# What is basic physics worth?: Orders of magnitude, energy, and overconfidence in technical refinements

Abstract : Physics is often perceived as a science of complex and precise calculations, making possible any sorts of technical miracles'' in the midst of which we live. However, the basis of the discipline does not lie in these refinements, but in a small number of laws that should be rigorously applied; it also lies in the physicists' ability to perform justified approximations. A striking and well documented feature of 9/11 attacks in New York City is persisting fires and high temperatures in the World Trade Center ruins. Infrared thermography measurements have been made, just after the event as well as weeks and months later, which allow to estimate surface temperature and corresponding areas, and the cooling characteristic time of the place. Cooling of a hot body in a colder environment occurs thanks to conduction, convection and radiation. Taking into account only free convection, and performing only orders of magnitude calculations because of a lack of accurate data, it is possible to get a lower estimate of the total heat released at Ground Zero. Combining the heat estimate with the maximum energy/mass ratio of all chemical carriers, we can rule out that they were the only source of heat released at Ground Zero, and therefore consider nuclear energy as a necessary solution. Only the opportunistic use of a built-in nuclear demolition feature, designed at the same time as the World Trade Center itself, is a technically viable explanation. Some literature search about pacific use of nuclear explosives as envisaged in the 1960s shows that such an idea, if surprising today, was not unthinkable in the context of the time. Using such sources we propose a general mechanism for the destruction of the World Trade Center, focusing on the shockwave effects and on subsidence crater formation. Some secondary effects need further investigation.
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https://hal.archives-ouvertes.fr/hal-02004696
Contributor : François Roby Connect in order to contact the contributor
Submitted on : Monday, February 18, 2019 - 4:58:10 PM
Last modification on : Sunday, June 26, 2022 - 2:36:51 AM
Long-term archiving on: : Sunday, May 19, 2019 - 5:58:53 PM

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WIBPW-2019-02-18.pdf
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• HAL Id : hal-02004696, version 3

### Citation

François Roby. What is basic physics worth?: Orders of magnitude, energy, and overconfidence in technical refinements. 2019. ⟨hal-02004696v3⟩

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