Book contents
- Frontmatter
- Contents
- Preface and Philosophy
- Abbreviations and acronyms
- Part I Planetary perspective
- Part II Earth: the dynamic planet
- Part III Radial and lateral structure
- Part IV Sampling the Earth
- Part V Mineral physics
- Part VI Origin and evolution of the layers and blobs
- Part VII Energetics
- References and notes
- Appendix
- Index
Part VII - Energetics
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface and Philosophy
- Abbreviations and acronyms
- Part I Planetary perspective
- Part II Earth: the dynamic planet
- Part III Radial and lateral structure
- Part IV Sampling the Earth
- Part V Mineral physics
- Part VI Origin and evolution of the layers and blobs
- Part VII Energetics
- References and notes
- Appendix
- Index
Summary
By 2025, a population of 8.2 billion would require an energy use of 55 TW!
WISE News Communique November 27, 1992Overview
Lord Kelvin assumed that the Earth started as a molten ball and calculated that it cooled to its present condition by thermal conduction. The still molten part was kept uniform by convection and the frozen bits sank to the center. Kelvin knew that Earth's temperature increased downward into deep mines and guessed that the Earth began as molten rock at 7000 °F. By solving Fourier's equation, Kelvin found that it would take a hundred million years for the Earth's temperature gradient to level out to one degree every 50 feet. In numbers haughty for their implied plus or minus nothing, Kelvin's final estimate, in 1897, for the age of the Earth was 24 million years. This calculation established that the Earth had a finite age rather than the prevailing geologic wisdom that there was ‘no vestige of a beginning, no prospect of an end’ or that Earth's age was ‘incomprehensibly vast’.
On hindsight we know that uncertainties in the assumptions and parameters are such that Kelvin could have concluded that an Earth cooled by conduction was tens to hundreds of times older than he published, even without internal heat sources.
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- New Theory of the Earth , pp. 331 - 332Publisher: Cambridge University PressPrint publication year: 2007