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As the air, Shu was considered to be a cooling, and thus calming, influence, and pacifier. Due to the association with dry air, calm, and thus Ma'at [5] (truth, justice, order, and balance), Shu was depicted as the dry air/atmosphere between the Earth and sky, separating the two realms after the event of the First Occasion. [6]
Empedocles also proved (at least to his own satisfaction) that air was a separate substance by observing that a bucket inverted in water did not become filled with water, a pocket of air remaining trapped inside. [10] Fire, earth, air, and water have become the most popular set of classical elements in modern interpretations.
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth itself.
In 1862, Lord Kelvin calculated the age of the Earth at between 20 million and 400 million years by assuming that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface to cool to its present temperature. Since uniformitarianism required a much older Earth, there was a contradiction.
The warm period was followed by a gradual decline, of about 0.1 to 0.3 °C per millennium, until about two centuries ago. However, on a sub-millennial scale, there were regional warm periods superimposed on this decline. [2] [3] [4] For other temperature fluctuations, see temperature record. For other past climate fluctuation, see paleoclimatology.
Late Cenomanian sea surface temperatures (SSTs) in the equatorial Atlantic Ocean were substantially warmer than today (~27-29 °C). [2] Turonian equatorial SSTs are conservatively estimated based on δ18O and high p CO 2 estimates to have been ~32 °C, but may have been as high as 36 °C. [ 10 ]
The geologic temperature record are changes in Earth's environment as determined from geologic evidence on multi-million to billion (10 9) year time scales. The study of past temperatures provides an important paleoenvironmental insight because it is a component of the climate and oceanography of the time.
Another 2021 study found that 98.7% of climate experts indicated that the Earth is getting warmer mostly because of human activity. [101] In 1988 the WMO established the Intergovernmental Panel on Climate Change with the support of the UNEP. The IPCC continues its work through the present day, and issues a series of Assessment Reports and ...