Does light travel in straight line ? what is a striaght line ?

Question

Can we really know if a line is striaght ?

Answer 1

the straight lines that are absolutely straight to us are actuallly bend...the closest that we can visualise it is as a straight line from noth pole to south pole on earth seen at an angle from the earth...same goes with the 'straight lines' that light is...so straight lines are not absolute...they are relative..

Answer 2

Light travels in a geodesic (according to the principle of least action) which is a straight line in the absence of significant gravitational fields.

A geodesic is the shortest distance between two points in a given space, whatever its metric. If the metric is Euclidean, the geodesic is a straight line.

Answer 3

if i'm not mistaken light travels in wavelengths but to the naked eye it looks straight.

Answer 4

For ordinary purposes (like geometrical optics), yes.  More accurately, light travels between 2 points by the path that takes the shortest time (this is known as Fermat's Principle of Least Time).  On a plane, and in 3-dimensional, Euclidean space, this is a straight line.  You can prove that by assuming Fermat's principle and using Euler's equation (from the calculus of variations).  

However, Einstein's picture changed our understanding of the cosmos from 3D space to 4D spacetime.  Now, it seems, the universe isn't a fixed, isotropic vacuum but a changing, contorted fabric with valleys and such (you know the rubber sheet analogy).  Again using Fermat's principle, the shortest distance between any 2 points is what is known as a "geodesic".  On the surface of a sphere, these are arcs of circles.  In the constantly-changing landscape of the cosmos, these are quite complicated.

Take-home point: Light travels in geodesics.

Answer 5

Straight line is usually thought as mathematical line in Euclidean space.

Exactly one line goes through any two points and this is also the shortest path between them.

Answer 6

a straight line is the shortest distance between two points. I d'm not sure about the light thing though.

Answer 7

Light always travels in a straight line until and unless a medium is applied to it