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The Physical Aspect of Time
The Physical Aspect of Time
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This ebook edition has been proofed, corrected and compiled to be read with without errors!
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an excerpt from the beginning:
During recent years mathematicians and philosophers have been much occupied in analysing the fundamental conceptions on which the different sciences are based, with the result that many things which were formerly regarded as quite simple and axiomatic can no longer be regarded as such. The tendency has, of course, been to make definitions as precise as possible, and to make descriptions of phenomena approximate to reality as we know it, and not to a preconceived idea of what the description ought to be.
Many difficulties arise, however, in a careful examination of the fundamental concepts of any science, and this is soon found to be the case when we commence to examine the ideas of space and time which are fundamental in all physical and metaphysical enquiries.
In the case of time, for instance, it is found that we have to examine the connection between time as it is known to us by the mind's experience, i.e., psychological time, and time as it is measured by the course of physical phenomena, i.e., physical time.
With regard to psychological time, it has been contested that it is purely qualitative, in other words that we are quite unable to decide intuitively whether two intervals of time are equal or not. This means that there is no fixed method by which two sequences of events may be compared in the mind. The comparisons which actually occur give a qualitative description of events, inasmuch as the sequence of processes is generally unaltered in direct perception and in memory, but the lack of a standard set of units invariably connected with the method of comparison, prevents the description from being a true quantitative one.
This being the case, we are met with a fundamental difficulty when we try to analyse the idea of simultaneity as presented to us by the mind.
If we could represent an event by a point on a line, the idea of simultaneity would be quite simple, for two events could be regarded as simultaneous when their representative points were coincident. In reality such a representation is not valid, there is no sensation of such a simple nature that it can be represented by a point on a line. If we adopt a representation by means of an interval on a line, we obtain what is probably a truer representation of an event as regards its duration; but if we suppose that two events are simultaneous when their representative intervals have a common part, it is clear that two events which are simultaneous with the same event would not necessarily be simultaneous with one another.
It will be realised after a little thought that we can only obtain a satisfactory definition of simultaneity by introducing the idea of the measurement of time; we are thus obliged to consider the physical aspect of time in order to understand the idea of simultaneity.
An observer provided with an instrument for measuring time, such as a clock or a pendulum, can attach a definite number to each event that occurs. In some cases he may find it difficult to decide as to which of two consecutive numbers should be attached to an event; but we shall suppose that he has a consistent method of avoiding the difficulty, as, for example, by always choosing the larger number of the two.
***
an excerpt from the beginning:
During recent years mathematicians and philosophers have been much occupied in analysing the fundamental conceptions on which the different sciences are based, with the result that many things which were formerly regarded as quite simple and axiomatic can no longer be regarded as such. The tendency has, of course, been to make definitions as precise as possible, and to make descriptions of phenomena approximate to reality as we know it, and not to a preconceived idea of what the description ought to be.
Many difficulties arise, however, in a careful examination of the fundamental concepts of any science, and this is soon found to be the case when we commence to examine the ideas of space and time which are fundamental in all physical and metaphysical enquiries.
In the case of time, for instance, it is found that we have to examine the connection between time as it is known to us by the mind's experience, i.e., psychological time, and time as it is measured by the course of physical phenomena, i.e., physical time.
With regard to psychological time, it has been contested that it is purely qualitative, in other words that we are quite unable to decide intuitively whether two intervals of time are equal or not. This means that there is no fixed method by which two sequences of events may be compared in the mind. The comparisons which actually occur give a qualitative description of events, inasmuch as the sequence of processes is generally unaltered in direct perception and in memory, but the lack of a standard set of units invariably connected with the method of comparison, prevents the description from being a true quantitative one.
This being the case, we are met with a fundamental difficulty when we try to analyse the idea of simultaneity as presented to us by the mind.
If we could represent an event by a point on a line, the idea of simultaneity would be quite simple, for two events could be regarded as simultaneous when their representative points were coincident. In reality such a representation is not valid, there is no sensation of such a simple nature that it can be represented by a point on a line. If we adopt a representation by means of an interval on a line, we obtain what is probably a truer representation of an event as regards its duration; but if we suppose that two events are simultaneous when their representative intervals have a common part, it is clear that two events which are simultaneous with the same event would not necessarily be simultaneous with one another.
It will be realised after a little thought that we can only obtain a satisfactory definition of simultaneity by introducing the idea of the measurement of time; we are thus obliged to consider the physical aspect of time in order to understand the idea of simultaneity.
An observer provided with an instrument for measuring time, such as a clock or a pendulum, can attach a definite number to each event that occurs. In some cases he may find it difficult to decide as to which of two consecutive numbers should be attached to an event; but we shall suppose that he has a consistent method of avoiding the difficulty, as, for example, by always choosing the larger number of the two.
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