TIME. This word may be considered either with reference to our abstract idea of the thing signified by it, or to the measures of it which have been contrived for use in the business of life. Something on the first point of view will be found in the article SPACE AND TIM?, to which the following may be added.
When we think of time in the usual manner, it is of a real thing external to ourselves, which we cannot help imagining to have an existence and a measure, both of which would remain though those who now speculate upon the conception were annihilated. A little more consideration shows that wo are indebted for the idea to suc cessions of observed events, or at least for the power of applying the idea to external objects. No description can bo adequate; if we Pay that change necessarily implies time, and that the perception of that which is being different from that which was, suggests the notion of an interval, we see that we have already fully assumed the idea of time in the words is and ices. But we may say that space and the objects which fill it exist independently of ourselves, and would undergo changes though we were not in existence to perceive them, and that therefore the times which those changes require would also exist ; this involves the whole of the most abstruse part of metaphysics, and is much beyond the scope of our article. We shall therefore turn to the mode of measuring time ; we have a thorough conviction that time is a magnitude, that is, has its more and less. We must ask ourselves in the first instance what we mean by a greater or a smaller time.
In the perception of time as a magnitude, that is, of intervals of time as containing more or less of duration, wo refer in the first Instance to a habit derived from continual acquaintance with those great natural successions on which the usual actions of our lives depend, with which we can constantly, though unconsciously, compare the duration of our thoughts and actions. There is no more an long or short time than there is an absolutely great or little space ; these words are only comparative. If, for example, any one were to affirm that the universe was continually growing less and leas, all its altering in the same proportion, and the dimensions of the ruman race with the rest, in such manner that the whole solar system would now go into a nutshell, such as nut-shells were a thousand years ago, it would be impossible either for him to prove it, if true, or for any one else to' prove the contradiction, if false. In like manner if any one wore to say that the revolutions of all the heavenly bodies were continually accelerating, but that the properties of matter were also continually altering, and the speed with which ideas are formed and communicated, and muscular efforts tnado, con tinually increasing: it would be impossible to prove a contradiction. The oriental story is the best illustration of this :—A prince was ridiculing the legend of Mohammed being taken up by an angel, and holding many long conferences with his Creator, and having many views of heaven and hell to the smallest details, in so short a time, speaking with reference to things upon earth, that on his being brought back, the water had not quite flowed out of a jug which he had dropped from hia hand when the angel caught him. A magician at the court
of this prince checked his laughter by offering to prove the possibility of the story, if his highness would only dip his head into a basin of water. The prince consented, and the instant his head was immersed, found himself lying by the sea-shore in a strange country. After a reasonable quantity of malediction upon the magician, lie found him self obliged by hunger to go to a neighbouring town, and seek the means of support.. In time ho became independent, married, and brought up a family, but was gradually stripped of all his substance by losses, and buried his wife and children. One day he threw himself into the sea to bathe, and on lifting his head out of the water, found that lie had only lifted it out of the basin, the magician and the other courtiers standing round. On his bitterly reproaching the magician, the latter assuredhim, and was confirmed by all the bystanders, that he had done nothing but just dip his head into the basin and lift it out again. Of course the prince expressed no more doubts about the story of Mohammed, and however much any reader of the two tales may think that neither is true, a little reflection will show that either might be so. Perhaps the allegory might have been suggested by what is known to take place in dreams ; there is evidence enough that ninny of the longest of these illusions really occupy no more than, if so much a.9, a second or two by the pendulum. [Desalts] In the laws of motion it seems as if, so to speak, matter took cogni saneo of time ; a particle of matter will continue to describe equal spaces in equal times, until acted on by force from without. Yet it would be possible to state this law IV follows, in such a manner as to avoid the comparison of quantities of duration. If two particles acted on by no external are at A and a at the same epoch of dura tion, and at B and 6 at the same subsequent epoch, then if A o be in times A n, and if a c be m times a b, the law of motion is that o and c will be respectively attained at the same instaut. The mathematician will readily see that the equations of motion do not depend upon the absolute recognition of time as a measurable quantity,but that any moving particle, as a, being acted on by no force, the distance A c, described in the time t, might be introduced into all forrnulte instead of the time, without any question as to whether, time being physically considered, the space A c varies as the time. It is enough that the uninfluenced motion of any other particle should be connected with that of the standard particle by the law above described. But though we can thus avoid the idea of measurement of time, we cannot get rid of its existence or of the notion of succession of epochs; grant that wo can reduce dynamics to a theory of simultaneous positions of particles of matter, without reference to the absolute length of time employed in passing from one position to another, there is still the notion of time in the notion of simultaneous. But, nevertheless, the idea of succession thus introduced is hardly, if at all, more physical than that which comes into most of the branches of pure mathematics, a point on which it will be worth while to dwell for a moment.