Little Green Apples
God didn't make little
green apples
And it don't rain in Indianapolis in the
summertime
And there's no such thing as Doctor Seuss
Or Disneyland, and Mother Goose, no nursery
rhyme.
What does a falling
apple tell us about gravity?
Space-time tells mass-energy how to move. Mass-energy tells
space-time how to curve. If space‑time did not curve, then we would live in a Euclidean
world. In most applications, the curvature is so small that we tend to approximate
spacetime as flat, i.e. our approximate Frame of Reference is Euclidean. But
the curvature is there nonetheless, which makes the absolute Frame of Reference
non-Euclidean.
If space-time is curved, then the question is that curvature
positive, i.e. spherical, or negative, i.e. hyperbolic. If the curvature is positive
and the radius of the sphere is exceptionally large compared to a typical distance,
then space-time can be treated as virtually flat. If the curvature is negative,
its radius is NOT a factor.
Mass-energy should move along the shortest path in space-time.
That is what Newton’s First Law says: “An object at rest stays at rest and an
object in motion stays in motion with the same speed and in the same direction
unless acted upon by an unbalanced force.” The shortest path in in the same direction in
spacetime is the hypotenuse between two points, i.e. a geodesic. If space‑time
is curved hyperbolically, and the curve of space-time determines the geodesic
over which mass-energy will move, then gravity is an apparent force, like Centrifugal
Force or the Coriolis Force. If there are two objects, then the geodesic between
those two objects is the distance in space-time between those two objects. If spacetime
is curved, then the object with less mass‑energy will move towards the object
with more mass‑energy. Thus what we interpret as gravity, is because we
interpret that movement as Euclidean and it is really an apparent force if spacetime
has a hyperbolic curvature. If two objects have exactly the same mass-energy,
if both objects are not moving, then they should NOT move towards each other.[1]
Consider Newton’s apocryphal apple falling from a tree. How
might that be interpreted in hyperbolic, non-Euclidean space-time? In Euclidean
space-time, the apple moves from the tree to the surface of the Earth. It would keep moving towards the center of the Earth, but the Pauli Exclusion principle, that two
objects can not occupy the same space at the same time, says it can not pass through
the surface of the Earth. In non-Euclidean space-time, the apple and the Earth
are both moving, e.g. the Earth is
moving around the Sun, etc. It is just that both are moving at the same speed
and in the same direction. Thus to an observer in our Euclidean frame of reference
on the Earth, it only appears that the apple is not moving before it falls. Since
the apple is much smaller than the earth, it should fall towards the earth. The
path that it follows is the geodesic in space‑time. What appears to be an attraction
between the two objects is merely the smaller object moving according to the
curvature of space-time.
[1]
Assuming those objects both have the same charge, etc. If they have opposite electrical
charges, then the electromagnetic force will attract them, which IS an
application of a force.