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Earth formed around 4.54 billion years ago, approximately one-third the age of the universe, by accretion from the solar nebula. [4] [5] [6] Volcanic outgassing probably created the primordial atmosphere and then the ocean, but the early atmosphere contained almost no oxygen.
In 1862, the physicist William Thomson, 1st Baron Kelvin published calculations that fixed the age of Earth at between 20 million and 400 million years. He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface temperature gradient to decrease to its present value.
Philipp Daniel Lippert [ de], Dactyliothec, 1767. Eratosthenes of Cyrene ( / ɛrəˈtɒsθəniːz /; Greek: Ἐρατοσθένης [eratostʰénɛːs]; c. 276 BC – c. 195/194 BC) was a Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of ...
The Earth's magnetic field was established 3.5 billion years ago. The solar wind flux was about 100 times the value of the modern Sun , so the presence of the magnetic field helped prevent the planet's atmosphere from being stripped away, which is what probably happened to the atmosphere of Mars .
Lorentz factor γ as a function of fraction of given velocity and speed of light. Its initial value is 1 (when v = 0 ); and as velocity approaches the speed of light (v → c) γ increases without bound (γ → ∞). α (Lorentz factor inverse) as a function of velocity—a circular arc. In the table below, the left-hand column shows speeds as ...
Alpha Centauri ( α Centauri, α Cen, or Alpha Cen) is a triple star system in the southern constellation of Centaurus. It consists of three stars: Rigil Kentaurus ( α Centauri A ), Toliman ( α Centauri B ), and Proxima Centauri ( α Centauri C ). [14] Proxima Centauri is the closest star to the Sun at 4.2465 light-years (1.3020 pc ).
The Linux version began with the version 4 beta of Google Earth, as a native port using the Qt toolkit. The Free Software Foundation considers the development of a free compatible client for Google Earth to be a High Priority Free Software Project. Google Earth was released for Android on February 22, 2010, and on iOS on October 27, 2008.
Plasma beta. The beta of a plasma, symbolized by β, is the ratio of the plasma pressure ( p = n kB T) to the magnetic pressure ( pmag = B ²/2 μ0 ). The term is commonly used in studies of the Sun and Earth's magnetic field, and in the field of fusion power designs. In the fusion power field, plasma is often confined using strong magnets.