Prove Impossible to Orbit Earth in <80 Minutes

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The discussion centers on proving that an object cannot orbit Earth in less than 80 minutes, referencing the principles of gravitational force and circular motion. The Cavendish experiment is mentioned as a foundational experiment in measuring gravitational forces, although its details are not elaborated upon. Participants are encouraged to use algebra and the formula F = ma to explore the mechanics of orbital motion. The conversation highlights a need for clarity on the topic and suggests looking up resources for further understanding. Overall, the discussion emphasizes the relationship between gravitational forces and orbital periods.
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"Describe the objective, apparatus, and results of the cavendish expirment?"
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Question2: Prove (using algebra) that it is impossible to go around (orbit around) Earth in less than 80 min..

I honestly have never heard of this... can some one explain it to me? or give me some links about it?
 
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re Cavendish expt just search on the web.
re 2nd part:
Do you know how to use F = ma for an object going in circular orbit about the Earth?
 
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