See also my time-line for an account
of when particular things happened. Thechnically, that's concerned with
positions (in time) while the following is concerned with intervals (separations
in time). Note that there is a natural equivalence between length scales and time scales, via a factor of the speed
of light; though we relate to the two rather differently. Likewise, aside from
an arguable unit of cycles
of something repeated, inversion yields an
equivalence between times and frequencies. Note
that the Planck unit of time, 0.13512e-42 s, is so ludicrously small as to be
negligible for any physical process.
Over the last 800 k yr, rates of change in atmospheric CO2 concentrations have (except very recently) been at most 30 parts per million over a thousand years – but 1989 to 2006 also saw increases of 30 parts per million.
The Milky Way and Andromeda are expected to pass close to one another in about 2 G yr and, after a second close pass, to fuse together in about 5 G yr – which is roughly how long our Sun is expected to last before turning into a planetary nebula.
Written by Eddy.