This note is about the concept of time, cf. process, arrow of time, etc.

Key Issues

  • Age of things can vary greatly
  • What are the meaningful ages? Generations? Connect to Temporal

Smil observes that:

Not surprisingly, natural growth rates of some extremophilic microbes can be extraordinarily slow, with generation times orders of magnitude longer than is typical for common soil or aquatic bacteria. Yayanos et al. (1981) reported that an obligate barophilic (pressure-tolerant) isolate, retrieved from a dead amphipod Hirondella gigas captured at the depth of 10,476 meters in Mariana Trench (the world’s deepest ocean bottom), had the optimal generation times of about 33 hours at 2°C under 103.5 MPa prevailing at its origin. Similarly, Pseudomonas bathycetes, the first species isolated from a sediment sample taken from the trench, has generation time of 33 days (Kato et al. 1998). In contrast, generation times of thermophilic and piezophilic (pressure-tolerant) microbes in South Africa’s deep gold mines (more than 2 km) are estimated to be on the order of 1,000 years (Horikoshi 2016).

And also:

And then there are microbes buried deep in the mud under the floor of the deepest ocean trenches that can grow even at gravity more than 400,000 times greater than at the Earth’s surface but “we cannot estimate the generation times of [these] extremophiles … They have individual biological clocks, so the scale of their time axis will be different” (Horikoshi 2016, 151). But even the span between 20 minutes for average generation time of common gut and soil bacteria and 1,000 years of generation time for barophilic extremophiles amounts to the difference of seven orders of magnitude, and it is not improbable that the difference may be up to ten orders of magnitude for as yet undocumented extremophilic microbes.

Smil, Vaclav. Growth: From Microorganisms to Megacities. Cambridge, MA: MIT Press, 2019.

In Physics

Smolin, Lee. Time Reborn: From the Crisis in Physics to the Future of the Universe. Boston: Houghton Mifflin Harcourt, 2013.

In Geology

Bjornerud, Marcia. Timefulness: How Thinking Like a Geologist Can Help Save the World. Princeton: Princeton University Press, 2018.

In Biology

Money, Nicholas P. Nature Fast and Nature Slow: How Life Works, from Fractions of a Second to Billions of Years. London: Reaktion Books, 2021.