The Miller-Urey Experiment:
The Miller-Urey experiment was a pioneering study conducted by Stanley L. Miller and Harold C. Urey in 1952. It aimed to simulate the conditions of early Earth and investigate the possibility of chemical reactions leading to the formation of organic molecules, such as amino acids, the building blocks of life.

Experimental Setup:
1. Atmosphere:
- Miller-Urey experiment simulated the atmosphere of early Earth, which was believed to be composed of methane (CH4), ammonia (NH3), water vapor (H2O), and hydrogen (H2).
- These gases were introduced into a closed system, representing the early Earth's atmosphere.

2. Energy Source:
- In order to simulate the energy sources of early Earth, Miller used electrical sparks to mimic lightning.
- Electric discharges were passed through the mixture of gases in the closed system.

3. Heat Source:
- A water flask was used as a heat source to create a cycle of evaporation and condensation, representing the water cycle on early Earth.

Chemical Reactions:
1. Sparking:
- The electrical discharges provided the necessary energy to initiate chemical reactions.
- They acted as a source of heat and simulated the lightning strikes that were prevalent on early Earth.

2. Formation of Organic Molecules:
- The energy from the electrical sparks caused the gases in the atmosphere to react and form organic molecules.
- Amino acids, the building blocks of proteins, were synthesized as a result of these reactions.
- Other organic compounds, such as sugars and nucleotides, were also produced.

Ratios of Gases:
The exact ratio of methane, ammonia, and hydrogen in the Miller-Urey experiment varied depending on the specific conditions and setup. However, a commonly used ratio in the experiment was 2 parts methane, 2 parts ammonia, and 1 part hydrogen.

- Methane (CH4): 2 parts
- Ammonia (NH3): 2 parts
- Hydrogen (H2): 1 part

This ratio was chosen based on the understanding of the composition of the early Earth's atmosphere at the time of the experiment. It aimed to create an environment that could support the synthesis of organic molecules, particularly amino acids.

Conclusion:
The Miller-Urey experiment demonstrated that organic molecules, such as amino acids, could be synthesized under conditions similar to those on early Earth. This provided evidence for the possibility of the spontaneous formation of organic compounds, which eventually led to the emergence of life on our planet. The experiment was a groundbreaking step in understanding the origins of life and has paved the way for further research in the field of prebiotic chemistry.