Time stream

The timestream or time stream is a metaphorical conception of time as a stream, a flowing body of water. In Brave New Words: The Oxford Dictionary of Science Fiction, the term is more narrowly defined as: "the series of all events from past to future, especially when conceived of as one of many such series". Timestream is the normal passage or flow of time and its historical developments, within a given dimension of reality. The concept of the time stream, and the ability to travel within and around it, are the fundamentals of a genre of science fiction.

This conception has been widely used in mythology and in fiction.

This analogy is useful in several ways:

Science fiction scholar Andrew Sawyer writes, "The paradoxes of time — do we move in time, or does it move by us? Does it exist or is it merely an illusion of our limited perception? — are puzzles that exercise both physicists and philosophers..."

Brian Stableford writes of the historical and philosophical concepts of time (and using the terminology of "flow"),

Like space, it is a basic aspect of experience; early philosophical treatments of the idea hesitated in a similar fashion over the question of whether time could be said to exist apart from the objects manifesting its effects. The manner of time's experience is, however, markedly different from that of space; time appears to 'flow' unidirectionally from the past into the future, bearing all existence with it, encapsulated in the momentary present.
The controversy as to whether time's flow is the very essence of reality or a mere allusion was already sharp in Classical times, Heraclitus holding to the former view while Parmenides and Zeno were convinced of the latter.

The ancient Greek philosopher Heraclitus was famous for a statement that has been translated in many ways, most commonly as "No man ever steps in the same river twice," which is often called his "flux [flow] doctrine." An essayist for the Stanford Encyclopedia of Philosophy explained it in this manner: "Everything is in flux (in the sense that 'everything is always flowing in some respects'...) ..."

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