Q.In 1953 S. L. Miller created primitive earth conditions in the laboratory and gave experimental evidence for origin of first form of life from pre-existing non-living organic molecules. The primitive earth conditions created include:

Miller recreated what scientists believed the early Earth's atmosphere looked like roughly four billion years ago. The key conditions were high temperature to mimic the heat from volcanic activity and lightning storms, which provided the energy needed to drive chemical reactions. The atmosphere he used was a reducing one, meaning it had no free oxygen but instead contained gases like methane, ammonia, hydrogen, and water vapour. These simple inorganic molecules, when subjected to electric sparks simulating lightning, combined to form amino acids and other organic compounds—the building blocks of life. …

Stanley Miller's 1953 experiment stands as one of the most elegant demonstrations in the history of biology. Working under Harold Urey at the University of Chicago, Miller set out to test a bold hypothesis: that the simple organic molecules necessary for life could have arisen spontaneously from inorganic precursors on the early Earth, without any divine spark or mysterious vital force. The question was whether the raw chemistry of a young planet could, by itself, produce amino acids and other building blocks of life.

To answer this, Miller had to think like a planetary scientist. What was Earth like four billion years ago, long before oxygen-breathing organisms transformed the atmosphere? The consensus view, shaped by Urey and the Russian biochemist Oparin, held that the primitive atmosphere was fundamentally different from today's. There was no free oxygen—photosynthetic life had not yet evolved to pump it out. Instead, the atmosphere was reducing, meaning it contained hydrogen-rich gases that readily donated electrons. The key components were methane, ammonia, water vapour, and hydrogen itself.

Miller's apparatus was deceptively simple: a sealed glass system with one flask of boiling water (simulating the ocean) and another containing the gas mixture. Electric sparks—standing in for lightning or volcanic electrical discharges—crackled through the gases, driving chemical reactions. High temperatures from the boiling water and the energy from the sparks mimicked the violent, storm-wracked conditions of early Earth, when volcanic activity was far more intense than today and the planet's surface was still cooling from its fiery birth. …

Reason backward from the goal of the experiment: Miller wanted to show non-living molecules could form life's building blocks, which needs (i) an energy source violent enough to break simple bonds and (ii) an atmosphere that will not destroy the organic products as …