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The Purple Earth Hypothesis (PEH) is an astrobiological hypothesis, first proposed by molecular biologist Shiladitya DasSarma in 2007, [1] that the earliest photosynthetic life forms of Early Earth were based on the simpler molecule retinal rather than the more complex porphyrin-based chlorophyll, making the surface biosphere appear purplish ...
In the 19th century, luminiferous aether (or ether), meaning light-bearing aether, was a theorized medium for the propagation of light. James Clerk Maxwell developed a model to explain electric and magnetic phenomena using the aether, a model that led to what are now called Maxwell's equations and the understanding that light is an ...
Earth may have had a ring made up of a broken asteroid over 400 million years ago, a study finds. The Saturn-like feature could explain a climate shift at the time.
It was first proposed and tested as part of Earth's atmospheric evolution in the late 1970s. An atmosphere that contained about 1,000 times the present atmospheric level (or PAL) was found to be consistent with the evolutionary path of Earth's carbon cycle and solar evolution. [14] [15] [16]
14th century – Several European mathematicians and astronomers develop the theory of Earth's rotation including Nicole Oresme. Oresme also give logical reasoning, empirical evidence and mathematical proofs for his notion. [53] [54] 15th century – Nicholas of Cusa proposes that the Earth rotates on its axis in his book, On Learned Ignorance ...
A new scientific theory connects mysterious structures deep within Earth's mantle to a violent collision with the protoplanet Theia. A new scientific theory connects mysterious structures deep ...
The theory postulates that light has always the same velocity in respect to the source. [A 28] However de Sitter noted that emitter theory predicted several optical effects that were not seen in observations of binary stars in which the light from the two stars could be measured in a spectrometer. If emission theory were correct, the light from ...
The Rare Earth hypothesis argues that planets with complex life, like Earth, are exceptionally rare.. In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity, such as sexually reproducing, multicellular organisms on Earth, and subsequently human intelligence, required an improbable combination of astrophysical ...