Logarithmic timeline
# Logarithmic timeline

A logarithmic timeline is a timeline laid out according to a logarithmic scale. This necessarily implies a zero point and an infinity point, neither of which can be displayed. The most natural zero point is the Big Bang, looking forward, but the most common is the ever-changing present, looking backward. (Also possible is a zero point in the present, looking forward to the infinite future.)

The idea of presenting history logarithmically goes back at least to 1932, when John B. Sparks copyrighted his chart "Histomap of Evolution". Around the same time it was also explored by the cyberneticist Heinz von Foerster, who used it to propose that memories naturally fade in an exponential manner. Logarithmic timelines have also been used in futures studies to justify the idea of a technological singularity.

A logarithmic scale enables events throughout time to be presented accurately, but enables more events to be included closer to one end. Sparks explained this by stating:

    As we travel forward in geological time the more complex is the evolution of life forms and the more are the changes to be recorded. Further, the most recent periods of evolution hold the most interest for us. We need therefore increasingly more space for our outline the nearer we approach modern times, and the logarithmic scale fulfills just this condition without any break in the continuity.

Two examples of such timelines are shown below, while a more comprehensive version (similar to that of Sparks' "Histomap") can be found at Detailed logarithmic timeline.

## Example of a forward-looking logarithmic timeline

In this table each row is defined in seconds after the Big Bang, with earliest at the top of the chart. (see Cosmological decade)

| Seconds after Big Bang | Period |
| - | - |
| $10^{−45}$ to $10^{−40}$ | Planck epoch |
| $10^{−40}$ to $10^{−35}$ | Planck epoch |
| $10^{−35}$ to $10^{−30}$ | Grand unification epoch |
| $10^{−30}$ to $10^{−25}$ | Grand unification epoch |
| $10^{−25}$ to $10^{−20}$ | Grand unification epoch |
| $10^{−20}$ to $10^{−15}$ | Grand unification epoch |
| $10^{−15}$ to $10^{−10}$ | Electroweak epoch |
| $10^{−10}$ to $10^{−5}$ | Electroweak epoch |
| $10^{−5}$ to $10^0$ | Hadron epoch |
| $10^0$ to $10^5$ | Lepton epoch |
| $10^5$ to $10^{10}$ | Epoch of Nucleosynthesis |
| $10^{10}$ to $10^{15}$ | Epoch of Galaxies |
| $10^{15}$ to $10^{20}$ | Epoch of Galaxies |

The present time is approximately $4.3×10^{17}$ seconds after the Big Bang; the Sun and Earth formed about $2×10^{17}$ seconds after the Big Bang. $10^{20}$ seconds is 3 trillion years $(3×10^{12}$ years) in the future.

## Example of a backward-looking logarithmic timeline

In this table each row is defined in years ago, that is, years before the present date, with the most recent at the top of the chart. Each event is an occurrence of an observed or inferred process. (Note that the logarithmic scale never actually gets to zero.)

| Years ago | Period | Event, invention or historical development |
| - | - | - |
| $10^{−3}$ to $10^{−2}$ | last 3 days | See, for example, the content of Today's events, Yesterday's and the day before. |
| $10^{−2}$ to $10^{−1}$ | last 36 days | See, for example, the content in Portal:Current events |
| $10^{−1}$ to $10^0$ | last year | See, for example, Events in 2022 |
| $10^0$ to $10^1$ | 2012 onward | Internet, biotechnology, nanotechnology, global warming, more... |
| $10^1$ to $10^2$ | 20th century | Car to spacecraft, nuclear power, antibiotics, electronics, totalitarianism, world wars, more... |
| $10^2$ to $10^3$ | 1000 to 1900 | Renaissance, printing press, Industrial Revolution, colonialism, firearms, steam engine, more... |
| $10^3$ to $10^4$ | Start of Holocene, 8000 BCE to CE 1000, Neolithic, Bronze Age, Iron Age | Cities, empires, writing, wheel, civilization, religions, philosophy, more... |
| $10^4$ to $10^5$ | Pleistocene ends, Paleolithic ends, Mesolithic, beginning of Neolithic | Ice Age, music, art, cave paintings, dance, tally stick, medicine, Neandertal extinction, Flores Man extinction, advanced Homo erectus sub-species extinction, Ice Age ends, domestication – agriculture and animal husbandry |
| $10^5$ to $10^6$ | Pleistocene, Paleolithic | Humans (150 kya), language, spirituality |
| $10^6$ to $10^7$ | Pliocene, Paleolithic begins, Lower Paleolithic | hunting-gathering, tools, fire |
| $10^7$ to $10^8$ | Late Cretaceous, Cenozoic | Grasses, mammals, Cretaceous–Paleogene extinction event |
| $10^8$ to $10^9$ | Paleozoic, Mesozoic | Cambrian explosion of life, animals, flowering plants, Permian–Triassic extinction event |
| $10^9$ to $1.4×10^{10}$ | Precambrian, cosmology | Big Bang, Galaxy formation and evolution, Earth, life |
