Terasecond and longer

A **terasecond** (symbol:  **Ts**) is one trillion seconds. That is about 31,700 years. It can be written as **10<sup>12</sup> seconds**.

Here is a list of time spans longer than 1 terasecond:
- 10<sup>15</sup> seconds = 1 _petasecond_ = 31.7 million years
- 10<sup>18</sup> seconds = 1 _exasecond_ = 31.7 billion years
- 10<sup>21</sup> seconds = 1 _zettasecond_ = 31.7 trillion years
- 10<sup>24</sup> seconds = 1 _yottasecond_ = 31.7 quadrillion years
- 10<sup>27</sup> seconds = 1 _ronnasecond_ = 31.7 quintillion years
- 10<sup>30</sup> seconds = 1 _quettasecond_ = 31.7 sextillion years

## Teraseconds

Here are some examples of events that take this long:
- 75,000 years — time since the ancestors of the Indigenous Australians reached Australia
- 76,000 years — half-life of nickel-59
- 154,000 years — half-life of neptunium-236
- 159,200 years — half-life of uranium-233
- 200,000 years — age of _Homo sapiens_
- 211,100 years — half-life of technetium-99
- 250,000 years — age of _Homo neanderthalensis_
- 301,000 years — half-life of chlorine-36
- 340,000 years -- half-life of curium-248
- 379,000 years -- time after the Big Bang until cosmic microwave background radiation began
- ~700,000 years -- time since the earth's magnetic field last changed
- 1,000,000 years -- the lifespan of a blue supergiant star
- 1,530,000 years -- half-life of zirconium-93
- 2,600,000 years -- amount of time the Paleolithic era lasted
- 2,600,000 years -- half-life of technetium-97
- 3.74 million years -- half-life of manganese-53
- 4 million years -- time since the last ice age
- 4.2 million years -- half-life of technetium-98
- 6.5 million years  -- half-life of palladium-107
- 15.6 million years -- half-life of curium-247
- 20 million years -- time since the first forms of grass appeared
- 23.42 million years -- half-life of uranium-236
- 26 million years -- time since the first elephants were born

## Petaseconds

- 34 million years -- time since the evolution of the cat
- 34.7 million years -- half-life of niobium-92
- 49 million years -- time since the whales returned to the water
- 60 million years -- time since the evolution of the first primates.
- 135 million years -- time since end of Jurassic and beginning of Cretaceous period
- 250 million years -- Galactic year - an orbit around the center of the Milky way of our Sun and the Solar system
- 251.4 million years -- time since the Permian–Triassic extinction event
- 280 million years -- time since end of Carboniferous and beginning of Permian Period.
- 390 million years - first fishapods
- 575 million years -  age of the oldest animal fossils
- 580 million years - time since the end of a possible Snowball Earth ice age
- 703.8 million years - half-life of uranium-235
- 750 million years - time since the beginning of a possible ice age
- 1277 million years - half-life of potassium-40
- 1.8-2.1 billion years - age of the earliest eukaryotes
- 2.3 billion years - time since the first known ice age
- 3.5 to 3.8 billion years  -  age of oldest records of life: stromatolites and  cyanobacteria
- 4.468 billion years  -  half-life of uranium-238
- 4.5 billion years  -  age of the Earth
- 13.7 ± 0.2 billion years (4e17 seconds)  -  age of the universe according to the Big Bang theory
- 20 billion years  -  time until the end of the universe in the Big Rip scenario

## Exaseconds

- 100 billion (10<sup>11</sup>) years -- If the universe is closed, the lifetime of the universe
- Some radioisotopes have very long half-lives:
    - (1.4 ± 0.4) × 10<sup>17</sup> years – vanadium-50
    - (1.9 ± 0.2) × 10<sup>19</sup> years – bismuth-209
    - (3.1 ± 0.4) × 10<sup>19</sup> years – cadmium-116
    - (2.2 ± 0.3) × 10<sup>24</sup> years – tellurium-128