What's good in small concentrations, but lethal in higher? What's a glaring red flag you're encroaching on a lethal concentration?

ilex@lemmy.world to No Stupid Questions@lemmy.world – 102 points –

Like Fluoride or Oxygen.

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I think General Relativity is based on the idea that a frame of reference that's in freefall is equivalent to one that in a gravity free region of space (at least that was one of Einstein's Gedankenexperiments that led him to his theory of GR).

Having said that, in reality a sufficiently strong gravitational field will cause a tidal effect, which will crush you along one axis and pull you apart along another.

There was definitely something like that - I am not sure if free-fall and being accelerated in a gravitational field are the same though. It may be that GR is talking about moving along lines in space-time that have the same gravitational potential (orbits), and moving across potential lines counts as an accelerated frame of reference in which you wouldn't observe the same as in a reference frame moving at constant speed.

I was thinking of the Equivalence Principle:

the equivalence of gravitational and inertial mass, and Albert Einstein's observation that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.

okay, but that would be an accelerated frame of reference, not equivalent to one that is "gravity free"