Search results
Results from the WOW.Com Content Network
The glasses from this period contain high levels of barium oxide and lead, distinguishing them from the soda–lime–silica glasses of Western Asia and Mesopotamia. [32] At the end of the Han Dynasty (AD 220), the lead-barium glass tradition declined, with glass production only resuming during the 4th and 5th centuries AD. [ 33 ]
The Earth phase, Terra phase, terrestrial phase, or phase of Earth, is the shape of the directly sunlit portion of Earth as viewed from the Moon (or elsewhere extraterrestrially). From the Moon, Earth phases gradually and cyclically change over the period of a synodic month (about 29.53 days), as the orbital positions of the Moon around Earth ...
The geologic time scale, proportionally represented as a log-spiral with some major events in Earth's history. A megaannus (Ma) represents one million (10 6) years.. The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth.
c. 4,500 Ma – Sun enters main sequence: a solar wind sweeps the Earth-Moon system clear of debris (mainly dust and gas). End of the Early Bombardment Phase. Basin Groups Era begins on Earth. c. 4,450 Ma – 100 million years after the Moon formed, the first lunar crust, formed of lunar anorthosite, differentiates from lower magmas. The ...
No long-range order is present, although there is local ordering to the tetrahedral arrangement of oxygen (O) atoms around the silicon (Si) atoms. Microscopically, a single crystal has atoms in a near-perfect periodic arrangement; a polycrystal is composed of many microscopic crystals; and an amorphous solid such as glass has no periodic ...
The Shortt–Synchronome clock, an electrical driven pendulum clock designed in 1921, was the first clock to be a more accurate timekeeper than the Earth itself. [167] A succession of innovations and discoveries led to the invention of the modern quartz timer. The vacuum tube oscillator was invented in 1912. [168]
One of the most important events of the Proterozoic was the accumulation of oxygen in the Earth's atmosphere. Though oxygen is believed to have been released by photosynthesis as far back as the Archean Eon, it could not build up to any significant degree until mineral sinks of unoxidized sulfur and iron had been exhausted. Until roughly 2.3 ...
The first eon in Earth's history, the Hadean, begins with 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 Earth's crust and Earth itself.