Periodic Unit

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Quantitative relationships between various time units are shown in the following table.

Any predetermined amount of time that is accepted as a standard for measuring or expressing duration is referred to as a "unit of time." The second, which is defined as roughly 9 billion oscillations of the caesium atom, is the fundamental time unit of the International System of Units (SI) and, by extension, most of the Western world. In the modern SI system, "[the second] is defined by taking the fixed numerical value of the cesium frequency," ΔνCs , the frequency of the cesium 133 atom in its unperturbed ground-state hyperfine transition, to be 9 192 631 770 in the unit Hz, which is equal to s1. "[1]

Time was often measured in terms of astronomical events in the past.

  • Solar-based; during this year, Earth completed one revolution around the sun The Olympiad (4 years), the lustrum (5 years), the indiction (15 years), the decade (10 years), the century (100 years), and the millennium (1000 years).
  • Using the Moon's orbital period around the Earth as the basis for the month
  • Earth-based [a href="MY_REDIRECT_PREFIX" target="_blank">span>citation needed/span>]; the time it takes for the Earth to rotate on its own axis, as measured by a sundial. The seven-day week and the fourteen-day fortnight both have their origins in this base. The hour (1/24 of a day) is one of the day's divisions; the minute (60 seconds) and the second (3600 seconds) came next. The second one was adopted as the scientific international unit (SI units).
  • Using the apparent motion of the stars and constellations across the sky, sidereal time is used to determine the passage of time on the celestial sphere.

It is necessary to intercalate these units because their relationships are inconsistent. Because 12 times 28 is 336, which is less than 365, a year cannot be divided into 12 months of 28 days each. According to the moon's orbital definition, a lunar month has exactly 28 3 days According to the Gregorian calendar, this is the year 365.2425 months require correction for leap years and leap seconds As a result, scientific definitions of these units are now based on multiples of seconds.

Time can be measured in nanoseconds and milliseconds, both of which are multiples of a second.

Historical [ edit ]

Most ancient civilizations based their calendars on the solar year, the moon, and the 24-hour day. Sumerian, Egyptian, Chinese, Babylonian, ancient Attic, Buddhist, Hindu, Islamic, Icelandic, Mayan, and Republican-era French calendars are all examples of such systems.

The modern Gregorian calendar is based on the Julian calendar, which in turn was derived from the Roman calendar.

Scientific [ edit ]

  • Light in a vacuum travels at the speed of the Jiffy, which is equal to one fermi (about the size of a nucleon) per second.
  • Time taken by light to travel one Planck length is denoted by the Planck time.
  • For engineering purposes, the TU (Time Unit) is defined as 1024 s.
  • Sedimentation rates (typically of proteins) are measured in Svedbergs. It is defined as 100 fs, or 1013 seconds.
  • The rotation of the galaxy provides the basis for the galactic year, which is typically expressed in millennia. [2]
  • Using the geological time scale, we can correlate stratigraphy with epochs. Events in Earth's distant past are quantified and assigned to discrete time periods. The Cretaceous-Paleogene extinction event, for instance, marks the transition between the Cretaceous and Paleogene epochs. A supereon, which is made up of eons, is the largest unit of time. From eons, we get eras, which are further subdivided into decades, centuries, and epochs. It's not a real mathematical unit because different geological and historical events determine the length of different epochs, ages, periods, eras, and eons.

The light-year is not a measure of time, but rather a measure of distance (approximately 9 5.05 petameters (9.454254954880 km)

List [ edit ]

Timing units Name Length Notes In Planck time1 5.39 × 10−44 s The duration of a photon's journey along a single Planck length yoctosecond 10−24 s Timescale: 1/septisecond (Physics) in a flash 3 × 10−24 s How long it takes for light to travel a distance of one fermi (roughly the size of a nucleon) in a perfectly transparent vacuum zeptosecond 10−21 s Sextillionth of a second NIST's strontium atomic clock serves as a standard for measuring time. At present, a time interval of 247 zeptoseconds is the smallest one that can be measured. [3] attosecond 10−18 s Five hundred millionths of a second femtosecond 10−15 s Shortness of time equal to one quadrillionth of a second Fastest lasers have short pulses. Svedberg 10−13 s Sedimentation rates (typically of proteins) are measured in terms of time units. picosecond 10−12 s Ten-hundred-thousandth of a second nanosecond 10−9 s Half a billionth of a second It's the right moment for molecules to glow shake 10−8 s Ten nanoseconds, a common measure of time's speed, microsecond 10−6 s Timescale of one millionth of a second The s Symbol millisecond 10−3 s 1/1,000 of a second Stopwatches' smallest time increment (Electronics) in a flash ~10-3 s The interval between the cycles of an ac power supply Another informal way of referring to a brief time frame second 1 s Time's basic SI unit minute 60 s milliday 1/1000 d Advertised as a " The Swatch Group "beat" the competition. moment 1/25 of a solar day ( 90 s in general) Length of this medieval measure of time, used by astronomers to calculate planetary motions, varies with the passage of the seasons. [4] In common usage, it can also mean a relatively short amount of time. kilosecond 103 s Roughly 17 minutes hour 60 min day 24 h The most common timekeeping measurement in the world today. week 7 d Historically, this time of day was also known as "sennight." megasecond 106 s About 11 6 days fortnight 2 weeks 14 days Lunar Calendar 27 d   4 h   48 min  – 29 d   12 h There are many different ways to define a lunar month. month 28–31 d Periods of 30 days are sometimes used. quarantine 40 d (roughly 5.2 cents) 71 weeks) To keep apart or in isolation as a health precaution against the spread of an infectious disease. Forty days of seclusion has historical significance. The word "quarantine" comes from the Middle English word "quarentine," which comes from the Italian word "quarantina," which means "forty days," and refers to the length of time Venetians traditionally kept plague-infected ships waiting off port. semester 18 weeks A section of the school year [5] Also used in this sense; the literal translation is "six months." lunar year 354.37 d year 12 mo 365 or 366 d annual cycle 365 d 5213 days (52 weeks) hurricane season 365 d   5 h   48 min   45.216 s [6] Average Dates in the Gregorian calendar 365 d   5 h   49 min   12 s Average annual solar cycle 365 d   6 h   9 min   9.763 5456  s leap year 366 d 52 weeks and 2 d olympiad 4 yr Similarly, the four-year interval between Olympic Games is often referred to as a quadrennium (plural: quadrennia or quadrenniums). When wishing loved ones a "happy quadrennium" on February 29th, for example, the term refers to the four-year period between leap years. citation needed[quote missing] lustrum 5 yr The time between Roman censuses was relatively short. decade 10 yr indiction 15 yr Assessment timespan (Roman Empire). score 20 yr gigasecond 109 s About 31 7 years jubilee 50 yr century 100 yr millennium 1000 yr Similar to the kiloannum. terasecond 1012 s Roughly 31,709 years megaannum 106 yr Synonymous with "Megayear" One million years (abbreviated Ma in geology) or one thousand millennia (plural of millennium) petasecond 1015 s Approximately 31,709,791 years cosmic calendar 2.3 × 108 yr The time it takes for the Solar System to complete one orbit around the Galactic Center (approximately 230,000,000 years[2]). a decade of cosmology a function of logarithms Whether C 1 begins 10 seconds or 10 years after the Big Bang is a matter of definition; either way, it's 10 times the length of the previous cosmological decade. aeon 109 yr Also means an infinite amount of time, or one billion years. kalpa 4.32 × 109 yr Term drawn from Hindu mythology Approximately 4,320,000,000 years exasecond 1018 s Approximately 31,709,791,983 years Slightly over 2 Three times the age of the universe as it is today zettasecond 1021 s Approximately 31,709,791,983,764 years yottasecond 1024 s To the nearest 31.709 x 10()()()()

Interrelation [ edit ]

Schematic representation of time in various dimensions The three astronomical bodies associated with the different time units are also depicted in the diagram.

Formal time units are all multiples of each other in scale. The second, which is based on an atomic process, the day, which is an integral multiple of seconds, and the year, which is usually 365 days, are the most widely used units of time. These three units form the basis for all others.

See also [ edit ]

References [ edit ]

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