Cloud Chamber

The only lines connecting two points that are truly straight are those that are (1) imagined, that is to say, non-material (Euclidian lines) that can exist only in the brain and, (2) lines physically drawn between two points and regarded only in the isolated frame of reference in which they are rendered.

Any line physically drawn (drawn, meaning accounting for the passage of time during which the line is actually rendered) can never be straight if one considers the ‘nested’ frames of reference in which the rendering of the line plays out.

By nested, I mean the set of frames of reference nested within one another whose ultimate extent (number of frames) is unknowable.  Example: the frame of reference (inertial and otherwise) of the solar system is nested within the frame of reference of the galaxy, which in turn is nested within the local group of galaxies, which in turn is nested in a still larger frame of reference (the totality of which are ultimately indeterminate).

Consequently, when viewed cosmologically, what appears to be a straight line drawn between two points on a piece of paper in a particular room somewhere on earth is anything but straight. Its profile/path is ultimately indeterminate, and its length is ultimately unmeasurable. Consequently, that straight line viewed cosmologically will appear as a scribble.

When scientists speak of objects traveling in a straight line, like in the oft referred to train traveling down a track alongside a platform, the path of the train is straight only in reference to the tracks, assuming they are presumed straight. However, viewed from a vantage well outside that frame of reference, the train is moving along a cosmological path that is anything but straight. Likewise, beams of light in vacuo do not travel in straight lines for two reasons. First, they are shifted off a straight course to greater or lesser degrees by gravitational forces. Also, if space is expanding (a concept I question), it seems that no path of any object (such as a photon) can follow a straight line unless that path just happens to coincide with a radial line associated with the volumetric expansion of space.

The following somewhat humorous quote seems applicable:

“Every body continues in its state of rest or uniform motion in a straight line, except insofar as it doesn’t.”

Sir Arthur Eddington 1882-1944

British astronomer, physicist and mathematician