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Unit of Time in Physics is ‘Seconds’. Time is a measure of a continuous sequence of existence and change in our surroundings. It is an intriguing notion, something that is abstract yet governs all aspects of life.
- Time is a component quantity of various measurements used to sequence events.
- It is measured using different units that are employed in different ways depending on the situation.
- Time is measured in units such as Seconds, Minutes, and Hours.
- The SI Unit of Time is Second.
Read More: NCERT Solutions For Class 11 Physics Units and Measurements
Key Terms: Time, Unit of Time, Second, Minute, Hour, Supereon, System of Units, Carbon-14 Analysis, Christian Era
What is Time?
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Time is the progression of existence in the past, present, and future. Time is one of the seven fundamental physical quantities in both the International System of Quantities and the International System of Units (SI). The existence of events is measured using different units of time. The most commonly used units of time are:
- Second
- Minute
- Hour
Time
Time is an important subject of study in religion, philosophy, and science. The concept of time is incorporated into diverse fields such as business, industry, sports, sciences, etc.
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What is a Unit?
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A unit is a globally recognized standard for the measurement of physical quantities.
- A measurement is made up of a numeric quantity and a corresponding unit.
- Fundamental Units are units for fundamental or base quantities such as length, time, and so on.
- Derived Units are units that are created by combining fundamental units.
- System of Units is made up of both fundamental and derived units.
Units and Measurements Detailed Video Explanation
Frequently Asked QuestionsQues. What is the Unit of Time? Ans. The SI Unit of Time is ‘Seconds’. Ques. What are three Units of Time? Ans. The three popular units of time are Seconds, Minutes, and Hours. Ques. What is the Smallest Unit of Time? Ans. Zeptosecond is the smallest unit of time. It is one trillionth of a billionth of a second. Ques. Who Invented Time? Ans. The basic notion of measurement of time began with the invention of sundials in ancient Egypt sometime prior to 1500 B.C. |
SI Unit of Time
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SI Units are defined as the standard units of measurement laid out by the International System of Units (SI). The SI unit of Time is the Second which is commonly abbreviated as s or sec.
| The SI unit of Time is Seconds. |
In 1967, the 13th General Conference on Weights and Measures defined Second as “9,192,631,770 periods of radiation related with the transition between the two hyperfine levels of the ground state of the cesium-133 atom”.
Largest Unit of Time
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Other Units of Time
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There are various other units of time that can be used for its measurement. The other accepted units of time are:
- Minute
- Hour
- Day
- Week
- Month
- Year
Units of Time
When dealing with extended periods of time, multiples of years are sometimes used to denote a certain time range.
- One decade is equivalent to 10 years.
- One century is equal to 100 years.
- One millennium is equal to 1,000 years.
- One mega-annum is about 1,000,000 years.
Here is a conversion chart of the commonly used units of time:
| Units of Time | |
|---|---|
| Minute | 60 Seconds |
| Hour | 60 Minutes, or 3,600 Seconds |
| Day | 24 Hours, or 86,400 Seconds |
| Week | 7 Days, or 604,800 Seconds |
| Month | 28-31 Days, or 2,419,200-2,678.400 Seconds |
| Year | 365.25 Days, or 31,557,600 Seconds |
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Measurement of Time
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Measurement of Time is defined as a method of measuring the length or duration of time. Second, minute, hour, day, week, fortnight, month, year, and century are the common units of measurement of time.
- Time is measured using different methods in different parts of the world.
- The Common or Christian Era is the most widely used method of measuring time.
- 'Shalivahan Shaka' and 'Vikram Samvat' are two eras that are used in India to measure time.
- The 'Hijri Era' is used to measure time in Muslim countries.
- 'Shahenshahi Era' is used by the Parsi Community in India.
The scientific methods used for estimating the dates are:
- Carbon-14 Analysis
- Tree Rings Analysis (Dendrochronology)
Both of these methods are referred to as 'dating techniques’.
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Time as An Illusion
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Measurement of Time has evolved significantly from patterns of changing day to night till sundials and the modern digital clock. Time has been a debatable concept with Dr. Rovelli, a theoretical physicist, stating that time is just an illusion. According to him, time is a complex set of events that supplements us to explain the past, present, and future sequences.
Albert Einstein addressed the malleability of time by combining time with space through his relativistic space-time theory which claimed that the local time is a function of one relative speed (or proximity) to the mass. Einstein made the following claims in his classical theory of relativity:
- Motion is described as a function of time, such as 10 meters per second, 20 miles per hour, or so.
- Unless we define time, the mathematical explanation of velocity is debatable.
- Nothing in the cosmos is either in constant motion or at rest. All of the bodies are moving in relation to one another.
- Time began with the Big Bang, and we currently exist between the past and the unknown, chaotic future.
- As a result, time is a persistent illusion.
- To comprehend time, one must first comprehend relativity, which is a critical concept.
Things to Remember
- Time is a measure of the progression of events from the past to the present into the future.
- It is measured using different units and methods throughout the world.
- The SI Unit of Time is Second.
- Minute, Hour, Day, Week, Month, and Year are some of the most popular and commonly used units of time.
- Supereon is the largest unit of time which is made up of eons.
- Christian Era, Shalivahan Shaka, Hijri Era, and Shahenshahi Era are some of the common methods of measuring time.
- Time can be measured through scientific processes such as Carbon Dating and Tree Ring Analysis.
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Sample Questions
Ques. State the different Units of Time. (2 Marks)
Ans. The different units of time are as follows:
- Second
- Minute
- Hour
- Day
- Week
- Month
- Year
Ques. Who was the first to invent the Concept of Time? (2 Marks)
Ans. The Egyptians invented sundials in around 1500 B.C., which allowed them to measure time. However, the time measured by the Egyptians is not the same as the time recorded by modern clocks since sundials are used to tell the time of day only when there is sunlight due to the obvious location of the Sun in the sky.
Ques. How are Years used to define a Time Range? (2 Marks)
Ans. Years are used to denote a time range dealing with an extended period of time.
- 1 Decade = 10 Years
- 1 Century = 100 Years
- 1 Millennium = 1000 Years
- 1 Mega-annum = 1,000,000 Years
Ques. What are the different Units of a Second? (3 Marks)
Ans. The unit of a second from the smallest to the largest values are:
- Decisecond (1/10th of a second)
- Centisecond (1/100th of a second)
- Millisecond (1/1000th of a second)
- Microsecond (One-millionth of a second)
- Nanosecond (One-billionth of a second)
- Picosecond (One-trillionth of a second)
- Femtosecond (One-quadrillionth of a second)
- Attosecond (One-quintillionth of a second)
- Zeptosecond (One-sextillionth of a second)
- Yoctosecond (One-septillionth of a second)
- Planck Time
Ques. What are the different methods used throughout the world to measure time? (3 Marks)
Ans. Time is measured using different methods throughout the communities in the world.
- Common or Christian Era: It is one of the most widely used methods of measuring time.
- Shalivahan Shaka and Vikram Samvat: These are two eras that are used in India to measure time.
- Hijri Era: It is a method that is used to measure time in Muslim countries.
- Shahenshahi Era: This method is used by the Parsi Community in India.
Ques. What is the value of 1 nano-second in a second?
A. 10-9
B. 10-6
C. 10-8
D. 1010 (2 Marks)
Ans. (A) 10-9
Explanation: A nanosecond (ns) is a time unit defined by the International System of Units that equals one billionth of a second. The prefix nano and the unit second combine to produce the term nanosecond. It has the symbol ns.
Ques. What is the SI Unit of Time? (1 Mark)
Ans. The SI unit of Time is the Second. Scientifically, second has been defined as "the time stretch equivalent to 9192631770 times of radiation relating to the progress between the two hyperfine levels of the ground state of cesium-133 particle.”
Ques. How is time converted into different units? (3 Marks)
Ans. Time can be converted into different units using the conversion chart given below:
- 1 Minute = 60 Seconds
- 1 Hour = 60 Minutes
- 1 Day = 24 Hours
- 1 Week = 7 Days
- 1 Month = 4 Weeks
- 1 Year = 12 Months
Ques. How does Time work? (2 Marks)
Ans. Time was regarded as a constant, independent force for centuries, that governed the progress of the universe. However, the description of time changed in 1905 with Albert Einstein's theory of special relativity. The theory combined space and time into a single field, one with measurements that vary depending on the relative motion or gravitational forces of objects within it. Thus, it basically stated that time is relative.
Ques. Is there really a thing as time? (2 Marks)
Ans. Yes, time really exists. One may estimate the time by applying the idea of the relative velocity of one item relative to another object going by. The full revolution of the planet takes a year, similar to how the second hand of a clock makes up the minutes. Thus, there is a concept of time.
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