Does light travel in a straight line, or over the shortest distance?

The basic principle that is true in any case is that light travels along the shortest distance, which is guaranteed by the principle of minimum action, Hamiltonian's principle (the true state of motion of an object is such that the Hamiltonian functional takes an extremum). So experimentally defining the shortest distance is defined by the path of light.

In physics (note the difference from the geometric definition), in general straight space, we define the route of light as a straight line, and from the above principles at the same time, we define that a straight line is the shortest route, in space-time bent by gravity field, although light is not a "straight line", but still takes the shortest route, or in other words, according to the definition, the straight line in curved space-time is originally curved.

Hence the definition of cosmic space measurement: the path taken by light rays is called geodesics, which represents the shortest path in space.

This is also why the sum of the internal angles of a triangle in the universe is not equal to 180 degrees, because the definition of a straight line has changed, and it is no longer a priori the concept of a straight line in people's minds.

Light travels in a straight line, so it's the shortest distance

Light travels in a straight line, and of course if it is near a black hole, it will bend due to strong gravitational pull. As for the shortest distance transmission, that's what it means, but I haven't heard of the concept... Beg.

Straight line propagation, the shortest straight line between two points, ah, is the shortest.

According to Fermat's principle, light travels along a path with a smooth path of nearby optical paths. In layman's terms, it is the path that takes the shortest time.

Light travels in a straight line, but refraction and reflection also occur.

The light radiates outward in a spherical state, and locally it travels in a straight line.

Light travels in a straight line in the same homogeneous medium.

1. Light propagates in a straight line in the same homogeneous medium. The linear propagation of light is an important foundation of geometrical optics, with which imaging problems can be solved concisely. The human eye determines the position of an object or image based on the straight line propagation of light.

2. In order to represent the propagation of light, we usually use a straight line with an arrow to represent the path and direction of light. Such a straight line is called light. Light travels in a straight line in the same homogeneous medium.

3. Through Qing Lead's long-term observation of light, it was discovered that the light that hits the ground along the gap between the leaves of the dense forest forms a ray-like beam, and the same is true of the daylight that enters the house from a small window. A large number of observational facts have led to the realization that light travels in a straight line. In order to prove this property of light, about 24,500 years ago, the former outstanding scientist Mo Zhai and his students completed the world's first experiment on the inverted image of small holes, and discovered and explained the principle of small hole inverted images.

Although he is not talking about imaging but about shadowing, the principle is the same.

4. Make a small hole in the wall of the sunrise of a dark hut, and the person stands outside the house facing the hole, and an upside-down figure appears on the opposite wall of the house. Why is there such a strange phenomenon Mo Jia Ming Bureau explained that the light passes through the small hole like an arrow, it travels in a straight line, the human head covers the light above, the shadow is below, the human foot covers the light below, and the shadow is on the top, forming an inverted shadow. This is the first scientific explanation of the linear propagation of light.