Dizziness

Spinning
is not the same
as falling

Falling
is grave
and hastened

What is so different
about falling downstairs
or into space?

But spinning…
is there a relative
or universal?

From Wikipedia article on “Mach’s Principle”:

So strongly did Einstein believe at that time in the relativity of inertia that in 1918 he stated as being on an equal footing three principles on which a satisfactory theory of gravitation should rest:

1. The principle of relativity as expressed by general covariance.
2. The principle of equivalence.
3. Mach’s principle (the first time this term entered the literature): … that the gµν are completely determined by the mass of bodies, more generally by Tµν.

In 1922, Einstein noted that others were satisfied to proceed without this [third] criterion and added, “This contentedness will appear incomprehensible to a later generation however.”

It must be said that, as far as I can see, to this day, Mach’s principle has not brought physics decisively farther. It must also be said that the origin of inertia is and remains the most obscure subject in the theory of particles and fields. Mach’s principle may therefore have a future – but not without the quantum theory.

— Abraham Pais, in Subtle is the Lord: the Science and the Life of Albert Einstein (Oxford University Press, 2005), pp. 287–288.

Image credit: The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda (18 September 2010), Adam Evans..