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Unit of Time - SI Unit, CGS Unit & Other Time Units, FAQs

Unit of Time - SI Unit, CGS Unit & Other Time Units, FAQs

Vishal kumarUpdated on 02 Jul 2025, 04:59 PM IST

We all have experienced time and have seen its amazing and phenomenon results.
So, in this article we will study and will try to find out what is time, what is unit, what is unit of time, what is the SI unit of time, what is basic unit of time, how much one second is equal to and what is standard unit of time.

Unit of Time - SI Unit, CGS Unit & Other Time Units, FAQs
Unit of Time

time

First let’s discuss about,

What is time? Definition of time in simple words.

As soon as we hear the word, we think of something which is continuous in nature and makes the life easier by categorizing it in seconds, minutes, hours, days, weeks, months and years. Hence, order of life is being categorized from past events to present and then to the future events.

Also read -

What is unit?

There are many types of units in physics, because of a large number of independent quantities existing for measuring different physical or non - physical quantities. Length, mass and time three basic quantities which are unique and all time necessary. Therefore, they have three separate units for their system of measurement hence it is required to define system of units a system of unit is a collection of unit in which certain units are chosen as fundamental and all others are derived from them this system is called absolute system of unit in most system mass length and time are connected considered to be fundamental quantities and their units are called fundamental units the following are some system of units which are used commonly

1 . cgs system of units the unit of length is centimeter ( cm ), the unit of mass is gram ( g ) and the unit of time is second (s) .

2 . mks system of units the unit of length is meter (m) , the unit of mass is kilogram (kg) , the unit of time here also is second (s) .

3 . fps system of units here unit of length is measured in foot (ft) , the unit of mass is calculated in pound (lb) and the unit of time is seconds (s) . but this system of unit is no more in use widely used system of unit is metric system of units .

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Unit of time

There are various units of time.

As, we have already discussed about that Second, minute, hour, day, week, month and year are the terms or we can say the basic unit of time that we consider. These are time measurement units.

All these units of time can be in a relation as under:

60 seconds is equal to 1 minute and 1 minute is equal to 60 seconds .

Also,
60 minutes is equal to 1 hour and 1 hour is equal to 60 minutes .

24 hours is equal to 1 day (day and night) , 7 days is equal to 1 week

12 months is equal to 1 year , 52 weeks is equal to 1 year .

365 days or 366 days makes a year and 10 years make a decade .

50 years make half century and 100 years make a century .

These are some general units of time that we use in our daily life for making our life sort.

Related Topics Link,

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Commonly Asked Questions

Q: How does time dilation in special relativity challenge our understanding of time as absolute?
A:
Time dilation in special relativity shows that time is not absolute but relative to the observer's frame of reference. It predicts that time passes more slowly for objects moving at high speeds relative to an observer, contradicting our everyday experience of time as a constant, universal quantity.
Q: What is the concept of "now" in physics, and why is it problematic?
A:
The concept of "now" or simultaneity is problematic in physics, especially in special relativity. Events that appear simultaneous to one observer may not be simultaneous to another observer in a different reference frame. This challenges our intuitive understanding of a universal "present moment" across the universe.
Q: What is Planck time and why is it significant?
A:
Planck time is the smallest measurable unit of time, approximately 5.39 × 10^-44 seconds. It's significant because it represents the time scale at which quantum effects of gravity become relevant. Below this scale, our current understanding of physics breaks down, and a theory of quantum gravity would be needed.
Q: What is the difference between proper time and coordinate time in relativity?
A:
Proper time is the time measured by a clock carried by an observer in their own reference frame. Coordinate time is the time measured in a specific coordinate system, often by a distant observer. In relativity, proper time can differ from coordinate time due to effects like time dilation.
Q: How does gravity affect the passage of time according to general relativity?
A:
According to general relativity, gravity causes time dilation. Time passes more slowly in stronger gravitational fields. This means that clocks on Earth's surface tick slightly slower than clocks at higher altitudes where the gravitational field is weaker. This effect, though small on Earth, becomes significant near massive objects like black holes.

What is SI (standard unit of time) unit of time?

The basic or SI (standard unit of time) unit of time is second (SI units of other physical quantities are: metre for length, kilogram for mass, ampere for current, kelvin for calculating temperature, candela for measuring luminous intensity, and mole is considered for the amount of substance). The second can be shown as a symbol by s or sec.

As soon as this system came into existence the SI system, a second is physically in terms of science, we define time in physics in more accurate and absolute atomic concept as “the time of 9,192,631,770 periods of the radiation be consistent with the transitions between 2 levels of the ground (zero) state of the caesium 133 atom”, this definition was made even more exact with the stipulation that this means to a caesium atom at rest 0° Kelvin temperature. This is known as 1 second of time.

Some basic SI units of time chart are

For less than a second,

Deci second is equal to 1/10 second cent second is equal to 1/100 second millisecond is equal to 1/1,000 second microsecond is equal to 1/1,000,000 second

nanosecond is equal to 10-9 second

picosecond is equal to 10-12 second

femtosecond is equal to 10-15 second

attosecond is equal to 10-18 second

zeptosecond is equal to 10-21 second

yoctosecond is equal to 10-24 second

For more than a second

Deca second is equal to 10 seconds hector second is equal to 100 seconds kilo second is equal to 1,000 seconds (about 16.7 minutes) mega second = 1,000,000 seconds (about 11.6 days)

Giga second = 109 seconds (about 31.7 years)

Tera second = 1012 seconds (about 31,700 years)

Peta second = 115 seconds (about 31.7 million years)

Exa second = 1018 seconds (about 31.7 billion years)

Zetta second = 1021 seconds (about 31.7 trillion years)

Yotta second = 1024 seconds (about 31.7 quadrillion years)

Now, in this article we have understood the concept of what is time, what is unit, what is unit of time, what is the SI unit of time, what is basic unit of time, how much one second is equal to and what is standard unit of time.

Also check-

NCERT Physics Notes:

Commonly Asked Questions

Q: What is the SI unit of time?
A:
The SI unit of time is the second (s). It is one of the seven base units in the International System of Units (SI) and is used as the fundamental unit for measuring time in scientific and everyday contexts.
Q: How is the second defined in modern physics?
A:
The modern definition of a second is based on atomic physics. It is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom at rest at a temperature of 0 K.
Q: What is the CGS unit of time?
A:
The CGS (centimeter-gram-second) unit of time is also the second (s). Although the CGS system uses different units for length and mass compared to SI, it shares the same unit for time.
Q: Why do we need different time units besides seconds?
A:
Different time units are needed to conveniently express various durations. Seconds are suitable for short intervals, while minutes, hours, days, and years are more practical for longer periods. This allows for easier communication and understanding of time in different contexts.
Q: How does a leap second affect our timekeeping?
A:
A leap second is occasionally added to Coordinated Universal Time (UTC) to account for the slowing of Earth's rotation. It ensures that atomic time (extremely precise) stays synchronized with solar time (based on Earth's rotation). This adjustment is crucial for maintaining accurate global timekeeping systems.

Frequently Asked Questions (FAQs)

Q: What is the significance of the Planck time in quantum gravity theories?
A:
Planck time (approximately 10^-43 seconds) is theoretically the smallest meaningful unit of time. At this scale, quantum effects of gravity become
Q: How does the concept of time apply to the evolution of quantum states?
A:
The evolution of quantum states over time is described by the time-dependent Schrödinger equation. This equation shows how the wavefunction of a quantum system changes with time, allowing predictions about future states. In quantum mechanics, time is treated as a parameter, not an observable, leading to interesting consequences for our understanding of time at the quantum level.
Q: What is the role of time in the formulation of Maxwell's equations?
A:
Time plays a crucial role in Maxwell's equations, which describe the behavior of electric and magnetic fields. These equations include time derivatives, showing how changing electric fields create magnetic fields and vice versa. This time-dependence led to the prediction of electromagnetic waves, traveling at the speed of light, fundamentally linking time, space, and electromagnetism.
Q: What is the relationship between time and the speed of light?
A:
The speed of light (c) is a fundamental constant in physics and plays a crucial role in our understanding of time. According to special relativity, c is the maximum speed at which information or matter can travel. It sets a limit on causality and defines the structure of spacetime. The constancy of c leads to effects like time dilation and length contraction at high speeds.
Q: How do we measure the age of the universe?
A:
The age of the universe is primarily determined by measuring the cosmic microwave background radiation and the rate of expansion of the universe. By analyzing the properties of this radiation and using models of cosmic evolution, scientists can trace back to the Big Bang. Current estimates put the age of the universe at about 13.8 billion years.
Q: What is the role of time in quantum entanglement?
A:
Time plays a complex role in quantum entanglement. Entangled particles show correlated properties instantaneously, regardless of their separation in space, which seems to challenge our understanding of causality and time. This "spooky action at a distance," as Einstein called it, doesn't allow for faster-than-light communication but raises questions about the nature of time and information in quantum systems.
Q: How does time feature in Feynman diagrams?
A:
In Feynman diagrams, which are used to visualize particle interactions in quantum field theory, time is typically represented as progressing upward on the vertical axis. These diagrams allow physicists to represent complex quantum processes, including the creation and annihilation of particles, in a time-ordered manner, helping to calculate probabilities of different outcomes.
Q: What is the concept of imaginary time in theoretical physics?
A:
Imaginary time is a mathematical concept used in quantum mechanics and cosmology. It involves treating time as an imaginary number (multiplied by i, the square root of -1). This approach can simplify certain calculations and has been used in theories about the early universe, potentially removing the singularity at the Big Bang.
Q: How does time factor into the measurement problem in quantum mechanics?
A:
The measurement problem in quantum mechanics involves the apparent collapse of a quantum state upon measurement. Time plays a crucial role here, as the act of measurement is considered an instantaneous event that causes the wavefunction to collapse. This raises questions about the nature of time in quantum processes and the role of the observer in quantum mechanics.
Q: What is the significance of the Chronon in theoretical physics?
A:
The Chronon is a hypothetical unit of time proposed as the smallest possible measurable interval. While not widely accepted, the concept explores the idea that time might be quantized at extremely small scales, similar to how energy is quantized in quantum mechanics. This could have implications for our understanding of time at the most fundamental level.
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