A precedes B and some in which B precedes A. Also there
can be no velocity quick enough to carry a material particle from A to
B or from B to A. These different measure-systems with their
divergences of time-reckoning are puzzling, and to some extent affront
our common sense. It is not the usual way in which we think of the
Universe. We think of one necessary time-system and one necessary space.
According to the new theory, there are an indefinite number of
discordant time-series and an indefinite number of distinct spaces. Any
correlated pair, a time-system and a space-system, will do in which to
fit our description of the Universe. We find that under given conditions
our measurements are necessarily made in some one pair which together
form our natural measure-system. The difficulty as to discordant
time-systems is partly solved by distinguishing between what I call the
creative advance of nature, which is not properly serial at all, and any
one time series. We habitually muddle together this creative advance,
which we experience and know as the perpetual transition of nature into
novelty, with the single-time series which we naturally employ for
measurement. The various time-series each measure some aspect of the
creative advance, and the whole bundle of them express all the
properties of this advance which are measurable. The reason why we have
not previously noted this difference of time-series is the very small
difference of properties between any two such series. Any observable
phenomena due to this cause depend on the square of the ratio of any
velocity entering into the observation to the velocity of light. Now
light takes about fifty minutes to get round the earth's orbit; and the
earth takes rather more than 17,531 half-hours to do the same. Hence all
the effects due to this motion are of the order of the ratio of one to
the square of 10,000. Accordingly an earth-man and a sun-man have only
neglected effects whose quantitative magnitudes all contain the factor
1/10^8. Evidently such effects can only be noted by means of the most
refined observations. They have been observed however. Suppose we
compare two observations on the velocity of light made with the same
apparatus as we turn it through a right angle. The velocity of the earth
relatively to the sun is in one direction, the velocity of light
relatively to the ether should be the same in all directions. Hence if
space when we take the ether as at rest mean