Thursday, 15 February 2018

soft question - Do perfect spheres exist in nature?


Often in physics, Objects are approximated as spherical. However do any perfectly spherical objects actually exist in nature?



Answer



No, but it doesn't matter.


The theories that approximate things using spheres are ones in which the final result (the number you measure, the reading on your meter, whatever) depends continuously in some sense on the deviations from sphericity. More symbolically, for any $\varepsilon$ tolerance you allow in your measurement (none of our measurements are infinitely precise), there exists a $\delta$ such that any real object "within $\delta$" of being a sphere will give the same measurement to within $\varepsilon$.


It is not that theories are invalid because they assume something "wrong" about nature. Instead, you have to understand that there is always an implicit statement about how "real" behavior approaches the model as deviations from the model's assumptions get smaller.


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