thought to be only from living organisms
• Significant breakthrough, leading to the field of Prebiotic Chemistry

Broader Implications

• Uncertainty about gases on ancient Earth
• Experiments show life's molecules can form in various environments
• Sugars, lipids, amino acids found on meteorites
• Suggests such molecules could form throughout the solar system and galaxy

Conclusion

• Miller-Urey Experiment:
  • Simulated ancient Earth conditions
  • Demonstrated biomolecules can form under ancient Earth-like conditions
  • Transformed speculation about life's chemical origins into testable science
• Ongoing research seeks to explore the origins of life
• Funded by Center for Chemical Evolution, NSF, and NASA

Acknowledgments and Support

• Special thanks to chemist Eric Parker and financial contributors
• Ways to support: Website and Patreon