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Second (s) - Unit Information & Conversion

Symbol:s
Plural:seconds
Category:Time

What is a Second?

Definition

The second is the base unit of time in the International System of Units (SI). It is defined by taking the fixed numerical value of the caesium frequency ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom, to be 9,192,631,770 when expressed in the unit Hz, which is equal to s⁻¹.

History

Historically, the second was defined as 1/86,400 of a mean solar day. However, variations in the Earth's rotation led to the need for a more precise, constant definition. The atomic definition based on the caesium-133 atom was adopted in 1967.

Common Uses

  • Base Unit: The fundamental unit for all time measurements in science, engineering, and daily life.
  • Timing: Used universally for clocks, watches, timers, and scheduling.
  • Physics: Essential in defining derived units like velocity (meters per second), acceleration (meters per second squared), frequency (Hertz, or cycles per second), and force (Newtons).
  • Computing: Used as a base for measuring intervals, timeouts, and durations, although often subdivided into milliseconds, microseconds, or nanoseconds for finer measurements.
  • Everyday Life: Counting heartbeats, measuring short durations, coordinating activities.

Unit FAQs

What is the base unit of time in the SI system?

The second (s) is the base unit of time.

Why is the second defined using atoms?

The atomic definition provides a much more stable and precise standard than relying on the Earth's rotation, which fluctuates slightly.

How many seconds are in a minute?

There are 60 seconds in a minute.

How many seconds are in an hour?

There are 3,600 seconds in an hour (60 seconds/minute * 60 minutes/hour).

Second Conversion Formulas

To Minute:

1 s = 0.016667 min
Example: 5 seconds = 0.083333 minutes

To Hour:

1 s = 0.000278 h
Example: 5 seconds = 0.001389 hours

To Day:

1 s = 0.000012 d
Example: 5 seconds = 0.000058 days

To Week:

1 s = 0.000002 wk
Example: 5 seconds = 0.000008 weeks

To Month:

1 s = 3.8026e-7 mo
Example: 5 seconds = 0.000002 months

To Year:

1 s = 3.1689e-8 yr
Example: 5 seconds = 1.5844e-7 years

To Millisecond:

1 s = 1000 ms
Example: 5 seconds = 5000 milliseconds

To Microsecond:

1 s = 1000000 μs
Example: 5 seconds = 5000000 microseconds

To Nanosecond:

1 s = 1000000000 ns
Example: 5 seconds = 5000000000 nanoseconds

To Decade:

1 s = 3.1689e-9 dec
Example: 5 seconds = 1.5844e-8 decades

To Century:

1 s = 3.1689e-10 c
Example: 5 seconds = 1.5844e-9 centuries

To Millennium:

1 s = 3.1689e-11 ka
Example: 5 seconds = 1.5844e-10 millennia

To Fortnight:

1 s = 8.2672e-7 fn
Example: 5 seconds = 0.000004 fortnights

To Planck Time:

1 s = 1.8549434242255614e+43 tP
Example: 5 seconds = 9.274717121127807e+43 Planck times

To Shake:

1 s = 100000000 shake
Example: 5 seconds = 500000000 shakes

To Sidereal Day:

1 s = 0.000012 sidereal day
Example: 5 seconds = 0.000058 sidereal days

To Sidereal Year:

1 s = 3.1688e-8 sidereal year
Example: 5 seconds = 1.5844e-7 sidereal years

Convert Second

Need to convert Second to other time units? Use our conversion tool.

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Second Quick Info

s
Symbol:s
Category:Time
System:Various
Convert Second

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