The Physical Worldornament
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The Restless universe
Introduction to The restless Universe

1 The lawful Universe

2 The clockwork Universe

3 The irreversible Universe

4 The intangible Universe

5 The uncertain Universe

6 Closing items


Other titles in the Physical World series

Describing motion

Predicting motion

Classical physics of matter

Static fields and potentials

Dynamic fields and waves

Quantum physics: an introduction

Quantum physics of matter

Answer and comments

See Question 1.5 with its relevant text

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Question 1.5
Would it be fair to say that special relativity has the effect of leaving each observer completely free to make his or her own decision about what constitutes time?

Q1.5 According to special relativity, different observers disagree about how to slice space-time up into space and time. But observers are not free to make arbitrary choices. All observers must find that light travels at a constant speed of c = 2.998 x 108 metres per second, and this will not be possible if an observer uses a clock that is running slower and slower, for example. The definition of time is made quite naturally in special relativity as the time ticked on a regularly running clock that travels with the observer.

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