Why does light travel in a straight line?

Question

Light comes from the sun using particles called photons. It would seem that they line up in the form of an electromagnetic wave and propergate across space radially but in straight lines. How do the photons know which way is straight? Why don't they just go off in different directions and disburse?

Answer 1

Light DOES always travel in a straight line. It is true that close to a massive object the light may 'appear' to bend, but this is simply because mass bends space - a straight line through curved space is still a straight line. So the reason that light travels in a straight line is because a straight line is actiually DEFINED as the path taken by a beam of light!

Answer 2

Because the Universe is lazy.

Basically all physical processes in the Universe follow the "path of least resistance", or more properly obey the principle of least action. This is why apples fall straight down from trees etc.

In fact light does not always go in straight lines. When there is a large gravitating body around (like a star), space-time becomes curved. The shortest path in a curved space-time is a geodesic - a curved line. This is like the flight path from London to New York - the shortest route is not a straight line across the surface of the Earth between the two, but a curved line called a Great Circle.

Observation of the curvature of the paths of light passing the Sun (made during an eclipse) was the first confirmation of the Theory of General Relativity.

Answer 3

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RE:
Why does light travel in a straight line?
Light comes from the sun using particles called photons. It would seem that they line up in the form of an electromagnetic wave and propergate across space radially but in straight lines. How do the photons know which way is straight? Why don't they just go off in different directions and...

Answer 4

For these purposes, it is important to think of light as a particle. A particle with a set velocity will always travel in a straight line unless acted upon by an outside force. Just like if you were to hit a baseball, gravity nonwithstanding, it would keep going in one direction. A source of light such as the sun does indeed radiate light in all directions, like a point source. Once those photons are emitted, however, they behave like any other particle at a constant velocity.

Answer 5

Whether light is photon or wave or both, by its nature it goes straight.

If it was changing its path haphazardly from time to time, we will say light has no definite path and it can travel haphazardly.

There are many ways to prove that light travels in straight line. Any elementary physics book gives the experiment to show that light travels in straight line.

Only living things can change their path according to their will. Non living things obey only natural physics laws. The laws are based on experiments.

However, Gauss theorem and Poynting’s vector and Maxwell’s equation show clearly that light travels in straight line.

Answer 6

Light has two properties. It can act as particles or as a wave. This phenomena is not yet understood of why this happens, but there is a clear evidece that light has these two properties. Now, to answer you question, light does not necessary travel in straight lines. There was an experiment done to see what happens when the light passes close to a dense object. The light actually was bent as the gravity affected it. The bent was not significan, but it was detectable. Also, speaking of black holes, the light is sucked by these black holes. The light takes a rollercoaster ride down the black hole in a circular motion. What happens to the light after it is sucked by the black hole is not known.

Answer 7

Everything will travel in a straight line unless an external net force is applied, causing them to change path.

It is possible to change the path of light. This happens all the time. Massive objects will bend the path of a photon due to the space itself also being warped by the object. Lenses "bend" light to direct it to a particular location, etc.

So basically, something can't change unless there is a cause.

Answer 8

actually light follows the curvature of space and time. As there is nothing between the sun and the earth - space is flat - so light moves in a straight path. But when light passees very close to a massive object - they do bend e.g. light from distant stars whose light comes very close to Sun. This is experimentally proved long ago during solar eclipse. See the link below -

Answer 9

Light goes straight but if a opaque object touches it will stop and the light wont go through opaque objects but transparent lets all the light through unlike translucent it lets some light go thorough but not all of the light but opaque doesn t let any like go through which makes a shadow . So the light goes straight and its also unknown why it goes straight



sorry if I am wrong or and grammar forgive me :) and :(

Answer 10

This is simply because a straight line is the shortest distance between any 2 points.
The photons of light move that way so that the least energy is expended.