Quest for Equation of Life: Scientific Constraints on How We Spend Our Time

  • Kazuo YanoEmail author
Part of the Service Science: Research and Innovations in the Service Economy book series (SSRI)


How much time do you spend on each activity today? This is one of the central issues of optimization in a broad spectrum of services and personal activities. However, conventionally, the time allocation and prioritization have been out of the scope of science, but a matter of managerial or personal decision making.

This chapter, based on longitudinal measurement of human dynamics, denies this and uncovers that the time for any activity is constrained by the thermodynamics-based upper limit. The derived formula, the same form as that for Carnot efficiency of a heat engine based on the entropy-maximizing principle, is found to be governing the daily human activity process. This physics-based understanding of human time-allocation changes the framework of optimization in any activities and also provides novel principle for better productivity, e.g., through balanced motion-bandwidth utilization, in service, work, education, and life.


Service science Knowledge worker Productivity Time usage Energy Entropy Thermodynamic law Acceleration Activity Sensor 



I would like to thank K. Kawamoto, T. Tanaka, K. Aiki, H. Kuriyama for measurement, N. Masuda, H. Kubota, N. Sato and A. Sato for discussion and comments, T. Akitomi, J. Watanabe, K. Ara, H. Takeda for suggestions on modeling. Anonymous statistical data were obtained with written consent having policy for information handling and ethics.


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  1. 1.Research and Development Group, Hitachi Ltd.KokubunjiJapan

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