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The solar system was a mass of swirling gas and dust. Over time, gravity pulled the materials together to form the sun. This resulted in the sun becoming the center of the solar system.
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Scientists believe that the planets formed at this time through repeated collisions of space debris.
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Earth became larger as gravity pulled more debris together. This was the beginning of the formation of the Earth we know today.
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Collisions between space debris and Earth released large amounts of thermal energy, sometimes melting large portions of the Earth's surface.
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The Earth is estimated to be four billions years old. This was determined by studying layers of sedimentary rock.
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Little or no oxygen existed on Earth. Therefore, the first cells are predicted to be anaroebic, heterotrophic prokaryotes that ate organic molecules.
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Stromalites were discovered. Stromalites are layered structures that form from colonies of cells.
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Some forms of life became photosynthetic. Scientists infer this because of chemical evidence of photosynthetic activity.
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Earth bagan to look like the Earth of today.
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Oxygen levels reached the levels that they are today.
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A theory suggests that a type of small aerobic prokaryote was swallowed by a larger anarerobic prokaryote and began to live inside the bigger cell at this time. Then, it was inferred that the small prokaryote evolved into the modern mitochondria. This theory is called endosymbiosis.
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The ozone (O3) formed. This protected organisms from harmful UV rays so they could exist on land.
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Francesco Redi noticed the different developmental stages of flies. Redi preformed an experiment and discovered that the theory of spontaneous regeneration is false.
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Microscopes began to be used for scientific research.
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Lazzaro Spallanzani performed an experiment, hypothesizing that microorganisms come from other microorganisms (biogenesis).
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Stanley L. Miller and Harold C. Urey preformed an experiment using Oparin’s hypothesis that Earth’s gases would form simple organic compounds at high temperatures. They performed this experiment by putting the specific gases in a chamber and using electric sparks to drive the chemical reactions. It resulted in organic molecules forming, which proved Oparin's hypothesis.
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Louis Pasteur cleared up the controversy of spontaneous generation by performing an experiment. He won a prize from the Paris Academy of Science.
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Lynn Margulis developed the theory of endosymbiosis, which theorized that early prokaryotic cells had a mutual relationship.
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Thomas Cech discovered a kind of RNA in unicellular eukaryotes that acts as a catalyst. He referred to it as a ribozyme.
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Scientists Alexander I. Oparin and John B. S. Haldane hypothesised that the early atmosphere contained ammonia, hydrogen gas, water vapor, and carbon compounds and these gases formed organic compounds at high temperatures.
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Sidney Fox did extensive research on cell structure. This included studying microspheres and coacervates.
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Radiometric dating began to be used. This is a method of determining the age of various materials. This is completed by measuring the quantity of a specific radioactive isotope in an object.
