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 Originally Posted by OngBonga
Maybe in this case the ground does behave like a perfectly rigid surface.
Perfect rigidity is problematic in the same ways, it just takes a bit of Einstein to see it.
You can google Born Rigidity (named after physicist Max Born) to see why it's problematic, but it's pretty heady to understand.
IDK, though... your knowledge of Einstein's Relativity is way above the average Joe, so maybe you can dig it.
If an object is perfectly rigid, then it cannot experience length contraction, but then it cannot accelerate at all.
This takes more than a passing glance to prove, and an old model is to imagine 2 identical rockets connected by a thread. The 2 rockets are exactly the same and accelerate in exactly the same direction such that the tension on the string is constant. For all intents and purposes, they are 1 rigid object, just a funny shape.
The thread is needlessly thin to show that it simply must change length or break... and if it breaks, then that's a problem... 'cause it means that a perfectly rigid body must change shape in order to not break... which is a contradiction with "perfectly rigid."
Ergo, it cannot be real. It would be the hypothetical immovable object.
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