The second, the base unit of time in the International System of Units (SI), has roots dating back to ancient civilizations. Originally defined through astronomical events, the second was once 1/86,400 of a day, based on Earth’s rotation. However, the Earth’s rotation isn’t perfectly consistent due to gravitational interactions and geological activity, making this measurement imprecise for modern needs.
Today, the second is defined by atomic perfection: it is the duration of 9,192,631,770 periods of the radiation corresponding to a specific transition in the cesium-133 atom. This definition, adopted in 1967, takes advantage of atomic clocks, which can measure time with incredible accuracy, losing only about a second every hundreds of millions of years. Such precision is essential for technologies like GPS, telecommunications, and the synchronization of global networks.
A year is not just 365 days of Earth spinning around the Sun; it’s a complex time unit that cultures have historically calculated differently. While the Gregorian calendar defines a year as 365.2425 days to keep in sync with the Earth’s orbit, ancient Egyptians relied on a calendar year of precisely 365 days, which caused their calendar to drift from the solar year over centuries. Fascinatingly, Julius Caesar reformed the Roman calendar in 46 BC, introducing the idea of a leap year every four years.
In astronomy, a sidereal year, measuring 365.25636 days, accounts for Earth’s movement relative to distant stars, differing slightly from our calendar year. This subtle difference accumulates, necessitating leap years to maintain seasonal consistency. Moreover, a light-year, often misunderstood as a time measurement, is actually the distance light travels in one year—about 5.88 trillion miles!
Seconds | Years |
---|---|
0
s
|
0
year
|
50
s
|
1.5844e-6
year
|
100
s
|
3.16881e-6
year
|
150
s
|
4.75321e-6
year
|
200
s
|
6.33762e-6
year
|
250
s
|
7.92202e-6
year
|
300
s
|
9.50643e-6
year
|
350
s
|
1.10908e-5
year
|
400
s
|
1.26752e-5
year
|
450
s
|
1.42596e-5
year
|
500
s
|
0.000015844
year
|
550
s
|
1.74284e-5
year
|
600
s
|
1.90129e-5
year
|
650
s
|
2.05973e-5
year
|
700
s
|
2.21817e-5
year
|
750
s
|
2.37661e-5
year
|
800
s
|
2.53505e-5
year
|
850
s
|
2.69349e-5
year
|
900
s
|
2.85193e-5
year
|
950
s
|
3.01037e-5
year
|
1000
s
|
3.16881e-5
year
|
1050
s
|
3.32725e-5
year
|
1100
s
|
3.48569e-5
year
|
1150
s
|
3.64413e-5
year
|
1200
s
|
3.80257e-5
year
|
1250
s
|
3.96101e-5
year
|
1300
s
|
4.11945e-5
year
|
1350
s
|
4.27789e-5
year
|
1400
s
|
4.43633e-5
year
|
1450
s
|
4.59477e-5
year
|
1500
s
|
4.75321e-5
year
|
1550
s
|
4.91165e-5
year
|
1600
s
|
5.07009e-5
year
|
1650
s
|
5.22853e-5
year
|
1700
s
|
5.38697e-5
year
|
1750
s
|
5.54542e-5
year
|
1800
s
|
5.70386e-5
year
|
1850
s
|
0.000058623
year
|
1900
s
|
6.02074e-5
year
|
1950
s
|
6.17918e-5
year
|
2000
s
|
6.33762e-5
year
|
2050
s
|
6.49606e-5
year
|
2100
s
|
0.000066545
year
|
2150
s
|
6.81294e-5
year
|
2200
s
|
6.97138e-5
year
|
2250
s
|
7.12982e-5
year
|
2300
s
|
7.28826e-5
year
|
2350
s
|
0.000074467
year
|
2400
s
|
7.60514e-5
year
|
2450
s
|
7.76358e-5
year
|
2500
s
|
7.92202e-5
year
|
2550
s
|
8.08046e-5
year
|
2600
s
|
0.000082389
year
|
2650
s
|
8.39734e-5
year
|
2700
s
|
8.55578e-5
year
|
2750
s
|
8.71422e-5
year
|
2800
s
|
8.87266e-5
year
|
2850
s
|
9.03111e-5
year
|
2900
s
|
9.18955e-5
year
|
2950
s
|
9.34799e-5
year
|
3000
s
|
9.50643e-5
year
|
3050
s
|
9.66487e-5
year
|
3100
s
|
9.82331e-5
year
|
3150
s
|
9.98175e-5
year
|
3200
s
|
0.000101402
year
|
3250
s
|
0.000102986
year
|
3300
s
|
0.000104571
year
|
3350
s
|
0.000106155
year
|
3400
s
|
0.000107739
year
|
3450
s
|
0.000109324
year
|
3500
s
|
0.000110908
year
|
3550
s
|
0.000112493
year
|
3600
s
|
0.000114077
year
|
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