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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. It is a system of chronological dating that uses ...
Orders of magnitude (time) An order of magnitude of time is usually a decimal prefix or decimal order-of-magnitude quantity together with a base unit of time, like a microsecond or a million years. In some cases, the order of magnitude may be implied (usually 1), like a "second" or "year". In other cases, the quantity name implies the base unit ...
A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world, is the second, defined as about 9 billion oscillations of the caesium atom. The exact modern SI definition is " [The second] is ...
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, and into the future. [1] [2] [3] It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the ...
Time scale may refer to: Time standard, a specification of either the rate at which time passes, points in time, or both. A duration or quantity of time: Orders of magnitude (time) as a power of 10 in seconds; A specific unit of time. Geological time scale, a scale that divides up the history of Earth into scientifically meaningful periods.
Before Present. Before Present (BP) or " years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the ...
International Atomic Time. International Atomic Time (abbreviated TAI, from its French name temps atomique international[ 1 ]) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid. [ 2 ] TAI is a weighted average of the time kept by over 450 atomic clocks in over 80 national ...
The Quaternary (/ kwəˈtɜːrnəri, ˈkwɒtərnɛri / kwə-TUR-nə-ree, KWOT-ər-nerr-ee) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). [ 4 ] It follows the Neogene Period and spans from 2.58 million years ago to the present. [ 5 ]